318 and 360 pistons

Posted By: Clayton

318 and 360 pistons - 06/24/12 09:46 PM

I have a stock 318 and a set of 30 over 360 pistons, can I safely bore a 318 to the 30 over 360 pistons? 318 is 3.91 bore and the 360 pistons are 4.030. Can it be done and what does the 318 need to be bored to? Thanks, Clay

Posted By: Dakota_Don

Re: 318 and 360 pistons - 06/24/12 10:28 PM

ummm no

Posted By: dennismopar73

Re: 318 and 360 pistons - 06/24/12 10:33 PM

Quote:

ummm no

some one may say yes,, BUT I WONT!!

HI DON!

Posted By: 69L78Nova

Re: 318 and 360 pistons - 06/24/12 10:39 PM

Quote:

what does the 318 need

360 casting numbers

Posted By: Clayton

Re: 318 and 360 pistons - 06/24/12 11:24 PM

If my math is right I would only have to bore the 318 to 40 over, a 318 won't take a 40 overbore?

Posted By: 70AARcuda

Re: 318 and 360 pistons - 06/24/12 11:52 PM

Quote:

If my math is right I would only have to bore the 318 to 40 over, a 318 won't take a 40 overbore?

360 .030 is 4.030
318 is 3.91

you will need to bore the 318 .120...good luck on that...

Posted By: Clayton

Re: 318 and 360 pistons - 06/24/12 11:55 PM

Duh...now I see where I calculated wrong:)

Posted By: RapidRobert

Re: 318 and 360 pistons - 06/24/12 11:55 PM

Not likely a 318 would take that much oversize plus the compression height of the 318 and 360 pistons is different & will not interchange

Posted By: Baxter61

Re: 318 and 360 pistons - 06/25/12 12:08 AM

Have it checked, then you will know. And as stated the 360 pistons wont directly work, youll either need to find an old 3.58 crank with 318/340 mains or have a 360 crank turned down.

Posted By: Reggie

Re: 318 and 360 pistons - 06/25/12 01:06 AM

Comparison pic with 360 piston in the middle. It will probably be a low compression dog...

Attached picture 7264074-LAPistons_340L360C318R.jpg

Posted By: Supercuda

Re: 318 and 360 pistons - 06/25/12 02:11 AM

Some have taken the old POLY 318 out that far and put a 3.58" stroke crank in them too.

But an LA 318? I would say no.

Posted By: scratchnfotraction

Re: 318 and 360 pistons - 06/25/12 01:52 PM

Quote:

Some have taken the old POLY 318 out that far and put a 3.58" stroke crank in them too. But an LA 318? I would say no.

I have an old magazine artical that did this with a poly block 318,.120 over bore,3.58 stroke crank. forgot what pistons,I will dig it up and re-read it.

seems I have saw LA 318s bored for sleeves to go to .120 overbore at my local machine shop,said it was the only way unless a LA 318 was sonic checked to see if it was thick enuff for a large bore. very few but a couple have been found from what he said.

a few have said you can cut a 360 crank to fit the LA 318,then use early lopo 318 pistons with some clearceing on the piston pin boss and skirts, which will also help on the balanceing. makes a 346 stroker IIRC.

what I am doing is a cut down 3.58 stroke crank,.030 318 roller cam block, 349 stroker pistons, should be plenty torque for my truck and I had all of it exept pistons.

Posted By: dogdays

Re: 318 and 360 pistons - 06/26/12 02:15 AM

So how much are you paying to get the crank mains turned down?
I wanna know.
R.

Posted By: gogo318

Re: 318 and 360 pistons - 06/27/12 05:43 AM

Quote:

If my math is right I would only have to bore the 318 to 40 over, a 318 won't take a 40 overbore?

i have a 83 318 i went 40 over with trws and you never seen an engine like 7 grand so much

Posted By: 340SHORTY

Re: 318 and 360 pistons - 06/27/12 03:10 PM

Quote:

Quote:

If my math is right I would only have to bore the 318 to 40 over, a 318 won't take a 40 overbore?

i have a 83 318 i went 40 over with trws and you never seen an engine like 7 grand so much

what are you useing to verify 7000 RPM?

Posted By: patrick

Re: 318 and 360 pistons - 06/27/12 03:14 PM

Quote:

If my math is right I would only have to bore the 318 to 40 over, a 318 won't take a 40 overbore?

stock 318 bore is 3.91. .030 over 360 is 4.030....re-do your math. I get .120" over (or about 1/8")

then you have the compression height problem. a 318 has a 3.31 stroke, with pistons about 1.72" compression height stock. a 360 has a 3.58" stroke with ~1.6" compression height pistons, so if you used the stock 318 crank, you'd be like .2" down in the hole, and have no compression....

Posted By: cptn60

Re: 318 and 360 pistons - 06/27/12 03:17 PM

Quote:

Quote:

Quote:

If my math is right I would only have to bore the 318 to 40 over, a 318 won't take a 40 overbore?

i have a 83 318 i went 40 over with trws and you never seen an engine like 7 grand so much

what are you useing to verify 7000 RPM?

Probably the size of the hole in the side of the block where the rod went

Posted By: Supercuda

Re: 318 and 360 pistons - 06/27/12 03:26 PM

Quote:

Quote:

Quote:

Quote:

If my math is right I would only have to bore the 318 to 40 over, a 318 won't take a 40 overbore?

i have a 83 318 i went 40 over with trws and you never seen an engine like 7 grand so much

what are you useing to verify 7000 RPM?

Probably the size of the hole in the side of the block where the rod went

Or a tach in 4 cylinder mode