Cam Opinion

[mike7570]

We have gone 10.75 @ 141 with a dead stock 302 HO shortblock and ported iron E7 heads and ported stock intake and plenum.  Joe-JDC

141 is what my SG car ran at 9.50's et, no traction with that 302?

[Joe-JDC]

Traction was an issue, showroom clean street car with all the options.  LX coupe, 5 speed with 8 psi.  Just saying that a camshaft is not necessary for a stockish engine to perform well with boost.  Did break the axles, had to upgrade to 31 spline Mosers, and traction lock.  Joe-JDC

[My427stang]

N/M

[cammerfe]

Some years ago, I had Comp spec a cam for a 397 I was building. I asked for the street manners of a 'AA' '64 427 engine with all the later technology they could put in it.

They sent me a 242-248 on 110, with .652-.666 lift. When we finished the break-in, of about 20 minutes at about 3000, and running it up and down during that time, it idled at about 850 with a wonderful bit of lope. I loved it!

KS

[blykins]

You know, the fact of the matter is that a lot of cams will work.  For any given build, I could probably use a Comp 270H, 282S, etc., etc., and the engine would make power and the customer would be very happy.  However, it's not until you start comparing camshafts that you find that there are better ways of doing things, making improvements, etc. 

For instance, I built a 445 with Trick Flow heads, Performer RPM, 10.3:1 compression, QFT 780VS carb, roller rockers, Canton pan, etc., etc., and made 547 hp @ 5500 and 588 lb-ft of torque. 

I also built a 445 with Trick Flow heads, Performer RPM, 10.3:1 compression, QFT 780VS carb, roller rockers, etc., etc., and made 536 hp @ 5500 and 575 lb-ft of torque. 

Do you know what the difference was?  If you didn't notice the "guess the horsepower game" thread that was centered around this, I was testing two camshafts.  One was 231/239 @ .050", .630" lift, 114 LSA on a 105.  The other cam was a 231/235 @ .050", .630" lift, 113 LSA on a 105. 

Those are seemingly miniscule changes that the average guy would think nothing about.  And even though I purposefully kept the overlap exactly the same to eliminate that as a variable, there was 11 hp difference and 13 lb-ft of torque difference on the peaks.  You may think that 11 hp and 13 lb-ft isn't that much, but if you paid for a new cam, would you rather have more hp or less?

It's not until you try back to back camshafts that you really learn what some engines/combinations like.  Until then, you could be leaving some power on the table.  Unfortunately, I don't think a lot of cam companies get back to back testing feedback, especially on engines that are not mainstream, like the FE, Cleveland, etc.  IMO, that's why I think engine builders sometimes have a better handle on what an engine combination wants than a cam grinder.

This reply wasn't in response to anyone in particular, just random thoughts at 6:20 in the morning, waiting for the caffeine to start working. 

[1968galaxie]

Are you going to replace the camshaft used in the second 445 Trick Flow engine build? (i assume both customers paid for custom cams)
The first design you used made 11 hp and 13 ft lbs more than the second cam design.

When testing ANY two camshafts in a build comparison clearly there will be one better and one less optimum for the combination.

An interesting comparison would have been a similar duration/rpm range standard hydro roller "catalog cam".

Nice builds nonetheless!

[cjshaker]

If you build 2 identical engines, I wonder what the variance would be in hp and tq output, on an average? I know theoretically they should be the same, but I'd be surprised if they were identical.

[blykins]

Are you going to replace the camshaft used in the second 445 Trick Flow engine build? (i assume both customers paid for custom cams)
The first design you used made 11 hp and 13 ft lbs more than the second cam design.

When testing ANY two camshafts in a build comparison clearly there will be one better and one less optimum for the combination.

An interesting comparison would have been a similar duration/rpm range standard hydro roller "catalog cam".

Nice builds nonetheless!

Yes, and knowing how to choose the better cam is where the experience comes in. 

I'm not going to replace it.  He was wanting 475 hp and he got more than he wanted. 

I haven't tested against "shelf cams" because I don't want to pay for them and end up with something I can't use.   But I have tested against other custom cam grinders' cams.  I was up 28 peak hp and 10 average horsepower in one engine against another guy's cam.  That was a cam swap in the same engine on the same day, actually within a couple hours of each other. 

[chilly460]

Agreed, it would be very interesting to run a custom vs a modern shelf cam.  There's so little difference in price, makes all the sense in the world to have a cam guy spec a grind who's familiar with your combo, engine idiosyncracies, and head/intake flow figures....but would still be interesting to see what it's worth.   Hell, I'd be happy to see a comparison of something like a shelf single pattern vs XE cams from Comp, as I still see a LOT of recommendations for something like a 270H or 282S.  That said, still not going to be an absolute as the comparison on any one combo is only so valuable for any other combo with it's own variables. 

[CV355]

You know, the fact of the matter is that a lot of cams will work.  For any given build, I could probably use a Comp 270H, 282S, etc., etc., and the engine would make power and the customer would be very happy.  However, it's not until you start comparing camshafts that you find that there are better ways of doing things, making improvements, etc. 

For instance, I built a 445 with Trick Flow heads, Performer RPM, 10.3:1 compression, QFT 780VS carb, roller rockers, Canton pan, etc., etc., and made 547 hp @ 5500 and 588 lb-ft of torque. 

I also built a 445 with Trick Flow heads, Performer RPM, 10.3:1 compression, QFT 780VS carb, roller rockers, etc., etc., and made 536 hp @ 5500 and 575 lb-ft of torque. 

Do you know what the difference was?  If you didn't notice the "guess the horsepower game" thread that was centered around this, I was testing two camshafts.  One was 231/239 @ .050", .630" lift, 114 LSA on a 105.  The other cam was a 231/235 @ .050", .630" lift, 113 LSA on a 105. 

Those are seemingly miniscule changes that the average guy would think nothing about.  And even though I purposefully kept the overlap exactly the same to eliminate that as a variable, there was 11 hp difference and 13 lb-ft of torque difference on the peaks.  You may think that 11 hp and 13 lb-ft isn't that much, but if you paid for a new cam, would you rather have more hp or less?

It's not until you try back to back camshafts that you really learn what some engines/combinations like.  Until then, you could be leaving some power on the table.  Unfortunately, I don't think a lot of cam companies get back to back testing feedback, especially on engines that are not mainstream, like the FE, Cleveland, etc.  IMO, that's why I think engine builders sometimes have a better handle on what an engine combination wants than a cam grinder.

This reply wasn't in response to anyone in particular, just random thoughts at 6:20 in the morning, waiting for the caffeine to start working.

Interesting info, I hadn't thought of that, to be honest. I guess part of it comes down to factors that are hard to quantify or control becoming a deterrent in finite testing.  Back when I had my drag car, one particular day we did 3 back to back dyno tests, let it cool completely, and then 3 more.  The HP/TQ figures were all over the place- probably around 40hp-50hp range with no real changes to tuning.  Granted, it was a bizarre turbo setup that I doubt had been done before on that particular family of engine, and it was a chassis dyno, not an engine dyno. 

If you're doing back to back tests and are able to differentiate ~1-2% differences, that's impressive.  A lot of people will think "eh, the dyno is a tool, it's close enough."  If you're actually doing testing to that level, that is cool.

If you build 2 identical engines, I wonder what the variance would be in hp and tq output, on an average? I know theoretically they should be the same, but I'd be surprised if they were identical.

I suppose that comes down to the precision of the components going into the engine and how they are both broken in.  We hear of "factory freaks" now and then, but that's mainly just a statistical anomaly that worked in the buyer's favor. 

I'm curious what Brent has to say on that topic.

[blykins]

An engine dyno will repeat within 1-2 hp on back to back to back tests, as long as the water and oil temperatures are kept the same.   They are accurate enough that if you're watching during the first 3-4 pulls on a fresh engine, you will see it gain on every pull and then level out.  Once it levels out, it's extremely repeatable.   

Chassis dynos on high horsepower vehicles not only have to worry about the temperatures of the transmission, rearend, converter loss, etc., but also traction loss on the rollers.  On a big power engine, it would be simple to "lose" 40-50 hp somewhere.

The variance between two similar engines should also be very close.  The factory freaks that you're referring to is just basic manufacturing tolerances that aren't checked and corrected at assembly.  If a particular engine gets a piston that goes to zero deck height, the cam timing is dead on where it should be, then the next engine has the pistons .005" in the hole and the cam is retarded/advanced past optimal, then you can see some good variation. 

The cam test from above was a continued "back-up test" to what I've been doing for years, but to also see how much duration played a role versus overlap.   I always split the duration based on the intake/exhaust flow of the cylinder head, but it's nice to verify your practices every once and again, especially with new combinations.  I'm one of the guys who likes to try different things, so I can have more data to pull from.  If I send out 10 cams and no one reports back, or no one compares it to another cam from another grinder, I have no real comparative data.