Inliners International Forums General Discussion Hi Performance Isky Cam Spec for Chevy Standard: say what?

Greetings . . .

This past weekend I was reading the '56 printing of Ed Iskenderian's book on valve timing:

In the back he includes a catalog of camshafts that can be purchased outright - inlcuding some interesting regrinds.

I was checking out the specs on the the dual pattern D.P. #2 for the 216:

The exhaust timing seems crazy (67-33). 280 degrees of duration? That's 30 degrees longer than the intake - and longer than any of the other grinds on the page! Is this perhaps a misprint?

Any insights will be greatly appreciated.

Keith

My guess is these were advertized figures and not the actual numbers. This was also published long before the cam industry started using a standard. I think Harvey Crane of Crane Cams(past employee of Iskenderian) introduced using .050 valve lift as a starting point for these measurements and the rest of the cam industry picked up on it. There some cam manufactures such as mellings and GM factory cams which still do not use these standards--.006 is used quite offen. With out some explanation as to the amount of valve lift and the location of the piston when these numbers where posted, who knows !! Ed Iskenderian was and still is quite an Inovater to say the least and he may have found some HP gains by letting the exhaust stay open longer. Just some thoughts--Paul

Thanks Paul . . .

I am hip to the distintion between .050 duration versus the overall duration off the seat. It helps to describe the cam profile - specifically how agressively or gradually the lobe accelerates the valve up to maximum lift.

I am thinking of approaching Isky to regrind a cam to this spec. Perhaps they still have the specs or can retrieve them from an archive.

My project is a '49 fast back. The plan is to be outward stock but with period correct hop-up parts and mods. Nothing newer than say '53 or '54.

I am interested in this camspec for several reasons. First is that it's a proven design for the 216 that was sold commercially. Second is that I have read that cams for "road jobs" are best to stay conservative on intake duration and go longer on the exhaust duration -- a dual grind -- not unlike stock. Lastly, the advertised lift on this cam is modest - only .375 at the valve - or .25 at the lobe. This is desirable because I plan is to run 1.7:1 ratio rockers on the intake (Barkers) and I don't want to abuse the springs.

Keith

Keith,

Would that book happen to have any info on Buick straight 8 cams, specifically for the 248 inch, but maybe for the 320 inch as well.
I just had my cam reground to .489 inch lift at valve and 236 degrees @.050 lift duration for both intake and exhaust. I am wondering how this might compare to Isky's specs. I believe the "advertised" duration of my regrind is something like 280+ degrees. Thanks, Mark

For 37 Special:

I have an old Crane cam book from 1970 that lists a lot of now "obsolete" engines. I'd be happy to dig it out and pass on whatever Crane had available for your Buick back then if you would like a comparison on their stuff as well.

For others that are running other vintage engines I'd be happy to do the same.

Mike, I would appreciate that. There's very little info currently available on these old Buick eights. I am lucky enough to have a local machine shop owner who used to build and race these engines back in the day.
He feels pretty confident that I will be able to suprise a lot of V-8 equipped cars with the right combination of torque, transmission, and rear end ratio.
I will be running the factory dual carb manifold with dual TBIs and the factory split dual exhaust manifold.

37 Special, here is what was listed for Buick straight 8 cams in the 1973 Crane Handbook:

M-272-C *Ltd Street / Oval Track, 272 degr; 236 @.050, .437 lift. .016 / .018 hot clrnce

F-302-HI hi rpm, *Drag / Oval Track, 302 degr; 259 @ .050, .516 lift. .028 / .032 hot clrnce.

F-268/380-2-8 CompuCam, *Drag only, 332/342 degr; 268/278 @.050, .570/.580 lift, .022 / .024 hot clrnce.

These are all solid lifter cams and Crane didn't specify engine size at all on that page so I guess all Buick Straight 8's had the same cam dimensions, etc. They also didn't print any recommendations for compression ratios that worked with each grind.

Don't be confused by the CompuCam. This cam had nothing to do with on board computers. It was a model of Crane's profiles that were designed on a computer.

It is noted that all these cams for the Buick are regrinds on your cam. The price was $90 and you could also buy the recommended complete spring and retainer kit for another $50. Now all you have to do is call them and see if they will sell you a regrind and the kit for $140 in 2004 money!!!

Hope this info is of some help to you.
Mike

Thanks Mike. Considering that your info was over 30 years old, that pricing seems really high. I had a place called Cam Technologies grind my cam. The specs look very close to M-272-C grind you mentioned. They charged $165 and that included a bake-on graphite coating to reduce friction.

Hello 37 Special . . .

None of the Isky specs lift as high your regrind . . .

The last page of the book in the "Guaranteed Regrind Cams" section inlcudes an entry that reads:

---------------------------------------------------------------------------------------------------------
BUICK
Parabolic *T23 Full, E2 Track Rev Master, and ** #2 LDB Track
............................................................................................................$ 74.00
16 Chilled Iron Lifters ................................................................................. 31.10
16 Adjustable Tubular Pushrods ................................................................... 40.00
16 Racing Inner Valve Springs ....................................................................... 6.40
.................................................Cam and Recommended Kit.......................$151.50

*Same characteristics as O2A **Same characteristics as Crossflow #2
---------------------------------------------------------------------------------------------------------

The specs for these regrinds are found on page 55 under PACKARD, NASH, HUDSON GROUPS - STUDEBAKER (Golden Hawk):

O-2A.................Timing.....Lift......Clearance........Duration
Intake................12-54...0.385......0.015..............246
Exhaust............. 52-14...0.385......0.015..............246

E2 RevMaster.....Timing.....Lift......Clearance.........Duration
Intake.................18-58...0.42......0.018...............256
Exhaust...............56-20...0.42......0.018...............256

#2 LDB..............Timing.....Lift......Clearance..........Duration
Intake................26-65....0.42.....0.018................271
Exhaust..............64-27....0.42.....0.018................271

The only place I found specs for grinds labeled "Crossflow" was on page 55 under CHRYSLER, DE SOTO, DODGE, PLYMOUTH - IMPERIAL OHV V8:

#2 Crossflow......Timing.....Lift.......Clearance.........Duration
Intake................24-67...0.42.......0.018...............271
Exhaust..............61-30...0.42.......0.018...............271

And did you check out the price? A hundred-fifty bucks was a boat load of money in '56!

No wonder some of these old speed parts are so rare -- how many guys could have afforded to buy them in the first place?

regards,
Keith

Hey Paulweldit . . .

This evening I built a 360 cell spread sheet to model the 'advertised' duration versus the .050 lift spec for the DP #2 regrind. The cells in the spread sheet go from 1 to 360 oriented to TDC.

The intake has an advertised duration of 250.

Based on the valve events documented in the book the model indicates that the valve would open at 345 degrees ATDC (on the exhaust stroke) and stay open until 235 degrees ATDC. Assuming a constant lobe lift of .002 per degree of rotation - maximum lift should occur at 110 degrees ATDC. With 1.5:1 rocker ratio the intake valve is only beyond .050 lift from 1 degree ATDC until 219 degrees ATDC - or 218 degrees.

For the exhaust the advertised duration is 280.

The valve events would occur at 113 degrees ATDC and 31 degrees ATDC. Assuming a constant lobe lift of .0018 per degree of rotation - maximum lift should occur at 252 degrees ATDC. Again with a 1.5:1 rocker ratio the model suggests that the exhaust valve is only beyond .050 lift from 130 degress ATDC until 14 degrees ATDC - or 244 degrees.

These are much more reasonable numbers and lead me to think that this may well be the right cam for my ride.

regards,
stock49

Thanks for all the info, guys. The fellow who did my regrind suggested that I run a manual transmission with this grind, which was my plan from the start. I also will be converting the w/s wipers to electric. This leaves me with the brakes. I originally wanted to use power brakes. The brakes are 10.5 inch GM disks on the front (using '79 Malibu calipers) and 9.5 inch GM drums in the rear (I plan to upgrade to disks someday). I have a concern that I may not have enough vacuum for the brake booster and I do not want to run a back-up electric vacuum pump. Would it be better to run a dual diaphram booster or use manual brakes with a large bore m/c?