[xllr8]

the problem is that I'm running "186" now and the smaller combustion chamber will give me at least 9.9 compression. I'm not sure of the deck height or gasket thickness but, I would like to avoid going beyond a .035 quench area . Does anyone have any info or past experiance ,dealing with this ?

 

[Busted Knuckles]

I don't think compression is as much of a problem as lift. With the Vortec lift limited to around .460 or so, that cam is probably well over that spec. By the time you have the heads machined for screw-in studs and bigger springs, you're really close to the cost of some Sportsman or Iron Eagles that will both outflow the heck out of Vortecs.

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[flywheel]

xllr8,Chevy Highperformance mag (jan issue) has done a build up of a std. 350 eng. and used some vortec heads and the xe268h cam with .477/.480 lift.They also say the heads work well excess of .500 lift,so they used some 1.6:1 rockers to get more lift out of the same cam.
Check out the last couple issues of CHP mag they got a good article on the build up of the base 240hp crate engine to a 400plus hp small block.\
Rick

 

[TH]

If you'd like a little more info about Vortecs and the related hardware then check out the link below. You can also send me some email and I'll give you even deeper detail. We just screwed this together this summer, so it's all fresh in my noggin'. I can tell you how to do it cheap, or how to spend a little extra. I'm likin' the power out of ours right now.

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Tom H.
Member #259
Indianapolis,IN www.iquest.net/~bharold/chevelle/

 

[L6571SS]

I also did a Vortec motor this summer and all did was get better springs, you can get a set from Crane for less than a $100 bucks that can take more than .500 lift. Watch for retainer valve seal clearance problems with more than .480 lift though.

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JT
71 SS Vortec 355
www.angelfire.com/co/KellyMotorsports

 

[Jimmy P]

I've had ALOT of learning experiences so far.
After porting and installing bigger valves and trying alot of different combinations, here's what worked the best. lightly pocket port the exhaust port and install 1.60 exh valves. Back cut the intake valves. If you mill the heads more than .015 and install .015-.020 head gaskets, you'll have to use legnthened push rods (+ .100 I think) Other rules are: No standard dampers can be used. Buy the springs from Comp Cams or Crane for LT-1 heads for .500 lift. DON'T use regular springs with dampers. Also the spring seats are machined for BIGGER than stock springs. We have used 1.44 springs w/o dampers without problems.Also, if you plan to use the GM valve cover adaptors, you can't run the "stepped up" type of push rod guides. Use the Isky flat types if you are going to use screw in studs which are highly recommended for any cam with lift of over .500. You can safely go to .600 lift even with milled heads and flat top pistons. No worry there. Um....can't think of anything else right now. Good Luck!

 

[Jimmy P]

I've had ALOT of learning experiences so far.
After porting and installing bigger valves and trying alot of different combinations, here's what worked the best. lightly pocket port the exhaust port and install 1.60 exh valves. Back cut the intake valves. If you mill the heads more than .015 and install .015-.020 head gaskets, you'll have to use legnthened push rods (+ .100 I think) Other rules are: No standard dampers can be used. Buy the springs from Comp Cams or Crane for LT-1 heads for .500 lift. DON'T use regular springs with dampers. Also the spring seats are machined for BIGGER than stock springs. We have used 1.44 springs w/o dampers without problems.Also, if you plan to use the GM valve cover adaptors, you can't run the "stepped up" type of push rod guides. Use the Isky flat types if you are going to use screw in studs which are highly recommended for any cam with lift of over .500. You can safely go to .600 lift even with milled heads and flat top pistons. No worry there. Um....can't think of anything else right now. Good Luck!

 

[TH]

I'll go with JT on this one. He and I have VERY similar motors (it's almost creepy---we'll even be running the same rear gears once his are instlled). You can get away with just the aftermarket springs. We used the stock retainers and haven't had any probs with a .480 cam. You need to use either the factory self-aligning rockers or get the heads machined for screw studs. Unless you're gonna get crazy on the motor I'd say save the bucks and find the stock SA rockers for cheap. These heads flow well out of the box, only need to grind some on the short side of the exhaust port.

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Tom H.
Member #259
Indianapolis,IN www.iquest.net/~bharold/chevelle/

 

[xllr8]

Thanks alot for all of your replies ;I've read those articles previously and got the ideas there. My main concern is the 9.9 compression I'll get coming from 68 cc "186" heads

 

[TH]

We run flattops and a steel head gasket. My brother has figured the compression to 10.5:1 or thereabouts (deck been milled). We put 92 or 93 in it and have had no problems with detonation thus far. Vortecs are supposed to like less timing too, which is nice, nothin' like a little detonation resistance.

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Tom H.
Member #259
Indianapolis,IN www.iquest.net/~bharold/chevelle/