SBC 350 & Thumpr Cam ?

[BillySS]

I would really think about at least a 3.42 gear to wake it up. And def change the valve springs as a lil insurance.

 

[lurchsmalibu]

The 80's called and want their 2.56 rear gearing back! J/K... 8) Any stall TC? It should be compatible, but will be a dog at first. You may not get the RPM's that you want because of the stock valve train. :-k

lurch,, the stock valve train won't be the problem,,it'll be the smaller intake runners..

I know the technicalities of the flow.....you may have had better luck than a few of my buddies that tried a comp cam with the 480 lift that was floating valves at around 5200 RPM's. shrug.gif

 

[Night Stalker]

I know the technicalities of the flow.....you may have had better luck than a few of my buddies that tried a comp cam with the 480 lift that was floating valves at around 5200 RPM's. shrug.gif

Lurch,,,,,,,to answer your question here is the spec's from comp on this guys camshaft he's asking about. Take note of where the power band comes in and goes out at.. Now any cam company over rates the peak rpm's for any smaller motor or app. Also take note that a hydralic camshaft will float the valve sooner than a solid on any given day...So as for you to say your buddies in the past had bad endvours with a 480 lift camshaft floating at 5200 rpms sounds to be about right in performance of the cam ..

Product Line COMP Cams Thumpr Hydraulic Flat Tappet Camshafts
Summit Racing Part Number CCA-12-600-4

Cam Style Hydraulic flat tappet
Basic Operating RPM Range 2,000-5,800
Intake Duration at 050 inch Lift 227
Exhaust Duration at 050 inch Lift 241
Duration at 050 inch Lift 227 int./241 exh.
Advertised Intake Duration 279
Advertised Exhaust Duration 297
Advertised Duration 279 int./297 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.479 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.465 in.
Valve Lift with Factory Rocker Arm Ratio 0.479 int./0.465 exh. lift
Lobe Separation (degrees) 107

 

[cttandy]

I have been considering a thumper cam myself when I rebuild the 385. I am not looking for the fastest car in town, I just want it to sound aggressive. I am currently running some sort of marine crate motor 350 heads. They have no casting number but have pretty big valves in them.

 

[lurchsmalibu]

I know the technicalities of the flow.....you may have had better luck than a few of my buddies that tried a comp cam with the 480 lift that was floating valves at around 5200 RPM's. shrug.gif

Lurch,,,,,,,to answer your question here is the spec's from comp on this guys camshaft he's asking about. Take note of where the power band comes in and goes out at.. Now any cam company over rates the peak rpm's for any smaller motor or app. Also take note that a hydralic camshaft will float the valve sooner than a solid on any given day...So as for you to say your buddies in the past had bad endvours with a 480 lift camshaft floating at 5200 rpms sounds to be about right in performance of the cam ..

Product Line COMP Cams Thumpr Hydraulic Flat Tappet Camshafts
Summit Racing Part Number CCA-12-600-4




Cam Style Hydraulic flat tappet
Basic Operating RPM Range 2,000-5,800
Intake Duration at 050 inch Lift 227
Exhaust Duration at 050 inch Lift 241
Duration at 050 inch Lift 227 int./241 exh.
Advertised Intake Duration 279
Advertised Exhaust Duration 297
Advertised Duration 279 int./297 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.479 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.465 in.
Valve Lift with Factory Rocker Arm Ratio 0.479 int./0.465 exh. lift
Lobe Separation (degrees) 107

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Thanks 8)

 

[pgamedog]

Just for my own knowledge would piston to valve clearance be an issue. I was told .450 max lift on stock components.

 

[Night Stalker]

Just for my own knowledge would piston to valve clearance be an issue. I was told .450 max lift on stock components.

nope.

 

[Dyno Donny]

I'm not trying to step on any ones toes here but assuming that a stock spring will work with as much as a .500 lift or even something as low as a .425 lift is a very dangerous assumption and could prove to be a very costly one. I think you should re-think that one before you destroy an engine. While it may have worked with one cam grind, it could get you into trouble in a hurry assuming that it will work on another grind with different duration numbers. Add to this that GM has used so many different springs and installed heights over the years, you have to know what you are starting with. Springs are cheep compared to other engine parts.
.

 

[Night Stalker]

I'm not trying to step on any ones toes here but assuming that a stock spring will work with as much as a .500 lift or even something as low as a .425 lift is a very dangerous assumption and could prove to be a very costly one. I think you should re-think that one before you destroy an engine. While it may have worked with one cam grind, it could get you into trouble in a hurry assuming that it will work on another grind with different duration numbers. Add to this that GM has used so many different springs and installed heights over the years, you have to know what you are starting with. Springs are cheep compared to other engine parts.
.

Good point,,,,,,,,,,but take a look at the GM LT-1 motors that ran only up to a .490 lift cam in most of the early motors and then look at the install height which in most case's of GM didn't go above the 1.850 mark.. #-o