Venomantidote95

Idk havent thought that far ahead lol!

Joel5.0

Lets try to bring this back on track...... take two 331 setups (or 347, I don't know why ci's are so feared)...... for example:

#1. 3.25" stroke, 4cc FT piston, 0 deck, 58cc CC (Combustion Chamber). .047 HG thickness ~ 10.45:1 SCR

#2. 3.25 stroke, 14.2cc dished piston, .001" deck height in the hole, 49cc CC, .041" HG thickness ~ 10.43:1 SCR

I will always choose #2. Make the piston crown a mirror image of the CC = another reason to choose #2.

Supercharging or turbo is added afterward?..... time to make sure those cam events are correct. Is that too aggressive and might cause reliability or pre-detonation issues, not if done right. And as proven by Ford with a dual turbo, 10.0:1 SCR, 12 psi boost, capable of reliably running on 87 octane OEM setup. Piston used?.... mini dome with a localized pocket, a la diesel and CC's in the 52cc-56cc range.





What does the above piston crown geometry show you regarding flame propagation? .....BTW.... that is an OEM setup. Doesn't it look very similar to..... (focus on the crown)



What about the N/A kingdom.... like the new 5.0L Coyote? Take a look at the 11.0:1 OEM piston used.....



Is it a mini-dome piston?.... yup.....but I have $20 that says that when it finally goes turbo-DI... , the OEM piston will also look like a diesel piston. BTW..... I'm expecting a delivery of a 12 psi Paxton SC this month for a daily driver 2011 5.0L California Special I'm doing some work on. Yup.... boost added to a 11.0:1 SCR OEM engine.

To summarize..... I would rather move some of the combustion chamber to the dynamic piston side in order to keep SCR at bay in our traditional windsors. Why?..... it does allow for more performance at any rev level + it allows you to simply focus on an overlooked area to achieve performance and driveability...... valves timing. Obviously, with cylinder heads that are up to the task...... TFS TW 190 or CNC 185, Victor Jr., AFR 205+, etc.

Joel5.0

Almost forgot........ ..... what's with this "equality syndrome" when comparing engine setups? A 302/331/347 setup with flattop pistons at the same SCR when compared to a dished piston.... will, does have, needs to be different in many areas. That is the reality and the areas where you capitalize. Different configurations but at the same SCR! Isn't that what engine building tinkering is all about?

Does that make any comparison an invalid exercise?.... ... Au contraire!.... it makes it more valuable and representative. IOW.... if your "equalizer" is SCR....... a comparison between pistons at the same SCR will OBVIOUSLY have a difference on their piston crown geometry..... it is what it is required to "equalize" one to the other. Get it?

67mustang302

I wish someone would make heads with small chambers for stock stroke engines. A 302 with a dish and a small chamber at 10-11:1 or more would be a neat little engine. Nice setup especially for a ci limited class race engine.

Of course, I wonder if it could even be done from a practical standpoint, given the need to fit 2 valves and have a properly shaped chamber.

mjr46

To the OP my apologies, OFF TOPIC responses removed. I look forward to seeing the empirical proof/results of your build

simpkins_44

Hey sorry that I haven’t got back to you guys for a bit I’ve been busy with midterms. also Sorry for the outbreak on the post and this discussion being turned into a debate more or less.

thank you joel5.0 there is some great stuff you brought up. I noticed you mentioned the 347, I am not afraid of the 347’s extra volume if anything id opt for it. however I decided to go with a smaller engine for multiple reasons. I don’t want to interfere with the oil ring on the pistons like as the 347 pistons do, this is why I choose probe pistons they shorten up the piston without interfering with the oil ring. Also in a 347 the rod to stroke ratio is lower then that of a 331 or 302 this increased rod angle puts extra stress on the cylinder walls and the short oil ring interfered pistons and piston skirts this could be avoided by using longer rods and a shorter stroke. there are many people out there that swear by 347’s and say they are just as reliable as the 331, I don’t disagree I have no reason to. I just believe that there is enough power to be made out of a 331,without the added stresses. Also by using a 5.4” rod the rod angle is limited to 17.51 degrees just slightly over the stock 17.14 degrees and although the added stroke I was able to keep the rod to stroke ratio similar to that of the 302. With this longer rod there will be a longer dwell time at TDC and BDC, this can aid in power gains with a longer burn and more direct force to the crank through the rod and piston assembly, also valves can more accurately be open for a longer period of time(engine cycle wise).

I get what your trying to say about equalizing the static compression ratio not the volume. This is a great idea with most definite benefits for the dished piston set up. However I cant for the life of me find a 49cc head other then for Chevy applications. I desided I would see if I could take a small chamber head and see how far I could take it down. I crunched some numbers and got some opinions and it turns out that a 58cc head can be milled down plus or minus 5cc or about 0.025”(depending on the head, ill be getting confirmation from the manufacture). Also the block can be milled down 0.011” leaving the piston 0.005 out of the hole with a 0.040” gasket this leaves quench at 0.035. This will lower the overall chamber volume down to 74.15cc from 80.959cc and allow for a static compression ratio of 10.029:1. I’m not so sure that these numbers are reasonable and if I can get this work done to all the parts with 100% precision. I feel that getting pistons made may be less money for the same results. What do you think??

As for supercharging or turbo charging I’m not sure yet I like the idea of a supercharger but I don’t want to base any decisions on it since its not a “for sure”. also my understanding is that either set up could be supercharged(or turbo’d) as long as valve timing and a few other things are addressed. Another thing cylinder heads, I like the idea of AFR’s and victor jr.(are cheap) and trick flow twisted wedge heads WONT work. the piston design wouldn’t work with the combustion chamber design of the twisted wedge unless custom pistons are made. Ill call or email the manufactures of both heads and see what kind of room I have for milling.

But I guess that’s all I have for you for now. Let me know what you think. Thanks for the posts. Hit me back.

Joel5.0

Cool .... hope you ace those. BTW.... what is wrong with a little debate? Aren't discussions debates by nature?

The R:S, the oil rings pack location, and the extra load/wear..... ... the list of the never ending misconceptions.

If R:S was such an issue, why are there OEM engines that can go north of 350k abusive miles even though the R:S is "worse" than the 347 configurations? Examples?.... Ford 4.9L engine (rod: 6.210" and stroke: 3.980") with a 1.560 R:S? ... or the Toyota 1.8L 3T-C engine = 1.577 R:S?

Oil rings pack intersection...... that is an assembler issue besides, you can opt for the 5.315" rod length 347 configuration. Going back to the R:S "issue"...... did you know that the new OEM Coyote 5.0L has a R:S lower than a 331 stroker? ... and shorter pistons skirts BTW.

4.03" bore/.039" thick HG + "0" deck + 14.2cc pistons (inline valves chamber) + 52cc chamber = 10.14:1 SCR. A combustion chamber milled down to 52cc and you should be able achieve it. Increase the stroke to 3.4"..... and a 54cc chamber will net 10.3:1 SCR.

Custom pistons for the TW's?...... all you need is Probe's #14846



Which will make the SCR number 10.3:1 with a 56cc chamber due to its 13.9cc dish.

simpkins_44

Thanks for the post back Joel5.0 and once again sorry for the late reply.

Yes some debate can be a good thing however debates that rest unresolved and off topic are not so good.

I have heard of both sides of the argument on rod to stroke ratios and each opinion holds truth. However I have read into the 4.6L and the new coyote 5.0L both have cylinder differing alloy sleeves then that of used in a 302 block. Also many new blocks use some sort of coatings on both the piston and in some cases on the cylinder walls to limit friction. There is also another variable that is left uncovered in many of these debates on rod to stroke ratios. The friction of piston and cylinder has far many more variables then just rod and stroke same with energy transfer to the crank. I do feel that rod to stroke ratio is a inaccurate equation to relate to friction and dependency of an engine. There is far more to think about then of rod length and stroke length relations when thinking of friction and reliability. Also a more intense(smaller) rod to stroke ratio will provide a less efficient amount of energy transferred to the crank. this doesn’t mean its not as powerful it just means its less efficient at transferring energy from the combustion gasses to the crank(mainly because of the friction but other variables do play out in this also).

With a longer rod it is understood that dwell time at TDS and BDC is extended and power transfer to the crank is increased depending on this relation but not solidly as a quotient or a ratio. this extended dwell time in relation to the rod and stroke ratio is understandable, however it doesn’t seem right to say the an engines efficiency in transferring power to the crank is entirely dependent on the rod to stroke ratio. It seems that this power transfer is more easily seen as a exponential equation rather then a quotient. This would explain how newer import motors can survive with lower then 1.5:1 rod to stroke ratios. The affects also seem relative to the weight and design of the piston. A piston with a shorter skirt will have more “slap” and puts more pressure on the piston rings. some of friction related problems in engines such as you listed are “solved” by heavier balancing weights(acting as dampers for vibrations and slap), low friction coated surfaces(on pistons and in some cases cylinders), lighter weight pistons(because of the need to have less weight on the side wall) with shorter skirts(for less friction area) that fit “tighter” in the cylinder(reducing slap and putting the majority of the friction on the rings) and also smaller bores helps in import engines. These can help reduce the friction but these are not practiced on many 302 based motors and can be expensive to do.

So yes I do agree with you however another thing to keep in mind when looking at the coyote engine is that its oil ring was not interfered by the piston pin. And yes the coyote does have a worse rod to stroke ratio (1.62547952:1) then that of a 331 stroker(1.661538462:1) but it has a better ratio then the 347 (1.588235294:1). also the coyotes pistons walls have been coated in some sort of friction reduction materials(as seen in the photo at http://www.mustang50magazine.com/tec.../photo_26.html on the skirts and around the compression ring groove) These pistons also have a “tighter” fit in the cylinder bore.

I like the idea of a 347 stroker but it does seem to have more stresses then that of the 331. There is still a lot of power to be made out of a 331 before I would absolutely need the extra 16cubic inches.

To get a 52cc chamber head you would need to mill down the head on the plus side of 0.033”. that sounds like quite a bit I might be wrong though. With the heads milled down 0.025” and the block taken down 0.011” this would opt for 10.29:1. I know that heads and blocks can be milled and squared up but to what accuracy can they do this??? If I could do the block down to 8.195” and do the heads down the 0.025” it would be better compression and have a better quench distance. Think this would be possible and worth doing???

I like this but what are the benefits and restrictions of trick flow heads??? what stroke its this compression ratio at 3.25” or 3.4”???

Sorry for the excessive lengths on the posts but I had lots of ground to cover. Hopefully I can get back to reply’s quicker then the last two times. But thanks for the posts. Hope at least a couple more come my way. Thanks.

Joel5.0

Coatings on the cylinder walls? Anyway..... the data, experience and facts presented previously are 1980'ish tech.

Nope......
long rod = higher dwell time @TDC shorter dwell @BDC
short rod = shorter dwell time @TDC higher dwell @BDC
long rod = slower accelerating piston from TDC
short rod = faster accelerating piston from TDC

And again.... the facts gathered from the field using regular '80's tech components and accumulated through decades, dispel most of the theorized concepts or concerns regarding reliability and performance. Or does that mean that any of the 351w based strokers will not last? BTW... you may want to read this "Rod Lengths/Ratios: Much ado about almost nothing" article focused on performance..... reliability and endurance has been demonstrated for years.

Yup..... for a stock engine with a 7500 RPM red-line stock, the OEM also takes all the precautions it deems correct, as the underside piston oil "cooling squirters". Same device the HEMI's also use stock although they don't have a small R:S (1.745 and 1.712) + the same Molykote coating on the piston skirts.

IOW.... the reliability increasing techniques/devices, coatings use are not exclusive of a single characteristic like R:S...... as it is attempted to be inferred selectively otherwise, 1.7xx+ R:S engine setups wouldn't have a need for such technologies to be used and increase their manufacturing costs, or would they?

BTW.... do you know what is the R:S of the 5.4L (331 ci) engine used in trucks, cars by Ford?..... 1.598. Do they have engine reliability problems attributed to the R:S?...... nope, I've worked in cases with 170k+ miles on their odometer.

YCYDYP........ .... yet the reasoning behind it is not 100% correct.

Milling heads down to increase compression is as old as the IC engine itself. The 3T-C engine sample I used regarding endurance (mine, moons ago) had its stock head milled down .030" causing the use of a little spacer to compensate for the timing chain dampener increased slack + aftermarket heads usually sin on the thicker deck side to exactly provide for those type of plans.

Stroke used was 3.25". Benefits of Trickflow heads? ... you do have some homework to do. I will only say that they are usually weight penalized in some racing classes and another positive is less intake valve shrouding concerns.

Summarizing though..... R:S ratio has been used as the "excuse card" for everything covering oil consumption, engine reliability, lack of performance, etc....... all cases with very common real causes that are avoided like the plague. These go from operator/assembler error, utilization of the wrong components, bad machining of engine components, etc. Or haven't you heard about the LSx engine piston slap problems even though R:S is in the 1.68 range? Or the GM LTx with an OEM R:S of 1.57?

Can a 331 perform and last?... yup .... so can a 347 or 363 or 306 or 408...... but focusing on a single parameter (aka R:S) to choose any over the others is not, in my humble experience, the correct thing to do.