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With a deck height around 9.59 ...

you will need a compression height of 1.33 on your pistons.

Do the Math...

9.59- 6.20-(4.125/2)=1.325

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The piston will not clear the counterweights at BDC. This is part of the reason for the 6.200" rod.

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I'd like to see you run a 6.2/6.25/6.3-ish" SBC rod, I wouldn't build-in a sub 1.5:1 rod ratio so long as there was an economical piston choice to make it work.

Also when you add those cubes you may need to go to a custom dish in order to get the cr you want.

I'd research AndyF's 427 motor, maybe you can run the same piston/rod as he did...it's in the small block tech archives.

I have a small block ford motor that is 4.04" x 4.17" stroke with a 6.123" mopar length rod....it's fine with the shorter RR....but the 351W deck is 9.5 vs 9.6 AND my motor is built to peak right at 5500 so I never take it over 6000-6200....by design....I wanted a 427FE type torque/power curve as similar to an original 65 cobra as possible.

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thanks for the info man! How do i calculate rod ratio? this is all new to me so im kinda figuring things out by trying to play with numbers

Also, the only reason I went to a 6" rod was because I couldnt find a piston and 6.2 or bigger rod combo that would fit in the stock deck...or maybe i wasnt calculating properly...guess i should go back at it

If anybody has done a combo like this and would care to share what they used, please share

im gonna check out andy's thread in the meantime

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thanks for the info man! How do i calculate rod ratio? this is all new to me so im kinda figuring things out by trying to play with numbers

Also, the only reason I went to a 6" rod was because I couldnt find a piston and 6.2 or bigger rod combo that would fit in the stock deck...or maybe i wasnt calculating properly...guess i should go back at it

If anybody has done a combo like this and would care to share what they used, please share

im gonna check out andy's thread in the meantime

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I had Diamond change the pin height on my pistons
and it was only $35 to change the height for the set
when I had them made... that was just over a month
ago... mine is a 416ci but with a deck of 9.53
(I believe it is... numbers are out in the shop)

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sorry to sound totally newbie, but is changing the pin height the same as changing the compression height of a piston? just want to make sure its not another term or something

If its that cheap, that should definitely open up some possibilities for pistons instead of the almost 800 dollar JE ones

What combination are you using to get 416? Im assuming thats based off the 340 main? what was the pin height before and after the custom order?

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thanks for the info man! How do i calculate rod ratio? this is all new to me so im kinda figuring things out by trying to play with numbers

Also, the only reason I went to a 6" rod was because I couldnt find a piston and 6.2 or bigger rod combo that would fit in the stock deck...or maybe i wasnt calculating properly...guess i should go back at it

If anybody has done a combo like this and would care to share what they used, please share

im gonna check out andy's thread in the meantime

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I had Diamond change the pin height on my pistons
and it was only $35 to change the height for the set
when I had them made... that was just over a month
ago... mine is a 416ci but with a deck of 9.53
(I believe it is... numbers are out in the shop)

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sorry to sound totally newbie, but is changing the pin height the same as changing the compression height of a piston? just want to make sure its not another term or something

If its that cheap, that should definitely open up some possibilities for pistons instead of the almost 800 dollar JE ones

What combination are you using to get 416? Im assuming thats based off the 340 main? what was the pin height before and after the custom order?

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Yes its the compression height... its cheap so dont
think your stuck with some piston off the shelf...
I also had then open up the valve diameter on the
intake to clear my 2.08 intake valves
EDIT
Mine is a 4.070 bore with a 4" crank with chevy
6.125 rods.... based on a 340 block

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you would be way ahead of the game to get with a builder and have them spec out your motor. save you a lot of trouble in the long run

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you would be way ahead of the game to get with a builder and have them spec out your motor. save you a lot of trouble in the long run

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your probably right about saving me the trouble, but ive always been the type to try and figure things out on my own...helps me learn something and save some money in the long run (i would hope)...Im only 21, so ive got a brain ready to soak in info, and a small wallet lol

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you would be way ahead of the game to get with a builder and have them spec out your motor. save you a lot of trouble in the long run

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your probably right about saving me the trouble, but ive always been the type to try and figure things out on my own...helps me learn something and save some money in the long run (i would hope)...Im only 21, so ive got a brain ready to soak in info, and a small wallet lol

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all the more reason to get somebody who knows what they are doing. unfortunatly learning usally cost you more money.

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the cubes will help more if you have the heads to match. if not it probably wont make much difference. as far as the blocks go it depends on what your goal is. factory sb are pretty strong imo. there are lots of good builders on here. Dan is doing the machine work on my stroker now.

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the list is endless, beat machine, Dwayne Porter(fast68plynouth),BG racing I could go n for a while good luck

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the cubes will help more if you have the heads to match. if not it probably wont make much difference. as far as the blocks go it depends on what your goal is. factory sb are pretty strong imo. there are lots of good builders on here. Dan is doing the machine work on my stroker now.

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who are some other builders on here that I can get in touch with for this? I know Brian at IMM is one, Competition Wedge another, but who else is there?

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I like the 4" 6.123 rod combo but I don't think I'd hesitate to run the 4.125 with the 6.2 rod and the SBC journals with a set of Brian's RHS heads. spread the lobe centers out a bit (at least 110) and try to shift some of the massive torque upstairs which will also help your power curve above the peak, the curve will be more linear (less abrupt peaky) as well which should be easier on the block overall with the heads you are planning. I would lean toward a 340 victor with some plenum work, again you don't want or need a ton of help in the upper bottom range once you give it some throttle, a good single plane will actually help make the combo more tractible/predictable off idle and in rainy conditions, especially in a nose heavy 4 speed car. A Hydraulic in the 242I/248E range or a solid in the 250I/256E range should be about right for the best balance for broad flat torque and strong top end power with an 850'ish double pumper. ~18-22 initial with another ~12-14 in the distributor with a relatively slow centrifugal advance will make it a very good steet performer without it blowing off the tires around every corner like a too quick advance will do....unless you're running fat and very sticky meats.

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Well Said!

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you would be way ahead of the game to get with a builder and have them spec out your motor. save you a lot of trouble in the long run

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i agree with Tony, im starting to gather parts for my budget R5 421" and helps to get good advice from guys that has been there and done it.

Bob

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(I've bought parts and services from 2 in this very thread ), a lot of these guys I've known for years...even the ones I 'debate' with from time to time, I think we still respect eachother's opinions and we're all still 'buds'.

A lot of these guys volunteer VAST amounts of knowledge and experience and deliver the hard core content to this site, give 'em a shot

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hey, i resemble that remark.
sometimes a lively debate nets some great information to share and that's usually a good thing.

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Matt,
There are a few reasons to not bother going beyond 4". The return on investment for the expense of custom parts and shortening service life just don't make sense to me. I decided to ask a few questions of guys I consider knowledgable and the biggest seems to be the pistons with indeterminate service life as a close second. Noise will also be a factor using a piston that short in a street car. That can be addressed with offsetting the pin but you'll need to work with the piston manufacturer to get something that addresses the issues as best as could be.
IMO - Build a 4" arm, forged crank setup, with reasonable heads, and worry about "bigger" and "more" when you've already maxxed what the 4" engine can do for you. If bigger wasn't better we'd all have 318s with 360 pie tins. But there comes a time when return on investment ends up making bigger less better.

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mshred,

I respect and appreciate you at a young age asking all of these well-thought out questions.

A very wise engine builder named Joe Sherman once said "$1 in the heads is worth $3 in the shortblock." I've found this to be more true than you know, don't sweat it there's plenty of 408-416's out there that crush big blocks all day long.

My build the best nicest forged 408 you can afford to build and enjoy it! Take what you learn from the experience of building it and look forward to rolling that knowledge in to the next one, pretty much what I've been doing for 30-odd years now

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