Head Porting

[Zr1 Destroyer]

Originally Posted by Locobob

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

Hasn't hurt either of my zr1 engines......funny how these knowledgeable people have never tried this in an lt5 before...hmmm!

Anyways....lookin good. Wish the heads came from the factory looking more like yours....a lot of power hidden in there!

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's an aircooled head vs. a liquid cooled head.......bad comparison!

[Pete]

I didn't wanna take a chance so all i do is taper the guides,basicly like the IH's injector boss.
Left the length alone.

I think our guides are short enough from the factory.
Just be careful grinding on them make sure the grinder/carbide doesn't jump on the guide,they are made something like pot matel.

Use a steel cutting carbide.
Had a guide break/drop on me,it wasn't pretty.

Also wanna add, don't do much if at all just polish and blend in the guide for the exhaust ports.

From the stock flow #'s that i have after your done with the intakes you will be at about 75-80% Intake/Exhaust Ratio

Pete

[blackjack]

Originally Posted by Zr1 Destroyer

Hasn't hurt either of my zr1 engines......funny how these knowledgeable people have never tried this in an lt5 before...hmmm!

Anyways....lookin good. Wish the heads came from the factory looking more like yours....a lot of power hidden in there!


That's an aircooled head vs. a liquid cooled head.......bad comparison!

it doesnt matter if your heads are air or liquid cooled....the exhaust guides will run a lot hotter than the intake ones,as they are exposed to direct combustion,and hot exhaust gases..i should add that the harley guides stick out in the ports a lot more than the lt5 guides
bj

[Locobob]

Getting pretty close to done with this project, mainly just some fine tuning left. Here are some more pics of the work coming along:

Port matching the injector housings to the heads.


Alignment dowel pin for port matching injector housing to head.


Intake ports almost done.

[FU]

You do good work Bob

[4DSZR1]

Looks outstanding Rob!

[1990 415]

beautiful!

[Paul Workman]

Originally Posted by Locobob

Getting pretty close to done with this project, mainly just some fine tuning left. Here are some more pics of the work coming along:

Port matching the injector housings to the heads.

In this picture the top of the runners are siamesed, no? I'm curious about that: Is it a result of opening up the ports and the "septum" being narrow at the top and the ports simply merge, or was that portion of the septum removed (siamesed) in a deliberate way?

Very interesting thread, BTW. Oh! I took your advice on the porting process - grind a bit, sand a bit and measure, then grind a bit, etc... It's working out very nice so far This my first LT5 porting attempt (plenum and IHs only, for now), and I really appreciate you, Pete, Marc H, Lee, and Dom and others willing to show me where the "bread crumbs" are through the woods. Maybe next winter I'll fuss with the heads. Between now and then (if then) I'll be soaking up all I can about it. Your pix go a loooong way to explaining at least some of the mysteries! Thanks so much for sharing, Bob!

P.

[Jim Nolan]

Locobob,

When you did my injector housings and plenum I finally had it dynoed, 349hp at the wheels. Not bad for a 375 motor. Aaron Scott has the car now and he's porting the heads, adding headers and changing the rear end to a 3:90. That should be for a good gain.

Question; In conversation with him I thought he mentioned burning the chip to open loop what's the down side to this?

[Nick]

Looks great Rob!