OK guys I have the oppertunity to purchase some aluminum L98 heads from a TPI Corvette (86-91 application), I believe they are 58cc. I have an '88 iroc which is stock with a 305HO. Will these heads bolt right onto my engine and will I see a benefit and/or performance gain?

I was seriously considering some world s/c torquer heads until these came up... and at some point I want to upgrade to a 350 which would make the torquer heads useless. :shrug:

Thanks for your input, and yes I did a search

 

The heads will bolt up but your intake will not. Been down this road. I've been told there are adapters to make it work however.

 

No adapters, you use a different intake or modify the center 4 bolts on your current intake. They are also missing an accessory bolt hole and EGR if you need that.

 

Thanks Dr.NickRiviera and madmax...

I was planning on buying a TPIS Big Mouth Intake somewhere down the road.. that should resolve the intake issue? Mabey I'll have to buy it sooner rather then later

...and install a ZZ3 cam at the same time. Those three components should work well together? (aluminum L98 heads, big mouth intake, ZZ3 cam??) ...I'll probably need a custom chip burned at that time. Will this be a good combo, all bolt together, and produce some good power? Will the stock springs etc on the L98 heads handle the lift of the cam? What else will be needed?

Thanks for any answers!

 

the stock springs should handle .500 lift assuming they are new.

 

Having seen this idea for the 305's before I'm wondering what head gaskets you use?
Larry.

 

350 gaskets. Most of them are the same anyways for 305/350....or at least from what I've been told.

Really though, the aluminum L98 heads have a different intake mounting pattern? I wasn't aware of this. I thought the aluminum L98s should have the same bolt pattern as an '88 '081 head. I know the LT1 motors had a different bolt pattern, but I didn't think the vette L98's did.

 

Yep, early intake bolt pattern.

 

well as you can see from my sig i am running them on my '86, my intake bolted right on, and yes they were #113 castings off a '90 corvette. i love them, they gave me so much more midrange power and torque it is like a new car, great head for the money. i gasket matched them to my intake, mildly cleaned up the bowls, and polished the combution chambers. i am convinced there is at least a 13.7 in the car with a real exhaust and custom chip. i also have a similar plan to use them on a future build up of a 383.

 

Yes, or do as madmax has suggested and enlongate the center bolt holes in your original base.
Yes, Yes (but re-read madmax's first reply again), and Yes.

 

Thanks for everything guys. :lala:

Mark 89Formula - what about his reply? The EGR comment... I assume that a custom chip will take care of that. What else can I do? Any other suggestions or ideas on what to do about the EGR? Also, for which accessory is the bolt hole missing?

 

Yes, you can disable EGR in the chip. If you want to retain the EGR then you'll need something like the Vettes used; a stainless tube that taps into the header/manifold as a source. That's what the guys converting to the Vortec heads who have to keep EGR are doing. I'd disable it if your emissions laws don't require it.

The front of the Vette heads have two bolt holes near the valve cover mating surface. The back of the head has an additional hole closer to the block mating surface. I took a look under my hood but couldn't see which accessory(s) would use the missing hole in the front of the head. Sorry. I understand it's just a matter of drilling this additional hole, but I haven't done it yet myself because my Vette heads are still under the workbench. Maybe you could use the accessory bracketry as a template.

 

The alum L98 heads have the "early" ( pre 87 ) intake bolt angle. Your '88 305 has the 87-later intake bolt arrangement. You can modify your intake to work, it's just a matter of hogging out the holes in the intake enough to be able to bolt it up. Then using washers on the bolts to prevent oil seepage.

 

The EGR is ONLY critical if you MUST have one installed to pass emissions. If not, then it doesn't matter.

 

Maybe I missed something, but aren't the 305 HOs the L69s? If so, then there weren't any in 88 from my understanding. Did you drop this in from an older F body? Or are you just calling your 88 305 an HO?

 

Yes 92blue, actually I was reading on another thread earlier today where someone stated this line in the RPO decoder is incorrect (or something along those lines);

LB9 : ENGINE, GAS, 8 CYL, 5.0L, TPI, HO

So for whatever reason it lists HO but it apparently doesn't mean high output, or perhaps it is not even supposed to be there?

...perhaps my engine is just a two-bit-HO?

my bad.. sorry for the incorrect thread title.

 

No problem.

 

92, while the LB9 TPI 305 did produce the MOST HP out of the 305 (dual cat SD version being the most), you are correct that the L69 4bbl 305 was referred to as the "H.O." 305.