Ok, here's the deal. My friend and I finished rebuilding an L98 motor from the bottom to the heads. It was a stock rebuild and we'll be dropping it into his Monte SS. He's going to run a carb setup and all we have for an intake manifold is an older Edelborck carb intake manifold that was ported to match Felpro 1205 gaskets which make the intake outlet ports on the manifold bigger than the intake ports on the stock L98 heads.

Can we run this manifold without any problems? What exactly would happen if he ran this manifold on that engine? This motor made 240HP stock, would he really lose THAT much by putting a mismatached intake on there? Thanks in advance

 

Hmmmm.....

Let's consider the ZZ4. This is essentially a L98 short block, with L98 heads on it (the aluminum version); and a real mild carb cam, and a real simple dual-plane street intake.

The ZZ4 makes 345 HP.

The L98 made 240 HP.

Now that's not strictly apples-to-apples, since the one is with headers and the other with manifolds; let's assume the L98 manifolds cost it 40 HP (generous IMHO based on experience), and that therefore the motor with the one induction system is 345 HP, and the same motor with the other induction system is 280 HP.

So how much HP are you going to lose by putting a carb on there, anyway?

 

Oh no, I know that power gains with a carb are going to be different than the TPI system. The L98 block we have has L98 iorn heads on it. The engine is originally from an 89 IROC.

what i'm asking is, what will happen if we put an intake manifold with larger intake outlet ports onto an engine with cylinder heads that have smaller intake ports? I know that the air smacking into the sharp edges will cause turbulence, but will this turbulence affect the performance by a lot?

 

Better to have too much intake for your heads than too much head for your intake. You could always port match the heads.

 

Its actually good to have a mis-match like that, it creates a little vortex in the flow keeping the fuel suspended in the air.

 

Oh that...

Yes it will affect performance somewhat, but not hugely. The worst effect will be from air stagnating at teh exit of the intake port, and the fuel dropping out of suspension right there, where it can accumulate if the bottom of the intake port is lower than the head port.

 

Being an EFI guy I'm so use to seeing everything with lots of 000s after the first number and the dollar sign.

Intakes are cheap as dirt IMO. If you want/plan to keep the existing intake for a future head upgrade, just buy a better matching intake (Felpro 1204) for now. A good intake of that size is readily available and can be had cheap. Check for used ones on e-Bay or local wrecking yard.

When you finally do your head upgrade, you can recover most of the money it cost you by re-selling it. If you don't have any future plans for the existing intake, you could sell that to pay for the one you want.

Don't buy new - buy used.



(PS: Hey RB - good to see you).