Hot cam

[Steve Robinson]

I have a '65 roadster with the 327/365hp engine. It runs beautifully--I bought it restored and was told the engine had been rebuilt within the last 2,000 miles. In flipping through parts catalogues--Ecklers, Corvette America, etc.--I see a lot of info on cams that will supposedly add another 75-100hp to my small block. I have also been told by a performance shop here (I live in suburban Atlanta) that with an investment of around $2,000, I can get that sort of performance boost with a longer-duration cam, and some re-porting of the heads. My question has to do with the change in driveability at low rpms, and whether, overall, this sort of work is worth it for a car that is street-driven. Thank you. sr

[Patrick H.]

Re: Hot cam

Steve,

It all depends what you want to do to with the car. Realize that with the 365 horse motor, you already HAVE a cam as good or better as what you see advertised. For proof, just compare the cam specs between theirs and yours. Also realize that you really won't get 75-100 HP unless you have a tired L-48 that needed a rebuild anyway, and just freshening the motor gives you 40 hp.

Yes, you could add more horsepower, but it will definitely affect driveability if you go for a radical cam. Some head work may help IF THE TECHNICIAN KNOWS WHAT THEY ARE DOING AND USE A FLOW BENCH but it might also hurt. Not only that, but with a radical cam and head work, your car gains power on the top end (for the most part), which is not where you do street driving.

My 71 is mildly modified with the equivalent of the GM 315 horse cam and 2.02/1.60 valves, with hypereutectic pistons. It's enough to better the original configuration, but really is similar to the L-82 specs. Sure I'd love even more power, but my car is extremely streetable on today's gas, with a 600rpm idle and 6000rpm redline.

In short, yes it is possible, but is it worth it? Especially if the car runs great? Or are you better off buying a non-number matching car to drop in a "built" motor someday?

Food for thought.

[Patrick H.]

Re: Hot cam

Steve,

It all depends what you want to do to with the car. Realize that with the 365 horse motor, you already HAVE a cam as good or better as what you see advertised. For proof, just compare the cam specs between theirs and yours. Also realize that you really won't get 75-100 HP unless you have a tired L-48 that needed a rebuild anyway, and just freshening the motor gives you 40 hp.

Yes, you could add more horsepower, but it will definitely affect driveability if you go for a radical cam. Some head work may help IF THE TECHNICIAN KNOWS WHAT THEY ARE DOING AND USE A FLOW BENCH but it might also hurt. Not only that, but with a radical cam and head work, your car gains power on the top end (for the most part), which is not where you do street driving.

My 71 is mildly modified with the equivalent of the GM 315 horse cam and 2.02/1.60 valves, with hypereutectic pistons. It's enough to better the original configuration, but really is similar to the L-82 specs. Sure I'd love even more power, but my car is extremely streetable on today's gas, with a 600rpm idle and 6000rpm redline.

In short, yes it is possible, but is it worth it? Especially if the car runs great? Or are you better off buying a non-number matching car to drop in a "built" motor someday?

Food for thought.

[Steve Robinson]

Re: Hot cam

Patrick, thanks very much. sr

[Steve Robinson]

Re: Hot cam

Patrick, thanks very much. sr

[Fred Oliva]

Re: Hot cam

Hi,

The 365 HP engine already has a fairly long duration cam. This manifests itself by the 'lumpy' idle. The characteristics of an engine with this type of camshaft is a strong mid to hi RPM powerband but not great torque in the low RPM range. My '64 365 HP car is a dog below 3000 RPM (even with a 3.70:1 rear) but turns into a beast above 3500 RPM. In contrast, my '93 LT1 Vette has (had) a milder cam & more torque on the low end. It's real interesting to drive one then the other -- a real lesson in torque vs horsepower.

The bottom line here is if you go to a more radical cam (more duration) than you already have, you MAY get more horespower, but it will likely be at a higher RPM range, and POSSIBLY (probably) at the sacrifice at additional low RPM torque. You need to ask yourself what you prefer. Remember that bigger is not always better. The numbers quoted by vendors may be true if you take basic lo po small block & use their cam as well as other tricks, but your engine is fairly hot rodded already. You would might be better off investing the money in head work as you stated.

Be aware that porting heads involves the same tradeoffs between low RPM torque & higher RPM horsepower. Porting is a fairly complex science (probably more of an art). At the risk of oversimplification, when you make a port larger, you allow more air to flow thru the port which will give your engine the ability to flow better at higher RPM, however, if too much material is removed, the intake charge velocity is reduced which will reduce low RPM torque.

Many talented head guys can do some mild cleanup of the bowl & port area that can give good hi RPM improvement without too much cost in torque. I had this done to my '93 since I prefer a stronger midrange powrband. Got a SLIGHTLY more radical cam too. The car is alot more fun to drive now! No noticable difference in the low end, but the midrange really kicks you in the butt!

In the end, it's really what you prefer. Myself, I wouldn't put a longer duration cam in the '64 because it's already a bit much for the street.

Hope this helps.

Fred Oliva

[Fred Oliva]

Re: Hot cam

Hi,

The 365 HP engine already has a fairly long duration cam. This manifests itself by the 'lumpy' idle. The characteristics of an engine with this type of camshaft is a strong mid to hi RPM powerband but not great torque in the low RPM range. My '64 365 HP car is a dog below 3000 RPM (even with a 3.70:1 rear) but turns into a beast above 3500 RPM. In contrast, my '93 LT1 Vette has (had) a milder cam & more torque on the low end. It's real interesting to drive one then the other -- a real lesson in torque vs horsepower.

The bottom line here is if you go to a more radical cam (more duration) than you already have, you MAY get more horespower, but it will likely be at a higher RPM range, and POSSIBLY (probably) at the sacrifice at additional low RPM torque. You need to ask yourself what you prefer. Remember that bigger is not always better. The numbers quoted by vendors may be true if you take basic lo po small block & use their cam as well as other tricks, but your engine is fairly hot rodded already. You would might be better off investing the money in head work as you stated.

Be aware that porting heads involves the same tradeoffs between low RPM torque & higher RPM horsepower. Porting is a fairly complex science (probably more of an art). At the risk of oversimplification, when you make a port larger, you allow more air to flow thru the port which will give your engine the ability to flow better at higher RPM, however, if too much material is removed, the intake charge velocity is reduced which will reduce low RPM torque.

Many talented head guys can do some mild cleanup of the bowl & port area that can give good hi RPM improvement without too much cost in torque. I had this done to my '93 since I prefer a stronger midrange powrband. Got a SLIGHTLY more radical cam too. The car is alot more fun to drive now! No noticable difference in the low end, but the midrange really kicks you in the butt!

In the end, it's really what you prefer. Myself, I wouldn't put a longer duration cam in the '64 because it's already a bit much for the street.

Hope this helps.

Fred Oliva

[Mike]

Re: Hot cam

Fred:

Thanks for a very lucid and down-to-earth explanaton of the pros and cons of a "hot" cam. Helped me make the decision to stay where I'm at.

Mike

[Mike]

Re: Hot cam

Fred:

Thanks for a very lucid and down-to-earth explanaton of the pros and cons of a "hot" cam. Helped me make the decision to stay where I'm at.

Mike

[steve robinson]

Re: Hot cam

Thanks also to Fred for clarity on this question. I, too, will stay put.

[steve robinson]

Re: Hot cam

Thanks also to Fred for clarity on this question. I, too, will stay put.