gm muscle

Hello everyone,
I hope anyone reading this can give me suggestions, insight and things to avoid.

I'm kicking around the idea of upgrading the cylinder heads on my '89 Camaro with the L98 motor. The only upgrades are emmisions-leagal ceramic coated edelbrock headers, Borla exhaust system and K&N filters. Otherwise, the car is completely stock.
I'd like to keep the heads that it has now, but taking them to a local machine shop to do the usual high-performance work. I was also thinking of enlarging the itake valves to 2.02 and 1.65 on the exhaust. Upgrading to beehive springs is also a thought.

I'm not looking for super power gains, but I would like to see about 25 Hp.
Would this upset the ecm?
Are the stock injectors good enough?
Do I need to go to a larger throttle body?

My local machine shop said everything would come out to about $1100.

What are your thoughts and suggestions?
Thanks!!

Blackdog36

iTrader: (3)

$1,100 seems like a lot of money. For that price you can get some Trickflow aluminum heads or some other brand. You might not need to upgrade valves and springs for the slight power increase you mentioned. I think biggest issue with stock L98 heads are the exhaust ports. Maybe only a good port job on intake and exhaust would be best and cost a lot less. You could also add 1.6 rockers.

Once you get over 300-350 HP you have to start thinking about upgrading transmission and rear end. Sounds like power levels you want will be below or at this level. Stock throttle body should be fine. Might be good idea to get used set of larger aftermarket TPI runners. ECM tune may not be necessary but would be good to make max power out of your upgrades. Check around some local dyno shops, they maybe able to do ECM tuning for reasonable price since your mods are not radical.

gm muscle

The runners on the Corvette for the same year are longer. The hood on the 'Vette is also a little taller. Will I have clearance issues? If not, should I try to get some stock 'Vette runners?

Blackdog36

iTrader: (3)

I don't think vette intake is much different from the camaros if at all. I believe vettes had better aluminum heads later on and maybe different cam??? Main restriction with stock TPI runners are their small diameters. Most aftermarket ones are shorter too and that helps. There a few companies that make good aftermarket runners but they are $350-400, maybe you can find some good used ones. Can you tell us what the $1,100 from the machine shop entailed? Just want to make sure what you are having them quote. Some taller gears like 3.23or 3.42 would help alot too. Camaros have some decent clearance under hoods for larger aftermarket intakes. Corvettes have way less clearance followed by firebirds.

Hopefully somebody else can chime in but I think with your minor mods, you will not need new injectors or tune ecm. You will need adjustable fuel pressure regulator to increase fuel since flow more air--> more power.

gm muscle

The work my machine says they'll perform is:
1. Installing bronze guides
2. Short turn on the bowls?
3. Larger valves-intake and exhaust
4. port and polish
5. 1.6 roller rockers
6. upgraded springs

Could I expect to get bigger power gains than expected? I know I could get some aluminum heads for the same price, but then it wouldn't be original.

Blackdog36

iTrader: (3)

I know where you are comming from. I'm looking to upgrade my car but keep it stock in apperance and intent as I can. I'm thinking about a more aggresive 350 build with FIRST TPI intake, high lift cam and AFR heads.

People have upgraded stock heads like you mentioned and got pretty good flow results (search for some posts). However I think even good rebuilt heads will have less flow and HP potential than aftermarket heads. I would port existing heads for less money (no new valve work) or buy decent aftermarket heads for that price. Heads seem to be critical component to making good power. You can still put aftermarket heads on your engine and resuse stock valve covers. Nobody will know what heads you have just by looking at engine bay.

That head work will give you good power gains. You would get some more with a better cam like the LT1 which I believe is still pretty mild but step up from stock.

Check out these posts:
https://www.thirdgen.org/forums/tpi/...eads-suck.html
https://www.thirdgen.org/forums/tpi/...stick-l98.html
https://www.thirdgen.org/forums/tpi/...vs-buying.html

vetteoz

iTrader: (13)

Gains to be seen from head work but still restricted by stock intake.You have air going through a hole; making one part bigger will not have as great effect is rest stays same size.
I could not justify $1100 for rework when you can buy off the shelf , proven performance for $1000.
Port the heads only and put spare $$$ towards intake upgrade.

Blackdog36

iTrader: (3)

I was thinking about this last night and I believe we are making it too complicated. $1,100 is too much money to spend on stock heads. You already have taken care of exhaust with headers and catback. Also sounds like you are happy with cars performance but looking for a little bit more. Porting heads and larger intake runners will give you 25-30 hp increase but more importantly power in the higher rpm band (4000-5200) that your car doesn't have now.

Spend a few bucks ($400-500) on porting heads (especially exhaust port) and maybe 1.6 roller rockers if price isn't too great. Aftermarket large tube runners are $400 new and you might be able to find some used ones around $250 or $300. You will also need adjustable fuel pressure regulator for $90. That will give your car a nice power upgrade and you won't have to worry about upgrading converter, cam, transmission, injectors, throttle body and rear end. You could also self port your TPI intake manifold base and plenum for a little more HP.

You'll spend around $1,200 now for upgrades and can always upgrade to strong 350 or 383 build in future. In the meantime you can enjoy a nice power upgrade without spending a lot of money.

Damon

You have a MAF-style TPI system on your 89. It's much more forgiving of changes to the engine's basic breathing characteristics than later speed/density systems. It can handle a 25-30HP bump from better flowing heads just fine without reprogramming.

Porting out old stock heads is getting a little iffy vs. the cost of a nice set of aftermarket heads, as you have found. But there are some advantages that sometimes get overlooked. Like that 87-up bolt pattern your heads and intake have- not all aftermaket heads are available in that pattern. And your stock heads have an exhaust crossover passage so your EGR system remains functional- not all aftermarket heads have that either. And, of course, you won't have any issues with emissions if your area requires a visual inspection if you stick with stock castings.

I wouldn't bother with bigger valves if you want to keep the cost down- a simple pocket port job and a 3 angle valve job will get you considerable flow improvement, especially on the exhaust side without spending megabucks- easily the 25-30 you're hoping for. Likewise, the high ratio roller rockers are pricey but don't offer a huge improvement in power.

Old hot rodders used to say that power is made within 1/2 an inch on either side of the valve seats and that's still true today. Work in that area will get you better bang for the buck than just about anything short of nitrous.

gmsoldier

if u have that kind of money to spend then i would go with some nice aftermarket heads, edelbrock makes some nice 190cc 2.02, 1.65 heads that are fairly priced, and if you dont want people to know they aren't original, just have the engraved logo milled off the ends and paint them up. if u want to save some bucks then i would invest in an electric grinder and some carbide bits, and try to straighten out the turn on intake port, maybe clean up the floor of the port a lil bit (your just tryin to make as straight of a line as you can to the valve), and PORT MATCH the heads and intake! there is much to be gained just by doing these, i even went as far as to "tear drop" the valve guide, tryin to make as smooth of a transition as possible. there is little to be gained on the exhaust port, but if your in there n e way, u could just smooth it out. then get your machine shop to do the valve job. if your gonna upgrade to some real spring pressure then your gonna need screw-in rocker studs, and i would also have them machined for positive valve seals. you could even bump the compression a lil while your in there. you can only make as much power as the heads will allow, so you may as well start there, and work your way up. just my

gm muscle

Thanks for all of the great info. and support. My machinist said the amount invested wont return the power gains I can get from aftermarket aluminum heads. Maybe I'll compromise some with port work, but now go all out.
Still unsure.

Damon

I'll have to say I'm with GMsoldier in this case. Edelbrock Performer heads (not the RPM version- they don't have an exhaust crossover port to keep your EGR functional) are fairly underrated. Friend of a friend is running low 12s with them right out of the box on a 350 in an all-steel Chevelle (no power adders).

If you want to go a step or two better than just porting your stock heads, this would be a solid choice. And they're available in the oddball 87-up intake bolt pattern. They also happen to fit like stock- no weird "gotchas" like the raised exhaust ports or raised valve cover rails common on some other aftermarket heads.

They are not the best heads in the aftermarket world, but they do just fine and are truly a "bolt on". They'll also knock about 40 lbs. off the front of your car since they're aluminum.