Intake question for the engine guru's....

[72MARIO]

Jason what MPG are you getting ?

[68/72parts]

Just another opinion!!! Im running a stock headed 350 with a comp rv grind cam and the rpm airgap manifold, along with a edlebrock 650 thunder series carb. The truck is a 68 half 2wheel drive and has 308 gears with a t10 4speed. The Air gap works great with this combo and I probably picked up 5hp or so from 1800 and up. I live in B.C and the cold weather isnt to much of a problem with the air gap. you just need to run some sort of heat riser during winter and that solves the carb icing problems. I would recommend this manifold for your application and cam. Especially with the lower rear gear. My throttle response is amazing and thats with a tall gear 4 speed. I get 18mpg on the freeway and around 12to 15 in town, depending on my right foot. One advantage to the Airgap is that it leaves you room to upgrade later and still deliver more power everywhere. You can never have enough power!!!! LOL. with a 1500rpm stall you should have lots of bottom end if you use a slightly smaller cam. Just my 2 bits!!

[Jason915]

Originally Posted by c10crazy

jason915, I bet your new power came from the cam mostly!. The 4x4 cam is way better technology. I have never heard RPM intakes are designed for the "specific weight" of a vehicle. They are designed for the RPM usage.

Edelbrock has it in black and white right on the box that the RPM intake comes in designed for cars that weigh 3600# or less

[Jason915]

Originally Posted by 72MARIO

Jason what MPG are you getting ?

10-11.25 MPG

[70rs/ss]

Stock Production Vortec Iron Head 885
This head can be seen as a sleeper when compared to other GM production heads. It outflows the LT-1 aluminum Corvette head on the intake side, plus its mid lift numbers are very impressive. This head is perfect when iron heads are required. GM designed this head and put it on trucks as well as on the later Impala SS but with a different intake bolt pattern. As for production pieces these are one of our favorites.


According to carcraft.com's cylinder head database, the Vortec head likes around 500 lift, or high 400's. Based on the cfm the head will flow at that lift, anything smaller will be leaving power on the table and anything bigger is a waste as well. the Performer RPM air-gap will work best, put a bigger stahl, around 2500rpm and ditch the 1.6 rocker idea, they are just a crutch to make smaller cams bigger without swapping the cam. Picking a cam without knowing what your cylinder head will flow is at best guessing, and more times than not you will be dissappointed with your uneducated guess. Call comp cams up, I do not care if you like or hate comp cams, but thier cam help is the best info out there and you can equate the lift and duration to any cam grinder. Good Luck. I have the spec sheet from tha carcraft site, but cannot attach it for some reason, but look it up they tested several heads (like 500 or so) and they are all on the same machine at the same setting, so there is no bogus inflation to sell a head, just good useful info!!