OK guys, I've been doing some reading and I have a simple question. I have a stock set of 8445 heads that were just redone- new valve job and seals, new valves and a set of Kirban Springs. I'm keeping this build up pretty simple on my 4.1. I'm wondering if I'll have any clearence issues with my cam? My cam is a Comp 216/218 with a max gross valve lift of .485/.489. What do you guys think?
Max Gross Valve lift, Stock Heads
- Thread starter jdpolzin
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Plenty of room, those 8 to 1 pistons have valve reliefs.
You planning on running what thickness head gasket?
BW
You planning on running what thickness head gasket?
BW
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Maybe thats where i went wrong on my 4.1 .040 with hypers.
I only had a 204 214 napa cam, it doesnt have alot of lift to that camshaft.
Already blew mine up.
Once i tear it apart, i will let you know what i screwed up.
BW
I only had a 204 214 napa cam, it doesnt have alot of lift to that camshaft.
Already blew mine up.
Once i tear it apart, i will let you know what i screwed up.
BW
I would think a 257 c.i. motor would need slightly more cam than a 204/214. I'm just starting to play with cams a little more and getting to learn them a little better. It just seems to me that you would need to let that motor breathe a little more?
WarWagon
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Read the reply in this thread. http://www.turbobuick.com/forums/before-black-non-sfi-tech/306555-4-1-n.html
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Its a buick motor, it doesnt matter what cam you have in it. Mild to wild, it just depends on convertor rpm and what power range your looking for. I had a D5 convertor and a smaller than ta49 turbo on it, and ported heads.
Nice power range, could have been wild with larger 66 turbo and 60s, but whats the point, the hypers arent that great of pistons and would have broke it from too much power.
Sucks for me... She is collecting snow right now.
BW
dr_frankenstein
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TurboSpeed
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check you valve guide clearance, I think stock is .455 untill they hit the ex. guide.
TurboSpeed
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+++1 what bison said.
+3 With Brian. We did this same thing a while ago but I don't have the link to the thread. I measured a set of 293 heads and it was either just under or just over .450. The guides will need to be cut down Jeremy. We also had a B4Black guy that tried a .448 lift cam on a new rebuild and kissed the pistons in less than a minute.
The hypers don't have valve reliefs if I remember right. You may just have to much lift.
I'm going to take the heads back to the machine shop and have the guides cut to make sure. Thanks for the info guys.
The Hypers dont have the valve relief cut into them. I'm pretty sre TurboBob has a set of Hypers in his 4.1 with more lift than i do. I'll get ahold of him and see if he had any issues with the valves.
Do you guys really think I'm going to have issues with the valve clearing the tops of the pistons at .489 lift? Loks like I'm going to need to do some measuring. I should be able to rotate the motor over once it's assembled and see if I can hear anything ticking, or will the valve open more while the motor is running? It should right?
Also, wouldnt that indicate that he had some timing out of whack?
If they were dished hypers i wouldnt be to concerned
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I am confused with the last few posts.... What is the max lift you could have with those pistons, felpro 1000's and stock heads?
I had some .040 hypers and a 204 214 cam that had what i thought advertised as .426 lift. Ported and surfaced heads, no issues for 700 miles.
I put 700 miles on it with no issues, and one day it had issues at WOT..
Sounded like a rod cam loose, and then got off the highway and cranked it over and the timing is off, chain may have broke also.
So with the 4.1 and those pistons, so anyone else reading, what is the largest lift cam you can run before you have to fly cut the pistons?
My pistons were dished, stock valves, and its a completely wasted engine with a small lift cam.
BW
I had some .040 hypers and a 204 214 cam that had what i thought advertised as .426 lift. Ported and surfaced heads, no issues for 700 miles.
I put 700 miles on it with no issues, and one day it had issues at WOT..
Sounded like a rod cam loose, and then got off the highway and cranked it over and the timing is off, chain may have broke also.
So with the 4.1 and those pistons, so anyone else reading, what is the largest lift cam you can run before you have to fly cut the pistons?
My pistons were dished, stock valves, and its a completely wasted engine with a small lift cam.
BW
You can do a quick check with some clay on top of the pistons Jeremy. Lorenzo had the block and heads milled just enough to kiss the top of the pistons on 3 pistons. He used a set of hypers as well is why I mentioned it. A .426 and a .489 are .063 different in total lift Bryan, that why I sugested for him to check. Just so he doesn't have an issue. You really need at least a .020 clearance to be good but you can run it closer if you're careful.
Big Turbo Scott
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Lift
!st issue: Put a retainer and locks on the stem of one Int/Exh valve (no spring or locator). With a set of cailpers measure from the top of the seal to the bottom of the retainers or locks whichever gives the smallest measurement. On some heads, the locks hang below the retainer. That measurement must be larger than your max lift plus .040-.060. 2nd issue: Wipe the top of the pistons clean with solvent and apply some clay in the vicinity of the valves if the heads were on. Dab some oil on the clay so that it releases the valves after leaving an impression. Install heads ,with checking springs, with out the gasket. Snug up a couple bolts. Install two pushrods and compress each lifter so that it is solid (or get one solid lifter). Rotate motor. Pull the heads off and measure the last amount of clay left by the valve. If your valves are no closer than .060 to the piston,your guaranteed safe. If not, add compressed gasket thickness. If your still too tight then make changes. HTH!
Scott
!st issue: Put a retainer and locks on the stem of one Int/Exh valve (no spring or locator). With a set of cailpers measure from the top of the seal to the bottom of the retainers or locks whichever gives the smallest measurement. On some heads, the locks hang below the retainer. That measurement must be larger than your max lift plus .040-.060. 2nd issue: Wipe the top of the pistons clean with solvent and apply some clay in the vicinity of the valves if the heads were on. Dab some oil on the clay so that it releases the valves after leaving an impression. Install heads ,with checking springs, with out the gasket. Snug up a couple bolts. Install two pushrods and compress each lifter so that it is solid (or get one solid lifter). Rotate motor. Pull the heads off and measure the last amount of clay left by the valve. If your valves are no closer than .060 to the piston,your guaranteed safe. If not, add compressed gasket thickness. If your still too tight then make changes. HTH!
Scott
Some good reading here. I brought the motor back to Chicago to have the cam bearings replaced again (they narled up the rear installing the first set, good thing I checked it). They are also going to cut the guides down to clear a .510 lift cam. I did actually read up on valve to piston clearence and ran across he clay trick (or playdough!) and will be checking it as well!
The Hypers are dished pistons, but I think it owuld be a good idea to check this anyways. I wonder how long of a duration on the exhaust side would allow the piston to actually hit the valve? The intake valve should never be open to hit the piston at TDC right?
The Hypers are dished pistons, but I think it owuld be a good idea to check this anyways. I wonder how long of a duration on the exhaust side would allow the piston to actually hit the valve? The intake valve should never be open to hit the piston at TDC right?
