Does anyone know if an 89 vette came with 3 angle valve seats or backcut valves? Just wondering what my stock aluminum heads came with or without.

 

No and No.

 

I’m going to assume it’s No to the 3 angle seats & back cut valves vs you don’t know as no & no…

 

I don't think rklessdriver makes very many posts saying he doesn't know. Dan

 

Hahaha, nothing bad meant just double checking!

 

Correct. I was just working on a set of 113s for my Dad's engine project few weeks ago and I was taken back by how bad they were stock... its been a good 20yrs since I touched the last set before these. The GM Fast Burn like is used on 604 crate engine is way better and them and the Vortec cast iron used on 602 crates are the only factory heads I have touched in a long time. Just no call for the work anymore.

The factory valves just have a 45* seat angle.... its easy enough for a machinist to put a 30* back cut on the factory valves. Plenty of room to if you want.

The factory Intake seat has a 45* about .150" wide (when new) and about a 75* bowl cut below it but it's where the factory machined the throat of the casting to size after installation of the seat inserts not part of the valve job per say. There is no top cut just 90* of the seat insert. The Exhaust seat is similar but from what I have seen tge bowl cut dosen't touch the seat insert very much.

These heads can pick up a little with a good 3 angle valve job and 30* back cut on the intake valves.
Will

 

I really appreciate your knowledge on this one! It’s pretty surprising to me that the single seat angle is the same that was used on my 37 Hudson, which I’ve already improved to a 3-angle seats & 30° back cut valves. The good part of that is there is room to improve these stock heads. As David Vizard says, the throat & seats are the biggest restrictions & 1st place to focus on fixing. As we know the aftermarket heads (AFR, etc) are unbelievable these days especially if one needs/wants the flow they offer for a build. However these heads can be made to work well, especially if one is keeping the original TPI intake setup & doing modest upgrades.

Personally, I love the low rpm torque my 89’s L98 engine has & I’d be sick if I ever lost that. My vette currently doesn’t drop off until around 5200rpm which isn’t an issue for me. So if I keep my vette with the factory TPI I’ll keep the stock heads but sometime give them a freshen up & messaging plus bump compression when they are off. Now if I was to build a 383 stroke then I’d be on a set of aftermarket heads.

Not having ported a set of heads I recently picked up a couple of Vizard’s books to ready myself for that venture in the future. Do you have any advice on the subject of head work?