HP500 Piston to valve clearance
 

Does anyone know if a crane "651" cam will work in an otherwise stock HP500 and have enough piston to valve clearance? Stock heads and stock JE pistons...I plan to measure anyway, but curious from anyone with experience on this set-up. Thanks. :drink:

Re: HP500 Piston to valve clearance
 

That cam has .034 more intake lift and .020 more exhaust. I would think that it is a big cam for a stock compression low displacement engine. I was going to use that cam on a 9:1 Whippled 540 with dry tail pipes. I am sure the experts will chime in.

Re: HP500 Piston to valve clearance
 

Too big. Unless you plan to spin the engine over 6000 rpm. Use the 741 instead. It will clear the pistons however.

Re: HP500 Piston to valve clearance
 

It will be blown and turn 6000+, thanks for the info partiyacht.

Re: HP500 Piston to valve clearance
 

Want to buy a pair of 651's? I think I still have a set of the correct length pushrods for GM heads also. Only about 40 hrs.

Re: HP500 Piston to valve clearance
 

The 651 is not a blower cam. Blowers do not like lead. Cam is way to big for blown 502 even at a max of 6000 rpm.

Chris

Re: HP500 Piston to valve clearance
 

Crane has it in their blower cam section. It would not be my choice either. I should say "had", on their old web site.

Re: HP500 Piston to valve clearance
 

Parti,
In the 15 years I have been messing with camshafts and lobe designs for engine combinations I have NEVER had a shaft ground with advance to go into a blower enigne. It makes no sense to open a valve early when you have something that is going to stuff air and fuel into the chamber.

Chris

Re: HP500 Piston to valve clearance
 

Thanks for the info cstraub.

Re: HP500 Piston to valve clearance
 

Chris;

What cam would you use, hydralic roller? Stock 500HP except for 8-71's and (2) 825 blower carbs.

I gotta tell you though, I know several people who run that cam on blown 502's with great success, not only on the dyno but in their boats.

Re: HP500 Piston to valve clearance
 

Jdnca1,
Compared to what other cams. I get this response alot and I ask the same question, "What other cam profiles were tried in the combination and how much more power did this cam make over the others tried?" The response is almost always nothing else was tried. So as far as runs good, runs good compared to what. Please I am not picking on you I just like people to think out of the box.

Cam, I have no idea. Depends on what the heads are flowing, boost, static compression, and on and on. I don't guess.

Chris

Re: HP500 Piston to valve clearance
 

STOCK 500HP.......

8.75:1, stock GM heads, 8-71 blower 7# boost, no chiller.....

I don't think 800HP and 775 tq are so bad with a 651 cam and the above set-up.

What "off the shelf" hydralic roller cam do you have experience with on an otherwise stock 500HP with a mid sized roots blower? What were your results? How did the cams you tried compare? Asuming you've done this, how was your referenced motor set up?

Crane seems torn between a 741 and 651. I've had several custom ground cams in the past and I know that would be the "best" route...BUT, I don't want to do a custom with this motor....I'm not looking for every last ounce of TQ and power, its frankly not needed.

Re: HP500 Piston to valve clearance
 

Cost of HP?
Shelf Cam Cost $329, HP increase 40HP Cost per HP $8.22
Custom Cam Cost $410. HP increase 75 Cost per HP $5.46

I don't look at it as getting every last ounce, I look at it as money well spent.

Chris

Re: HP500 Piston to valve clearance
 

I'm assuming you have no experience with that application, is that correct?

I also look at this from experience that 35hp usually doen't move the needle at these kind of power levels in a boat...a race car is another story. If you want every ounce, why mess with a hydralic roller? a solid will run circles around it :p

Patri, thanks again for the answer to my original question.

Re: HP500 Piston to valve clearance
 

I know Frank (10X) with COPS uses 651's in his blower motors but he has 588's and they do idle rough. I still think a cam like a 741 would be a better choice in a 502. They make power up to 5600 in a n/a application. With a supercharger pushing it should rev to 6000.

Re: HP500 Piston to valve clearance
 

jdnca1,
Plenty of experience. As I know with stock "CASTINGS" core shift is terrible and intake ports both short and long can vary as much as 20 cfm...add that difference to the valve job on the heads and you could have as much as 50 cfm difference in castings, so it is my experience to recommend camshaft after flow numbers are known. People remember the good for 15 minutes, they remember the bad for years.

Chris

Re: HP500 Piston to valve clearance
 

cstraub,
Remember these guys aren't building NASCAR motors and in many cases these type of bolt-ons happen without even removing the heads. I am quite sure the cam issue is very debatable even if the best cam is chosen. Ideally all of us weekend warriors would get the heads flowed, then ported and matched, then choose a custom ground cam to fit the application. Unfortunately most of us can't afford to do that. :D I agree with your thought process that if you really want the best possible stick this should be done.

JDNCA1
Check the piston to valve clearance by using some light springs on your motors. :D

Re: HP500 Piston to valve clearance
 

Wette,
I understand, but buying 1 right cam is cheaper then buying 1 or 2 wrong cams.

Chris

Re: HP500 Piston to valve clearance
 

I felt the same way. I had an idea in my head and I looked for someone to validate it. Those that didn't I found myself debating my stubborness with them.
CSTRAUB knows.
RMBuilder knows.

If you are looking for a compromise, then say that.

The problem with free advice is that if it's "good", you never hear about. If it's "bad" you'll hear about it every damn day.

I don't want to argue. I compromise like crazy because I have short arms and I'm ok with that. These guys know their stuff and right is well, right...

Re: HP500 Piston to valve clearance
 

Jeez the poor guy asks for opinions on piston to valve clearance and gets just about everything but the answer he is looking for. :D Now saying the cam is too large is not really what I call free advice without really backing it up with a better recommendation. The more I think about it 8.75:1 with iron heads is not ideal for a pump gas blower motor so the larger cam may kill a little power but make the motor a little less prone to detonation. Just a thought. :rolleyes:

Re: HP500 Piston to valve clearance
 

Maybe I should go with the old standby Nickerson blower cam....252/258 @.050 .680/.708" 114CL solid roller. :p If it were an all out race motor like my old 632" was then I would sweat all the "small" details and worry about every ounce of power. It's not, motor is being built to utilize most of its original parts and 1 of (2) cams I've seen work many many times for the application. If it were, the GM heads would be in the corner and the motor would have a solid roller in it.

I'm not the type of person that would hold anyone accountable for their advise good or bad especially in a forum...in this business, SH*T happens and parts will break. If I couldn't live with that then I would buy a bayliner or pontoon.

Bryon, you're right there are some knowledgable people on the boards, there's also some knowledgable people at the cam companies, teague, nickerson, etc. IMHO, there is no substitute for the knowledge of several people you personally know and trust who "have been there and done that" so to speak, especially in this business. Most of the people on here I don't know from "Adam" so while I respect some of their opinions, I always fall back on what's been proven to work. Remember, everythings a compromise unlees you are starting from scratch and bulding an all out race motor...I've done that too, and it was a compromise...but I didn't want to spend the coin on Sonny's Chief heads or try to make a bravo live @7000+rpm. :eek: :drink:

Re: HP500 Piston to valve clearance
 

here is the cam i had in my 502 with a b m 420 8.5 lbs of boost and dart pro ones it worked great it almost made the same power as my 548 with the same heads and cam 6.5lbs of boost
http://www.cranecams.com/?show=brows...tType=camshaft

Re: HP500 Piston to valve clearance
 

Vette,
Your right. If the heads are not milled, stock deck, .041" thick gasket,and the cam phasing is left as it is ground, you should have plenty of PV clearance. Checking springs can be bought from Powerhouse, a division of Comp.

Chris