Installing larver valve seats

[Guest]

Ok here is my question. Can you install the larger HO valves into the non HO heads by having the larger valve seats installed? I am wondering if you can put the larger valves into the heads that came with the smaller valves

Now dont' say its not worth it and not to bother as I know this. I just want to know if its possible that is all

These are for the gen 1 iron heads. S10 camaro to Fiero heads

Thanks

Shaun

[bszopi]

It'd be cheaper to just buy the larger valve heads than to have the work done...

[RednBlack]

I agree with Brad. The machine work to install larger valve seats is very pricey and I'm not even sure if the casting has enough material to do it. Better off shopping for the heads.

[geoffinbc]

He never asked what it would cost. He even said that in the question.

Yes the work could be done there is room, the heads are the same.

[RacerX11]

The casting is the same for HO vs. non-HO iron heads. The ONLY difference is the valve and seat sizes. It is not very expensive at all to have the larger valve seats installed. It is comparable to installing new seats of the same size. I don't remember the exact price, but I think it was around $50 for the pair, parts and labor.

I did this to a set of heads several years ago when two of my HO heads came up cracked. The machine shop had some non-HO castings sitting around, so they upgraded them. After the larger seats were installed, you couldn?t tell them apart.

If you have a good shop do the install, you shouldn?t have a problem. After the seat is cut and installed, you will have some casting that overlaps the bowl area that will need to be cleaned up. My machinist just used the tool for cutting the seat hole to clean it up.

Marty

[geoffinbc]

There ya go... Take is from Racer's experience.

[Guest]

Awesome. Thanks guys. This is all I wanted to know.

I have a set of gen 1 aluminum heads here with the smaller valves(ended up being smaller afterall) and I was checking to see if larger ones could be installed. This is good news.

Gen 1 aluminum heads with HO valves. Oh yea!

[RacerX11]

Hang on a second here...back up. You asked about gen1 heads, not these special gen1 aluminum heads. My comments were in regards to the production iron castings.

With this custom heads, all bets are off. I don't know if these aluminum heads would be the same. They may be the same casting as the iron heads, but that doesn't mean it will work. By cutting the larger seats, you may weaken the heads.

If these are the "special" gen1 heads that were part of the all-aluminum "corvette eater" Fiero engine, as you theorize they are, they should already have the large valves. The HO valves had been around since '81, so if they don't already have the large valves, GM probably had a good reason not to do it.

Marty

[geoffinbc]

HO valves did not show up until EFI did in 1985/86

[RacerX11]

Wrong. The HO valves debuted in the carbed 135 HP HO 2.8 engine in the '81 X-11. The HO engine came with the hotter cam, higher compression pistons, cross-drilled crank journals, and big-valve HO heads. The EFI engine in '85 was simply the carbed HO engine with a MPFI induction system and larger crank journals.

http://users.spec.net/home/emxjc/v6_60_history.html

Marty

[geoffinbc]

Oh that HO engine... What was that used on? Wasent it like one special car or something?

[RidgeRunner]

X-11, like he said.

[RacerX11]

It was first used in the X-11, then later available as an optional engine in regular Citations, Omegas, and Pheonix, as well as the Celebrity.

Its the same engine as the MPFI, just with a carb.

Marty

[SappySE107]

So the 81 HO has the larger crank mains? I thought they all had the weak crank till 85.

[RacerX11]

No, the larger crank mains came in mid-year '85. There are some early '85 MPFI engines with small mains, so the crank change was not specific to the EFI introduction.

Marty