Cam Question

[MidLifer]

Need to tap some of the infinite wisdom on this forum again. A few years back I bought a rebuilt 350 for my truck. The block was a 3970010 4-bolt main originally from a 1980 truck. The guy had built it for his Chevelle, and the engine was basically done with stock pistons, rods, etc, but with an aggressive cam. I've attached the grind card with the specs.

I recently picked up a rebuilt 700R4 to replace the SM465 4-speed that is in the truck. I called the guy who built the trans and asked for his help to select a torque converter. He wanted to know the RPM Range of the cam. Unfortunately the grind card does not specify this. And I haven't (yet) found a site where I can enter the specs and calculate this.

So my first question is - can anyone tell me, based on this cam spec, a 4.10 14-bolt open rear, 32" tires and a 700R4, what stall speed I should select to best match the engine?

My second question is, if I use this truck as a weekend driver, occasionally load up the bed and occasionally tow a trailer with it, will I be better off putting a stock cam back in the engine and using a low-stall converter? The transmission guy was pushing me in that direction. I understand the heat issue with high-stall converters, just wondering if it's something to really worry about.

[Marv D]

That looks like one of the old Melling RV cams. 234/234 @ 0.050" is a LOT for a stock (basically 8:1 motor)

If your not gong to change cam to something more in line with stock (like a Comp 268H with 212 @ 0.050) and a split patern to help out the exhaust,, then get a lockup converter with around 1800-2000 stall. The low 1st gear ratio of the 700R (3.06:1) should have plenty of huevos even with the effective gear of the tall tire.

Your lockup control and TV cable adjustment is going to be key in reliability and making you happy with this swap.

[MidLifer]

I'm going to try to get back in touch with the guy who built the engine and see what he may have done to match the cam with compression. The guy did not impress me as a fool. He was an old-timer who built drag cars and street cars. This engine was for the latter and he said to me "that cam ain't too lumpy"...

Marv, you called it a "RV" cam, which was a term I hadn't heard before. I of course Googled it and read through a HAMB thread that said these cams were built for low-end torque, is that correct? If so, then I would think it would be a good cam for a truck.

I just don't want to pull and mess with a working engine if I don't have to. All I really need/want to do is pull the trans, fit in the new one and put a new rear main seal in while I'm there. I can live with the low vacuum (brakes work fine, and I installed a vac can as backup protection) and the cold idle variability. Once the truck comes up to temperature, it runs like a champ.

[Bigdav160]

I'd put in a stock 1800 rpm converter

[Blue Rat]

Originally Posted by Marv D

That looks like one of the old Melling RV cams. 234/234 @ 0.050" is a LOT for a stock (basically 8:1 motor)

If your not gong to change cam to something more in line with stock (like a Comp 268H with 212 @ 0.050) and a split patern to help out the exhaust,, then get a lockup converter with around 1800-2000 stall. The low 1st gear ratio of the 700R (3.06:1) should have plenty of huevos even with the effective gear of the tall tire.

Your lockup control and TV cable adjustment is going to be key in reliability and making you happy with this swap.

Ditto, that is a lot of camshaft for this setup.

[Marv D]

No Midlifer,, back in the late 70's and early 80's a mild performance cam was termed a RV cam if it was anything more than basically stock specs. They typically had LONG lazy ramps, .44 to .49 lift, and were most were a straight pattern like this (both intake and exhaust same duration and lift,, like Comps "Magnum" line). They were in about every flat bottom boat on the lake that had open headers They were something above stock, but less than a solid lifter 'race' cam. I guess you could say the term 'RV CAM' took the place of the "3/4" cam of the 60's. Recreational vehicle then meaning something driven for recreation not so much a daily driver. (like a speed boat, offroad jeep, sand buggies etc)

By comparison,, todays advertised duration of 292° is around 5-7° more 0.050 diration than cams of back then.

IMO you probably don't have enough compression to suport either!

If the builder can't give you an 'exact' compression ratio calculated from the parts he used and measured,,, (if he says 'about 10:1) the info is probably just better than an internet guess. You really need to KNOW EXACT static compression before you can do muh of anything but guess.

[MidLifer]

No way to measure compression and estimate from there? The engine runs fine and produces good power. I would venture a guess that if he mismatched the cam with the comp ratio it would run like sh!t, no?

Trying to find the guy's number but he has a common name and it was 3 years ago.

[68post]

Run a compression test and it will tell ,( somewhat ),how close the cam and static compression are matched.

According to your engine size, vehicle weight , and this cam - I'd use an approx. 2,200 to 2,500 stall. In a high quality brand.

Coan, Continental, PTC... etc.

[MidLifer]

Thanks 68post. So, assuming ambient air pressure of 14.7 at sea level, if I get a reading of 145 that would mean 10:1, correct?

[68post]

That's a great question that I don't yet know the answer to. I know you don't want it to be lower than that (145) or extremely high either ( 200+).

[68post]

That cam would be great street cam, for a 383 or 407 with a set of heads that flow around 75% or higher intake to exhaust and 9.5 to 10.5 compression.

[Captainfab]

If you intend to use your truck as a truck as it sounds you will from time to time, that cam will not be what you want. I agree that you will need to know what compression ratio the engine has, before a recomendation on a cam can be made.