building a race 2.7 stroker

[Hiro]

Hi to all,
I'm not sure I've shown these pics in a same thread before,
So here is where I am with my 2.7 stroker.

Main parts for the short block are:
- a 2.3 diesel cranckshaft offset grinded to 89.4mm stroke
- a set of Mantzel forged rods (48mm journal & 135mm c-c length)
- a set of custom JE pistons (97mm bore & 28.5mm cd) with Total Seal rings

[Hiro]

the crank was modified with a dowel pin for the flywheel,
a stock 240mm flywheel was lightened & modified for a S10 clutch combo,
crank + flywheel + clutch cover assembly was balanced,
total weight of this assembly: 28.8kg

[Hiro]

the crank was already offset grinded when I purchased it,
as I did not know the exact amount of offset,
I measured the stroke using a stock 2.4 piston,
knowing the amount of above-deck @ TDC & the length of the rod:

http://www.opelgt.com/forums/attachm...aft-27kit4.jpg

[Hiro]

the 2.3 diesel crank has a wider rear bearing,
this bearing can be fitted into a std CIH rear cap using a 2mm thick shim,
all other crank bearings are compatible with the std CIH block:

[Hiro]

if you put this 2mm shim @ the rear or front of the rear main cap the crank will move accordingly,
this may upset the front/aft location of the timing gear & distributor drive gear.
I therefore compared the timing gear location with a std CIH crank situation:
if you put the 2mm shim @ rear of the main cap, the timing gear will move 0.5mm rearward,
if you put the 2mm shim @ front of the main cap, the timing gear will move 1.5mm forward,
so it's better to put the shim @ rear of the main cap.

when the crank was offset grinded the oiling hole moved a tad forward on the rod journal,
the Mantzel rods use wide BMW bearings that nicely cover the oiling hole,
but putting the 2mm shim @ rear of the main cap will pull the crank rearward,
this will also help keeping the rod centered on the oiling hole.

[Hiro]

some test fitting in the block now:
the block was decked for proper headgasket seating,
piston cd was calculated to be 0.2mm above deck,
now piston protrudes 0.35mm @ TDC,
this is OK with a 1.5mm thick race headgasket.

the rod small end is free between the piston pin bosses,
may require some shims to limit the front/aft slack,
although some 2.7 stroker perform nicely without any shims.

the 2.0 block needs some grinding to clear the rods,
oil gallery is in the way as usual,
but also the lower part of the bores,
I aimed at a minimum clearance of 1mm everywhere.

[Hiro]

I plan to use this 2.2 head fitted with 50mm Imotec inlet valves,
unfortunately this head has gigantic chamber volumes (64cc...),
so I needed quite a tall piston dome to get a decent CR.

valve notches were cc'ed to be 4.3cc
dome volume was calculated to be 12.7cc
using a 1.5x98mm headgasket CR will be 11.2
fair enough for this crappy rod ratio CIH.

[jeff denton]

It looks like the crank has been lightened. Did you balance it?
I was curious what a 28 kg flywheel/clutch/pressure plate weighed in pounds, so I had it converted. 64 pounds. It is massive! Is that gonna be okay?
The pistons look beautiful. Your Total Seal rings will be gapless, I hope?
Final question, where do we find a diesel crank?

[jordan]

That's quite the engine build there, If I am seeing it correctly are the valves slightly siamesed? How exactly does that work with the overlap? Looks great though, what type of rpm's is it destined to see? Considerably lower with the added displacement?

[booeman]

Originally Posted by jeff denton It looks like the crank has been lightened. Did you balance it? I was curious what a 28 kg flywheel/clutch/pressure plate weighed in pounds, so I had it converted. 64 pounds. It is massive! Is that gonna be okay? The pistons look beautiful. Your Total Seal rings will be gapless, I hope? Final question, where do we find a diesel crank?

I think he includes the crank in the 28 kg weight.

[kwilford]

Originally Posted by jeff denton I was curious what a 28 kg flywheel/clutch/pressure plate weighed in pounds, so I had it converted. 64 pounds. It is massive! Is that gonna be okay?

I think that includes the crank, n'est pas?

[wrench459]

From the data you gave us
R/S ratio is 1.51 ok i rounded off
My best advise is to make the most cylinder pressure @ 14 degrees atdc
How you do that is up to you.

[jeff denton]

Ah, yes, I see that he did in fact have the crank included. I feel better now...
Jordan, you can't siamese valves. They sure are close, though. Couldn't get any bigger valves in there! The top cuts above the seats run together, that's what you're seeing.
Yes the R/S ratio is not very good. Wasn't there once an idea to use the diesel block, and longer rods?

[Hiro]

Originally Posted by jeff denton It looks like the crank has been lightened. Did you balance it? I was curious what a 28 kg flywheel/clutch/pressure plate weighed in pounds, so I had it converted. 64 pounds. It is massive! Is that gonna be okay? The pistons look beautiful. Your Total Seal rings will be gapless, I hope? Final question, where do we find a diesel crank?

the 23D crank is very heavy (20+kg),
this one was lowered to 16kg & balanced with flywheel + clutch cover.
the total assembly was 32kg on my first race 2.4,
then 27kg on my second race 2.5 and they both rev nicely to 8200+rpm.
I guess the weight is somewhat proportional to displacement,
this 2.7 will rev to 7500rpm max so it should be OK.
yes my Total Seal are gapless.
the 23D engine was fitted on RekordE some SenatorA and lots of OmegaA,
we trashed many of these cars in the 70s-80s,
some are still in junkyards or on Ebay.de of course!
Hiro

[Hiro]

Originally Posted by jordan That's quite the engine build there, If I am seeing it correctly are the valves slightly siamesed? How exactly does that work with the overlap? Looks great though, what type of rpm's is it destined to see? Considerably lower with the added displacement?

yes the steel seats are overlapping clearly,
valve to valve clearance is 1mm only,
this head was already used before apparently without damage,
actually this 50/40mm valve setup is close to Bob's 1.94/1.60.
rod ratio is a crappy 1.51 only,
so max rev will be 7500rpm or better 7000-7200rpm for added safety.
Hiro

[Hiro]

Originally Posted by wrench459 From the data you gave us R/S ratio is 1.51 ok i rounded off My best advise is to make the most cylinder pressure @ 14 degrees atdc How you do that is up to you.

yes this will also depend upon ignition timing & the cam profile,
not yet decided the cam but probably close to Cam Technique's F328-10 or slightly bigger,
I don't want too much cylinder pressure but not sure I will succeed,
probably will start with 22-24° max ignition advance?
Hiro

[Hiro]

Originally Posted by jeff denton Ah, yes, I see that he did in fact have the crank included. I feel better now... Jordan, you can't siamese valves. They sure are close, though. Couldn't get any bigger valves in there! The top cuts above the seats run together, that's what you're seeing. Yes the R/S ratio is not very good. Wasn't there once an idea to use the diesel block, and longer rods?

yes Jeff the diesel "tall deck" CIH is my next dream,
I did not fetch my 23D diesel block nor checked detailed measurements,
this is scheduled soon but I've hurt my back so everything is slower now...
Hiro

[Hiro]

Originally Posted by booeman I think he includes the crank in the 28 kg weight.

yes crank included!

[Hiro]

Originally Posted by kwilford I think that includes the crank, n'est pas?

oui!
le vilebrequin est inclu.
(wierd word "vilebrequin" stands for crankshaft,
don't know the origin of this word...)

[wrench459]

Originally Posted by Hiro yes this will also depend upon ignition timing & the cam profile, not yet decided the cam but probably close to Cam Technique's F328-10 or slightly bigger, I don't want too much cylinder pressure but not sure I will succeed, probably will start with 22-24° max ignition advance? Hiro

I'm not very good at explaining this but I will give it a try with hopes that other people will chime in and clarify.
Short rods pull the piston away from tdc very fast so they like cams with a narrow LSA in the range of 100-103 degrees.
Long rods 1.7-1.9 rod ratio or more move the piston slower away from tdc
and like a wider lsa cam 114 or so degrees.
My point is to make maximum cylinder pressure at 14 degrees from tdc.
That will put the most force on the crank pin at the right time and you'll go faster..cross fingers

[jeff denton]

And yet another very important thing to consider in the "long rod" theory is the "supercharging" effect that happens at the end of the intake stroke; because the piston dwells shorter at BDC when you have a longer rod. This changes "dynamic compression ratio". Does funny things to the intake tract reversion effect, so the valve closing time may need an adjustment.
That tall deck diesel block really is key to this long stroke engine. Or a revival of the "spacer plate" idea we were kicking around once.
Then there was my latest "what if" profound revelation that happened recently. Suppose the deck of the head just above the piston were milled out so that the piston could protrude a lot higher than .005" from the block? What happens: longer rod. Smaller combustion chamber. Less block decking.

[Hiro]

Originally Posted by wrench459 I'm not very good at explaining this but I will give it a try with hopes that other people will chime in and clarify. Short rods pull the piston away from tdc very fast so they like cams with a narrow LSA in the range of 100-103 degrees. Long rods 1.7-1.9 rod ratio or more move the piston slower away from tdc and like a wider lsa cam 114 or so degrees. My point is to make maximum cylinder pressure at 14 degrees from tdc. That will put the most force on the crank pin at the right time and you'll go faster..cross fingers

on the other hand the increased stroke slowers the piston at TDC,
and LSA 100°-103° is not ideal for big CIH,
that's what I've seen on my race 2.4 & 2.5
so it will be LSA 110° or even 112° for this one.
Hiro.

[Hiro]

Originally Posted by jeff denton And yet another very important thing to consider in the "long rod" theory is the "supercharging" effect that happens at the end of the intake stroke; because the piston dwells shorter at BDC when you have a longer rod. This changes "dynamic compression ratio". Does funny things to the intake tract reversion effect, so the valve closing time may need an adjustment. That tall deck diesel block really is key to this long stroke engine. Or a revival of the "spacer plate" idea we were kicking around once. Then there was my latest "what if" profound revelation that happened recently. Suppose the deck of the head just above the piston were milled out so that the piston could protrude a lot higher than .005" from the block? What happens: longer rod. Smaller combustion chamber. Less block decking.

hum...
not a lot of room to mill there specially if you use big valves,
then if piston protrudes too much the fire ring will sit high,
I don't know how to deal with this?
Hiro

[jeff denton]

Yeah, there are some things to be worked out here... I think the ring going higher is a good thing, right? And the valve seats need to be sunk a bit deeper.
Anything for a smaller chamber volume!

[wrench459]

Originally Posted by Hiro on the other hand the increased stroke slowers the piston at TDC, and LSA 100°-103° is not ideal for big CIH, that's what I've seen on my race 2.4 & 2.5 so it will be LSA 110° or even 112° for this one. Hiro.

Your right Hiro.
I got it backwards off to the corner I go!!