400 Stroker pistons

[m79ded]

Hi

I am planning on putting together a 400 stroker motor. I was looking at piston choices and realized that 1.32 comp height pistons are appropriate for what I am planning to do. I was told to be careful about piston wobble in the bore because of the short comp height and the smaller piston. Is that true? I am planning a street motor and aiming for about 500HP so reliability and drivability is a must.If I have a choice of short or long rod which would be recomended? for a more reliable engine. I will be doinf either a 451 or 470 ci

Thanks

 

[Meep-Meep]

I'm building a 451 for a member here and we went with SRP's set at zero deck with a cut down 440 crank and 440 LY rods. You asked about rod length so be prepared for this thread to go to 5 pages! LOL. Some will say short rod and some will say long. I say Chrysler had it figured out pretty well and the result was time tested and it works so I went with the standard ratio of 1.80:1. Thinking back I probably could have gone with the lower ratio 400 rod without any ill effects, or for that matter any drastic improvements. I'd like to know if someone can tell the difference between the 1.696:1 vs. 1.802:1 rod ratio engine by driving it. What does make sense in this build, and something that might actually be measurable, is the drastic weight reduction to the reciprocating assembly.

Now to cram 470 cubes into that short package would require a short rod and result in a very low R/S ratio. Too low of a ratio might play hell on the thrust side of the piston and scrub off power due to friction. It is also said that low R/S engines don't rev well and tend to "vibrate" at high RPM. Mechanically speaking I think there is a point of ideal R/S ratio to balance torque and component wear. Again, the engineers knew something back in 1958 when these things were designed. The R/S ratio changes the torque of the motor and can be very beneficial to be on the low side if you want a tractor. A lot of newer engines run low R/S ratios probably for the torque reason but they are not of a 1958 design either. Note: The engine in the Honda S2000 has a R/S ratio of 1.82:1. It also has a red line of 9000 RPM!

 

[68 Sport Satellite]

I was also told that the 470ci motor will generate more heat than the 451ci, so me thinks the 451 will last longer, but I may be wrong....

 

[HT413]

Sorry I dont have an answer for you, but this might be some food for thought? I've been considering doing the 400/470 stroker kit as well and noticed there is a difference between 440 source's and muscle motors kits. 440 source has the lower rod ratio (shorter rod) and muscle motors kit has a longer rod but is a couple hundred $$ more expensive. So at least you have options.

440 source/Muscle motors
CID 470/470
Stroke 3.915/3.915
Rod Length 6.535 chevy/6.700 chevy
Rod Ratio 1.669/1.711
Piston Compression Height 1.480/1.320

Honestly, we're talking just 2.5% difference in Rod Ratio yet 12.1% taller compression height. So it seems to me with the 440 source kit, you get a more stable piston but maybe a tad more side loading from the shorter rod and a tad heavier rotating assembly with the taller piston? But in the opinions I've received from a few guys with far more experience than me (not hard to do since i've never built a motor), the 1.32" piston is just fine, is plenty stable plus you get (in their opinions) the better (longer rod ratio) plus the slightly lighter rotating assembly.

Told ya I didnt have an answer for you.

 

[Supershafts]

You want the shorter rod, trust me, i can tell you as i have had them all or still have them, short rod big ports, large cam = more power longer torque curve.

I have a 489" version of the 470, it runs cool, i have a 500", i had a couple 451's, one was a 440 in small package and one was just the crank and the shorter rod version, i have 408's and 418's always stay with the short rod and keep everything else big, big ports on the intake and heads and cam stay over 260@50, and i'd go even more and use good heads.
.

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I have RR at 1.5, there is no horrendus issue, BBC are 1.5 ratio also.... Stay away from that lazy moving air RR that the bb has at 1.8, that's a rpm Ratio, you want low end than you want the shorter rod, it's amazing that the thought is Chrysler had it figured out..... Really, have you paid attention to the mistakes mopar has made over the years...

 

[Meep-Meep]

No one engine is perfect but it's amazing that those lazy 1.8:1 RR MoPars even ran at all. That even lazier RR engine with the funny heads with ports and valves too big was a disaster as well. And it was a miracle that my old 383 with a 1.89:1 RR propelled a 3700 lb B body into the 12's with mild modifications. But on a serious note, let's take a look at the options in making power and how one can best reach their goal while keeping in a reasonable budget.

If you wanted to get some real bang for the buck, where would be your main focus?

1) Camshaft, heads and exhaust on the as designed bottom end?
2) Rod ratio change from 1.8:1 to 1.65:1?

My point is you will get far greater results when addressing the valve events and exhaust on whatever platform was given to you by the manufacturer. While your points on a low RR are valid, changing the rod ratio is expensive for the gains realized - especially for the average street car guy who wants to burn rubber and knock down some decent 1/4 mile times. I make no judgements about your knowledge and ability but I think you just need to come out of the closet and admit you want to be a big block 1.6:1 RR or small block 1.5:1 RR Chevy guy.

 

[m79ded]

Noticed in both cases especially 1.32 that there is a good assortment of pistons available for them.The reason I was concerned about wobble in the bore is because a guy I know did a 400 with 4.15 crank and the eagle/Mahle kit came with very short pistons in fact even shorter 1.12 that oil rings supports are needed. The thing sounds like a bad diesel when near idle and after he called mahle the answer was " It's the nature of the beast can't do anything about it With short pistons like that it's to be expected."

 

[Meep-Meep]

Noticed in both cases especially 1.32 that there is a good assortment of pistons available for them.The reason I was concerned about wobble in the bore is because a guy I know did a 400 with 4.15 crank and the eagle/Mahle kit came with very short pistons in fact even shorter 1.12 that oil rings supports are needed. The thing sounds like a bad diesel when near idle and after he called mahle the answer was " It's the nature of the beast can't do anything about it With short pistons like that it's to be expected."

There is only so much you can cram into a small package. It's all about spreading the compromise over the largest area possible if you want the best of all worlds. But if you are willing to give up something then decide what is most important to keep and throw out the junk. For me, if I wanted something that sounded like a diesel I'd buy one!

 

[Supershafts]

No one engine is perfect but it's amazing that those lazy 1.8:1 RR MoPars even ran at all. That even lazier RR engine with the funny heads with ports and valves too big was a disaster as well. And it was a miracle that my old 383 with a 1.89:1 RR propelled a 3700 lb B body into the 12's with mild modifications. But on a serious note, let's take a look at the options in making power and how one can best reach their goal while keeping in a reasonable budget.

If you wanted to get some real bang for the buck, where would be your main focus?

1) Camshaft, heads and exhaust on the as designed bottom end?
2) Rod ratio change from 1.8:1 to 1.65:1?

My point is you will get far greater results when addressing the valve events and exhaust on whatever platform was given to you by the manufacturer. While your points on a low RR are valid, changing the rod ratio is expensive for the gains realized - especially for the average street car guy who wants to burn rubber and knock down some decent 1/4 mile times. I make no judgements about your knowledge and ability but I think you just need to come out of the closet and admit you want to be a big block 1.6:1 RR or small block 1.5:1 RR Chevy guy.

Whats the BIG expense using the short rod when the pistons nowaday are right on the shelf, the hemi was lazy to and why it needed to rpm, you really didn't just say the hemi was a perfect combo, it needed to rpm all because of that rr and the heads being to much for the rr.. Forget it, what is the big expense, i have more short RR motors than you have motors funny part is there was no BIG expense in using the better more power short RR.

Noticed in both cases especially 1.32 that there is a good assortment of pistons available for them.The reason I was concerned about wobble in the bore is because a guy I know did a 400 with 4.15 crank and the eagle/Mahle kit came with very short pistons in fact even shorter 1.12 that oil rings supports are needed. The thing sounds like a bad diesel when near idle and after he called mahle the answer was " It's the nature of the beast can't do anything about it With short pistons like that it's to be expected."

That's because someone made the assembly to loose, using a longer rod also puts the wrist pin in the oil, i have done hundreds of motors with the pin in the oil none sound like diesels, my own motors don't sound like diesels.

 

[Red63440]

This is from a quote from IQ52

"400 block deck to 9.960", Icon IC837 piston, which would require 6.760" rod, ported 84cc Edelbrock RPM heads w/ springs, retainers and locks for the Comp Solid roller XR280R, Edelbrock RPM intake and 850 Mighty Dominator or Q950 Quick Fuel carburetor." This combination will run on pump gas and should yield app. 580 HP.

 

[Meep-Meep]

But those lazy RR Chryslers still made the numbers necessary to win races. If I want to make power, changing the RR from 1.8 to 1.7 is not where I'll be starting.

 

[HT413]

Sorry to kind of highjack your thread. Interesting how strongly some people feel on both sides of the RR argument. A quick look at the supposedly top 50 fastest muscle cars (realizing many arent muscle cars and some are missing - like the max wedges) shows that the top performing engines of the era are (obviously the order they appear on the list is affected by the cars they appeared in):

Ford 427 (RR 1.7167) as far as I can tell, ALL Ford 427's had this RR.
Chevy L72 427 (1.629)
440 (1.8048)
426 HEMI (1.8293)
454 LS6 (1.5338)
427 ZL1 (1.629)
427 L88 (1.629)
Buick 455 Stage 1 (1.6923)
Pontiac 455 SD (1.5736)
BOSS 429 (1.8398)
429 SCJ (1.83948)
Olds 455 W30 (1.5847)

Some of those engines had their issues (BOSS 429), but I dont know if any could be considered lazy. Now, again, I'm no engine builder at all, but those are all the fastest motors of the era yet their rod ratios are all over the map. Furthermore, 2 of the meanest motors of all, the 454 LS6 and the 426 HEMI are each on the opposite end of the spectrum (1.5338 and 1.8293). Lets also not forget the Max wedge motors with RR 1.8048. I've read how rod ratio affects cylinder pressure profiles, intake charge velocity, piston acceleration profiles, etc. So from the eye of a novice like myself just looking at history, am I wrong to say as long as your combination takes advantage of the particular rod ratio, you're good? And for novices such as myself, confusing issues like RR make it even more important to seek expert advice or at least copy known successful combinations rather than mixing and matching on our own.

Sources:
http://www.musclecarclub.com/musclecars/general/musclecars-50fast.shtml
http://users.erols.com/srweiss/tablersn.htm

 

[MikeStahl]

think those long rod motors have a lot to do with nascar and the power curve for those big tracks as in the lazy term it work well in that app...with the exception of the 440 cube was to big, 429 boss was headed to nascar until the outlaw of the hemi headed motors...if my memory is working

Mike

 

[Meep-Meep]

Sorry to kind of highjack your thread. Interesting how strongly some people feel on both sides of the RR argument. A quick look at the supposedly top 50 fastest muscle cars (realizing many arent muscle cars and some are missing - like the max wedges) shows that the top performing engines of the era are (obviously the order they appear on the list is affected by the cars they appeared in):

Ford 427 (RR 1.7167) as far as I can tell, ALL Ford 427's had this RR.
Chevy L72 427 (1.629)
440 (1.8048)
426 HEMI (1.8293)
454 LS6 (1.5338)
427 ZL1 (1.629)
427 L88 (1.629)
Buick 455 Stage 1 (1.6923)
Pontiac 455 SD (1.5736)
BOSS 429 (1.8398)
429 SCJ (1.83948)
Olds 455 W30 (1.5847)

Some of those engines had their issues (BOSS 429), but I dont know if any could be considered lazy. Now, again, I'm no engine builder at all, but those are all the fastest motors of the era yet their rod ratios are all over the map. Furthermore, 2 of the meanest motors of all, the 454 LS6 and the 426 HEMI are each on the opposite end of the spectrum (1.5338 and 1.8293). Lets also not forget the Max wedge motors with RR 1.8048. I've read how rod ratio affects cylinder pressure profiles, intake charge velocity, piston acceleration profiles, etc. So from the eye of a novice like myself just looking at history, am I wrong to say as long as your combination takes advantage of the particular rod ratio, you're good? And for novices such as myself, confusing issues like RR make it even more important to seek expert advice or at least copy known successful combinations rather than mixing and matching on our own.

Sources:
http://www.musclecarclub.com/musclecars/general/musclecars-50fast.shtml
http://users.erols.com/srweiss/tablersn.htm

I will agree. I'm no pro engine builder either but I do tend to pay attention to details and also the way things are manufactured.

The basic platform of engines in your list were all developed in the late 50's to early 60's (except the MK IV big block) and all had an original RR of around 1.75:1. This tells me that the engineers liked that RR for possibly the reason that it provides the best compromise of piston acceleration rates, side loading and torque curve. Now fast forward a few years and that same engine platform grew in cubic inches. The most economical way to increase displacement is with a longer stroke. So the 265 SBC eventually became a 400 in the same block dimension! The 389 Pontiac and 330 Olds became 455's, the 352 Ford became the 428, the Cad 390 became the 500. You get the point. Much of the displacement increase was done in the same dimension block so something had to give. Bottom line, the ideal rod ratio took the back seat to displacement, which did more for the bottom line. Cubic inches were winning races and people were beating a path to the dealership to drive home in that new 440 GTX or 455 SD Yak. I can almost hear someone saying "Who gives a rats *** about rod ratio as long as the engine would make it past the warranty period." If someone thought it was so important to keep the ideal 1.7-1.8:1 RR they would have done it. As it is now a lot of small 4 cyl engines are in the 1.60 range. Again, is this because it's so important for the engine or did the manufacturer have to use up old parts? I recall an ad from Ford about the then new 302. One of the sales points was boasting about the shorter, lighter and stronger con rod. 289 and 302 use the same piston but different crank so the rod becomes shorter. Ford must have figured that it was cheaper to make new rods than new pistons. The longer stroke crank was a given because bigger was better and bigger meant sales.

 

[Garys1969RR]

My 451 long rod motor runs great! Good enough to propel a 69 RR thru the 1/4 mile in 12.9 sec @ 108. This is at 5600 feet. The motor has 14cc Ross pistons with a 1.320 C/H. 550 grams. 509 cam, auto, 11 " torque converter, Holley 780, 3.91 gears. Oil ring is about 1/8 " or less above the wrist pin. Any longer stroke would need a shorter rod to keep it below the wrist pin. Supershafts has a lot of experience with these builds, and claims in a side by side comparison of 451s with the 2 rod lengths, the short rod motor runs better.

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And I realize my ET should be lower with 108 MPH thru the lights, still sorting things out.

 

[Supershafts]

I will agree. I'm no pro engine builder either but I do tend to pay attention to details and also the way things are manufactured.

.

Pay attention to details then and RR is a VERY IMPORTANT DETAIL you aren't paying attention to.
The way things are manufactured ARE NOT for performance, and comparing motors that were primarily for running Nascar is not the same, then sure the 440 was good as was the Hemi as was the RR for nascar where it lived all day at 7000rpm, and Anyone who owns a REAL hemi please chime in and DO TELL when does it start really coming on ????? RR plays the role in that, as it also effects the intake and heads volumes and ports.

Had the Hemi had the RR of a 1.5/1.6 IT WOULD BE a world of difference how it would have acted on the street and had better performance with those ports rather than having to be rpm'ed more than most people had the balls to turn them too...

FACTS are 1.7 and higher are lazy air movers and need RPM, they work better at high rpms. Lower RR they make better power sooner, hold a much longer torque curve, and utilize bigger ports better...............THAT's EXACTLY what the Hemi needs.

Im not telling you this because i have nothing better to do, im telling you this because i have quite a few motors that make TONS more power than the lazy RR motors built almost the same, when you build a 440 and cam it and comp it the same when you wear it out and move all that to a 400 and lose the long rod and keep EVERYTHING else and go faster, it sure as hell is not because of the 45 lb difference of weight.. It was because when moving the 440 into the 400 we left the one part out of the 440 and that was it's long rod... otherwise all i would have done was build a lighter 440.
Once you get into the 1.6 and 1.5's things get even better for motors where you want them to make KILLER power without needing to see big rpm, so why would you want a 1.8 RR on a street motor ??? YOU DO NOT, old school is old school, you gotta move away from it

Pay attention to this ONE detail.... more than 1.7 RR and you need RPM to move the air and make power, BECAUSE that RR is the issue in where everything works because it plays a huge role in piston speed....
Small RR and everything makes power sooner and holds it longer, piston speed is faster, pulling more air sooner, making more power if you can move the air that it is able to.

Even now Mopar still dropped the ball and hurt the fixed hemi with it's same stupidity in whoever chose that 1.77 ratio, you know what the Chevy's RR is, it sure as hell isn't 1.77

 

[MikeStahl]

thx supershafts......X2...better explanation...than my short version

 

[m79ded]

My 451 long rod motor runs great! Good enough to propel a 69 RR thru the 1/4 mile in 12.9 sec @ 108. This is at 5600 feet. The motor has 14cc Ross pistons with a 1.320 C/H. 550 grams. 509 cam, auto, 11 " torque converter, Holley 780, 3.91 gears. Oil ring is about 1/8 " or less above the wrist pin. Any longer stroke would need a shorter rod to keep it below the wrist pin. Supershafts has a lot of experience with these builds, and claims in a side by side comparison of 451s with the 2 rod lengths, the short rod motor runs better.



- - - Updated - - -

And I realize my ET should be lower with 108 MPH thru the lights, still sorting things out.

Very nice setup

- - - Updated - - -

Pay attention to details then and RR is a VERY IMPORTANT DETAIL you aren't paying attention to.
The way things are manufactured ARE NOT for performance, and comparing motors that were primarily for running Nascar is not the same, then sure the 440 was good as was the Hemi as was the RR for nascar where it lived all day at 7000rpm, and Anyone who owns a REAL hemi please chime in and DO TELL when does it start really coming on ????? RR plays the role in that, as it also effects the intake and heads volumes and ports.

Had the Hemi had the RR of a 1.5/1.6 IT WOULD BE a world of difference how it would have acted on the street and had better performance with those ports rather than having to be rpm'ed more than most people had the balls to turn them too...

FACTS are 1.7 and higher are lazy air movers and need RPM, they work better at high rpms. Lower RR they make better power sooner, hold a much longer torque curve, and utilize bigger ports better...............THAT's EXACTLY what the Hemi needs.

Im not telling you this because i have nothing better to do, im telling you this because i have quite a few motors that make TONS more power than the lazy RR motors built almost the same, when you build a 440 and cam it and comp it the same when you wear it out and move all that to a 400 and lose the long rod and keep EVERYTHING else and go faster, it sure as hell is not because of the 45 lb difference of weight.. It was because when moving the 440 into the 400 we left the one part out of the 440 and that was it's long rod... otherwise all i would have done was build a lighter 440.
Once you get into the 1.6 and 1.5's things get even better for motors where you want them to make KILLER power without needing to see big rpm, so why would you want a 1.8 RR on a street motor ??? YOU DO NOT, old school is old school, you gotta move away from it

Pay attention to this ONE detail.... more than 1.7 RR and you need RPM to move the air and make power, BECAUSE that RR is the issue in where everything works because it plays a huge role in piston speed....
Small RR and everything makes power sooner and holds it longer, piston speed is faster, pulling more air sooner, making more power if you can move the air that it is able to.

Even now Mopar still dropped the ball and hurt the fixed hemi with it's same stupidity in whoever chose that 1.77 ratio, you know what the Chevy's RR is, it sure as hell isn't 1.77

Thanks..........WOW this is the best explanation that I've heard you explained it so well and it all makes sense. I was stuck on the sideloads of small rods and was always thinking heat,friction,wear...etc and not really looking at the other side of the coin. So I think a 3.915 stroke with 6.535 rod should make a great street engine?

 

[Garys1969RR]

Well next build, I will try the 400 length rod in the 451, rather than the 440 length. Next question would be: What is the ideal RR in a big block Mopar? 1.5 or 1.6? A 3.75" stroke with a 400 rod length comes to 1.7 I believe. What is the RR in a 3.9" stroke motor with a 400 length rod?

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440 rod length is 6.76" 400/383 rod length is 6.358.

 

[HT413]

Mopar 400 rod length is 6.358", so w a 3.75" stroke, RR is 1.624. With a 3.915 stroke, RR is 1.599.