1970 Chevy truck w/comp thumpr cam

350/350
Summitracing alum. heads 170cc
Compcams thumpr cam
Summitracing 1.5 roller rockers
Edelbrock rpm airgap intake
Edelbrock victor series water pump
Both are endurashine
Hedman headers 1 5/8
AFB Carter 625cfm
MSD ignition w/6A box

Category:

Autos & Vehicles

Tags:

• 1970
• Chevy
• Truck
• comp
• cam
• thumpr

[denisaaj]

i just bought the whole kit and everything with the timing chain set and all, will my new 5.7L 350 from ATK Engines sound like this even though the exhaust stops underneath the car halfway? its a big exhaust too, 3in. . I'm worried though ill have to get a smaller exhaust and that'll be even more money out of my wallet :/

[cdrummer316]

@denisaaj It should sound close. What compression is your new engine? When I had this set up I was around 9.5:1. The thumpr cams like compression so I would say if your engine has at least 9.0:1 you should be fine. I would agree that your exhaust is too big. You need to step down to a 2 1/2" exhaust which will give you more back pressure. Oh and if your cam is a flat tappet be sure to use BREAK IN OIL not regular oil.

[thatguy3139]

Can I install just this cam? Or do I NEED other parts as well? I have a 88 c 1500 5.7 with a 4 barrel 600 carb headers and intakemanifold. Someone please get back with me on this ! ! !

[cdrummer316]

@thatguy3139 Yes you will need more than just this cam. Stock springs won't work. Part # 981-16 from comp are the valve springs you need. Also change your pushrods to comps part # 7372. Or you can buy the cam kit with all of this stuff plus a timing chain set. Thats the cheaper way to go and you are guaranteed to have the right stuff. Also it is mandatory to use BREAK IN OIL on flat tappet cams. Don't use regular oil you will regret it.

[Bishn0zle]

hey man sounds so sick. just wondering how much HP to the rears? and how much would you say cost you to build this motor just an estimate. thanks man ;)

[cdrummer316]

@Bishn0zle Don't know never had it ran on a dyno. My guess is around 300hp. As far as cost it depends on how you build it. If you cut corners on the bottom end like cast pistons, stock crank & rods then probably around $2000-2500. If you spend a little extra on pistons and get forged with some I beam rods from eagle and an eagle cast crank rated at 500hp then I would say around $3500. Also depends on what brand heads you buy. You can save alot or money by sticking with flat tappet cam

[old70chevy]

@thatguy3139 im buying the 279 thumpr cam for my old 350. after talking with several knowledgeable builders, you can use stock pushrods, #7372 are 7.800", same as stock pushrods. and if you absolutely had to you could probably get away with stock valve springs, but you will have valve float up top. basic terms it would run, but you will lose power in upper rpms cuz your valves will float. best bet to just buy the 981-16 springs from comp for $65 and put them in.

[jeremy63able]

im guessing this is the choppy idle? i want to get this cam for my 72 GMC truck and didn't know if it is the rough idle or choppy idle that sounds better.

[jman12897]

what kind of exhaust setup are you running?

[Bishn0zle]

@cdrummer316 oh cool as man. did you build it yourself? i love these cams man