Yes I agree about the gears and I've already purchased a set to get it to the right degree. I was just making sure it was safe to stick it out with the revolvers. Let us know if you get around to checking your 280's.

 

valve contact in these engines is very misunderstood. I guess it comes form the fear that the 4g63 is a full interference motor. If timing belt brakes, valves will bend.

Jumping teeth on the cam gear may or may not make valve clearance closer. depending on which way the gear is off, you may actually gain valve clearance. I have seen cars drive hear that were 4 teeth off on one gear and 1 off on the second. Down on power. I reset cam timing and away they go full power. I am certain it takes more than one tooth off in the wrong direct before valve contact is made.

I mentioned earlier about the strange valve contact noise. Here is what happen to me. A friend calls me up after installing some 280 cams. He says the vacuum is real low. I tell him to adjust gears to see if he can get vacuum to rise. He calls me back and says adjusting the intake cam just 2 degress makes the engine sound like their is valve contact. I had to here this myself so I tell him to bring it by. Sure enough the noise was very loud. Sound just like valves were touching. reset back to zero and the noise goes away. i inspected this engine for clearance with a boroscope. I estimate there was over .100 clearance

my guess on what was causing the noise was it was too large valve overlap that was causing sound waves that normally go out the exhaust were reverberating up the intake manifold. I wish we would have setup these cams on the dial indicator to see how far they were off. I suspect is was same issue as some of these revolvers.

 

Someone needs to do a study on the number of teeth off it takes to contact a TDC piston.

I do know the intake side needs to be off CW to get closer clearance and the exhaust the opposite, CCW. I think, if not then the opposite, but at least the intake and exhaust directions to be closer to piston are different

 

does that mean you'll be dialing in cams from now on when putting together a motor with after market cams

thanks again. i'll let the community know how these cams fair after degreeing by "tooth and gear". however it won't be for a few weeks as the motor isn't even in yet.

 

The point at which valve and piston make contact varies with the lift, duration, and LC settings of the cam, usually the intake cam.

The intake cam is historically the primary culprit with any engine. Advancing the intake cam too far is the most common aggravating factor.

 

Update

We assembled my friends Buschur head and short block today. Stuck in HKS 272's and after doing the timing belt degreed them.

LC of intake cam: 108 BTDC

LC of exhaust cam: 106 ATDC

Both had a duration at 5 thou of 224 degrees.

 

Those are fairly close, as HKS is published at 110/110. Still, it demonstrates several things:

(1) It's unlikely that any cam set will be spot-on spec, and this certainly can influence the overall results.

(2) The Revolver intake cam has serious QC issues, and I wouldn't run it without a thorough checking.

(3) A degree wheel, dial indicator, and adjustable cam gears are advantageous for anyone who is serious about performance. This has always been the case, and still is today.

 

+1000000000000000000000000000000000000000000000000 00000000000

 

Has anyone considered the effect on cam degreeing accuracy the lifters have? When not at operating oil pressure, I don't think one can be certain that some amount of valve movement isn't lost to the HLAs. If you just shut the engine off and the lifter's check valve is working, I guess it could be good enough... The only reason I never degreed my revolvers, which I still have sitting in a box, is that I just couldn't get motivated to swap in and adjust a pair of adjustable solid lifters.

This is very interesting information regardless of absolute accuracy however. There is no question that my car didn't behave quite right with the revolvers, and that the car behaved as though the intake cam was significantly advanced. The car made ridiculous low and midrange power, but sucked on the top end, and help way too much boost up top (32 psi vs 26 psi for HKS cams). Retarding the intake cam helped trap speeds and reduced top end boost levels.

WTF. If someone didn't just break into the car and steal my friggin tool box (with cam swap special tools), among many other things, I could be easily convinced to pick up a degree kit and check my HKS 280s and the Revolvers....

 

And you may want to do just that. I don't know if you saw our cam degreeing discussion, but verification with a degree wheel and a dial indicator revealed the Revolver intake cam to be well off-spec (LC much too far advanced).

Just FYI

 

We are still unsure about what to do with my friends Revolvers. We're not in a real hurry to put the engine in the car yet. We are afraid of three things I guess, one is that neither of us are very experienced with assembling motors. Two, that from speaking with a couple very experienced engine builders nobody has ever heard of a cam being off so much. And three, there is some questions like the notion of the HLA's effecting our measurements and possibly us doing something wrong.

That said, this isn't rocket science and it's quite easy to observe when spinning the crank through the intake stroke, that peak lift is occuring WAY too advanced.

Buschur said he's never had a problem with Revolvers. But I don't think Buschur degrees cams on his engine builds.

Marco at Magnus says the most he's seen a cam be off is like 6 or so crank degrees, but he's never touched revolvers.

My friend is debating between degreeing the revolvers to where they should be and running them... or just switching to HKS or JUN. Our main problem is we will always wonder how those revolvers woud have run.

 

Some have had issues with these (Revolver) cams, and it makes me wonder. And of course, because very, very few actually bother to check a set of cams for QC (and don't think for a minute they are all in spec), there isn't any other reported data with which to make a comparison.

If I were you, I might consider JUN, but if you happen to have a ported head and/or are chasing some serious power, I'd do something other than the HKS. The GSCs seem to be doing very well.

 

You bet, all 5 pages. I doubt it's any coincidence that my cams behave as though the intake is advanced, and these guys measured theirs to be just that.

 

The lifter does have a marked affect on the measurement. You are supossed to use a solid lifter to take measurements.

 

A solid tappet is what I used in the 'old days', but nevertheless, I have a difficult time believing that a HDL can make that much of a difference here.