I need help selecting a cam, I wiped a lobe on my current cam, a comp 294S. The car had too little vacuum, and poor idle. I'm mostly interested in a less radical hydraulic flat tappet, I just want something reliable with decent idle until I make further changes to the car. Car is a 1971 corvette, 4 speed (m20), I think the rear is 3.08 could be 3.36, appx 3200 lbs, .040 over 350, 1.5 roller rockers, patriot 190cc heads, hooker 1 7/8 sidepipes, LT-1 intake, 4150hp 750cfm holley. Valve springs are comp 986-16, if I can keep these installed that is preferred, but I can change them if needed. Thanks.

ETA: compression is around 10:1

 

Im going to assume cubic inches are 350. So so so many options, but given the rear gear I wouldnt get too wild. Comp cams has a free program called camquest that you can download and play with for hours. Naturally it only includes comp grinds, but its still kinda fun. Personally Id go with a 270s, but you want hydraulic. Something like a 268H off the top of my head would probably be nice, but Im sure there is something better

 

If you could afford it, hydraulic roller would beworth the extra money and you dont have to worry about a wiped lobe. Plus the lifters are reusable. What compression ratio are you running? There is a therory floating around basicaly stating that much past a xe 268 with modern oil and a flat tappet raises the odds of wiping a lobe.

 

Have to know compression ratio

 

That said this is a good cam if your under 10 to 1, works with your springs.
http://www.summitracing.com/parts/cc...make/chevrolet
With these lifters.
http://www.summitracing.com/parts/HRS-91116/ Nitrided cam with edm lubed lifter is the most durable you will get in a flat tappet. That said I would still go roller.

 

An "old school" easy on the valvetrain style cam ?

You don't have much gear, (as was mentioned already), so I'd keep it at /or under 224* on the intake and use a split pattern if that's what your heads need.

Better compare the reccomended springs for a new cam to those Comp springs.

That said, the 275DEH Comp cam lists the 986 springs as the upgraded spring above their 981 springs. This is in the "Dual Energy" line of cams and the only old school slower ramp cams in my 2002 catalog.

275/277 adv. , 219/229 @ .050, .462/.482 lift , 110* LS

..or Lunati Bare Bones 280/290, 214/224, 443/465, 112* LS $110.92 with lifters. Excellant throttle response and drives great with 3.08 gears.

Checkout some of the older Isky grinds too.

...just a couple...

 

It's easy to imagine why you didn't like the 294S on a 350 with 3.08 gears,..plus the 1-7/8" header tubes,..

Do you plan to keep the highway gears?

 

Bore is 4.04, pistons are flat top cheapo cast and they are slightly below the deck at TDC, didn't measure how far, I would guess .015-.020. I plugged all the numbers into my calculator and came up with 9.9:1, but I could be off a little one way or the other due to not knowing the exact depth in the hole and how many cc's to subtract for the pistons, I used 6cc dish in my calculator.

I'd put a roller in, but I would hate to spend the money only to grenade that cam due to crap floating in my engine from this cam and I don't have the money to have it torn down and rebuilt now. Plus, I plan to ditch the 3.08's, but that is far in the future. So, what I really need is a cam that will work with what I have now until I have a place to work on my car and put it together the way I want. I sent Isky an email to their tech support asking for their recommendation. Mechanic recommended a 284 comp hydraulic cam, 284 extreme energy I'm guessing, which seems like it might be better than what I have now but not sure if that is best for my gears. My oil apparently came out clean, so now I'm wondering if the cam was flat the whole time, it never ran great and swapping heads accomplished almost nothing.

Another question, I had to put longer pushrods in when I swapped heads to get the roller witness mark centered across the valve, if I swap cam and lifters, will the pushrods I have still be correct? How do you check the pushrod length with a hydraulic lifter? Have to pull the springs and put in checking springs on the valve?

 

Also, the lobe that was found to be flat was #5E. When I swapped the heads I ran it with the covers off and one of the #5 pushrods wasn't oiling. I can't remember which now though. I eventually took the intake off, pulled the lifter and found that the hole didn't go through and that lifter never oiled. I drilled the hole all the way through, re-installed, forgot to lash and ended up running the engine for about 30s with one or maybe both #5 valves with maybe .250" lash. I shut it off, realized my error, lashed and started it up again. My question is, did I wipe the #5E by running with excessive lash for only 30s? If I did, shouldn't there be a lot of metal in my oil/filter? Could the pushrod not getting oil cause an issue, I didn't think it would, I could see the rocker or pushrod wearing excessively, but the cam lobe I would have thought wouldn't have been affected?

 

284 cam is to big. The one I mentioned is almost to big but with your wide ratio 4 speed it will be good to go with an 1800 to 6000 powerband. With a 268 and your compression I would be worried about detonation with your cheapie pistons.

 

Thanks 63mako

 

63, tried to order the cam you recommended, but it won't ship until 1/21, how about this:

http://www.summitracing.com/parts/cc...make/chevrolet

 

Ditto on the 284 its too big you wont like it ran that one before.

 

The XE274H is not a bad cam; you could also try the XE268H which is a bit shorter but still on 110 deg lsa.

Even better might be the Comp N+ L79 Nostalgia Plus Hyd Camshaft which is 229/236 on 112 deg lsa which will be more friendly to your needs. It will have a larger power band and better vacuum.

 

Same cam no nitriding. In my world and if I were you after a wiped lobe I would do all in my power to avoid it happening again. I would wait the 2 weeks and spend the extra $100.
I almost posted up the Nostalgia plus cam above. If you don't want to wait on the nitrided version I would order the L79 nostagia plus because of the reduced lift and slightly milder ramp being easier on parts.

 

Check out Howard's hydraulic roller cams, there good for a budget minded roller. Did you cut the filter in half and inspect for metal? As far as checking push rod geometry if you use the same exact lifter the geometry would be the same, other wise use checker springs and recheck them. For the 9.9 to one or so maybe the xe 274 h for a flat tappet. I've never wiped a lobe but would imagine the chance for wiping another lobe with the flat tappet would increase greatly with any metal shavings floating around the engine from the last wiped lobe.

 

Found the nitrided cam at amazon and ordered it. I'm in a hurry because I'm not swapping the cam myself, and if my mechanic needs the space I'll have to have the car towed. Supposed to be here monday, hopefully I don't need to tow it. Thanks for the help and recommendations. I haven't cut the filter open, not sure if it matters now, can't afford to tear it down, not sure I even want to know.

 

Good choice, make sure you post back on how it runs and make sure there is plenty of moly based cam assembly lube on everything, grease it up well. Pre lube, 20 minute break in, break in oil, drain and refill with high ZDDP oil after break in. Take all the precautions and you should be fine.

 

Got it back today, runs ok, not a monster by any means but I guess you can only expect so much with 3.08s. Idle seems better, maybe a little more vacuum than before. I think it needs some finer tuning, it stumbles if you floor it, even if out of gear, backfired through the exhaust a couple times under moderate acceleration. Once it's moving it does start to pull pretty decent, but my tach is disconnected and I don't want to flog it too hard right now. Anyway, thanks for the help.

 

Sounds like timing issues. Make sure your mech and vac advance are working and your vacuum can is correct for the new cam. Email lars and get his timing papers.