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vortec head modification for .480 lift

20K views 34 replies 7 participants last post by  ap72 
#1 ·
Yes I have searched all over and I don't know what needs to be done to clear a .480 lift cam. Idk what that would cost either, so maybe some guesses? Thanks these are going on my 400 sbc.
 
#27 ·
cobalt327 said:
I'm guessing "89" is the cost.


My take on the retainers is that, yes- they are used w/8mm valves. But as long as the ID of the retainer (where the locks sit) is the same as the retainer for the 11/32" valve (we know they're both 7º), the retainers will work fine- provided you use the 11/32" locks and not try to use the 8mm locks.

This question also came up in THIS thread, although it was never really answered. But if my theory isn't correct, Spin would have surely dropped valves by now- provided that he has actually run this engine.
I'm pretty certain the ID is reduced for the smaller valvestem diameter, it is on all aftermarket 8mm retainers I can find, AND it is on the stock LS retainers. You could assemble it with 11/32 locks and incorrect retainers, it would just drastically reduce your installed height.
 
#28 · (Edited)
It's hard to tell exactly, but looking at his photo below (from the thread I linked to above), the top of the locks do look to be protruding a bit more than usual from the 3100 retainers. If that is the case, the ID of the 3100 retainer may be smaller and this will reduce the I/H of the spring- but I don't know what the 3100 retainer design will give for an I/H when used on the Vortec head, w/11/32" locks. For all I know, the 3100 retainer and the 11/32" locks might have a combined I/H of 1.8" or more- I can't tell from Spin's posts what's up w/that.

But- in ANY event I would have serious reservations using a set-up that didn't provide full engagement of the locks into the retainer's ID. I'd like to have a 3100 retainer and locks to measure. Just by looking at the 3100 locks should show easily if they're the same or thicker than the 11/32" locks- which they'd have to be (thicker that is) to work on a 8mm stem, yet have the same OD as a 11/32" lock.

It looks like what may be needed here, is a lock designed for the 3100 retainer's ID and the 11/32" valve stem's OD- unless that would make the locks too thin to be stable.

 
#29 ·
Summit makes a number of headers, coatings , etc. Clearing up, that these are the basic $89 buck headers for a 85 gm truck.

The inside retainer dia must be the same from votx retainer to v6 retainer, or work with the v6 locks. There might be an extra retainer somewhere, if found the measurements will be posted. The seal part number is not on the reciept, but will post that when it comes to light.

For posterity my crap measurements are saved. My spring measurements could not be repeated every time. My tools are junk.

free length 1.94"
Installed at 1.8 they were about 95lb seat and open 275 at .500
Installed at 1.6 it was 125 and 305

To clear up , the safe running lift is not 1/2" , the seal is going to touch. Lifts of .450-.460" cleared on votex heads with seals.
 
#31 ·
spinn said:
Summit makes a number of headers, coatings , etc. Clearing up, that these are the basic $89 buck headers for a 85 gm truck.

The inside retainer dia must be the same from votx retainer to v6 retainer, or work with the v6 locks. There might be an extra retainer somewhere, if found the measurements will be posted. The seal part number is not on the reciept, but will post that when it comes to light.

For posterity my crap measurements are saved. My spring measurements could not be repeated every time. My tools are junk.

free length 1.94"
Installed at 1.8 they were about 95lb seat and open 275 at .500
Installed at 1.6 it was 125 and 305

To clear up , the safe running lift is not 1/2" , the seal is going to touch. Lifts of .450-.460" cleared on votex heads with seals.
So your installed height with the 8mm locks and retainers was 1.600" Or is that 11/32 locks and 8mm retainers? Comp makes the proper retainer to run those beehive springs on a 11/32 valve stem with 11/32 locks, its like $65 a set for the retainers though. the tool to cut the guides down for better seals and reduced height is only $50, I bought one and have used it several times. A tap set can be picked up at Harbor Freight for like $20 (cheap but it works). Then you only have to buy shoulderless screw in studs and a Z28 spring kit to run a mild flat tappet cam with no worries. I've done that routine on a BUNCH of heads (usually i use better springs though) and it works great for a mild street engine.
 
#32 ·
spinn said:
Installed at 1.8 they were about 95lb seat and open 275 at .500
Installed at 1.6 it was 125 and 305
This would be a 360 lb/in rate.

This is very close to the Comp Cams spring p/n 26981. Seat 110# @1.7", open 292# @ 1.175 (0.525").

My question is why would GM this spring on the 3100? Maybe it's because of the redline of this engine. Or a tall installed height... Anyone know what the installed height is on the 3100? Or the redline? :confused: I know the redline of the '09 Impala 3.5L is 6400 and will rev higher.
 
#33 ·
cobalt327 said:
This would be a 360 lb/in rate.

This is very close to the Comp Cams spring p/n 26981. Seat 110# @1.7", open 292# @ 1.175 (0.525").

My question is why would GM this spring on the 3100? Maybe it's because of the redline of this engine. Or a tall installed height... Anyone know what the installed height is on the 3100? Or the redline? :confused: I know the redline of the '09 Impala 3.5L is 6400 and will rev higher.
I'm pretty sure its 1.800".
 
#34 · (Edited)
Run hard, whats that. It is drivin . The vehicle takes my scooters out by my brothers' kids for a blast. That is about 100 miles round trip. It does burnouts and the wide open downshifts that kick nice. Using a phone device with GPS an app for testng performance, claimed sub 16 quarter at 88 mph. To take it to a track is big money, and all the test and tune days are gone. Byron, Rt 66 ,and great lakes are busy, and have no time for my messing around. For the admit you might get 2-3 runs. This has been together many months.

The keeper/locks are stock from the vortec 906 heads. If someone works at a yard or parts depot, measure the v6 series 2 valves, that will tell if it is really 8mm or 11/32 .

GM advertised spring rate of 330-365lb/in depending on the .

Is sinking the spring seat the good way?

Did not mean to steal the thread.
 

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