Anyone have bigger runners for the L98?
- Thread starter Edmond
- Start date
E
Eagle85C4
Guest
By themselves...no. But if you open up the plenum and open up the intake to match...then you get a difference, add bigger heads and a mild can ...then you get a big difference.
I have come to find out that the big problem with the L98 is it's inability to breath due to the small heads.
I have come to find out that the big problem with the L98 is it's inability to breath due to the small heads.
- Thread starter
- #3
*89x2*
Well-known member
An old mag. test showed a GREAT improvement when just the LPE Box (Superram) was installed on a otherwise stock 1990 model.
That intake changed the whole design -vs- runners of a larger diam.
Hope this helps.
That intake changed the whole design -vs- runners of a larger diam.
Hope this helps.
E
Eagle85C4
Guest
Porting will not do the trick...the heads need a smaller combustion chamber to increase compression ratio....larger runners on the intake and and exhaust and larger valves to increase flow.
Adding a larger throttle body and runners and plenum and intake but leaving the heads alone is like watching fluid trying to flow out of an upturned 2 liter bottle....hence the term bottleneck. In the L-98 the heads are the bottle neck, porting is like making the bottle bigger but leaving the opening alone, it will still pour out at the same slow rate. Now cut the top of the bottle off and tip it upside down...what happens? Woosh...the contents are gone.
I have just been through all of this. First I added a larger exhaust with headers, free flow cat. All it did was cost me a bunch of low end torque. I added a ported and polished plenum, edelbrock runners and a ported and polished big mouth intake, 52 mm throttle body and larger injectors with a hypertech chip and it was like adding a 6 pack to a car made for a 2 barrel....the cam helped but it still was not right. When I went to 64cc chamber heads with 195 runners and 2.02/1.60 valves it came to life. look at my thread on iron or aluminum heads.....read Kens thread on building his motor. Talk to Jeff the moderator about chips You can't just add a piece here and there and expect results. Buy the pieces and when you get the whole package then pull the top off the motor and do it all at once. One of the things I have found out is that the bottom of the L-98 is tough, forged crank and forged pistons similar to the LT-1 great foundation to build on. take your time read everything you can and learn what will work and what won't. It will save you money and headaches...
Adding a larger throttle body and runners and plenum and intake but leaving the heads alone is like watching fluid trying to flow out of an upturned 2 liter bottle....hence the term bottleneck. In the L-98 the heads are the bottle neck, porting is like making the bottle bigger but leaving the opening alone, it will still pour out at the same slow rate. Now cut the top of the bottle off and tip it upside down...what happens? Woosh...the contents are gone.
I have just been through all of this. First I added a larger exhaust with headers, free flow cat. All it did was cost me a bunch of low end torque. I added a ported and polished plenum, edelbrock runners and a ported and polished big mouth intake, 52 mm throttle body and larger injectors with a hypertech chip and it was like adding a 6 pack to a car made for a 2 barrel....the cam helped but it still was not right. When I went to 64cc chamber heads with 195 runners and 2.02/1.60 valves it came to life. look at my thread on iron or aluminum heads.....read Kens thread on building his motor. Talk to Jeff the moderator about chips You can't just add a piece here and there and expect results. Buy the pieces and when you get the whole package then pull the top off the motor and do it all at once. One of the things I have found out is that the bottom of the L-98 is tough, forged crank and forged pistons similar to the LT-1 great foundation to build on. take your time read everything you can and learn what will work and what won't. It will save you money and headaches...
WhalePirot
Well-known member
Bigger ain't always better
When you enlarge the tubes, on either intake or exhaust, you lose velocity of the gas. Hence, your intake charge may be less with larger runners: your exhaust may not scavenge, as headers are supposed to, if their diameter is too large.
It's an air pump and should be engineered as a total SYTEM.
Mike
When you enlarge the tubes, on either intake or exhaust, you lose velocity of the gas. Hence, your intake charge may be less with larger runners: your exhaust may not scavenge, as headers are supposed to, if their diameter is too large.
It's an air pump and should be engineered as a total SYTEM.
Mike
vader86
Well-known member
The stock Dports on the 88 are good enough for about 350 Crank HP, little over 400 ported.
Then youll need headers to get the air out, which gives about 15hp on average. L98 catback is restrictive too, but not as bad as the manifolds.
But what youll really need is some bigger runners, (AS&M, SLP, LPE) and a fully ported plenum and a bigger base manifold. (TPiS bigmouth, LPE SR Base).
Then a slightly bigger cam like the zz9 or accel 211.
All depends on power goals.
Then youll need headers to get the air out, which gives about 15hp on average. L98 catback is restrictive too, but not as bad as the manifolds.
But what youll really need is some bigger runners, (AS&M, SLP, LPE) and a fully ported plenum and a bigger base manifold. (TPiS bigmouth, LPE SR Base).
Then a slightly bigger cam like the zz9 or accel 211.
All depends on power goals.
- Thread starter
- #8
vader86
Well-known member
Well it depends on what youre doing as to what results youll feel, If your butt is calibrated, youll feel 10-20hp gains. Youll at least notice that the car has a little better response in midrange power.
And these power results are measurable in track times, the amount of money spent is proportional to the change in track time usually
And these power results are measurable in track times, the amount of money spent is proportional to the change in track time usually
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