Head Porting

[Locobob]

Thought I'd share my latest project with you guys: porting or rather reporting my cylinder heads. The motor is a 368 put together by LPE back in the mid 90's. The heads are pretty gummed up, likely do in part to the car having an open loop only chip when I bought it. When we burned a new chip for it we had to be very conservative on the timing do to knock sensor activity, I suspect all the gunk in the heads may have something to do with that. Anyhow I did some measuring prior to getting started so here are the numbers:
Primary intake runners at narrowest point (just above the valve guide) 33mm high, 33.8mm wide
Secondary intake runners at same spot 33.3mm high, 35.6mm wide
Intake bowls just above the valve seat 34.8mm
Exhaust bowls just above the valve seat 33.8mm
Exhaust port at narrowest point (near union) 33mm
Exhaust port at header gasket surface 36.3mm high, 53.8mm wide

I found a few things about the prior head work suprising, one being the combustion chamber surface was pretty much left as cast - very porous. I was expecting to see a nice smooth surface below all the carbon build up. Thought smoothing and polishing the combustion chamber was standard fare for head porting. Here are a few pics of the combustion chambers before (with just a little clean-up) and after a bunch of very tedious hand work.







Here is a primary intake runner after a bit of work with a sanding drum

[Polo-1]

only 31 more holes to go Rob

how the cam cover repair looking any luck.

[tf95ZR1]

Wow, lots of work!
I'd be interested in the dyno # changes when its all back together.

[lbszr]

I went with a lot of your posts a year ago and ported upper with match porting heads, but didn't do heads even though they were off with great results, so thanks, guess it's a year late.


But if you post this kind of good info you'll have me pulling the heads again, not complaining though.

[jonszr1]

wow i have never seen heads that were ported that didnt have some combustion chambers smoothed out at least . bowl work is a very important part of head work . i will bet that bob really improves his power with his mods to the heads . thanx for sharing, sure opens ones eyes

[Zr1 Destroyer]

Holy valve guides batman......don't forget to nip those babies off!)

[Pete]

Great work Bob

I think all Zr-1's should have/get ported heads & top end.

Pete

[Locobob]

Originally Posted by Zr1 Destroyer

Holy valve guides batman......don't forget to nip those babies off!)

I've been giving the valve guides some serious thought. I've seen pics of some that have been ground right to the floor. I have also had a few knowledgable people opine that this is a bad idea and that I should just shape what's there and not reduce the length of the guides. A shorter guide would possibly be subject to increased wear from friction/heat. On the other hand the engine being an overhead cam design one would think the valve guides would be less critical than a pushrod design in respect to side loading. Hmmm

[blackjack]

in harley heads,we streamline the intake guide,but leave the exhaust guide ''chubby'',otherwise they become very hot at the end if too thin
bj
91/1735

[Locobob]

Originally Posted by blackjack

in harley heads,we streamline the intake guide,but leave the exhaust guide ''chubby'',otherwise they become very hot at the end if too thin
bj
91/1735

That would seem to make sense, thanks for the input.

Any other opinions on this?
What did you do with yours Pete? How bout you Flyin Ryan, any thoughts on this?

I'm currently favoring trimming them back some and then contouring - on the intake side at least. The exhaust side is a bit shorter already so I'll probably just do some shaping on it.