i have a 355 non roller it has 4vr flat tops,vortec heads, rpm air gap intake,its goin in a 3000lb car, auto with 3000stall i bought a comp 292h but im having second thoughts its 501/501 lift 244/244 @.50 could someone point me in the right direction of a flat tappet hydraulic cam that would make decent power im guessing the compression is right around 10.1 if you need more info ill try my best to give it thanks


oh and by the way im looking for straight line performance,not sound,not drivability,not a fuel sipping cruiser, i want to go 1320 feet as fast as the rest of my setup will let me

 

Unless you do work to change the springs ; stock Vortec springs are only good for .480 lift

 

yep.

Have you modified those vortecs at all?

 

The vortec heads could take advantage of longer duration on the exhaust side than the 292H has. 8 - 10 degrees more than the intake is about right. Lift is fine, I think the vortecs top out at about .550. A good valve job will help flow a lot. The XE274 from Comp Cams is a great cam for the 355,You would still be wise to have the guides cut with it, but it would be perfect with the Performer RPM, should flow enough for the vortec heads to 6500, a sweet idle at 800 rpm and crazy at 650! The compression is good for the cam too. I had one in a 305 then a 355. Gotta say, probably very close to the optimum cam for a good breathing 355. Not saying Comp is the only vendor making a cam like this. I've always had a solid appreciation for Crower's cams, Lunati is also a fine brand. What I'm getting at is the lift, duration, lobe centers, lsa and all are right about where they should be.
the 292h might be a bit long in overall duration and not a split duration cam, but it wll live a good bit longer than one of the XE series due to the lower acceleration rates on it's lobes.


Setting your timing correctly will make all the difference in your performance!
I'm assuming you aleady have a non computer HEI distributor? Get a centrifugal advance kit from Jegs or Accel (they come with new bushings). Make sure the centrifugal weights are moving freely on their bushings (use the original weights if they're not too corroded), replace the orignal springs with one silver and one blue spring (doesn't matter which side they're on). Disconnect the vacuum line that runs from the distributor to the carb and plug it at the distributor end. Set the static distributor timing to 32 degrees at 3000 rpm. warm the engine up with a nice 20 to 25 minute idle with an occasional mild rev, or better yet a 25 minute cruise, double check the static timing. Make a few full throttle runs in high gear at moderate rpms (like 2500- 4500) and keep an ear out for vibration or detonation rattle (ping). If you get a rattle, back off 2 degrees till it stops, then 2 more. you can adjust the static timing at idle after the inital setting. Re attach the vacuum line and take a test drive. If you get a rattle on steep hills, back off the timing 2 degrees at a time til it stops, then another 2 degrees.
I highly recommend an adjustable vacuum advance canister as well. If you use one, remember the little allen screw in the vacuum canister works backwards, you screw it in all the way, then back it out until you get detonation, then screw it in 2 turns. i find 10 turns out to be a good starting point. Adjustments can be made 2 turns at a time to get you dialed in.
This procedure should be repeated after any cam carb or intake swap.
advancing or retarding the cam is also a good way to make it work with your combination, but the changes might be less noticeable.
Eric B

 

with my stock heads, the way the seal to retainer clearance measured out, .550 lift would not be achievable. I didnt even go to .525. It is recommended .050" retainer to seal. I would definately cut the guides.

 

Its not just the springs. The clearance between the valve seals and the retainers is the first issue. Put a valve in, then the retainer and keepers, just without the spring. Carefully measure how far the valve can travel. Be extremely accurate here. Take the lowest of each of your exhaust and intake numbers, subtract a reasonable safety margin (some people say .060 I went a bit closer with only 20 or 30) and thats your max intake and exhaust lifts. Biggest cam I was able to go with was the lunati voodoo 60101 with like 469 on exhaust. One of them was like 495 with zero safety margin.

Yes vortecs like more cam on the exhaust than the intake because the in flows much better than the out. Too bad it also seems the max possible lift was lower on exhaust than intake on mine at least.

Springs are another issue entirely. Stock springs I hear are too weak to prevent float with anything bigger than low to mid 400s so if you're just under max lift, you'll still need to replace springs. And of course if you mod the valve guides for more lift and use a huge cam, you also need to worry about coil bind.

 

Or

http://www.alexsparts.com/products/V...AT-TAPPET.html

 

when i mentioned vortec heads topping out at about .550 lift i was referring to flow, not valve guide to retainer clearance. sorry, i should have been more clear there. guide to retainer clearance should be checked with any cam over .460 lift, also if 1.6: 1 rockers are used as that increases lift as well.

 

yeah I mistook you on that one. Dont they start to drop off flow wise at .490???


Even with the spring and retainer change I did, I still couldnt have run a .550" lift. Even with the set that is linked Id still measure them all. I just dont see how they can advertise that much with that kit. I wonder how much safety they are factoring in.

 

having your guides cut is relatively cheap insurance and will give you easily .550 lift capability provided your springs won't bind. i would always recommend using your cam manufacturers suggested springs! for the xe274 it's the 981-16 set, stock diameter so you don't have to cut the spring pockets. any bigger cam in the xe series requires bigger diameter springs. plan your valve train very carefully to avoid having to remove the heads after everything is running! it sucks to find your cam floats the valves and you have to pull your brand new motor apart to have the spring pockets cut!

 

my heads are worked so i can run up to .570 lift and im running spring to match the 292 cam i ran a 274xe cam in a previous build with vortecs and was not at all pleased with the performance im not a professional or any thing but i figure the heads start to stall around.500 so i dont need to be much over but i dont want to leave nothing on the table either thats why i went with the 292h cam i may just run the 292 and maybe 1.6 rockers on the exaust like i said iv got plenty of room between my retainer and seal so .534 with a 1.6 on the exaust plus the tiny bit of added duration shoudnt be a prob thanks for the help

 

What is your rear gear ratio?