Port & Polishing 4.3LX

***ColoradoDiablo*** · 11-25-2012, 02:56 AM

I'm getting started on my "new" engine. Torn down and ready to hit machine shop for boring work.
Anyway , has anyone done any porting or polishing on the 4.3 swirl port heads. I'm thinking about a little massage work and just wondering if anyone has done them before and if so , was there any improvement at all.
I know they are notoriously a bad flowing head

Thanks for any input

***mikeyt*** · 11-25-2012, 03:56 AM

This will be one for the 'gear heads' around here.

husker_fan · 11-25-2012, 05:11 AM

If you are talking about the heads that have the ramp looking swirled port under the intake valve......yes I've played with the v8 version. Waste of time. If you are keeping them, best thing you can do is make sure they have a good valve job done on them and a new set of springs. Alot of "port and polish" work that is done actually hurts performance. Remember you want a strong torque producing engine, not a high rpm horsepower one. I'd make my power with a good cam, and bump up the compression. You'll be pleasantly surprised.

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Oregondunes · 11-25-2012, 01:24 PM

I would agree. more lift and duration, strong valve springs (meaning, test em all and replace any that are weak), more compression

***mikeyt*** · 11-25-2012, 02:13 PM

How much additional compression can that 4.3 handle?

***ColoradoDiablo*** · 11-25-2012, 03:15 PM

My machinist told me to not go more than 9.5 to 1. Need more cam for anything more and not a lot of selection for cams that are idle to 5000 rpm either. Cam overlap also comes into play.(Bad news for a marine engine) Also I was told that the press in rocker studs will only take up to .480 lift , after that got use screw in studs.
I have Silvolite 9.0:1 , .030 over pistons to go in it , and am planning on milling the heads to get to my 9.5:1 goal.
And yes , I thought about a V8 instead. But I don't want the extra weight or the loss of the good fuel "mileage" that the 4.3 has , not to mention the gearing issue.

Oregondunes · 11-25-2012, 05:53 PM

Quote:

Originally Posted by ColoradoDiablo

My machinist told me to not go more than 9.5 to 1. Need more cam for anything more and not a lot of selection for cams that are idle to 5000 rpm either. Cam overlap also comes into play.(Bad news for a marine engine) Also I was told that the press in rocker studs will only take up to .480 lift , after that got use screw in studs.
I have Silvolite 9.0:1 , .030 over pistons to go in it , and am planning on milling the heads to get to my 9.5:1 goal.
And yes , I thought about a V8 instead. But I don't want the extra weight or the loss of the good fuel "mileage" that the 4.3 has , not to mention the gearing issue.

.030 over should get you close to the .5 compression ratio your looking for. However, there are several cams that offer way better performance and retain good fuel consumption. finding one that will pull hard right up to your desired max rev you want to run will be the key