sly-jeeper wrote:that's amazing that you can get away with 87 if its cool outside...
Well you'd be surprised at the number of naysayers who've said in the past that my stroker combination would be a disaster and ping like hell because it has a 0.088" quench. I blew that myth right out of the water and it didn't take anything exotic and expensive either.
My cooling system is completely stock except for a 180* t'stat. I even swapped a new OEM pump in 18 months ago when my Flowkooler decided to leak from the weep hole and the coolant temps. remained exactly the same. The radiator is a stock 2-row.
During my stroker build-up I smoothened the combustion chamber walls/piston dishes and feathered the edges to leave no sharp spots so I think that helped a lot. I'm even running the hottest Champion RC12LYC plugs year round (including 120*F summers).
Emissions? At today's annual vehicle inspection it passed with flying colors: CO 0.4%, HC 224ppm (NOx & CO2 not tested).
That is good to hear, I really do not want to deck the block much because it will increase compression and limit options if it needs to be rebuilt again but everyone keeps harping on quench. You are right in the danger zone and it sounds like it works fine. How did you get to 0.088 anyway? With a .051 gasket wouldn't you be at 0.0725"?
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Dino and myself have had this conversation many times. He lives in the UAE where his gasoline formulation is quite different then what we have here in the USA. So in a nutshell what works for him may not work for the USA folks.
We are all facing fuels that are laced with a federally mandated 10% ethanol. Ethanol is an oxygenator but its also carries less energy (BTU) then "normal" gasoline. Seems that engines that run ethanol like compression but are sensitive to spark timing. Another factor to keep in mind are the seasonal fuel blends the refineries produce. An engine that runs fine on the winter blend may not run as well as on the summer. Even if keeping the operating parameters the same. Chris J. and Ryan H. can attest to the tuning issues they have run into with this fact.
I am a staunch believer that quench (squish) has to be kept in the mid .040 range regardless of compression in order to achieve the full benefit of the stroker combination. Every stroker I have built has been built this way and so far none have had ping issues when fed properly. My own with advanced timing and a not so optimal AFR runs 9.65 and has no ping on 91. Will admit I have never ran 87 but that is not what I designed the engine to run on.
Yes we can start a conversation on DCR and SCR but the bottom line is you design the engine to do/run on particular parameters and treat it accordantly. Adding octane/pulling spark/dumping fuel to make up for poor quench is not acceptable IMHO.
sly-jeeper wrote:
I am a staunch believer that quench (squish) has to be kept in the mid .040 range regardless of compression in order to achieve the full benefit of the stroker combination. Every stroker I have built has been built this way and so far none have had ping issues when fed properly. My own with advanced timing and a not so optimal AFR runs 9.65 and has no ping on 91. Will admit I have never ran 87 but that is not what I designed the engine to run on.
Yes we can start a conversation on DCR and SCR but the bottom line is you design the engine to do/run on particular parameters and treat it accordantly. Adding octane/pulling spark/dumping fuel to make up for poor quench is not acceptable IMHO.
9.65 DCR??
I agree that adding octane/pulling spark/dumping fuel are not the right way to go but when trying to avoid ping my question is is increasing compression for the sake of reduced quench a good idea? Specifically for me, with IC944 and BajaBeast cam is it better to deck the block for quench or leave it for compression?
I could take it down to 0.005" and that would give me a .048 quench and leave .005 if it needs to be cleaned up in a future rebuild. It takes me from 9.2/7.8SCR/DCR to 9.5/8.05. I would think neither would ping but wonder which is the best way to go. I supposed the .005 deck would give a bit more power.
I agree that adding octane/pulling spark/dumping fuel are not the right way to go but when trying to avoid ping my question is is increasing compression for the sake of reduced quench a good idea? Specifically for me, with IC944 and BajaBeast cam is it better to deck the block for quench or leave it for compression?
Quench comes first followed by compression. Others will disagree but I am not an advocate of decking the block to achieve quench. Would much rather design the piston to achieve 0 deck and add or subtract to the piston to dial in the desired compression. Way to many variables in chamber volume to simply use a generic .0xx off the block. The head gets CC`ed and the volumes of each chamber are made to match. Yes it is a more complicated approach but the results are satisfying.
With the cost of the Icons being what they are. Made to order pistons are only a few bucks more.
9.65 is SCR .000 deck (pistons with lower pin height pushing them up a touch) and .043 compressed gasket. My next engine (daughters TJ ) I am looking to go 10.0 SCR (ethanol based fuel @ 10%) with the same deck but adding a bit of dome to the piston.
I can get the IC944s for $390, where can I can custom pistons for close to the same price? All I have seen are over $600 and the IC944s are already at the upper end of what I want to pay. I am pretty happy with the 4.2 power and I expect this engine will be near 2X so I just want an affordable, reliable engine with as little experimenting as possible.
RenoF250 wrote:That is good to hear, I really do not want to deck the block much because it will increase compression and limit options if it needs to be rebuilt again but everyone keeps harping on quench. You are right in the danger zone and it sounds like it works fine. How did you get to 0.088 anyway? With a .051 gasket wouldn't you be at 0.0725"?
Mine's an original poor man's stroker with the 4.2L rods and 677P pistons that I built nearly 10 years ago long before Keith Black introduced their IC944 pistons. Without milling the block deck and head surfaces the quench came out at 0.088" and the SCR at 9.25:1. The combination does indeed work for me but a quench that high isn't something I'd recommend. The modified poor man's stroker has a quench of 0.070" which is very close to a stock 4.0 and much better than the original poor man's, but even that's still higher than ideal.
Many engine builders recommend a quench not higher than 0.060" and preferably closer to 0.040". Unfortunately if you choose to use off-the-shelf pistons in a 4.0L block based stroker, you can only achieve a zero deck clearance (and a 0.043" quench) by milling a minimum of 0.027" off the block deck and that's if you use the IC944 pistons with 4.0L rods. If you use any of the 4.0L stock replacement pistons with 4.2L rods, you'd need to mill even more off the deck to reach zero deck clearance and the SCR would end up being over 10:1.
Designing the engine for a zero deck clearance and your desired SCR without milling the block deck requires custom pistons and I agree with jsawduste that this would be the ideal way to go, but whether you're willing to pay $600-$700 for a set of custom pistons is up to you. However if you consider the ~$500 cost of IC944 pistons plus the cost of milling the block to achieve zero deck clearance, the custom piston route does look rather appealing after all.
Cheromaniac wrote:
Designing the engine for a zero deck clearance and your desired SCR without milling the block deck requires custom pistons and I agree with jsawduste that this would be the ideal way to go, but whether you're willing to pay $600-$700 for a set of custom pistons is up to you. However if you consider the ~$500 cost of IC944 pistons plus the cost of milling the block to achieve zero deck clearance, the custom piston route does look rather appealing after all.
Also plus the cost to dish the IC944 pistons an additional amount to keep the compression ratio in check.
Thanks Dino for the support. I highly respect the effort you have put into the stroker world and am glad to be earning your respect.
Did you see the break down I posted a couple seeks ago on pistons costs ? Chris corrected me on the fact I called the ICON`s hyper when in fact they are forged. In any case. retail (944`s) without pins is ~550.0 USD. Mike Panetta quoted me 125 per hole with pins. Adding it all up a zero deck Diamond forged piston works out to be only a bit more in price.
Nice part is you can deck the block for flatness, set the center to centers on the rods then do the stack up and Diamond gives you exactly what you want with the desired compression. IMHO pretty hard to beat.
jeepxj3 wrote:Also plus the cost to dish the IC944 pistons an additional amount to keep the compression ratio in check.
Why? Its not like you need racing fuel with the IC944s as they are.
jsawduste wrote:Nice part is you can deck the block for flatness, set the center to centers on the rods then do the stack up and Diamond gives you exactly what you want with the desired compression. IMHO pretty hard to beat.
Custom pistons would be the way to go over cutting the deck. Although a longer rod would be an option as well. However, there aren't many 4.0L rod options that are longer.. IIRC the new Scat rod is still 6.125. And custom rods far out weight customs pistons in the price department. I still don't understand KB's logic in putting the piston so far down in the hole.
I was playing with the Compression Ratio Calculator and if you 'raise' the piston 0.026" or so to 0.00 deck, you raise the CR 0.5:1. Need to add about 5cc to the piston dish or combustion chamber volume to get back to your CR.
jsawduste wrote:Thanks Dino for the support. I highly respect the effort you have put into the stroker world and am glad to be earning your respect.
Did you see the break down I posted a couple seeks ago on pistons costs ? Chris corrected me on the fact I called the ICON`s hyper when in fact they are forged. In any case. retail (944`s) without pins is ~550.0 USD. Mike Panetta quoted me 125 per hole with pins. Adding it all up a zero deck Diamond forged piston works out to be only a bit more in price.
Nice part is you can deck the block for flatness, set the center to centers on the rods then do the stack up and Diamond gives you exactly what you want with the desired compression. IMHO pretty hard to beat.
The IC944s can be had for $400 without a problem - Titan lists for $399. I just talked to Diamond today and they said ~$170/hole that is more like $1k well over 2X the cost.
jeepxj3 wrote:Also plus the cost to dish the IC944 pistons an additional amount to keep the compression ratio in check.
Why? Its not like you need racing fuel with the IC944s as they are.
jsawduste wrote:Nice part is you can deck the block for flatness, set the center to centers on the rods then do the stack up and Diamond gives you exactly what you want with the desired compression. IMHO pretty hard to beat.
Custom pistons would be the way to go over cutting the deck. Although a longer rod would be an option as well. However, there aren't many 4.0L rod options that are longer.. IIRC the new Scat rod is still 6.125. And custom rods far out weight customs pistons in the price department. I still don't understand KB's logic in putting the piston so far down in the hole.
I am planning on running the 944s in an undecked block with 4.0 rods.
The 944s sit lower than stock? I did not realize that. I was thinking they would be at 0.0725" (0.0215 + 0.043 gasket) quench.
Did you talk to Panetta at Diamond ? For whatever reason his quote was far different then what you were given.
A longer rod wouldn't be a bad idea. say add .015-.018 to it and then have enough left over to flatten the deck. I need to look up what my Eagles were in length. I know they were longer the 4.0`s but I don`t recall how much.
jsawduste wrote:Did you talk to Panetta at Diamond ? For whatever reason his quote was far different then what you were given.
A longer rod wouldn't be a bad idea. say add .015-.018 to it and then have enough left over to flatten the deck. I need to look up what my Eagles were in length. I know they were longer the 4.0`s but I don`t recall how much.
And yes the Scats are 6.123/5 in length.
No I was talking to tech support asking about clearance and just happened to ask about price at the end. I will put in a custom form and see what they come back with.
jeepxj3 wrote:I still don't understand KB's logic in putting the piston so far down in the hole.
I just checked and it appeals the deck of the 944s is the same as a stock piston at .0215 down the hole correct?
I see stock pin height at 1.601" and the 944s at 1.353 + 0.248 in rod length difference = 1.601" The other stock pistons are sitting further in the hole. Why doesn't the compression ratio calculator account to pin height and rod length? It has rod length in there but without pin height it does not seem it is doing much. I guess you have to adjust the deck height to account for the pin height?
