My first build 1990 sbc removed the center bold heads put a set of 64 cc double hump heads that have has intake side ported a little bit also put a 4 inch highe rise aluminum intake with 750 holley and accel distributer has headers with flowmasters but just dont seem to run as strong as i thaught it would any ideas thanks.
The 1990 SBC is a TBI engine. They were set up as a well-matched, 180-hp engine. That means there isn't one single thing thats holding it back, it takes more than just heads and intake.
You did a good thing with the double humps, but not a great thing. The smaller chambers helped compression a wee bit, but not much with the dished pistons. Double hump heads were all the rage in 1966, but they don't flow much better than wheezer smog heads. The cam is pathetically wimpy... I'm talking like 166/178 duration at .050" lift.
The intake is a complete mismatch. So is the 750 carb. You are giving up low-end torque with the intake, then about the time the cam wimps out (around 3500 rpm) is where that intake would shine.
Basically you have a cam and compression that is suited for 500-4000 rpms, heads that are suited for 1000-5000 rpms, and an intake and carb that is suited for 3000-6000 rpms.
curtis 73 wrote: Basically you have a cam and compression that is suited for 500-4000 rpms, heads that are suited for 1000-5000 rpms, and an intake and carb that is suited for 3000-6000 rpms.
This^^^^ I cut my teeth back in the 80's building SBC,s The key to building a good one is getting all the parts and pieces to work together. When you get it right they are a thing of beauty!
On the intake, single or duel plane?
yep, way too much carb. Go down to a 650 single pump and a low rise dual plane manifold. you'll need a different cam while you've got it apart.
What kind of car is this in? A 350 TPI Camaro will have a different cam than a TBI truck for example.
Gearheadotaku wrote: what kind of car is this in? A 350 TPI Camaro will have a different cam than a TBI truck for example.
Very true... I didn't think of that.
TPI cam specs were somewhere in the neighborhood of 188/194 if I remember.... but that was a long time ago for my brain.
which heads did you take off the engine- some of the truck engines got the same heads as the L98 TPI F bodies, which was actually a pretty decent head for a driver type build where high end horsepower takes a back seat to low and mid range torque. i forget what the casting numbers are right off hand, but that's easy to find with a little google action. if you didn't have those heads, then you put slightly better heads on the engine then put way too much intake and carb on it..
what are you running for exhaust after the headers? pretty much every 350 up to about 500hp likes 2.5" duals with good flowing turbo mufflers..
you need a bigger cam to utilize the slightly better heads- the cam you need depends on the vehicle it's in, the transmission, the torque converter if it's an auto, the gearing in the rear end, and about a million other factors... also, are you going after mileage, driveability, massive torque for towing in a full size 4X4 truck, or high end power for racing in a Miata or something?
if the block is setup for the factory roller cam stuff, then consider going that route instead of putting in another flat tappet cam. they are just better in every way and they don't just decide to go flat one day..
what kind of ignition setup are you running, and how much initial, total, and vacuum advance is it giving you?
Welcome to the world of getting an engine almost set up. Read some books on building up a Chevy V-8 then get a set of parts to match what you want the engine to do. Set it up for low to mid range torque for street use and high end torque and lots of revs for racing or just wasting gasoline on the street.
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