I am currently researching to build a 402c.i. stroker from a 1966 Chrysler 318c.i. Poly using a recipe from a person who is a regular on this site and others. My question is---Does anyone have info on what piston I need to use or if you have built this motor before, what custom piston/company handles this application. I will be using a MPP 4" stroker crank on 318/340 mains and stock length(6.123") SCAT I-Beam rods. The block will be bored .090 over to a 4" bore.
I dont know how safe it is to go .090 over on a 318. It would be more easily done and not decrese the longevity of the block as much if you used a 360. Plus you have the options of going up to 426 cubic inches. a .090 overbore just doesnt seem safe to me.
Was 66 still a Poly? I didn't know that. Older pre thin wall blocks were bored .125 with great regularity in the old days. 270 GMC engines went .156 all the time. I had one that I ran with 22 lbs boost at Bonneville and El Mirage that never died.
After doing research,This peticular block was cast thick enough to safely overbore up to .090 over without a problem. that was one of my main concerns, but I have looked into it throughly and am confident that it can be done. Thanks for the advice though "Boynamedsue"
This block and heads came out of a 1966 Chrysler Imperial. I have ran all the casting numbers and head casting numbers. it was cast 1-18-1966 and has not been touched.
360 and a poly 318 are 2 dfferent animals so i doubt that is even an option to run a 360. i would definitely sonic check the block before boring that much and most machine shops should be able to order you the right pistons when they bore and deck it. they might even give you a better price than if you bought them direct. i like the poly motors i have thought of sticking one in my essex.
yeah i wasnt sure if it was a thick casting or not. some of the thinner castings can have heat problems when you take too much out of the cylinder bores. if you have a thick casting you have more metal to dissipate heat and its less likely to break. a guy i helped locate some parts for an LA series tried to go with a 426 stroker crank and .090 over pistons and heat destroyed the block in no time. Whats the motor going to be used for? daily, summer toy, or is it more purpose built?
"This block and heads came out of a 1966 Chrysler Imperial" 1966 Imperial: 440 only. You're not going to be able to order pistons, since AFAIK none of the major mans have any data re valve relief, dome shape, compression distance, skirt length etc. You should have all your other variables including static CR, valve sizes, cam lift, head mill, etc. done before you can plan pistons. Safe to go .090" does not mean it's a good idea.
'66 was the last year for the "poly". But I think someone is joshing you about coming out of a '66 Imperial. I believe they were all 440's. I suppose early in the year they could have been 413's. If you want to play with a poly 318, why not conert it to a Hemi. Can be done.
There's a very $$$ aftermarket hemi top end for the LA engines which could be retro-fit onto a poly, never seen one. As far as original parts: no hemi heads fit the poly A block. The conversions are limited to the 1955-58 Dodge and Chrysler poly engines.
Thanks guys for the info...I'll definatly take everything into concideration. this motor will be a mild compression street motor, but probably will never see any track time. All of the info I have seen on this motor says it is able to handle the "large" overbore and heat dosent seem to be a problem. But, you never know, I may flog the crap outta this thing and destroy it in a week. the thing I like about it is, its different. and its worth a shot to me. if it turns out to be a great motor, then awesome. IF NOT, then i'm a dumbass, and everyone can learn from my mistake. But all of your collective advice IS helpful and I take it seriously Thanks GUYS.
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