HI Folks! Advice requested Re 1989 IROC Z Vert build (to replace TPI 305 /AT

MISSION Reliable improvement in Torque and HP for street use.
Must be able to pass Ca. SMOG.
NO "Takeaways" from OE standards of starting, drive-ability, vacuum for brake operation, etc.


I don't know my axle ratio as my SPID is missing. My IROC's Dealer Order Form, lists G80, but NOT a ratio related RPO.

I am thinking a MABBCO (Yes, I know) L98 Long Block, because machine work and everything else is shy high, in Cali.

And a set of Enginequest CH350 I really LIKE the idea of Vortec chambers, mated to "stock" type heads.

https://www.ebay.com/itm/NEW-Chevrol...ebae%7Ciid%3A1



QUESTIONS: 1 Should I order the Hyperutectic FLATTOP Pistons? Would the bump in compression be too much for SMOG or 92 Octane Gas?
2 What about a CAM? I'd like to pick up some HP/Torque, without raising the Power Band, more than what GM would build and sell to the public. Will use stock torque convertor.
3 Who could supply a PROM, set up to meet the requirement I mention in MISSION?
4 Anything else?


Thank you in advance for your help! Mike Celi

 

PS I look forward to your input!

 

Just get a good used Vortec and change the cam and valve train. I'm running 325 RWHP on a stock bottom end with only new bearings and rings.

I would trust a used Vortec over some crate short block any day.

GD

 

As much as I would prefer a Vortec engine, I ruled it out due to EGR plumbing I don't wish to bring / discuss with SMOG Techs. But thank you!

I want to build an engine that looks like GM installed it in 1989.

 

You're probably aware but these guys have done a lot with high output engines and CA smog.

https://www.thirdgen.org/forums/sout...lifornia-area/

 

You link takes me to a TGO page with LOTS of different threads.

 

Yeah. That's their forum in general and there are a pile of threads in there that relate to your question. You'll have to do a little digging to see what strikes a chord. At the very least this is exactly what you're asking about.

 

Skinny z, Thanks for coming in and suggesting I search. I have and am requesting those with knowledge, who want to help, please feel free to do so. Thanks.

 

I am hoping someone on TGO, has tried Enginequest Chevy 350 heads. Or know someone who has. They have been around for over 10 years and are pretty unique. I really would like to give them a try, but would sure like to hear from others. Thanks.

 

You don't want to just find a set of #083s and have them re-worked? Wont make a ton of power but they will be pretty good. To keep it simple that's what I done with mine im building.

 

I have the EQ CH350G heads on the engine in my truck. They have pluses and minuses. If you get them, order them bare and get a machine shop to assemble them. If I could get a do over, I'd use something else.

Pluses:
much nicer casting than a stock vortec head
already machined for screw in studs
no retainer to seal clearance issues like a stock vortec head
has the heat riser for EGR

Minuses:
the components in the assembled heads aren't great and aren't setup properly
they have a vortec style intake port with 87-95 intake bolt pattern
--a stock intake gasket might seal a stock intake with careful assembly but will overhang the top of the port without a lot of trimming
--I used an Edelbrock intake and was able to seal a 1205 gasket with careful assembly but couldn't make that work with my stock TBI intake
--They recommend a 1255 gasket which fits the head well, but won't seal with any stock type manifold
I had to massage the center 4 bolt holes on my intake despite the heads having a 87-95 bolt pattern and my intake being designed for that bolt pattern
They don't have a CARB E.O. # so I'm not sure if they're legal in California
I borrowed the first 2 pictures from Schurkey, showing the sunken intake valves. The last one is mine showing retainer to seal clearance with the included retainers. The retainers for the beehive springs had even more clearance.

 

I would use stock Vortec heads over those. And just deal with the EGR by running a line from the y-pipe - corvette style. Many vehicles did this - it's not an uncommon thing to see so the smog check probably wouldn't bat an eye at it.

GD

 

Thanks, but I prefer to go with NEW EQ heads to NOT deal with changing out my lower intake, not to mention cali strict visual/sniff SMOG program.
EQ heads state they have Vortec CHAMBERS, in a head with the older L98 bolt pattern.

I want a stock OR MILD cam upgrade, so I don't think lift limitations or any excessive PROM programming, will be necessary. Can we work with this, Guys? Thanks

 

Sounds like intake fitment on the EQ heads sucks, and the assembled versions come with junk parts. And the TPI Vortec lower base fits great on stock Vortec heads. I mean you say you don't want to "deal" with it, but then you ARE going to have it apart anyway so.... from the sounds of what Arrg and Shurkey went through to use these, the stock Vortec's and matching lower base would likely be less work. If you are changing all the valve train parts and you are going to trade poor intake fitment for running an EGR pipe..... sounds to me like it's a relatively unknown vs. a very well known quantity. With the stock Vortec heads being the known quantity - made by GM so they actually fit. Versus the Chinese import knock off.

And the Vortec "chamber" isn't the big win for Vortec heads. It helps, but their big advantage comes from their intake port velocity. Which they had to change to seal on the 87-95 intake pattern or the port would be taller and wouldn't seal on the gasket.

And if lift/cam limitations are also off the table then stock Vortec's aren't going to be an issue. Though I would upgrade to LS6 beehive springs because they are CHEAP and it will rev smoother and higher.

Seems like you are stuck on the intake bolt pattern (get a Vortec base ya cheepskate), and the EGR - which if you route it properly they aren't even going to be able to see it. That's a minor and relatively easy fabrication job. Some flare fittings and either some steel tubing or a braided flex line.

GD

 

Vortec ports don't line up with just any SBC manifold so I've read. I had to search and found in this old thread https://www.thirdgen.org/forums/tech...-standard.html



EQ heads may suffer the same issue on a TPI base

 

Well,it seems from what yous pointed out, especially, "arrg" who has tried them, EQ heads will be a PITA. I was really excited about the prospect of getting Vortec chambers, without having to mess w/ new lower intake, EGR plumbing etc. IT is NOT just about $$, it is having to deal w/ SMOG and I do want a stock appearing engine. I might buy this

https://www.ebay.com/itm/GM-Chevrolet-350-5-7-Long-Block-1988-1989-1990-1991-1992-1993-1994-Roller-4-Bolt/253708804971?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908131621%26meid%3D5290488449064bb3897bd6601ae7df76%26pid%3D100678%26rk%3D11%26rkt%3D12%26mehot%3Dnone%26sd%3D151031015935%26itm%3D253708804971%26pmt%3D0%26noa%3D1%26pg%3D2380057&_trksid=p2380057.c100678.m3607&_trkparms=pageci%3A921492f8-dda7-11ea-b1f9-74dbd180fea9%7Cparentrq%3Ae99cd6f61730ad4d89998b32ffff7d17%7Ciid%3A1https://www.ebay.com/itm/GM-Chevrolet-350-5-7-Long-Block-1988-1989-1990-1991-1992-1993-1994-Roller-4-Bolt/253708804971?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908131621%26meid%3D5290488449064bb3897bd6601ae7df76%26pid%3D100678%26rk%3D11%26rkt%3D12%26mehot%3Dnone%26sd%3D151031015935%26itm%3D253708804971%26pmt%3D0%26noa%3D1%26pg%3D2380057&_trksid=p2380057.c100678.m3607&_trkparms=pageci%3A921492f8-dda7-11ea-b1f9-74dbd180fea9%7Cparentrq%3Ae99cd6f61730ad4d89998b32ffff7d17%7Ciid%3A1

Check bearing clearances, maybe pull the heads, and install it. Previous discussions on 305/350 L98 swap consensus was(on TGO F-Body forum) add a 350 EGR Valve, ESC, Injectors 22LB, and have a PROM burned for 350(or find a good used PROM) and it will run "perfectly".

Sure, I originally wanted a new GM L31R, but there gone and I ruled it out, for SMOG and added issues. Thanks again, what say yous?

Also, I may be reselling this IROC Z Vert, and before sale I will have full new paint and decals, stock type upholstery, convertible top, dash cap, injectors, rebuild F PSI regulator and lots more that I plan and have already done. It is a rust free, cali car, and I wanted to put in a "fresh" updated engine, drive it a bit, because this is what I LIKE. Fast, stock appearing. . I want thinks there is a market for F-Bodies, w/ updated power, stock appearing. I am not in this for "Profit" as there may be none, only the satisfaction of the build!

 

Ja85z28 used Aerohead heads: https://www.thirdgen.org/forums/tech...-aerohead.html

 

"Arrg" sounds like problems you had gasket wise, was trying to fit the EQ's to a TBI intake manifold. Correct?

Does this mean a TPI lower, would also have fitment problems?

I see in your first photo, the sloppy valve stem heights. What are you displaying in photos 2 and 3? Thanks.

 

I can shed a little light on this.

The first photo is showing a straight edge across all the valve tips. Notice the gap on the 2 exhaust valves in the center of the head. That could lead one to believe that the intake valves are sunken. Now the picture does not show the entire head, but from what I see, this is NOT a problem here. Aftermarket valves normally have different tip heights. If you look closely, you can see the difference between the intake and exhaust valve tip heights. What is more important here is consistency. All of the intake valves should be nearly equal to hitting the straight edge. And the same can be said for the exhausts. On a never-worked-on factory stock head, you actually can lay a straight edge along the tips and they all (both intakes & exhausts) will hit or nearly hit the straight edge.

Picture 2 is trying to show that the intake valve is sunken. Not true.

Picture 3 is showing the retainer-to-seal clearance, which I read as .612", which means that if you try to have an actual valve lift over .612, you ARE going to have a problem. You are also supposed to have a .090" safety margin. So this head set up as it currently shows, can handle a real-world valve lift of no more than .522" (.612 - .090).

 

Yes, I had problems with the stock TBI intake. I do not know if a stock TPI intake would work.

 

Your analysis of the photos is accurate. If the valve "problems" with these heads aren't really an issue, then I wish you had been in my garage to give me that advice before I spent the time and money to change out the valves.

 

So it sounds like the stem height variation, is acceptable for a mass manufacturered head. And, let me take a wild guess, my build w/ stock cam, or a MILDLY "bigger" cam, using stock rockers, will not produce lift any where near .522?

PLAN B Pull my 305 TPI and do a basic "Ring and valve job", which I'd rather not do.

SO, I telephoned two local machine shops, both in business a LONG time w/ good reputations. One quoted $250.00 basic clean and mag my old 305 heads, basic grind valves & seats, assemble. The other, said the heads were likely to need clean, mag, grind, install new exhaust seats, valves and some guides. $ 700. HENCE, you can see why, NEW EQ heads at $ 800 PR, is so tempting!!

Thank you both/all for your input.

 

Yes, it does not make economical sense to spend $700 when a new pair of (hopefully better) heads can be had for $800.
Many here (including me) will tell you to buy bare heads and separate valvetrain components and put them together yourself .
You will need a few specialty tools and be willing to learn how to use them.