I am checking out head upgrades for my L98.

I was looking at larger valves 2.02/1.6 and 2.05/1.6

The motor will have headers + cat back, accel intake and AS&M runners, 1.6rockers, stock cam.

The heads will get some port and bowl work.

Has anyone seen any useful gains going to larger valves on 083 heads and L98 tpi?

thx

 

I've read that bigger valves are a waste on the stock heads with a TPI, even if it's aftermarket.

....I don't have any personal experience though.

 

It's not the valve size that creates most of the restriction in the L98 heads, its the stuff in the way of getting to the valve. I wouldn't bother going bigger unless you need to have the seats recut anyway or need to buy new valves. If you are going to go through all the trouble of getting a new intake and messing around with the heads I can't see any reason at all why you wouldn't upgrade the cam too.

Edit: Also having the stock valves back cut helps much more than getting bigger ones that aren't back cut.

 

thx for the comments.

I don't want to change the cam because I don't want to have to change the prom. Eventually I will have to but for now I am trying to avoid driveability issues from cam changes.

Can you recommend a cam that I can use that would not force me to upgrade my chip yet would have useful lift and duration over stock?

About the valves, I read a chart published by TPIS that showed 083 heads with 1.94/1.5 vs 2.02/1.6 and there were definite improvements in flow. Not sure what that would translate to on the street but I was going to port and polish the heads (thats why I am pulling them off to begin with) and figured up the valves with 3 angle grind on top of it.

thx

 

All the other things you are upgrading will require a new chip just as much as a new cam requires one. If you're doing all the other stuff you owe it to yourself to get a real cam in there and start playing around with your own chips. I am terrible at recommending cams but I'm sure some other people will give you a few options, call any of the big cam manufacturers like Comp Cams and tell them what your setup is and they will recommend one.

 

It won't require a new chip, but would deffinitely run better w/ a custom chip. You'd be suprised how much a MAF(is yours?) car will let you get by with. It won't be optimum, but it'll still run good w/o any major issues. - I'd deff. put a cam in that thing. If not, you'll never see great perfomance. I'd reccomend calling some one like Comp cams and asking their thoughts. Even if you'd rather run a cheaper cam, it'd atleast get you some ballpark specs. A lot depends on what you intend on doing w/ the car. Do a search on here(you'll find lot of cam suggestions w/ similar set-ups). As for the heads, ported 083's can put out some good numbers(flow/power both) I wouldn't worry about changing the valve size though. Unless you're going w/ much more than what you have spec'd, the power for dollar just isn't there.

 

There is more than one way to improve flow. Larger lobe lifts, longer lobe duration, larger valves, larger ports, and altered valve timing can all affect flows. One thing to remember it that a TPI is sensitive to velocity as well as potential flow.

Is this in an '85? L98? Have you already changed the ECM?