Hey guys newbie here.i just bought an 87 iroc z with a tpi 350.it has 118k on it.i was wondering what would the best mods be for it.i have a $1200 budget. It already has edelbrock headers and a chip.i was thinking heads and a cam but not sure which ones are best.any help would be appreciated.

 

if the rest of the exhaust is not done do that

heads cam will net you some....but the manifold will restrict you....so you can either change it or port the lower manifold the plenum and a set of aftermarket runners....and port match everything.

if you do full bolt on's that will net you a good 40-50 HP over stock

 

It already has a flowmaster muffler.would i have to take the intake to a machine shop to have it ported? Also what would be the best heads,cam, runners for around $1200

 

It already has a flowmaster muffler.would i have to take the intake to a machine shop to have it ported? Also what would be the best heads,cam, runners for around $1200

 

I would prolly spend my money on headers and exhaust first, then see how much you have to play with.

 

hes got headers back....so we are good there....someone else may be able to chime in on a cam.

SLP runners are good after you port and siamese them, there is plenty of threads already active on this

no you don't NEED a machine shop to port, do some research and see if its something you are willing to tackle on your own....as far as heads go the most money saving would be had with have the stock heads ported and polished and stuffing them with bigger valves and such....thats the most cost effective way to do that....a set of aftermarket heads might run you the whole 1200

 

i would say the best tpi upgrade would be the FIRST TPI intake...it comes with its own throttlebody,plenum,rails,runners and base.. you have to do alot of portwork to the aftermarket tpi's to get them to have any real power..(trust me i have done it). the FIRST outflows all other aftermarket tpi parts.....

 

Good info and suggestions here as well.

https://www.thirdgen.org/tpimod1

 

You can get a Comp Cams camshaft that is "computer controlled" for $250,,, or you can find a LT1 cam from a 4th gen Z28 Camaro. A LT1 cam is around $50. But they are bit hard to find. When you find one and buy it, there are 2 major differences compard to the stock L98 cam. In certain years of the 4th gen Z28, the dowel pin was very long, or short. If you find one that is long, not to worry. Just grind down the dowel pin to a similar length to the L98 cam. The 2nd difference is that at the front of the cam of the LT1 cam, there is a missing round lobe ( not tear drop). That missing 17th lobe is not present because there is no mechanicaly fuel pump for the 4th gen Z28's. I have a LT1 cam in my 86 IROC and it is similar to a aftermarket comp cam. You cant go too wild on a cam because you will begin to lose vacuum. when you lose vacuum, the multiple sensors will throw bad voltage readings to the ECM and you will run into bad idle and bad acceleration. Good Luck. ohhh, port the plenum. knock down the lip just behind the throttlebody in the plenum. Here is a link to know what to port. http://www.gmtips.com/3rd-degree/dox...-port/port.htm

 

a lt1 cam is hardly worth anything over a l98 cam after doing all that work.... the two cams are so similar... the only time a "lt1" cam is worth it in a thirdgen is if you have a 305 auto car with the dreaded "baby" cam that has lift in the mid 3xx range.. other than that not worth it..the biggest cam you can go without headwork or computer tune is the crane 2032 cam 104224 cam....
http://www.summitracing.com/parts/CRN-104224/

its one of the biggest computer controlled cams for our cars..... i had it in my old l98.. without a tune or headwork... stock heads max out a 470 lift...

 

Do you have concrete evidence that the L98 and the LT1 cam are similar? How mush do the lift differ from both cams? I think that when adding a roller rocker systm with a 1.6 ratio would benefit either cams. What do you think?

 

yea the stock l98 cam that came in my car was 203/217 duration .415 .430 lift and 117lsa a stock 95 lt1 cam is 205/207 duration .447 .459 duration and 117 lsa.... its not worth all the hassel, time and money just to add .32/.29 lift difference that the lt1 cam provides.... in fact my duration is bigger than the lt1 cam and if you add 1.6 rockers to it then it will be a little higher in lift also...

 

Now that's what I like. A claim with numbers to prove it. Well said 88fastgta. So I should breath a bit better with 1.6 roller rockers. Sounds like a plan for me.

 

any time man..... i just wanted to save people the hassle over a lt1 cam swap only just to be upset by the results...... i think its only worth it for the cars with the baby cam... which i think is the 305 auto cars....

 

yeah it is. i have one hahahah

 

I always thought the earlier L98 cams were 207/213 .415/.430 117 lsa? Either way, its similar to LT1 cam but LT1 has abit more lift stock. easily can be matched with 1.6 rockers on the L98 cam.



L98 respond well to intake upgrades and 1.6 rockers. FIRST verify you have a well running motor. Do the typical first upgrades, regarding spark plugs, plug wires, distributor ignition module, HEI coil, etc. Make sure all the sensors are in working order. Verify base timing is 6-8 deg.

Once you do all that, then look into intake upgrades. I'd recommend FIRST TPI if you want to stick with TPI, and plan to do alot more mods down the road like heads/cam. Else aftermarket base and runners help alot too, its just that the FIRST package is a better overall deal in the end IF you plan to make alot of power down the road. The FIRST will support it but its 1000 bucks with everything you need. Aftermarket TPI is roughly the same but you can find bases and runners used here all the time for 500-600 bucks total. Maybe even less.

A set of 180 dollar comp magnum 1.6 rockers are a helpful addition. Combine that with a chip tune and your car will run mid lower 13's all day long with traction/2800-3000 stall/3.42 gears. No converter? Then it will run mid high 13's.

You already have exhaust, so open up the intake and let it eat. You are not ready for heads/cam upgrade and wont beable to do that for 1200 bucks.

 

no actually the later ones are a tiny bit smaller than mine... it just so happens that the 88 and 89 gta had the biggest factory cam besides the firehawk..... here is the stock cam info

https://www.thirdgen.org/mods3

 

Heres what the seller on ebay suggested.he was worried about the 1.6s hitting the stock valve covers.



http://cgi.ebay.com/ebaymotors/COMP-...-/200582515114

 

The only 1.6 rockers that won't fit with our factory center bolt valve covers are the bulky rockers. Comp Cams magnums will work because they are narrow. But the full fulcrum (all roller system) roller will fit but they cost almost $300. Now a while back I found a set of 16 full roller 1.6 ratio roller rockers that are extremely similar to the Comp Cams Magnum RR and they only cost $125 with free shipping. Here is the link to the the website. But you will have to fish around the website to find the 3/8 RR. http://www.skipwhiteperformance.com/...x?Item=PC-2328

 

Ok i will most likely be going with them.since the car has 118k on it should i replace the pushrods and springs to

 

Springs would be nice if you can, and naturally fresh pushrods are always a great upgrade but not needed really. I ran 1.6's on my L98 at 155k miles with stock springs/rods and it ran as good as ever...ran 12.9's with bolt ons...thats getting it done

 

you dont need new push rods. But I do recommend that you pull each one (MARK WHERE THE GO EXAMPLE, 1 goes to #1 cylinder, 3 goes to #3 cylinder) just for good measure. Now here is what you do, pull one and place it on a perfectly even plain such as a mirror. Roll it back and forth. the whole rod should be perfectly straight. If it is bowed and not perfectly straigh, it WILL need replacing. Also if you go with roller rockers, make sure and verify if the are self-aligned. If they are not self aligned, then you'll need to buy a set of "pushrod guide plates (you'll need 8 guide plates). As for valve springs, I use Edelbrock-5894. Or you can buy Edelbrock 5794. Its best to buy new springs because you dont want the old springs (which may be too spongy after 20+ years of service) to allow the lifter to actually leap off of the ramp on the camshaft lobe. Such leap off the cam lobe can cause a failure of the valvetrain.

 

here is what i have been looking at.

rockers
http://cgi.ebay.com/ebaymotors/COMP-...item2eb580bcd8

springs
http://cgi.ebay.com/ebaymotors/Edelb...item48401cced3