I SOMEHOW CAN'T FIND MY LAST POST REGARDING MY WOES WITH MY 351C. IT HAD OVERHEATED A COUPLE OF YEARS AGO, BUT I CHECKED EVERYTHING OUT & ALL SEEMS FINE. SINCE IT IS DOWN TO JUST THE SHORT BLOCK I'VE DECIDED ON A CAM CHANGE TO HELP OUT THE 351C. SINCE THE GIANT 4V PORTS REALLY COME ALIVE AT ABOUT 50 MPH I'M TRYING TO GET A LITTLE HELP W/THE LOWER TORQUE. THE MOTOR IS A 70 351C 4V WITH THE SMALL QUENCH CHAMBERS, BUT IT HAS DISH PISTONS(SURPRISE!). THE OLDER OWNER HAD A 2V ADAPTER PLATE ON THE CAR(70 COUGAR)WHEN WE BOUGHT IT, GUESS HE DIDN'T LIKE PUTTING IN PREMIUM ALL THE TIME. WELL HERE ARE THE 4 CAMS GRINDS & THEIR SPECS I'M THINKING ABOUT: 1. ISKY SUPERCAM 262//RPM RANGE 2000-5500, .488 LIFT, 262 DUR, 108 LOBE CENTER, 208 @ .050 3.08-3.70 AXLE RATIO ANY TRANS. 2. ISKY SUPERCAM 256//RPM RANGE 1500-4800, .492 LIFT, 256 DUR, 112 LOBE CENTER, 202 @ .050. STD AXLE RATIO 2.80 OR 3.00, ANY TRANS. 3. COMP CAMS 260H//RPM RANGE 1200-5200, .484 LIFT, 260 DUR, 110 LOBE CENTER, 212 @ .050 4. COMP CAMS 268H//RPM RANGE 1500-5500, .494 LIFT, 268 DUR, 110 LOBE CENTER, 218 @ .050 WHAT DO YOU GUYS THINK OUT THERE WOULD BENEFIT THIS MOTOR? THE ENGINE IS STOCK EXCEPT EDELBROCK 600 CFM CARB. IT HAS BRAND NEW SMALL BLOCK C6, DUAL EXH-STOCK MANIFOLDS, 9"REAR 2.80 GEARS(I HAVE A 3.25 3RD MEMBER TOO). IT'S RUNNING ABOUT 9.5 TO 1 COMP RATIO FROM WHAT I'VE BEEN TOLD. THANKS...
I would contact the cam manufacturers and give them the vehicle specs for assistance in selecting a cam. Would be a great opportunity to convert to a roller cam mainly due to the current oils that are available. Take a look at the port plates from MPG as well www.mpgheads.com/port_plates_a.php
I contacted Comp Cams twice before I bought a cam from them. I gave them all of the specs on my 393C stroker and both times, by different people, the number given to me by Comp Cams was: 32-246-4 / Extreme Energy 274H. I also have the quench heads and forged Keith Black dished pistons but my pistons were chosen to rid the engine of some of the compression created by stroking. I'm still at 10 to 1 with the pistons. I know the cam comes in a little higher in the RPM range but with a 4 speed and also choosing 390 gears, they said I shouldn't have a problem.
I would go with the Isky 262 simply because of it's narrower lobe centers. Both the Comp grinds are really meant for lower comp ratios (8 to 9 to 1) The comp ratio with the quench heads and dished pistons is going to be in the 10 to 1 range, not 9 to 9.5. Your motor would be pushing it with a 268H as far as octane requirements. But that's up to you. If you're comfortable running 89-93, go for the wider LSA cams(110-112 LSA) Or if you're planning on using E85 for fuel. As for the comment about the PO using a 2 bbl in place of a 4 bbl to use regular fuel, that's BS, carb size has nothing to do with octane requirements. The comp ratio, cam choice and ignition timing dictate this. Swapping intakes to an Edelbrock 351C-2V intake will also help as it's got smaller runners than the stock iron intake.
cam options Man thats going to be a hard one !! making bottom end torque with 351c 4v heads lol I would go the 262 with 108 lc and then have the floors of those overkill ports welded in!! or call my bff Bill at redline cams and cranks and have him custom grind the 268h with 107 or 108 lc, He is in Oregon and has great cams and pricing from mild to wild hydr, flat ,hydr roller or retro hydr roller and solid roller he can do them all he actually has all those grinds you mentioned and can set the lc anywhere you or he wants it !! there business # 1-541-967-4187 he is way better pricing than any other cam manufacture /grinder I know of bar none !!
Crap Crap Crap Crap Call Comp or Bullet Racing Cams and have them grind this one for you: Intake: .525" lift; 224 duration @ .050" Exhaust: .550" lift; 236 duration @ .050" 108 c/l Then install it 4 degrees advanced (104) Throw that out in the street and run over it with a truck. Get a good 780 cfm vacuum secondary Holley. Probably need .031 shooters. Jets will probably need to go up four numbers all around. Simple
He may have problems with that much lift and the stock rockers. And the long duration numbers arern't going to improve his bottomend.
You mentioned you had over heated the motor at some time. Did you look to see if the coolent restrictor is still underneath the thermostate housing? If it is gone this could easily cause the overheating especially if you don't have the correct HP water pump. Getting back to you wanting to bring the torque curve down using the 351C 4V heads...................a cam alone is not going to do this, you must increase the velocity of air without restricting the volumn of air going through those huge ports. Maverick1970 certainly gave you the answer when he suggested the MPG flat torque plates, if I were you I'd invest in the intake and exhaust plates before I would ever change cams.....IMHO And whatever you do, don't change to the 2V heads unless they are the closed chamber type...................the open chamber 2V heads will cause more problems with pre-ignition than they are worth. Good luck.
Well the restrictor plate is still there underneath the thermostat. It overheated because we had a small leak from a punctured radiator-small leak that was never taken care of. I do have a set of those port plates, which I'll use, so hopefully that will help some, also going to install a 3.25 gear set I have sitting here, right now it has 2.80 highway gears.
No he won't. Ran that cam with stock rockers in several different Clevelands for years. Single spring with a dampener clears just fine. Those duration numbers are not "long" by any means. Plus, when he advances the cam four degrees the bottom end will shock the crap out of you. :bananaman
