Vortec Max Lift (Warning!) [Archive] - Chevelle Tech

: Vortec Max Lift (Warning!)


hd99fxst
Oct 8th, 04, 9:52 AM
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. graemlins/clonk.gif 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. smile.gif 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. graemlins/clonk.gif

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. :mad: 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 graemlins/beers.gif ,
mark.

New68SS
Oct 8th, 04, 10:38 AM
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.

Wolfplace
Oct 8th, 04, 2:42 PM
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.

d1_bradley
Oct 8th, 04, 3:26 PM
This is why Pace and others sell Vortecs that have been modified for higher lift.

TH
Oct 8th, 04, 5:15 PM
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.

pdq67
Oct 8th, 04, 7:07 PM
Take about .100" off the bottom of the retainers... Then check the keepers installed to make sure everything fits...

pdq67

jakeshoe
Oct 9th, 04, 6:00 AM
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..

hd99fxst
Oct 9th, 04, 9:38 AM
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.

Wolfplace
Oct 9th, 04, 4:29 PM
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 (http://www.sdpc2000.com/cart.asp?action=prod_detail&catid=3539&pid=9063)

fijiman
Oct 11th, 04, 3:02 PM
Any verification of the LT4 springs, LT4 retainers, and umbrella seals combination to alleviate the problem?

New68SS
Oct 11th, 04, 3:20 PM
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.

Pat Kelley
Oct 13th, 04, 2:52 AM
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.

TH
Oct 13th, 04, 1:46 PM
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.

pdq67
Oct 13th, 04, 10:24 PM
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."

pdq67

jakeshoe
Oct 14th, 04, 3:05 AM
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.

hd99fxst
Oct 14th, 04, 9:23 AM
Some digging turned up the following:

GM 12551483 LT4 Springs 1.337" OD, .906" ID, 101# Seat, 333 #/".
GM 10212808 LT4 Spring Retainer, individual
GM 12495492 LT4 Springer Retainer, set
GM 12495494 LT4 Spring & Retainer Kit

Crane 10309-1 Valve Spring & Retainer Kit. 1.255" OD, .87" ID, 409#/". (About $150, several places online.)

Competition Motorsport CM614 1.26" OD, 110# @ 1.8", 325# @ 1.2"
Competition Motorsport CM613 1.26" OD, 130# @ 1.8", 360# @ 1.2"
Coil bind on both at 1.150". Advertised as good to .600". Both kits include chromemoly retainers and hardened locks. About $100 for the kit.

Anybody here tried the CM stuff? Several good posts about them on the impalassforum.

Cheers,
mark.

New68SS
Oct 14th, 04, 10:16 AM
Can someone explain why anyone would want to grind the retainers or machine the spring pockets or towers when you could use a set of LT4 springs and retainers and be done with it?

http://www.sdpc2000.com/catalog/3533/products/2005/LT4-SB-Chevrolet-Valve-Spring-Kit.htm

Can be had for about $50.00

jakeshoe
Oct 14th, 04, 1:00 PM
Yes, I can explain.
Unless you go to a longer valve, you will still run into retainer to guide clearance problems at lifts above about .500".
So the LT4 kit is not a a FIX. just because they fit doesn't mean they allow clearance.

Trial assemble a Vortec head soemtime and check the retainer to guide clearance with an LT4 retainer...

Wolfplace
Oct 14th, 04, 2:31 PM
Originally posted by New68SS:
Can someone explain why anyone would want to grind the retainers or machine the spring pockets or towers when you could use a set of LT4 springs and retainers and be done with it?

http://www.sdpc2000.com/catalog/3533/products/2005/LT4-SB-Chevrolet-Valve-Spring-Kit.htm

Can be had for about $50.00 =
And to add to what Jake said, I posted this link previously but here it is again.
Vortec Heads (http://www.sdpc2000.com/cart.asp?action=prod_detail&catid=3539&pid=9063)
Read the description of what they do when installing the LT4 retainers,
That's why I posted the link the first time so you could read their installation procedure.
They do not just stick the spring & retainers on they CUT THE GUIDES.

Or in simpler terms,, when all else fails, read the instructions :D

fijiman
Oct 14th, 04, 2:49 PM
Is the machining of the guides only for .500" lift and higher or anything over stock. I am planning on putting a .470" lift cam and I am starting to worry about how much extra problems may arise out of doing so. Can someone clear this up for me? Also, if the guides have to be machined down, how far do they need to go?

Wolfplace
Oct 14th, 04, 2:59 PM
Originally posted by fijiman:
Is the machining of the guides only for .500" lift and higher or anything over stock. I am planning on putting a .470" lift cam and I am starting to worry about how much extra problems may arise out of doing so. Can someone clear this up for me? Also, if the guides have to be machined down, how far do they need to go? =
Will,
With anything over .450 you should check the clearance between the bottom of the retainer & the seal.
I have seen some that would hit at .450-460 & some that would clear to .490.
I flowed a new set a while back & had to remove the seal to get to .450 on the bench.

blumont
Oct 14th, 04, 3:09 PM
When I had my vortecs first done for my 350 ,the guides had to be machined down for a .454 lift

New68SS
Oct 14th, 04, 3:34 PM
Originally posted by jakeshoe:
Yes, I can explain.
Unless you go to a longer valve, you will still run into retainer to guide clearance problems at lifts above about .500".
So the LT4 kit is not a a FIX. just because they fit doesn't mean they allow clearance.

Trial assemble a Vortec head soemtime and check the retainer to guide clearance with an LT4 retainer... Ok, now I see what you mean. I am runnin .454 lift and guess the retainer to guide clearance was fine.

jakeshoe
Oct 14th, 04, 4:55 PM
I've ran Vortecs with Vortec retainers, Z/28 springs with the damper removed, and .525" lift with NO cutting and still had room for the positive style valve seal.

But at .525 lift the retainer would JUST touch the seal. Deduct .018" valve lash and you got .018 clearance ;)

pdq67
Oct 14th, 04, 8:57 PM
I know Jake, I'm just passing info on...

And I'm really "shade-tree" too!!!

pdq67