General Category > Quadrajet Carb Talk and Tips
Best SBC Aluminum Intake for Street/Strip Qjet 355?
AHotRod:
Cliff and all,
I currently have a GM aluminum intake that I smoothed, blended, radiused and port matched to the heads,with my self built Q-Jet with Cliffs parts and book. It's a 9-1 compression, 355 , old World Sportsman II heads and a small hydraulic roller 210/215 @ .050 - .462 Int lift/.470 Exh lift on 110* C/L.
The engine runs fine, but is a bit of a pooch for a Hot Rod, runs out of steam by 4000 rpm, so I'm considering a camshaft change and asking if another intake would be in order, and if so, which one would you recommend?
The RPM range will be idle to 5500-ish, the rear gears are 3.55 and the Coupe weighs in at 2100 lbs.
Your thoughts?
Glenn
Mudsport96:
I don't believe the heads are the reason you lose steam at 4000 rpms. That camshaft is fairly tiny. Is your block a factory roller block or do you run retrofit rollers? Also, what is the max lift your heads can handle? The GM LT4 hot cam is a good choice but, if you're heads can't handle over .500 lift you have to stay with the 1.5 ratio rockers.
Do you have a manual trans or auto? Going with too much cam will be annoying with an auto and stock converter.
Heck I bet you could find a decent stock lt1 or lt4 cam on eBay, in a coupe weighing 2100 lbs it would hustle.
Cliff Ruggles:
In that RPM range you'll find it difficult to outran a factory intake. They are excellent parts and the iron ones help with thermal efficiency allowing for a leaner mixture to be used.
I know EVERYONE tosses them aside and runs right out and buys an Edelbrock Performer or RPM intake, but they don't do any better if as good as a stock one when teamed up with engines that are used from idle to 5500rpm's or so.
If you ever get the chance attend an NHRA sanctioned event and watch some of the SA cars run with those intakes.
The factory really did know what they were doing with these things. I took a Pontiac iron intake and modified it a bit under the carb to look like a Performer or RPM. Then dyno'd it on a 434cid engine making close to 500hp.
I also took a Pontiac HO intake (reproduction) and did the same thing.
The HO intake made 487hp
The RPM made 491hp
The factory iron intake made 497hp!
When I think back to how many intakes are sold each year for much smaller engines making much less power it still amazes me folks don't give the factory parts a chance and spend their money in other areas.
Anyhow, a very good cam for sure is the GM LT4 roller. It has a decent amount of seat timing and wide LSA. Pretty easy to make 400hp or so with it using the Sportsman heads. I like to see a bit more compression even with that cam, we build our 355's here with the Sportsman heads (64cc) and shoot for .025-.035" squish distance and mid 10's for compression. They will easily manage pump fuel as well. We also like the CS-179R camshaft if not going to a roller cam. It's basically a modern version of the 327/350hp cam, and will make great power in those engines with excellent street manners......Cliff
AHotRod:
I've had 2 NHRA Stock Eliminator cars, a L/SA '70 Buick Skylark GS 350 automatic and a I/SA '74 Corvette 350 and yes, with a stock-legal intake a guy could squeeze 375 HP out of it with those mountain motor 'stocker-camshafts'. A acid ported intake was worth 10-20 HP depending on who did it and how well you could find a way to get it all.
I'm not afraid to get after my intake and open it up some more.
Question: On the fuel delivery side, is it going to be necessary to run 1/2" fuel line (with a return) and an electric fuel pump to feed this street engine?
I've been driving it for many years on 3/8" fuel line and a factory stock Carter mechanical fuel pump.
Cliff Ruggles:
For most "street" engines under about 500hp very little need for a "race" type fuel system unless you will find perfect traction and run 1.6 or quicker 60' times. At least that's what I've seen here with this sort of thing......Cliff
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