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Old 09-18-2012, 01:27 AM
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smallblock383 smallblock383 is offline
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Quote:
Originally Posted by f-bird'88 View Post
you jumped onto a old thread with a lot of disinformation.
Here is the scoop on the 081 heads.
In stock as cast form they are pretty lame.
If you just bolt them on stock on your 350 keep you expectations modest.

If you are willing to do generous home port work to wake then up they can work very well.
See my post on porting 305 heads.
The 081 heads have a very shrouded combustion chamber and will
need some extra hand deshrouding work to allow larger 1.94x 1.60 valves and lots of flow.
The chamber will be bigger when you are all done.
Look at the similar 083 casting cousin to this head for inspiration.
Look at the vortec chamber and the chamber on other hi perf sbc heads too.

With generous hand porting and chamber rework and larger 1.94x 1.60 valves you can make this head into a good head for a street motor.
Its up to you to do the dirty work.

They flow about 185cfm and 130ex cfm stock.

Easy 230++cfm 180-190ex when done.

The small chamber allows and requires you to get creative with deshrouding and resshaping
and end up with a decent finished result around 62-64cc.
If you just throw them on stock all you will get is the benefit from the compression ratio raise. (more low and midrange torque)

sort of a diamond in the rough depending on how you see things.
If you are allergic to work, just go buy a aftermarket head.
If you are not willing to do the porting work yourself its not going to be very cost effective.
Not worth paying someone else to do the port work.

A 58cc chamber head on a flat top piston 350 does not create excessive compression ratio.
But will need 92 octane gas. Cheap 87 octane gas is not going to work.
They will end up around 62-65cc when all done unless you mill them back down.
On a 383 you will want a dished piston (approx -12cc)
you want to keep the true measured compression ratio under 11:1 for 92+pump gas
on a high perf street motor.
Its up to you to measure and calculate the compression ratio accurately.
You cannot determine the finished compression ratio by asking people on the internet.
I find a finished compression ratio of between 9.8 and 10.5:1 works real well.

Its all about how much effort you are willing to invest. A half baked lazy effort will get you a half baked lazy motor.
This is true when working with any of the stock sbc heads.



i dont mind working on them i spend alot time working on cars but what will i need to port them i never ported heads before i'm shore i can do it im knot a dumb *** and my buddy has a pair or 92 350 heads with mild port would them be better
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