rx7speed

what all would I need to do to get a setup like that

also what would be a good build up for it and how much would I prolly make?

ATOMonkey

If you want to go with off the shelf parts, then a 327 is a 3.25" crank. You'll probably want to use 6" rod which by the numbers using a stock 5.565 rod 400 piston will give you 65 thou piston deck clearance. Or you can use 400 pistons which are 4.125 made for a 5.7 rod and use off the shelf 6.2" rods. That's by my number, but I don't have good experience with destroking 400s.

If you bore the 400 block 30 over that's a 4.155 piston. These are 406 pistons.

RB83L69

Actually, neither of those combos comes anywhere close to working.... the first one will put the piston sticking about .185" out of the top of the block; and the 2nd one will leave them exactly .500", ½", out the top of the block.

As far as anything near stock goes, if you used a large journal 327 crank and stock 400 deck height pistons, with 5.8" rods, you come pretty close to havin gsomething that fits: you'd only gain .015" of deck clearance compared to a stock block. Of course you'd need bearing spacers to put the smaller main journal crank in a 400 block.

Probably the smartest thing to do would be to run the NASCAR stroke (3.31") and the 5.8 rods and stock pistons; if you did that, then with a stock deck height block, you'd have about .005" of "negative" deck clearance, i.e. pistons out of the block by .005". Then you could use a Fel-Pro 1044 or other thick head gasket.

I happen to have a set of Venolia pistons laying around for 5.7 rods and 327 stroke in a 400 block.... and a steel LJ 327 crank. Something my late little bro acquired years ago but never put together. Problem is, the pistons would give about 12½:1 CR in a 64cc head.

These are all variants on a 350 Chevrolet could/should have built, but for some reason never did, except for CID limited racing such as Winston Cup.

ATOMonkey

Really?

What did I mess up?

Edit: 5.7 + 3.75 = 9.45
6.2 + 3.25 = 9.45

??????????

Please tell what's wrong with my assumptions.

I figured it out. I was using the whole stroke length.

RB83L69

You messed up all over the place. You have to use half the stroke, and account for the "compression height" (distance from center of piston pin to top of piston).... and of course the actual height of a block.

Stock deck height (center of crank to head surface) is 9.025". So for example, ½ the stoke of a 350 (3.48") is 1.74"; plus 5.7" for the rod, plus the "compression height", plus the deck clearance (.025" nominal), should equal 9.025". Which it does if the "compression height" is 1.56", which of course just happens to be the compression height of a stock 350 piston. Likewise, for a stock 400 with a stroke of 3.75": ½ of that is 1.875"; plus 5.565"; plus 1.56"; +.025", adds up to the magic number of 9.025".

So: ½ the stroke of a 327 (3.25") is 1.625"; plus 5.8" for the rods that almost fit; plus 1.56" compression height; gives 8.985", which is .015" less than the 9" length of the stock 350 or 400 rotating assembly.

etc. .... take it from there.

ATOMonkey

Thanks. I had some brain failure there.

RB83L69

..it happens

SSC

CHP or hot rod I forget did a build like this a few years ago, sothing about how chevy sould have made the 350. They used fNord 300 I6 4.9l rods and had pistons like R8 was talking about. Thier build made a good 350hp/400+tq but the cost wasent worth the effort IMO. Its kinda like stoking a 305 all the effort for what a good 350 build will do.

mw66nova

iTrader: (13)

big piston x small stroke = big horsepower and no torque.

rx7speed

that something that is fine by me


low end torque doesn't mean anything to me

high rpm torque is what I want

mw66nova

iTrader: (13)

whatever dude, i would much rather be able to shred tires off idle than be able to spin my motor till 10000 rpm and my torque curve not come in till 4500, but to each his own.

rx7speed

I can still spin the tires


what do you think dumping the clutch is for


but not for the type of racing I like to do mid to high rpm power is what is needed...

also I don't really see why everyone gets so hung up on low end power

mw66nova

iTrader: (13)

low end power is good for launches with 3500stall converters for us automatic freaks. if i had a 5 or a 6 speed i would build a high rev motor too. but i enjoy the consistency of my automatic. also, a motor that isn't spun that high (say 6500) will stay together much longer without lots of maintenance with the valve train.

rx7speed

maybe so

but on a daily driver car... well least a piston motor... I wouldn't be spinning up all the time.


now my rotary, I still hit 7600 rpms all the time with 190k miles on the ticker and she is still going without touching the motor

BadSS

Cheapest is the 5.7" TRW 406 pistons (1.42" comp height) using the 5.94" PM rods from GM. You'll have .040 deck clearance with a 9.025 deck height,, so you'll need to "deck" the block at least .020" (assuming it's square,, which most aren't). No biggy. Mock assemble and check to see how much needs to come off each corner.

The most common is the 400 bore 3.48 pistons for 6" rods (1.26" compression height). You can use 6.125" rods with the 3.25 stroke and have a deck clearance of .015".

I'm sure they're other,,, these and the 5.565 rod 400 piston using 5.85" rods (1.56" comp height) and running a negative deck clearance of .010" (with a 9.025" deck height) are the only 4.155 bore / 3.25 stroke combos I've had anything to do with.

Considering 95+% of the folks out there can't properly dial in the car and engine combination for a standard bore and stroke 350, I consider the trick applications to be limited use combinations for the guys that really are going as fast as they can with a standard combination. Track only,,, and then only when limited to a 360 cid or less. They do seem to work a little better at the longer circle tracks and you see less a performance difference between the trick and standard combination at the local dirt track - where only a handfull of guy make best use of what they have anyway.

The cool factor is there,,, but I can't get past wasting a perfectly good 400 block,, unless like I said it was a limited cid or some kind of lb per cid class,,,, where the big bore short stroke higher reving engines have a slight HP per cid advantage.

rx7speed

I doubt I would build one. no money right now. also my turbo project for my rx7 is taking all my money right.... hehe money I don't have to spend .. wait wrong face


but if I do build a street car I'm still not sure as far as which setup I would go for.
I know high rpm cars vs low rpm car (powerband) each has an adv and disadvantage. anymore I have taken a liking to the high wind motors though, and would prolly want to build one. but it comes down to finding a car and getting the money for me right now.. niether I have for this swap.

still interested in how it is done and how much power can be made by doing so though.


thanx guys