Ive decided to go with a 396 stroker with either AFR or ported LT4 heads and i cant decide to go with a solid roller or a hydraulic cam. I would not care at all if i have to adjust valve lash, thats not a big deal.

My biggest concern would be drivability and highway mileage vs performance. I want to have roughly 450-500 rwhp + nitrous and still get 20+ mpg on the highway. Right now i have an lt1 with a cc305, headers, and cutout and on my last trip i got 31 mpg. I do alot of highway driving so mileage is important.

 

Engine specific topics belong on engine specific forums.... moving to LT1 Tech.

Somehow, if I was trying to build a 600flywheelHP engine, gas mileage would be down the list a bit as far as priorities. That said, my 381ci solid roller (a fairly mild cam, to pass NJ rolling emissions) would make 20MPG on the highway with the M6 and 3.73's. But it was only putting down 425rwHP because of the mild cam. As the cam gets bigger, the gas mileage is going to come down.

Are you running an M6 or an A4?..... that will affect the flywheel HP you need to make to put 500 to the rear wheels.

 

If you have an A4 and want 450+ rwhp N/A, forget about gas mileage... trust me, LOL.
Steve...

 

31 mpg with about 1/2 the rwhp. There's no free lunch here.

Cruise mileage isn't directly proportional to hp, but in the case of a 500 rwhp 396 is could be close (15-16mpg). Your 396 with all the cam it requires to make 500 rw won't really like the low rpm cruise you now have. IMO, you are in a either/or situation. You need to pick the performance/economy you want and have an engine/driveline designed to get as close to that as practical. Funny, that's what OEMs have to do on every car. It's a challenge, and requires a coordinated system.

Good luck.

 

Its an m6 with stock 3.42 rear

 

I totally understand that a huge cam will cause poor gas mileage, my main question was would it make any differnece if it was roller or hydraulic?

HP for HP are they roughly the same or does one get better mileage (ignoring the fact that solids tend to be MUCH wilder)

 

Well part of the mileage is due to the overlap area of teh camshaft. A HR cam will with the same specs have a larger effective overlap area than a solid roller. This is due to the lash area of the setups. While a HR cam has a lash area of around .006 a SR cam for a street car can be anywhere from .014 to .028. This means that for the same cam specs, the overlap at .050 will remain the same say 10degs of overlap.

Now think of the overlap area as a triangle. with the .050 measurement cutting the triangle in half thru the middle of it. When you add more and more lash to the system you are taking the bottom of the triangle and raising it so you can see how that effects the total overlap area.

So going with that the reason a solid is a much wilder camshaft is because the overlap area when the motor is running is much less than it would be on a HR camshaft, so if you can use X amount of overlap area on a HR cam to get the same amount on a SR cam you need to have more duration or less LSA or a combination of both.

So which one gets beter mileage, it all depends on the specs of the cam and valvetrain.

Bret

 

I dont mean to be grumpy, but nobody is answering the question... they are giving good info that most of us already know.

My question is if i have 2 cams that make roughly the exact same power and one is HR and one is SR (may be different grinds due to differnet nature) which would get better mileage?

 

With your goals of 450-500 rwhp, this can easily be done with a hydraulic roller. Gees, there's guys out there making 600-700 rwhp with a hydraulic roller, no sweat. You just don't need a solid roller. The bigger question for you is choosing the correct size cam.

 

On a hydraulic roller valvetrain the the lifter depends on a "hydraulic" effect to transfer the mechanical energy from the camshaft to the pushrod. In doing this, the overall lift of the lobe is slightly "absorbed" by the hydraulic lifter and the net lift at the valve is effectively less than the potential of the camshaft lobe.

The obvious difference on a solid roller setup is the fact that the lifter is solid. So less effective lift is "absorbed", and thus you have a more accurate valvetrain that will make more power.

However the tricky thing to note is that since a solid roller cam will be harder on the valve train, the very first part of the ramp is ground to be slightly slower so that the valve is not "hammered" off the seat. The overall ramp rate after that is significantly faster than that of a hydraulic cam.

As far as gas mileage comparisons, I can't vouch for that as I have never had a solid roller on the street.

 

Hmmmm Guess I have to simplify what I said then....

If you already know what I wrote then you would understand the reponse.

First if there is a HR and a SR cam with the same specs they will not make the same power.

Second, the SR would have less effective overlap due to the lash (see above post) so COULD get better gas milage, but most likely you will not run the same SR cam specs as a HR cam.

Bret

 

450-500rwhp..... Hmm NA or Blower, with a blower hell yeah that is easy.

Bret

 

Sorry, I meant to say with a blower or nitrous

You'd need a huge cam and heads to make that on a N/A motor, making it less streetable than if you had a blower or nitrous.

Also, I heard one guy mention on this board that Combination Motorsports in Las Vegas does not recommend solid rollers for most people-there is some kind of problem with the solid roller lifters not getting enough oil or something like that. I'd stay away from a solid roller if I were you.

 

check out the comp Endurex lifters. Have an extra grove going down to the roller for more oil.. and they're rebuildable too.

 

Only bad thing is that they only good up to a point on spring pressure and high RPM use. So if it's a drag only car then it would be a good idea to use something else.

Crower and Jesel also have some very good lifters.

Bret