Vortec Max Lift (Warning!) - Chevelle Tech
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post #1 of 25 (permalink) Old Oct 8th, 04, 8:52 AM Thread Starter
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Don't try this at home...

Here’s what happened when I ran a Competition Cams Comp Magnum 270H (.470" lift) on a set of stock Vortec heads. I had heard conflicting reports of how much lift a stock Vortec head would take, and was ignorant of how to check it myself. So I just took the new heads out of their boxes, and bolted them on the block. [img]graemlins/clonk.gif[/img] I also used Rhoads lifters – a pretty small cam for the Rhoads, but in a heavy car with highway gears I was after all the torque I could get. Ran great, once I got the ignition timing straightened away to eliminate the pinging. [img]smile.gif[/img] Some folks had told me any lift over .460" could be trouble, others said I would be OK up to .480". So, I gambled… and lost. [img]graemlins/clonk.gif[/img]

Shortly after rebuild, I found metal when I changed the oil, the #1 exhaust valve kept ticking (loose lash, even after being reset several times), and the motor started smoking. I guesstimate less than 5k miles total before the motor was pulled for diagnosis.

Photos and results at http://home.kih.net/~markj/id14.html

Any feedback / advice welcome.

Sorry for the link -- couldn't figure out how to post pictures here.

Cheers [img]graemlins/beers.gif[/img] ,
mark.
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post #2 of 25 (permalink) Old Oct 8th, 04, 9:38 AM
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I'm runnin the LT4 springs on my Vortec heads with a smaller .454 lift cam.

Those springs dropped right in without any machining on the pockets or towers. Good to .525 lift.

Good luck with the '51 P/U. I love em ole trucks.
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post #3 of 25 (permalink) Old Oct 8th, 04, 1:42 PM
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Quote:
Originally posted by New68SS:
I'm runnin the LT4 springs on my Vortec heads with a smaller .454 lift cam.

Those springs dropped right in without any machining on the pockets or towers. Good to .525 lift.

Good luck with the '51 P/U. I love em ole trucks.
=
The spring may well be good for .525 lift at the correct installed height but the problem is not the spring it is retainer to seal/guide interference.
This has nothing to do with what spring you run.

Anything over .450 lift should be checked on Vortec heads that are stock,,, no exceptions.

Mike (Wolfplace)
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post #4 of 25 (permalink) Old Oct 8th, 04, 2:26 PM
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This is why Pace and others sell Vortecs that have been modified for higher lift.
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post #5 of 25 (permalink) Old Oct 8th, 04, 4:15 PM
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I used to have a part number for a retainer that would give you, oh, like on tenth of an inch more room if you needed it when running a hotter cam on Vortecs.

It must be luck of the draw. We have run a .480 cam for three or four years now with many drag strip runs and have had no problems.

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post #6 of 25 (permalink) Old Oct 8th, 04, 6:07 PM
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Take about .100" off the bottom of the retainers... Then check the keepers installed to make sure everything fits...

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post #7 of 25 (permalink) Old Oct 9th, 04, 5:00 AM
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I've heard of people grinding the bottoms of the retainers off, I say they are absolutely playign with the wrong end of the barrel.

You can buy a cutter for less than $50 to reduce the diameter and height of the vortec guide boss.
Then run .500 or .533 positive seals and have LOTS of room.
AND use a nicer cheaper spring setup.

All you need is a half inch drill, the cutter (avail from Comp, Crane, Competition products) and a reamer...)

Takes 5-10 minutes on a set of bare heads..

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post #8 of 25 (permalink) Old Oct 9th, 04, 8:38 AM Thread Starter
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I was hoping to get back on the road without pulling the heads. (Swapping springs, modifying retainers, etc. on the block.) Can it be done this way?

Tom -- Are the special retainers you mention for more lift, the same as are usually paired with the LT4 springs? I would love the part number, if you come across it.

I was told LT4 Springs, LT4 Retainers, and umbrella seals would get me to .525" (more than enough for my current plan.) Is this right?

Is there a downside to cutting the guide boss (other than having to pull the heads)? Does shortening it make the valve less stable?

Happy to post so others can learn from my mistake -- thanks for not kicking me while I'm down. Yeah, I screwed up...

Cheers,
mark.
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post #9 of 25 (permalink) Old Oct 9th, 04, 3:29 PM
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Quote:
Originally posted by hd99fxst:
I was hoping to get back on the road without pulling the heads. (Swapping springs, modifying retainers, etc. on the block.) Can it be done this way?

Tom -- Are the special retainers you mention for more lift, the same as are usually paired with the LT4 springs? I would love the part number, if you come across it.

I was told LT4 Springs, LT4 Retainers, and umbrella seals would get me to .525" (more than enough for my current plan.) Is this right?

Is there a downside to cutting the guide boss (other than having to pull the heads)? Does shortening it make the valve less stable?

Happy to post so others can learn from my mistake -- thanks for not kicking me while I'm down. Yeah, I screwed up...

Cheers,
mark.
Mark,
First I agree completly with Jake, you do not want to cut the bottoms of the retainers.

Now,, go read this:
Vortec SB Chevrolet Cylinder Head w/ Valve Spring Upgrade

Mike (Wolfplace)
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post #10 of 25 (permalink) Old Oct 11th, 04, 2:02 PM
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Any verification of the LT4 springs, LT4 retainers, and umbrella seals combination to alleviate the problem?

Will Stewart
'71 Malibu, 383 ci, Vortec heads 280H cam, TH400/2400 stall converter and 10 bolt/3.73 gear and Eaton posi
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post #11 of 25 (permalink) Old Oct 11th, 04, 2:20 PM
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Quote:
Originally posted by fijiman:
Any verification of the LT4 springs, LT4 retainers, and umbrella seals combination to alleviate the problem?
That is exactly the comnponents that I used.

No problems, no machining.
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post #12 of 25 (permalink) Old Oct 13th, 04, 1:52 AM
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I don't know if this is accurate but I suspect that the guide height is not considered a critical dimension by Chevy. So the height can be anything within a pretty wide tolerance. That's probably why some heads can take .480" lift and other only .450" or so. Most likely the heads are designed for lift in the .420" or less range. If they provide adequate clearance for a stock cam, Chevy is happy.

Pat Kelley
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post #13 of 25 (permalink) Old Oct 13th, 04, 12:46 PM
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Sorry I did not check in on this again. The person who gave me the part number said that they had access to dimensions on these parts, and had simply picked one from a catalog that had the proper dimensions.

I will look back through my emails to see if I can find the number. It may take a good deal of looking. Sorry I don't have it readily available.

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post #14 of 25 (permalink) Old Oct 13th, 04, 9:24 PM
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I saved this form "DirtReynolds".

"You will love the Vortecs on a 400. Incredible torque and overall power. I bowl ported mine, and did some minor work in the runners. At a minimum, fully bowl work the exhausts, as they are the only real weak point on the Vortecs. You can use the stock intake and exhaust valves (which are back-cut from the factory) and the stock first-rate factory 3-angle valve grind. I came within a whisker of an 11-second pass in the heat of July running Vortecs on drag radials with a cheap Crane Blazer 234/244 hyd. cam. I ground off 3/16" off the bottoms of the factory retainers for retainer to guide clearance, and used Crane stock diameter valve springs."

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post #15 of 25 (permalink) Old Oct 14th, 04, 2:05 AM
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Paul,
While Dirt did a good job of making a budget Vortec combo work well, his grinding of the retainers is not soemthing I would even suggest...

I would rather see a person take a hand grinder to the top of the guide boss on the head, then chamfer it with a reamer, than do that.

There is no reason to grind on a component as critical as a valve spring retainer when you can do it correctly (and more easily, repeatably) with a $45 tool.

If you alter the temper of the retainer, cause a stress riser, go too far and the keepers come through the bottom, anything.. It just cost you a motor over a $45 investment that you can re-use over and over again.
I've done at least 10 sets of heads with my cutter. That works out to $4.50 a set so far...

I would buy it and then re-sell it for half the cost than take the risk of grinding a retainer.

It is like looking down the wrong end of a loaded gun..

Of course there are always those that say, well it worked for him. Good deal..

I'm one tightwad sucker and in that scenario I'd be dishing out the cash one way or the other to have the HEADS machined.

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