a 355 with the XE274 cam, im thinking of throwing vortec heads on it and a supervictor vortec manifold, 750 carb and headers. im just wondering if you guys think thats a good combo, if not please tell me what you think is with the 274 cam. and also if you have a combo close to this, what is it and what are some of your numbers

thanks

mike

The RPM range for the super victor vortec manifold is 3500 - 8000. That cam will poop out long before that. Put in a performer RPM vortec and you'll never look back.

Agreed w/ the RPM Manifold, a much better choice.

To make a proper choice on Cam and Cylinder head, especially with the compression sensitive vortecs please post your pistons and compression ratio.

I am close to pulling my engine for a complete overhaul, since the damn thing burns 1 quart of oil every 60 miles! I have been looking at the xe274h, and upgraded vortecs from scoggin-dickey, rpm air gap. I've got a 650VS holley, my engine is a 4 bolt block, probably will be 030 over once machined, I was thinking of getting the summit rebuild kit with speed pro forged pistons P/N TRW-L2256F30 (summit). They claim it will be 9.72:1 @ .020 in the hole...I assume that is with the head gaskets suppied in the kit. Wil it really be 9.72:1 and will that be too low for the xe274? Also if anyone can do the math, or knows, what would the compression be with a zero deck? Thanks for any help! graemlins/beers.gif graemlins/beers.gif

Do a search, didn't someone do back to back testing of the RPM vs. Victor with vortec heads? I remember the results being very close, with a little quicker times from the victor with out any real changes in driveability.

Steve

68malibu:

Assuming those pistons have 6cc valve relieves they will come out to 9.72 when you use a 64cc head and a 4.03 diameter head gasket with .041" thickness.

With a standard deck height of 9.025" those pistons will be .022" down the hole and with that cam you will have a DCR of 7.87. You will have a quench of .063" unless you deck the block or use a thinner gasket... that might or might not be a bad thing... it really depends on a lot of other stuff too.

Onabudget,
Please tell me what do you mean by that the vortecs are compression sensitive?? I thought the heart shaped fast burn chambers made em less sensitive for detonation because they run best with a smaller amount of total advance (around 32-34 degrees - instead of the 36-80 degrees which is commonly used in Small Block Chevy mills... Vortecs dont like pistons with domes though. Please explain what you refer to?
Thanks
Matt

Originally posted by BruteSBC:
a 355 with the XE274 cam, im thinking of throwing vortec heads on it and a supervictor vortec manifold, 750 carb and headers. im just wondering if you guys think thats a good combo, if not please tell me what you think is with the 274 cam. and also if you have a combo close to this, what is it and what are some of your numbers

thanks

mike I guess these guys got a little off track from your original question. :rolleyes:

To help you out a little bit you can look here (http://www.chevelles.com/forum/ultimatebb.php/topic/4/17068.html#000000) on an old post I made. It's a 383 so a 355 will be a little slower.

Rod

I'd go with the RPM manifold. A 274 cam doesn't need a single plane.

Originally posted by torquemaster:
Onabudget,
Please tell me what do you mean by that the vortecs are compression sensitive?? Thanks
Matt OK, I'll try.
Lets take a 350 with flat top pistons, put just about any performance type cam in it and a set old old camel humps and you'll almost never have any pre-ignition problems. Sorta like and 'old school' small block build. No problems.

Take that same 350 and slap a set of vortecs on it, paired with a 262ish cam, and you will probably have some pinging issues, but up the cam to a 274 and it might work great... or put in a dished piston to lower the compression and the 262 will perfrom good as well. The vortecs burn great, but this effects other issues that are way over my head.

I believe it has to do with the SCR v. DCR along with cylinder pressures and the speed of the burn in the vortec design combustion chamber. I don't understand all this stuff, but maybe Pat Kelly can describe what I'm trying to say a little bit better.

Pat appears to be the resident expert on this issue.

I was thinking about running around 10 CR and use a 274 cam or similar in a 383 engine. Do you guys think there will be any problem with the Vortecs??
Matt

For 10.0:1 a 270º cam is about the smallest cam you'd want to use and still run pump gas. For 10.2 a 274º cam. For 10.5 a 282 cam. Smaller than these and you may run into problems with pump gas. I'm not very familiar with vortecs but I understand they like less advance than conventional heads. That might be what onabudget is getting at.