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As ever a long overdue update!

Hi Dave, hope you managed to enjoy the last of your hill climb season, the virus has pretty halted the majority of events myself & friends attend, sad times. My name is Tom, I forget to say my actual name online so not surprised you couldn't see it :D to be honest most people talk to me via Facebook & the mx5 ITB group these days, using the mx5nutz website has been very quiet for me lately.

So where I am to date is:

- Short block built up including the oil pump / baffles / block support brace and sump fitted
- cylinder head ready except the exhaust valves needs shimming to get the correct lash (I ordered some from BOFI but sadly they sent me 7mm internal diameter shims rather than 6mm! they are sorting me out though which is great, always good service from BOFI in fairness)

I managed to take a fair few pictures when I was building the engine up so I'll get them posted with a little commentary!

First stage was to get the built short block onto the engine stand:

35d28ee3b6a0162805f0d2b52119dd1c.jpg


Open up the wrapping and do a quick visual inspection:

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Quick picture to show one of the new balance holes in the crank:

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Then it was time to double check all the torque settings on the main and rod bolts against spec:

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I didn't really need to do this stage as I trust the engine builders at ASD but it only takes 10 minutes to confirm everything is 100% before you seal it all up.

After this stage I check my piston oil squirter clearance, the first instance was a bit too tight:

d8827b141639446de3fb30d8449aedce.jpg


So I removed the oil squirters, modified the jet angle and refitted, ensuring I had minimum 3mm clearance between the squirter and the piston:

f59de824baa8d151371a5a46c583763a.jpg


This ensures that if I take the engine to 9000rpm, any piston movement / rocking at BDC doesn't come into contact with the oil squirter.

So back to following the blue mx5 1.8 manual progress, the rear crank seal housing was cleaned up ready for use (old silicone gasket is so annoying to remove) and a new rear main seal fitted:

ecce4f79f5cfcc1a60f9c026bb62c62c.jpg


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I forgot to take a picture of applying silicone & fitting it but its just as the manual states nothing fancy here.

Next step was the modified, billet geared oil pump install. I always lay everything out that I need prior to starting the process, always nice to know you have everything you need before fresh silicone is used. so we have a new crank oil seal, permatex RTV and a oil pump housing outlet oil ring.

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and here's the pump all fitted & ready to go:

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Moving onto the main block support plate, oil pump pickup and sump install. First step was to get the main items out and inspected:

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I had already previously installed my own viton gated baffle plates and I decided to try out the skid nation top baffle plate as well, nice bit of a kit and fits nicely around my custom pick up tube :

9a63c5e6a3b23d4aa04cbe533b1a6c5f.jpg


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So before I started to silicone everything up, thankfully, I decided to test fit everything beforehand. I soon realised that the MBSP had significant interference with the ARP main studs :(

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I had to modify two distinct parts of the MBSP, the first being the raised edge of the main cap mounting plate, here's the plate in stock form:

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Then modified to improve clearance, the lip would just touch the main stud nut:

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The second location was the metal directly above the main stud, I needed a clearance hole for all of the main studs as they were sitting too proud..... it took forever but here's the last test fit before cleaning up the cuts:

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now I knew everything would actually fit! Time to prime that oil pump and get some fresh break in oil circulated:

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I did this process 3 times, filled up the pump then turned the crank by hand to circulate the oil until the level was lost, start the process again. After the 2nd time I started to see oil coming out of the main/rod bearing areas so I was happy at that.

So after all the trimming and priming was done, the MBSP was siliconed onto the block and bolted down to each main cap with the pick up pipe also bolted down:

6bc5ec7e06fc4cbd6f623fbf3873cf5c.jpg


Finally to finish up the bottom end, the sump was siliconed up, fitted and bolted down:

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I really enjoyed this bottom end build, mainly because it was my engine and not someone else's this time around :lol: the trimming of the MBSP I was not expecting but it was easily solved. I also started to work on the cambelt tensioner side of things. I knew that by skimming .120 thou off the head I needed to account for the belt slack, although my previous experience with gates racing blue belts they are damn tight to fit standard! My first thought was to follow Quinn's advice which was to use the OEM tensioner which attaches to the spring, remove the metal backing plate so you end up with a tensioner that has a slot which would allow me to apply further pressure to the belt before tightening it.

373281faa88491fa9b964b85a6ab428e.jpg


But whilst trial fitting the modified tensioner, I noticed that after a certain amount of movement which would simulate 'additional tension' on the belt, the tensioner would start to fall off the waterpump aluminium base plate of which the tensioner sits on. After further inspection, It revealed that the modified tensioner has a thinner mounting boss than the original which wasn't helping the issue, see the picture below:

5b3e05b475ee5b8c64a76eb8ab57e511.jpg


At this stage I am unsure as to whether it will be ok or not, depends if I can achieve the correct tension before running out of water pump base plate. The other option is to drill out the old tensioner to match the other ones shape but I'd rather not unless I have too!

In other news, I have ordered myself a SPA digital signature series dual oil pressure & temperature gauge - very nice bit of kit but not cheap :eek: I'm also going to be changing the tyres this year, I was running 195/50/15 toyo R1R all round but I'm moving to toyo R888R with 205/50/15 rears and 195/50/15 fronts!
 

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layabout
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I'm moving to toyo R888R with 205/50/50 rears and 195/50/15 fronts!
aren't 50" rear wheels a little on the large size? :blink:

guess you'll have a serious tyre-rake as a result :lol: :lol: :lol:

also a 205 / 50 tyre on a 4'2" rim will be a bit........

the-donk-southern-fly-riding-high_1.jpg


:whistle:

Rich.
 

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Rich and I both have lathes
must be something to do with the name :rofl:

on a serious note, an insert would cure your issue :thumb-up2:
but look at the basic (& small diameter) pillar Vauxhall used to support the idler & tensioner rollers on their infamous '20XE' engines, does it need that much of the diameter to stabilise?

Rich.
 

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Ha good spot on the tyre sizes, I was rushing to finish up in my defence :lol:

I did consider an insert originally, but after a bit of research I found a couple of options from different engines. I've ordered one from a another Mazda/Kia engine, part number ADM57602 (52x25x9x23mm). The bolt hole is slightly tighter than the OEM bolt but I'll just file it for clearance if needed (only 0.6mm too tight nothing major and might get away with it depending on their manufacturing tolerances!).

The key difference is the mounting point of the pulley is actually smaller in diameter which will allow it to stay on the water pump boss easier. The pulley itself is also 5mm wider which gives me more comfort when pushing the RPMs as the belt might start doing some weird movements/vibrations at that point (Not unheard of with other high rpm engines but not really spoken about with high rpm mx5 engines so probably not an issue).

Dickie, the head is .120 skimmed and I'm using the 86mm JE custom pistons with it :thumb-up:

The pistons use a 6.9cc Dome which makes me achieve 13:1 compression ratio :driving:

I can write up the calculations if you wish to see them?
 

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layabout
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Ha good spot on the tyre sizes, I was rushing to finish up in my defence :lol:
Couldn't resist :whistle:

not really spoken about with high rpm mx5 engines
maybe thats because few people have high-revving mx5's?

well past the standard revlimiter area anyway :driving:

Rich.
 

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From my notes a short stroke build is definitely do-able, IF you could offset grind the crank by 3mm leaving you a 45mm journal then you could use Suzuki rods from a swift M15A VVTI (Aftermarket forged units are available) and drop your stroke to 83.5mm with the 1.8 crank or 82.1mm with the 1.6 crank (I'm assuming the rod journals are the same size on the 1.8 & 1.6 cranks but I'm not 100%). you can then use the 83-86.5mm bore (in 0.5mm increments) of the 1.8 block to get as close to your class limits.

I can't say I haven't researched it because I did but as ever there's 'no replacement for displacement' unless your class limited :D

Well I'm still waiting on my valve lash caps from BOFI, hopefully they will arrive next week.

The tensioner arrived this week so I managed to get sometime to figure if it is going to work - which it is!

Here's a picture of 2 standard tensioners (top & bottom right) and the new tensioner:

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And more importantly the mounting bosses of the tensioners in the same orientation as above:

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Thanks to the modern technology and manufacturing tolerances, needed to relieve the centre hole as it was roughly 1mm too tight:

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To try and explain the issue better, here's some pictures of the OEM tensioner with the backing plate removed being mounted in position:

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You can see light through the mounting hole showing how the tensioner mounting boss falls off the water pump pulley boss when placed in what I think will be my tensioner position.

The new tensioner on the other hand is always connected to the water pump mounting boss even when the tensioner is placed way beyond where I expect it to be needed thanks to its smaller diameter mounting boss:

e77efc73164cd0ac226e4ffdbe2260f2.jpg


For £20 and a bit of time on the dremel it was well worth it, gives me peace of mind & added safety factor as the pulley is slightly wider also.

Going back to the calculations of this engine build, here's a quick right up for the compression calculation:

Cylinder head volume: 42cc
Piston head volume: 6.9cc
Gasket thickness: 0.032" (0.8mm)
Deck clearance: 0.008" (0.2mm)
Gasket bore: 3.386" (86mm)
Cylinder bore diameter: 3.386" (86mm)
Stroke: 3.346" (85mm)

Static compression ratio: 13.05:1

Rod Length: 5.433" (138mm)
Inlet camshaft ABDC: 68

Dynamic compression ratio: 10.1:1

(These figures are actual measured figures for my engine, not "I've skimmed the head 30 thou so I have 14:1 compression on stock pistons" type of statements which I keep reading everywhere at the minute :lol: )

My dynamic compression is the highest I would feel comfortable running on Shell V-power Nitro+, which is 99 octane fuel. I'm really tempted to try some race fuel in this engine just to see what maximum power can be achieved (Using Oxygenated fuel not just higher octane) but I need to get the thing running first :lol:

Here's an interesting link to dynamic compression, a good read and matches well with what people in the hillclimb/autograss scene have talked about with me.

http://ftlracing.com/dynamiccr.htm

on the engine front, I have ordered a few more AN10 fittings for the oil cooler, still need the hoses/AN connectors but I'll order or make them up when the engine is in the car (I don't want too much hose as it'll look rubbish). thankfully with the placement of the oil cooler the hose length is roughly 500mm so really short which is great.

I also need to order or Fabricate an oil breather can with 2 x 19mm fittings and a filter but I'd do some internet shopping tonight and see what's available :D

Here's to hoping my valve lash caps turn up soon!
 

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layabout
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as you're not using the standard tensioner with it's 'pivot' setup, be carefull of a slotted adjustment without any kind of pivot or keyway as it could turn & possibly loosen (if you've my luck anyway :blink: )

I'm sure you wouldn't want that :yes:

have you gone larger diameter or kept same as origonal?

maybe easier to go larger diameter on the fixed idler?

or have I missed something :wallbash:

Rich.
 

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Loving the updates, as always. i'm looking forward to seeing what numbers it pulls.

I was going though your numbers (validating my calculation sheet) and I think you made a typeo on clearence, 0.008" is 0.2mm

Going back to the calculations of this engine build, here's a quick right up for the compression calculation:

Cylinder head volume: 42cc
Piston head volume: 6.9cc
Gasket thickness: 0.032" (0.8mm)
Deck clearance: 0.008" (0.002mm)
Gasket bore: 3.386" (86mm)
Cylinder bore diameter: 3.386" (86mm)
Stroke: 3.346" (85mm)

Static compression ratio: 13.05:1

Rod Length: 5.433" (138mm)
Inlet camshaft ABDC: 68

Dynamic compression ratio: 10.1:1

(These figures are actual measured figures for my engine, not "I've skimmed the head 30 thou so I have 14:1 compression on stock pistons" type of statements which I keep reading everywhere at the minute :lol: )
I was surprised at your deckheight (I could be mis understanding the direction) is -ve, the wossners in my build are 0.2mm above the block deck. even with this my calculated cr is woefully low at 11.2:1 compared to my targetted 12:1. Do you have much of an idea of skim to CC on the head? mine looks pretty virgin (50.8cc combustion chambers), so I've got plenty to go.

I'm yet to calculate my dynamic Cr, mainly because I have no idea where to time my Maruah cams to yet, so that'll be interesting to see.

With regards to the MBSP, the later one seems to be much more substantial, compared to the '98 one. sdo you think there is much to be gained in reliability by obtaining a later one?
 

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Discussion Starter · #153 ·
Thanks for the double check Ratty89, yes it was meant to be 0.2mm :lol: my piston would be smooching with the head around 8000rpm with 0.802mm piston to head clearance!

So my pistons are 0.2mm in the hole, for three reasons but the first is the critical one:

1 - Achieving the correct Piston to head clearance with my chosen head gasket of which is 0.8mm.

2 - I prefer to have as little combustion chamber intrusion from the piston as I can whilst obtaining my desired CR ratios, so I can maximise the scavenging effect of the exhaust manifold on the inlet charge.

3 - I prefer to use the smallest combustion chamber possible, this is to reduce the surface area in which the burnt air/fuel during combustion cycle can enact a force onto something that isn't moving! I want the combustion event to be utilised by pushing the piston down the hole (not spreading across the chamber, trying to ignite the whole chamber contents by which point the piston is further down the hole so the energy release is too late)

I've never researched pistons being set outside the hole so i don't fully appreciate the benefits or implications, sounds like some bed time reading to me :D

Do I have a rough idea about how much head skim = how much reduction in CC?

I do have some rules of thumb but I haven't proven them over testing different heads so I wouldn't like to say. I can tell you that on my latest cylinder head, which please bear in mind has had a lot of material removed around the inlet valves for promote flow as its a 86mm bore so I could, I have skimmed a total of .120 thou and obtained 42cc chambers. When I went from .100 thou skim to .120 skim I went from 44cc to 42cc respectively, although this is not an ideal representation because I was skimming the head to remove the valve shrouding on the rear of the inlet valve (the squish pad lip).

The MBSP is definitely worth it, tying as main main caps together as possible is always a good thing when dealing with higher RPMs. I actually designed a proper main bearing support plate which bolted down via the sump pan bolts/flange (Similar to honda K20 but that incorporates the main caps as well in the casting) but without going dry sump I couldn't live with the decreased ground clearance of my sump! The dry sump kit cost was roughly £2300 with a custom pan welded up from an old sump flange (Needed to do that to keep the cost down whilst retaining the half moon seals mounting faces). Considering the ease of which it is to fit one, no major mods, it's a no brainer if the engine is coming out (Buy a scrap yard VVT engine for £100, take what you need from it job done, sell your spare sump to the turbo people so they don't have to drill a return hole in situ, crazy :blink: )

Hey Zed, the tensioner is the same diameter as the OEM unit although the running surface which the belt runs on is every so slightly wider by a few mm. the plan is to utilise the original OEM sliding tensioner & spring and use the new tensioner to add additional static tension to the belt to account for the head skim. I'm not too concerned with the slot but you are right they can move. I've personally never had any issues, I use loctite blue on the threads and torque them up as required (I did torque check them after my 2 trackday of the year a few years back and they were still ok, not so much some of my suspension bolts though which like to undo themselves overtime). The only reason I was nervous to go bigger diameter on the fixed idler position was because I wasn't sure how much extra fixed tension I'd need although I could certainly reverse engineer the required diameter once I've got it tensioned with the new adjustable one!

Oh the woes of ordering from Cat Cams..... poor peolpe at BOFI I've been chasing them every 3-4 days and they can't get anything from Cat Cams about the order. They know its due in but when is another story!

It has put me back several weeks which is really annoying, I'm starting to loose my free time again with work and I wanted the engine ready for mapping mid December (I want the car running again before my firstborn arrives which is due very soon :D )
 

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Hi Tom, I thought I would drop an update on my engine in your thread if that's ok.

So hillclimb season is well and truly over now. I noted during this season a noticeable increase in oil consumption which needed investigation along with measuring the head flow. I need to establish what if any improvement's in flow had been achieved by KSP engines as no figure was ever forthcoming when I bought the engine as a part finished project some years back.

This week my head is going off to a local engineering firm who are experienced with competition head work and posses a flow bench.

I will also be sending them a standard BP4W head as a comparison. I would like to establish flow and port velocity on both heads and decide a way forward from there. It may be I have to start again using the standard head if material has been removed from the wrong places on my so called competition head. I cant recall what flow figures and port velocity you achieved on the current evolution of your head work. It would be nice to know that to use as a bench mark for my head.

As far as the oil consumption problem goes a quick check on the cylinder compression shows that it is down to about 160 psi per cylinder where as it was around 220psi 3 years ago when the engine was first built. There is a fair amount of wear on the rings and a little on the bores so a bottom end rebuild is in order too.

My aim for next season is to achieve 180 to 190 ft lbs ( currently 142 ft lbs ) and around 230 to 240 bhp ( currently 220 bhp )with engine that revs to 8900 rpm. I will update as progress is made if that's ok, i don't want you to think i'm hijacking your thread :) It just seems a good place to have all this NA tuning data.

I will look out for you on the facebook MX5 ITB group, i did not know it existed but have just joined so can share more info there too.

All the best for now, Dave
 

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Discussion Starter · #155 ·
Hi Dave,

no problems at all posting on this thread :thumb-up:

3 years of hillclimbing at 7000-9000rpm I'd say that engine has done you proud, the short rod ratio & high rpm is a killer combo for cylinder wall wear (One of the main reasons I went with long rod really).

Your definitely going about it in the right way with using a stock head as a baseline against your ported head. Just eye ball your stock head ports though because I've ported 14 (nearly done with the 15th) BP4W heads to date and they have significant differences in the port angle/direction in relation to the valves (Inlet side only, or at least so far). This is mainly on cylinder 4 inlet port but I've seen issues in 3 inlet port also. This caught me out one time because I started porting the head and realised that I couldn't push back cylinder 4 inlet ports back to match the valve centreline without hitting the water jacket :blink: In fairness I've only had 2 of those heads but its very obvious when you look down 4 inlet port (The valve closest to the back of the head). The port section around the valve guide area of this valve actually turns towards the front of the engine causing some shrouding of the valve which cannot be fully corrected.

Your engineering shop will be able to see it if your stock head has that issue, I'm guessing its a bit of core shift during the casting process but either way it doesn't help matters.

If you don't mind I'd rather link the cylinder head data than post it again (It could fill this thread up very quickly!): https://www.mx5nutz.com/forum/index.php?showtopic=383971&page=6

Just a quick note:

My cylinder head design is aimed to achieve peak intake & exhaust velocity around 6500-7000rpm (Intake is roughly 20FPS higher than exhaust at all times from a calculation perspective, with Intake at 320-340fps and exhaust 300-320fps).

This means my peak torque, hopefully around or just over 180ftlb, will be around 6500-7000rpm (222bhp - 240bhp). with my current 280 degree cam choice I think its do-able but only just. I really hope I can achieve 175ftlb at 7500rpm which would a nice 250bhp (we can only hope :lol: ) but I think an exhaust manifold re-design might well be needed for that!

In terms of your goals, we must remember that It is very difficult to achieve anything over 90ftlb per litre naturally aspirated (Its not impossible, my 211bhp engine was 93ftlb per litre for a short period). in your case with 1907cc (I think it was this?) then your looking at 171ftlb - 177ftlb, which I reckon you could easily achieve this with headwork / potentially different cams.

I get to cheat with the new engine being larger displacement at 1975cc: 178ftlb -184ftlb (If I get over 184ftlb then I'll dance all the way back home from the dyno :lol: )

The main obstacle I see with your build is that your power band range is quite uncharted for BPs (4500-9000rpm effectively) I have no doubts you'll get there but it will certainly be a challenge to increase your torque and hold onto the power like it did :)
 

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First of all I hope everyone has had or having a good Christmas break!

I still haven't received the valve lash shims from BOFI / Cat cams and I got a little peeved because it has halted my engine built for 7 weeks now :( I don't like to build an engine until I have everything to hand but after waiting so long I decided to get some progress to make myself feel better! I really tried to take pictures of every step but typical me I get engrossed into the build/focussed and forget about the pictures :lol:

So continuing from the last step which was installing the sump, I decided to double check everything at the top end of the engine:

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The first step was to verify the piston height at TDC, this was confirmed to be 0.2mm in the hole which is was what I asked for so good news.

The next step was confirming the hone was equal/even throughout all the 4 bores and make sure everything is clean and I had no issues here as well which was nice.

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I forgot to take pictures of the next bits but I fitted the ATI super damper & water pump onto the block, nothing special here just following the blue book and flying Miata's damper guidance notes.

The next step was yet another cleaning session which also included cleaning the headstud threads in the block, again nothing fancy but just needs to be done.

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Now I get to install the two dowel pins for the head gasket and the head studs, finger tight first for all studs then quarter turn to seat them properly

0edaa22f6ac9c77e2bf0b05a55f97a2e.jpg


Then install the gasket and lubricate the ARP studs with the supplied lubricant (Its easier to do this before the head goes on). Once the gasket/studs are lubricated the cylinders get a final wipe down before the head goes on

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Time to get the head inspected, cleaned down and ready for install. In the following pictures the inlet cam is lashed/torqued down ready to operate but the exhaust cam is not due to no lash shims!

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I love this next picture as it really shows how much extra airflow I have gained, especially around the short side radius at TDC to 15 degrees ATDC.

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Pop the head on the block and start tightening the head studs to spec (ARP provide an engine specific diagram and torque settings which is very nice and easy)

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That's where I finished up for the session, I popped the cam cover on the engine just for ingress protection but I still need those darn valve shims to finish up properly and time the engine up!

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So the next step is to confirm my maximum camshaft centerlines (I think it was 105 from memory was the tightest) and mark the maruha cam gears to ensure I don't exceed that point during dyno tuning. I still have further work to do on the oil sandwich plate/cooler takeoff point but that will most likely happen when the engine goes into the car as I need to understand all the limitations in the area for the hose positions.

I am still reviewing the cars gearing but that will be finalised once the dyno is complete and I understand the engine's powerband exactly rather than just theory.

Interesting link there Rich, seems an odd approach to just lengthen the rod ratio & limit your possibilities with the BP4W head (it really isn't anything amazing in the grand scheme of cylinder heads, even after much development). Everyone has their reasons though and I hope they can make it work. the rod ratio for mine is 1.62 but there's still meat left in the piston if you wanted a longer rod for the sacrifice of reliability/longevity.

Interestingly, I have a had many conversations with people about a long rod engine and its not a magical engine that will make XXX more power than a standard rod engine, its merely matching the engine design to the driving characteristics you want to subject it too. Many times I have been asked would I recommend a long rod motor over the standard length, and I always say:

'if your staying below 7500rpm regardless of induction and/or street driven stick with the stock geometry and build it strong. If your going for sustained high rpm (>7000rpm continuous or you are geared so your powerband is 6000-XXXX) racing or mainly track use then consider a long rod engine'

The short rod ratio in the standard BP makes for a very punchy throttle response & good mid range power, it also helps to pull harder on the inlet port during the start of the induction process and with the heads being not great in standard form and somewhat average performers fully developed, it will help you make more power.

Once you start to develop the cylinder head, you can trade off the pull on the induction stroke for reduced friction and 'potentially' more torque per combustion event (In theory this is the case but practically people have tested it with varying results).

But after saying all of that, the world would be boring if we didn't try things out and people all did the same thing :D
 

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re. the tappet shims, wouldn't hsave been easier / cheaper to have had some made locally? probably quicker :blink:

the BMW engine crossover is interesting, the possibilities are great BUT using a cylinderblock designed to run angled with a cylinderhead that runs vertical can cause fun :lol:

also, seen on fb that theres another intending to go 'long-rod' but he's not shared any info :rolleyes:

Rich.
 

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Hi Dickie, sounds good regarding your head work - I'm positive you'll get some gains from letting SRD work on it!

Happy new year to you all as well, we have made it to 2021 :D

I had a massive dose of motivation on new years eve as my skims from cat cams arrived (48hr delivery service from Belgium! crazy stuff) so I got the head all lashed up and ready for use.

The first check was to confirm my valve pocket positions and available clearance at TDC with different LSA's for both the intake and exhaust cam. This is the start of the process to confirming the working clearance of this engine. First step is to make sure everything has reasonable clearance at TDC using various LSAs (always test your maximum adjustments here!). The second stage is to confirm the valve to valve clearance at different cam gear positions. The last stage is actually timing the engine with plasticine inside using the maximum overlap setting of the cams to confirm adequate working clearances.

So the first stage was to add some plasticine to the valve pocket reliefs:

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Then the head was placed back onto the block but not torqued down (just incase they were incorrect I would feel hard resistance / see the head lift rather than bending the valve!). The cams were timed up from the cam spec card at 108 LSA (2.20mm lift at TDC):

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give the engine a slow full rotation ensuring to feel for any stiff resistance or see the head lift slightly. Once complete I then set the cams up for 106,104,102,100 LSA on both cams (one at a time of course) and performing the same procedure. Once completed the head is removed and the plasticine can be viewed:

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The next step is to take cuts of the plasticine and take measurements to confirm valve depth & radial clearance within the valve pocket

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After taking measurements I found that even with both cams on 100LSA (3.5mm lift at TDC):

The intake side was 2.3mm valve to piston depth clearance in the central valve pocket area and 1.5mm valve to piston radial clearance
The exhaust side was 4mm+ valve to piston depth clearance central valve area and 1.2mm valve to piston radial clearance.

I did note some sections where the intake valve got a bit tight to the piston around the ring land area of the valve pocket and taking measurements here showed roughly 1mm valve to piston depth clearance. so I have put a 102LSA limitation for the inlet cam gear which brings my minimum clearance to 1.5mm in this area which is more reasonable and makes me feel more comfortable for the last stage process.

Second stage is to check my valve to valve clearances on the bench, this involved getting the head back off the engine and chopping up/using an old timing belt the simulate how the timing belt works when properly installed (You must set the cams back to the cam card specs, in my case LSA 108, with the adjustable cam gears before doing this otherwise the results are not accurate!):

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So the first check is the find the clearance at the standard cam card LSA of 108:

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over 4mm clearance between the valves, no issues here.

Here's the valves with the LSA of 104 for both cams (Intake advanced +4 and Exhaust retarded -4)

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Starting to loose clearance pretty quickly now!

Here's the valves with the LSA of 100 for both cams (Worse case scenario, Intake advanced +8 and Exhaust retarded -8):

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less than 1mm clearance between the valves, bit tight for my tastes but doesn't touch!

I then starting testing different combination but in the end the 102 LSA limitation due to piston to valve depth clearance is the governing factor and valve to valve clearance isn't a concern going forward which is good to know for when I hit the dyno at some point!

I'm fairly certain that I will have to place another limitation on the LSA due to the working valve to piston clearance when I complete part 3 of the testing, this is due to the piston dwell between 15degrees before & after TDC and how the camshaft profile interacts with the valve to piston position. My guess would be an 104 LSA limitation but we'll find out soon enough :)
 
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