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351 piston/head

clc900

Jr. Member
Joined
May 20, 2002
Messages
57
I have a '69 351W with TRW L2378 pistons with a .160 dish. I took the stock heads off and planned to do a cam and head upgrade. My question is do I have to use different pistons if I jump up to a set of aluminum heads?

All this started by taking out the C4 and swapping in a 4R70W. I thought while I had everything pulled out I might as well add some power to the 351. It has a good bottom end and I don't really need stroker power so I thought a good am and some heads would be a great upgrade.

Any thoughts?

Thanks!
 

ENDLIFE

Sr. Member
Joined
Nov 17, 2011
Messages
453
The only time you have to change pistons is if you bore your block, if you want to change the compression ratio of your engine, or if you detonate through a piston. There's a ton of piston manufacturers out there, if your build isn't to serious you can get away with using basic pistons, but beware you will have to have your rotating assembly balanced if your piston weight isn't matched to your old pistons.
 
OP
OP
C

clc900

Jr. Member
Joined
May 20, 2002
Messages
57
Yes I would like to keep my pistons as I don't want the cost of a building a new short block. My concern is piston to valve clearance if I go with an aftermarket head with a new camshaft. Are you saying I shouldn't have any issues so a piston change is no needed?

Thanks
 

ENDLIFE

Sr. Member
Joined
Nov 17, 2011
Messages
453
A piston change shouldn't be necessary with just a change of heads. If your concern about clearance, then installed install your heads, rotate your crank, and see if your crank gets stopped by a valve. It's rare that you will need any modifications to your pistons or heads unless your building an engine that's over 11:1 and up, and then you need to worry about valve clearance.
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,833
There are enough different head options that you should be able to find one that will clear the pistons just fine and get you the compression ratio you are after. Biggest kicker is you are dealing with the short deck '69 block, that tends to play havoc with the quick CR calulators as they tend to default to the '71-'97 blocks with the taller deck. That short deck height can be around a 1 point increase in CR.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
The 2378 pistions are fairly low compression with the stock head which should have about 60cc chambers that puts you around 8.75-1. If you get heads with 58cc chambers you should be right about 9-1 compression.

Not saying that aftermarket heads wont gain you anything but you will really only see gains at the higher RPM's with them. You'll realize more gain with your cam choice than heads.
 

bmc69

Contributor
Bronco Guru
Joined
Jun 11, 2004
Messages
11,851
I would suggest the clay test for clearance...

Exactly.

It's a good idea to check the clearance because the aftermarket heads have large diameter valves and are often used with cams that have higher lift thn stock. So its a good idea to assemble one cylinder and run the clay test.
 
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