i just got a l98 with no tpi and no aluminum heads , it has 305 "081" castings, fully ported heads, i need a good cam, intake carb combo, its dailly driven, with 3.42 gears, thanks


Kevin

 

Well, you're gonna be up around 10:1 compression with 305 heads on an L-98 bottom end, so we'll want to make sure we use a cam with some duration to it to bleed off some cylinder pressure, but not take a torque hit becuase of it.

Also, your stock 305 heads are all done at about .470 lift so that's a top stop that we won't exceed or come too close to.

Comp Cams 268 High Enerrgy cam. 268/268 duration, 218/218 .050 duration, lift around .454/.454 if memory serves. 1.5 ratio rockers- take your pick there from stock to full roller- whatever your budget allows. 1.6s will take you over the .470 lift limit. You WILL install the springs that are recommended with this cam- don't even think of using the stock 305 springs unless you want the thing to nose-over from valve float at 5000 RPMs.

Intake- Standard Edlebrock Performer intake will fit nicely under the hood and makes plenty of power. Not as much as the Performer RPM, but that's going to pose hood clearance issues.

Carb- Don't go too small. A typical Holley 600 universal replacement carb is going to be a little too small. I'd go with something at least 750 CFM with vacuum secondaries. A holley will do fine, but they are usually pretty terrrible on gas mileage out of the box, not a lot better even with decent backyard tuning efforts. A well-tuned QJet will be every bit as fast as a Holley but with better mileage potential. They are a pain to tune if you don't know what you're doing with them, though.

 

is that cam a roller or mechanical, or does it matter, because i know the motor has a roller in it. thanks

 

I hate to point out the possible gotcha here, but are you sure it's not really a 305? might not be the heads that are wrong.

 

nope im 100 percent sure its a l98, i checked the casting numbers and then assembled it for my dad, when we got the motor we didnt get the aluminum heads, so we just threw some 305 heads on it, that we knew were good.

 

Are you driving the car it is going in to with a carbed engine now? If so, you may already have the carb you need.

 

Didn't notice what valves you are running in the ported 305 heads. Probably had to give up a few ccs for the larger ones when they where cut in so compression may be a little lower than 10:1.

But anyway I am running a L98 bottom end with 416 305 castings with compcams XR269HR cam. My heads have 2.02 / 1.60 vavles to help a little. The lift on that cam is .496/.503.

From what I have seen from flow numbers the heads peak between .450 and .500 inch lift. So I would think getting a cam with over .500 would be ideal. That way you spend some time in that lift range. No point it just barely hitting the peak and dropping off. My valves are longer that stock and my springs taller. You may have to check that if you go to .500 inches so that your retainers dont smack the top of your valve guides.

I haven't been able to get to the track yet due to wheather and other issues and probably won't till spring so all I can tell you is it feels pretty good. It spanks my friends stock L98 powered formula but can't hang with a new vette. So my guestamite is low 14 to high 13. I'll find out in spring. Or maybe I will have saved enough for some AFRs by then and never know.

 

Does anyone have an answer to the cam questions above?

 

DO you want a hyd roller cam or a hyd flat tappet cam?

 

roller cam

 

You have quite a few choices in a roller cam for this motor.

The cheapest would probabily be a LT-4 Hot Cam.
Some others would be Comp Cam's XR270HR-10
or a Crane Cams HR-284-2S-12 IG

You can check the specs you self on their online internet sites.
I would stongly consider using larger 1.94 valves on those
081 heads.
Just porting them without going with the larger valve will really limit the airflow. (horsepower)
Same with the intake and carb. A performer RPM 750 carb will fit under the hood fine with the right "GM Drop Base" aircleaner assembly.
Search my past posts for info and pics.... Keyword: L-88

 

You can install a flat tappet cam into any facotry roller block, which is why I suggested it. Flat tappet cams are still the bang/buck champs. A roller, if you already have a roller block and the lifters isn't too too bad for cost, but still more.

All L-98s should have come with a factory roller cam.