I measured the installed height of intake valve spring and it's 0.022" UNDER specification limit. Then I measured the distance from the valve seat on the head to the top of the valve stem tip and compared it to the same measurement on my old head where the installed height was correct and it's also 0.022" LOW - both measurements with the same valve locks and spring retainer to eliminate possibility of differences.
I realize you shim a valve spring when the installed height is too high, but what's the deal when it's too low?
Other than the wrong valves - what can cause this?
I haven't pulled the head off, yet, to actually measure the valve's overall height, but it seems it wasn't ground on the top since both measurements are off by the same amount.
It seems like the whole valve is sitting 22 thousandths low in the head??
Is it anything to worry about if the lifter pre-load works out?
Installed height (also called assembled height) is the dimension measured from the bottom of the outer edge of the valve spring retainer where the outer valve spring locates, to the spring pocket in the cylinder head, when the valve is closed.
Yes, that is what I've measured for installed height. I measured with a telescoping gauge which transferred the measurement to a vernier caliper. I even used a "hardware store" spring to hold the spring retainer completely open while putting the gauge under it.
Valve stem height, off of spring seat was measured with a 1" pipe nipple sitting down over the valve stem and bottomed on the spring seat. A telescoping gauge can then be dropped onto the top of the valve tip and then measured. They make a guage with a dial indicator and a zero'ing block which basically does the same thing.
I guess my question is what would make basically a stock head have a valve spring and valve tip height that is too low - in other words the whole valve and where it seats in relationship to the casting is sitting 22 thousandths low in the head.
When you grind the valve seats, you can push the valve up in the head, and thus you cut the top of the valve and shim the valve spring accordingly, but what can make it sit too low other than the wrong valve?
Also, nothing is sticking in the valve holding it open, the cylinder seals up and compressed air holds the valves open without a problem.
Maybe I'm just paraniod, but I picked the heads up from ebay and I've had valve train noise and trouble since putting them on and it's a case of buyer beware, so I'm questioning everything.
This whole thing is a long story no one wants to hear, so sorry for the long post. I replaced the lifters first with new ones. It quieted it down for the most part. Then the noise came back big time, tore it down to check preload - bleed down tool and all -found #1 exhaust way high in bleed down gap - then checked others and the exhaust's gaps were all higher than spec, but the intakes were within limits.
#1 Exhaust turned out to have a wiped lifter and cam lobe - that's why the gap was so high - bottom of lifter worn away.
In the process of putting new cam, lifters and springs in, I've been checking everything. The heads had unknown valves, springs and retainers installed. So I'm replacing all but the valves (maybe them too until this is done)
In checking for installed height, I find that the intake valves are too low - valve stem is lower than it needs to be - compared to E7 heads that were on the motor, before. The installed height is lower than specs as well - by the same amount - with the E7's I'm comparing too, right on spec.
I checked three more tonight and all of them are 0.019 - 0.022" short. I've been comparing installed height to 89 351W specs, so I checked the Explorer 5.0 specs and they are almost identical to the 89 specs (1.77-1.80) vs (1.78-1.81) I'm in the 1.55 range - too low.
Now I'm wondering if the intake valves are not the stock style valves and are less than the 5.70" specified overall length. Or are the spring retainers and valve locks different for a GT40P explorer motor than for a E7 truck engine?
I should just pull the head and measure the valve's height......
I realize a longer pushrod could take out the difference for the shorter valve tip height, but it might mess up the overall geometry a bit. Aftermarket keepers that are +.050" might raise the installed height of the spring within limit - but I just think something is wrong - these are stock heads that are supposedly equivalent to the E7's in valve train geometry.....
I'm really suspecting the valves as now I find each head had different valve stem seal styles on it! I know better - I should have pulled them apart and checked all this stuff first - so much for the quick bolt on upgrade...
They are GT40P heads. They were new castings, not installed on an engine. Stock bolt down stamped steel rockers. Flat tappet hyrdaulic cam - mild for low rpm torque. No studs - bolt down - so no adjustment other than pushrod length. Springs are stock springs for 1989 351W with flat tappet cam. I'm changing the ones that were on the heads as they had a higher spring rate since they were meant for a roller cam. They were aftermarket springs as they didn't have the exhaust rotators installed like the stock heads.
I'm going to pull the heads off, and take a valve out and measure the overall length to compare to the standard valve for this application. I guess I just don't trust what's there and need to know for sure.
Update - pulled a head off and confirmed the valve is the right one and it has the right overall length. Had a machinist check the valve stem height off the head and it's just barely within limit. He agrees that the installed height is low but it yielded 90# closed pressure rather than 83# at 1.78, so he didn't think it's anything to worry about.
What I did realize is that the person who assembled the heads used non-rotator springs and retainers - both springs the same height, not a shorter exhaust spring like stock. He used the same keepers on both valves and this resulted in a shorter installed height for the exhaust spring than the intake which the keepers were designed for. Don't they make kits with different keepers for intakes and exhausts to let the springs both sit at the same installed height?
I'm installing new springs and hardware, so I'm not re-using any of the old stuff, but now I'm wondering if the 0.10" shorter valve spring put enough additional pressure on the exhaust lobes of the cam to cause the wiped lobe. Assuming linear spring rate it's about 27 more pounds of pressure on the exhaust valvetrain than should have been there.
I just can't see how any of this caused the initial valve train noise....
I checked it before by measuring the bottomed out lifter gap - bleed-down wrench on rocker arm, bottom lifter on base circle of cam and measure gap between valve tip and bottom of rocker. That's how I found the bad lifter, when that gap was way out of range. Also looked for this by scribing lines on push-rod and measuring - not really accurate, though.
With intake off, I can look at lifter and confirm 0.020 when bolting down.
Fordfan, I am going through setting up valvesprings on gt40p heads right now.
with the stock p valves, stock retainers on intake & exhaust.
the intake side installed heights are 1.780-1.790
the exhaust uses a big rotator style retainer, installed heights of 1.590.
I am using a single spring with damper and a one piece retainer. the intake installed height was about 1.780, exhaust ended up at 1.690. I found from crane a set of 7 degree keepers that will allow a + .050" installed height. this put the exhaust at 1.740. on the spring tester, the 1.780 and 1.740 were less than 10 lbs apart, and they were in the 120-130 lbs range. I am using the crane 35-255-2 truck cam(xe254) and they recommend email@example.com. I figure after break in, they will be within a close range.
I do think it is easily possible that two heads have valve seats .020" difference in height. the stack up of shaving, vavle jobs, casting & core shift, etc....
edit: as for your valvetrain noise, if you were using a full height spring with the rotator style retainer on the exhaust there could have been coil bind or some type of mechanical interference....
Last edited by Jeff92f150; 06-09-2007 at 04:59 AM.
Reason: more info
Jeff - that's good feed back to compare my numbers to your numbers.
I ended up with 1.750 installed heights on my intake valves and right on spec for the exhaust valves. So my intakes ended up slightly further "down in the head" than yours. I used factory two piece intake valve retainers and factory keepers. On the exhaust I used the factory style rotators.
The later 351 specs - for 93 and up do permit an an insalled height down to 1.750. 93 wasn't a roller cam yet, but maybe the book meant 94 for the change?? At any rate the 1.750 was only 7 more pounds at installed height, which should not be a problem at all.
I actually just got it all back together yeserday and broke in the cam successfully. The no zinc in the new oil deal made this fun. For what it's worth I used shell rotella T 10-30 with the new CJ spec - I wanted CI spec with 1400 ppm zinc, but Shell assured me that the CJ spec still has 1200 ppm zinc which should be fine for flat tappet cams, according to them. I did use Crane's break in oil addative just to be safe as well.
All is well and I don't seem to have any valve train noise at all now with the new cam, lifters, valve springs and pushrods.
Prior to firing it up, I triple checked the preload on the lifters and all 16 were in spec with three different methods of checking - 1) Hold lifter down on base circle of cam and measure gap between top of valve stem and bottom of rocker - all with in the "preferred limit" 2) Dial indicator showing depth of preload on pushrod end of rocker from time the slack is taken out of the pushrod until the bolt is torqued and 3) Scribing lines on the pushrods to measure depth from unloaded until torqued. All methods showed that the pre-load on the lifters was right where it should be. Also counting the turns from time of contact until torqued yielded the correct amount as well as a 4th check.
What I've now realized is that the person who assembled the heads used the same keepers and retainers on the exhaust and the intake valves with no rotators on the exhaust. This ended up pushing the exhaust springs further down than they should have been adding additional pressure to them. I don't think they were binding as I measured that when this all started. If he would have used the keepers you mentioned, I think it would have been OK without the rotators. It sounds like that's what you're doing with no rotators. I can't believe I didn't notice something that is now so obvious when I put the heads on - I'll never do that again!
It was an exhaust lobe that was wiped out on my cam, so I wonder if the additional spring pressure coupled with springs that were stronger than the specified ones for my cam may have helped do the cam in.
I'm still not convinced I have the whole reason for the problem figured out, but at least it's running without any noise now. I wonder if my cam was on the way out before I even did the head change and all of the above helped it along....
Now I've got to put some miles on it and see how it runs.
Good luck with yours... I used the edelbrock cam that matches their efi intake so it will be interesting to see how it does compared to the old cam I had it in before which was very similar to their performer cam for the carb intake.
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