Thumpr cam, Stock Mopar HP Springs and HI!

[Raker43]

Hello All,

By way of introduction, my name is Cary and I Just picked up a 1970 Dodge Dart Swinger 340, 4 speed! She's a runner but needs the new heads that came with it due to three burnt exhaust valves. Have it torn down and heads being cleaned up a bit and new valves and springs being installed on NOS J heads cast 3769974 from around 1975. 2.02" intake and 1.60" exhaust. Received a Comp Cam today, Thumpr CL-20-600-4. 268/276 duration, .486/473 lift. Running the stock Carter AVS 625 Carb and stock intake manifold and cast iron exhaust. I'm throwing in some pics because we all love Pic's right!? I will try not to be a mooch and will always try to throw down some pics!

so I have a question and I hope the pics serve as some bait:

I have the Stock Mopar HP springs(part #P4120249) lift from .430-.500. I was wondering if any you out there have had experience with a similar set-up, i.e.,springs and cam with similar characteristics. I'm worried about the lift being too much and hitting a valve. Comp/Summit recommends their valve spring kit(995-16). Is this cam too aggressive or ok for the 340? New to the Mopar game. This baby just fell in my lap and I'm loving every minute of it so http://www.forabodiesonly.com/mopar/images/smilies/3gears.giffar!!!:burnout:

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Thanks All!

Cary

 

[Captainkirk]

Hello, and welcome to the madness!
I was running a similar setup on my 340...cam specs were .450/.475, 298/308 duration. I had the stock Mopar springs shimmed and they served me well with frequent forays at and above 6000. Obviously, better springs will give you better outcome, but when penny-pinching, every cent counts. As long as your machine shop says they meet spec and are shimmed they should do OK. Your lift is not nearly as aggressive as many grinds out there these days. If you can afford the better springs, do it, but only you know your budget.

 

[Raker43]

Thanks for your input. Valve float is my main concern with the stock springs but I think I'm going to be careful with this motor until I have the funds to punch it out and build it from the ground up. I'll try to stay away from 6k on the revs! Right now I just want to drive it and decide which direction to go with it. It's a very solid car with little to no real cancer and it came with a grip of parts I'd like to use while I get her revived and get to know her. Came out of a garage after 25 years of sitting. Needs some TLC.

 

[Captainkirk]

I never experienced any valve float to my knowledge. I think the 1.88's help by being lighter.

 

[RustyRatRod]

Nice lookin car. Welcome aboard. That's the correct part number for the Thumpr, but the duration specs you quoted are incorrect. Here is the cam by part number.

http://www.summitracing.com/parts/CCA-CL20-600-4/