Hydraulic cam limits?

[Dibbons]

Would like to experiment with the Moper factory hydraulic camshaft on my currect project: This is the 340 4-Speed {1968} camshaft with
* .445"/.456" Lift ~ 276*/284* Duration ~ 52* Overlap.

In my "prime" I always used solid lifter camshafts. I guess, now its time to "downgrade" to a hydraulic.

I wonder what the RPM limit of this 1968 camshaft would be with the factory style valve springs? Could I safely spin it above the standard 5500 RPM redline? (Probably use a stock manifold and 72 thermoquad). Maybe there wouldn't be any reason to reach for a higher horsepower peak. Just wondering for now and not sure what all the talk is about regarding lifter pump-up, valve float, etc.

 

[mmissile]

I think the stock parts won't give you any power above that rpm point, anyways. It'll sound better, that's for sure. Your torque-convertor and rear gearing will really have influence on anything more than stock.

 

[biomedtechguy]

As far as RPMs go, I am turning 6,100 with my 71 440 stock short block, stock 78 heads with Comp Cams items I installed: springs locks retainers and flat tappet hydraulic lifters, and whatever purple stripe hydraulic cam came in the car. Pulls strong all the way, and may go further, but I don't want to break anything. I believe that the old springs were my limiting factor, they were down from stock pressure, open and closed about 30% New valve train parts have really added power with no negative impact.

 

[383man]

I ran 12.30's @ 110 with the stock valvetrain in a very stock 383 but I used the old MP .484 cam and had Comp single valve springs. I shifted it about 5500 as it might have pushed a bit more but power wise it was a waste to push it more. They were stock 452 heads I mildly pocket ported. Ron

 

[biomedtechguy]

1st run this coming Sunday I am going to use 6k as my limit. 2nd 1/4 mile run I will try 5,500 and see what happens. Hopefully other factors (wheelspin, shift efficiency) will be consistent. The Comp Cams springs I have are the single outer spring with the inner flat spring.

 

[mopar 3 B]

Not much overlap there at 52 or was that a typeo? 383 flat tappet valve train had been gone through before purchasing car so I am not exact to other specs. Upper limit 6800 shift at 6200
if I get the handle moved in time. Track times unknown. Has a serious traction problem.

 

[biomedtechguy]

1st run this coming Sunday I am going to use 6k as my limit. 2nd 1/4 mile run I will try 5,500 and see what happens. Hopefully other factors (wheelspin, shift efficiency) will be consistent. The Comp Cams springs I have are the single outer spring with the inner flat spring.

Wheelspin ...wow! Seems like I grab better on most of the streets in 1st...not knocking the track, I walked it and it was sticky, but 1st gear and a couple of times 2nd was wheelspin, and I almost never spin 2nd on the street. So lots of pedaling and playing with launch effort. Street tires, no water. 13.99 @ 102 was the best I could do, and I am glad that I had 6k available without breaking anything, because I got there a few times.

 

[Dibbons]

Quote: from mopar 3 B " Not much overlap there at 52 or was that a typo?"

Depending on sources, I have seen overlap for the '68 four speed 340 camshaft as 52 degrees and 60 degrees. Now I'm not sure of the correct specs.