magnums on a cast crank 340????

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swinger340

swinger340

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Have a super nice running 72 low comp. Cast crank 340. Thinking about dumping some closed chambered 98 360 magnum heads on it to bump the comp. A little. Has anyone already tried this? Worth the time or not? already own the heads.
 
the cast 340 crank has no idea what heads are on the engine...
 
calculate the new compression using the smaller cc heads and see what you get.
a stock 72 340 may only be about 8.0:1...i'm thinking a good improvement
 
I'm calculating over a point in compression. A little more of a cam, and the mag heads w some port work should be some kind of improvement I'm thinking. Was hoping someone who has done it may be able to let me in on some real world gains
 
i just did the calculation as well and yes maybe 1 full point.
with a careful cam selection based on your gears,tires and converter
should be quite an improvement
 
Throw a set of Mr Gasket 1121 head gaskets on it too. 6cc vs the typical 12 cc common 8553 Fel Pro.
 
70aarcuda said:
the cast 340 crank has no idea what heads are on the engine...
Click to expand...
I had a buddy who built super stock engines and he used to put 1 .030 piston in an engine and leave the rest standard. When I questioned the wisdom of doing that he said "the motor don't care if that one piston is bigger" He broke several national records back in the day so he must have been right.
 
..all kidding aside i'm surprised no has tried this,since the magnum heads are
supposed to be so much better.
 
swinger340 said:
I'm calculating over a point in compression. A little more of a cam, and the mag heads w some port work should be some kind of improvement I'm thinking. Was hoping someone who has done it may be able to let me in on some real world gains
Click to expand...

Like the same people who put rhs heads on their 340?
 
Works good. I'm putting a set on my truck's LA 360 for the same reasons... Just run a conservative cam, the Hughes 1110 valve springs (other possibilities there for cheap beehives too), and a set of oil-through push rods and you're good to go. You can even run the LA valve covers.
 
Amc lifters,on a flat tappet hydraulic.Need the oil through push rods,oils like a Chev. X2,on Skrews 1121 Mr.Gasket suggestion.
 
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