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Edelbrock head valve question

beanhead

Straining The Limits Of Machine And Man
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A friend (formerly ford guy...he's been turned!) just picked up a notchback barracuda with a mildly built up 383. It runs pretty good but there is a slight rpm lope at idle with a little shake, like it's loading up somewhat. For a ford guy by birth he's pretty good with carbs and tuning so he's been checking with no change. Stock rocker setup on the Eddys with a comp 280H cam. Not real bad but we don't think it should be doing it. We were looking at the pass. side head and when I layed a straightedge across the valves the #8 exhaust was sitting about .060 lower. Problem? Valve not getting the proper movement? If so does he need to yank it and install a longer valve or is a trip to the machinist in order. Or a lash cap on that one maybe? Thanks for input guys
 
X2 on testing it, maybe something is wrong with that valve seat. I had an issue where only the exhaust side got new seats which left me with intake valves that were .090 higher than the exhausts
 
He said lower guys. Aluminum heads with seats, I would be concerned that the seat was falling out. Early production 4.7 and 5.7 heads had this issue, so I have seen it and fixed it a few times.

With higher valves due to wear sinking the valves, shorter pushrods and valve spring shims are cheaper than 8 more seats. I have only had one customer do all 16 seats in a FE head. Best repair is all new seats, but shorter pushrods are acceptable.
 
Maybe a bent valve?
I thought maybe, but they all spun and moved very smoothly by hand


Compression test/leak down test.
Did that this afternoon..150 to 158 not bad. Approx. 5000 miles on the rebuild

He said lower guys. Aluminum heads with seats, I would be concerned that the seat was falling out. Early production 4.7 and 5.7 heads had this issue, so I have seen it and fixed it a few times.

With higher valves due to wear sinking the valves, shorter pushrods and valve spring shims are cheaper than 8 more seats. I have only had one customer do all 16 seats in a FE head. Best repair is all new seats, but shorter pushrods are acceptable.
Thanks..these 84cc Edelbrocks have about 5000 miles on them, he understandably doesn't want to pull them and take them to a shop if he doesn't have to. Being relatively new I would hope it's not a wear issue, but we did find the other head has one lower valve also...I will pass this info along and we'll go from there. I want to help him figure it out so he doesn't relapse to the dreaded blue oval haha
 
Alrighty then just after I typed that last post, I got a phone call. He was checking pushrods on a piece of mirror glass and found a few that were slightly bent. Now, this doesn't necessarily solve the low valve stem issue but I told him that we need to get the checking pushrod in there and measure and get the right lengths... Probably going to be putting in a call to the Smith Bros soon...
 
Maybe try to measure from the top of the valve stem to the retainer or lock on the higher valve and compare to the others. Try to compare the installed heights.

I know on my build that the exhaust keepers touched together and it had my retainers sitting lower than the intakes. Installed height wasn't right either. I ground each set of keepers so there was a gap between and that brought the retainers up even with the intake ones.

The exhaust keepers are designed to touch so it lets the valve spin, helping with carbon removal. It will also wear on the grooves and keepers so I elected to gap them so they hold tight like the intakes do.
 
Maybe try to measure from the top of the valve stem to the retainer or lock on the higher valve and compare to the others. Try to compare the installed heights.

I know on my build that the exhaust keepers touched together and it had my retainers sitting lower than the intakes. Installed height wasn't right either. I ground each set of keepers so there was a gap between and that brought the retainers up even with the intake ones.

The exhaust keepers are designed to touch so it lets the valve spin, helping with carbon removal. It will also wear on the grooves and keepers so I elected to gap them so they hold tight like the intakes do.
Good stuff there thanks!
 
Edelbrock heads use single groove locks...... no valve rotation.

If the valve tip height is really .060 lower on the one valve....... that would be a lot.
It’s not likely(but not impossible either) that it came from edelbrock like that.

I’d do a leak down test to verify it doesn’t have a bent valve.
 
Edelbrock heads use single groove locks...... no valve rotation.

If the valve tip height is really .060 lower on the one valve....... that would be a lot.
It’s not likely(but not impossible either) that it came from edelbrock like that.

I’d do a leak down test to verify it doesn’t have a bent valve.
If it was bent it wouldn't slide straight and easy through the guide though, right? With the spring and hardware removed it drops right down, spins nice and looks straight. Compression was good on that cylinder, wouldn't the leakdown show okay too? He did talk about getting a tester over the weekend so I think he's gonna do the test also. (The height difference measured .030 with a feeler gauge by the way--sorry the .060 was a bad approximation:rolleyes:)
 
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Most of the time when a valve gets “tagged” by the piston, it results in the head of the valve getting knocked out of square with the stem.

Unless there was pretty heavy contact, the stem is usually still nice and straight.

While .030 tip height difference is better than .060....... they’re usually better than that from Edelbrock.
That’s not to say it couldn’t have been like that right ootb.

The chances are extremely low that the valve is too short.
If it’s a screw up from Edelbrock, the most likely scenario is the seat wasn’t cut to the correct depth.
 
Maybe a bent valve?

Like everyone said, check compression/leakdown for a bent valve. If the 383 was rebuilt with the flat top pistons without valve reliefs (I think the SpeedPro Forged L2315) it is easy to bend valves if the engine is over-reved. I did that on my 383 with stock heads and a cam about the same size.
 
"slight rpm lope at idle with a little shake" huh? Wonder why?

From the Comp Cams catalog.............."noticeable idle in 383"...........and that is for the 270H cam.

Now when you add another 10 degrees advertised and 7 degrees at .050, what are you going to get?

I don't know, my thinking is probably wrong......................again.
 
"slight rpm lope at idle with a little shake" huh? Wonder why?

From the Comp Cams catalog.............."noticeable idle in 383"...........and that is for the 270H cam.

Now when you add another 10 degrees advertised and 7 degrees at .050, what are you going to get?

I don't know, my thinking is probably wrong......................again.
Yeah you sure have a history of being wrong especially on valvetrain stuff! :D:D:D seriously though it's not the nice 'lope' you expect from just the hotter cam it was more an inconsistent stumbly idle, more so when warmed up. Cleans up okay with rpms. I really thought carb issue but he rebuilt and tuned it then discovered the bent pushrods..maybe the last guy got '3' and 'N' confused we'll see.
 
Edelbrock heads use single groove locks...... no valve rotation.

If the valve tip height is really .060 lower on the one valve....... that would be a lot.
It’s not likely(but not impossible either) that it came from edelbrock like that.

I’d do a leak down test to verify it doesn’t have a bent valve.
Edelbrock heads use single groove locks...... no valve rotation.

If the valve tip height is really .060 lower on the one valve....... that would be a lot.
It’s not likely(but not impossible either) that it came from edelbrock like that.

I’d do a leak down test to verify it doesn’t have a bent valve.

Continued excellent insight.
 
Most of the time when a valve gets “tagged” by the piston, it results in the head of the valve getting knocked out of square with the stem.

Unless there was pretty heavy contact, the stem is usually still nice and straight.

While .030 tip height difference is better than .060....... they’re usually better than that from Edelbrock.
That’s not to say it couldn’t have been like that right ootb.

The chances are extremely low that the valve is too short.
If it’s a screw up from Edelbrock, the most likely scenario is the seat wasn’t cut to the correct depth.
Thanks this makes sense. Since it's two valves out of 16 maybe there was slight contact, rods are bent on other cylinders as well so at this point he should pull the heads to really see what's going on. No big deal(header removal is a joy right?)
 
On a b body, it’s not that bad, a body is a bitch. But if ya need an extra hand, just let me know and I’ll come help.
 
Thanks Zack appreciate the offer, between him and I we'll get 'em out. Yeah A-bodies right? I think the bug's already bitten this guy. We were chatting a bit ago and he was like well if I have to pull the heads, I might as well pull the engine, and if I'm going to pull the engine maybe I'll price stroker kits and machine work and new parts...And on and on. He'll drive it until winter (fresno winter lol)
 
Fall Fling in Madera on the 29th. I’m trying to get stuff squared away to go, you guys might want to look into it. It’s only a half day, but a good show.
 
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