Warning... Chevy take...

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J

j par

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Customers car... Rebuilt 400 small block dart cast iron heads.. 220 or so duration, 500 or so lift.. Holley dp.. supposed to have hydraulic roller lifters.. rocker girdle..
So previously we oil pressure up and ran it on an engine engine stand and timed it. We put it in the car started it and it sounded good of course with open headers. He took it to have exhaust put on it and we drove it and everything was driving pretty good. We installed dual AF gauges that were reading 12.5.. a little Rich but it was running good so I just wanted to re-time it and read the plugs...
Previously took it on a small ten mile drive a little freeway a little town and it was running and reacting good. I went to rev it up a bit to check all in timing and it seemed like the rockers work clattering so bad that I just wasn't comfortable holding the RPMs up like that. My customer at first thought it was a rod knock but it really felt like clattering up top. So we took the driver side valve cover off took and the valve girdle.. the driver side loosening till they clatter and tightened 3/4 of a turn after clatter.. seemed to quiet that side down a bit but not totally. Went to the driver side did the same thing but I remember I had him do the second side so he would get some experience and when he let the number six intake and exhaust valve clatter and he would tighten it past the half a turn it would chug the motor down? So he left them at a half turn so the engine would stay running. at this point the engine still idling fine seemingly and we put the valve covers and the girdles and all that stuff back on... Start the car up and it runs like crap. RF gauges are at 15, 16 and 17? It baffles me that a valve adjustment could make the car run lean??? I checked fuel filter and it seemed clogged just a small bit but not really bad. I take the front window screw out of the Holly float bowl and it seems correct. I put it back in. I take the back one out and my customer says the af gage moved back down? I put it back in and now the gages are at 14-15? car is poppin like it has a lean issue and running rough... I'm going to go back Sunday and we're going to start with a cold valve adjustment and work from there. I almost want to think there's a collapsed lifter? Also how can any of this make the car run lean?...
anyways opinions are welcome, and it's nice to get it off my chest a little bit anyways. We'll get back at it on Sunday and get it fixed. Looks like no day off this weekend to work on my own stuff...
Thank you for anybody's help... I'll take all ideas into consideration for sure. Isn't that what this forum is for? Well maybe not Chevy stuff but cars stuff LOL general discussion... Thank you...
 
Burnt, chipped, or seized valve on number 6? The bog when adjusting would scare me, bending pushrods at that point? If the exhaust valve isn't sealing there it could cause a lean read from the af gauge.

O2 sensors don't read fuel, so a misfire can show up as lean...
 
Phreakish said:
Burnt, chipped, or seized valve on number 6? The bog when adjusting would scare me, bending pushrods at that point? If the exhaust valve isn't sealing there it could cause a lean read from the af gauge.

O2 sensors don't read fuel, so a misfire can show up as lean...
Click to expand...
I never did like the way that valve train sounded... To the owners discredit he let it set for three years before firing it. Lord knows. I don't have a world of confidence in the engine rebuilder he had took it to either. I've seen his work before and was not impressed. Well I was impressed but not in the way we want to be LOL.
It really sucks because you know we were driving it around and everything was happy happy but when you listen to the engine itself it did not sound super happy. And then to have to leave today and not have it running the way I would like it to really was stressful... I was figuring since it's has the same firing order as my Mopar I would just use my Mopar adjustment chart and figured that would be perfect??..
Screenshot_20200530-153257.png
 
missing linc said:
Popping back through the carb would suggest exhaust valve not opening, sbc are famous for wiping cam lobes on exhaust valves.
Click to expand...
It was more popping out the exhaust I didn't hear any popping in the carburetor. Again with it running at 12 5 the whole time and then all of a sudden 16 5 - 17 5? This is af gages were installed and calibrated today...
 
Same firing order should be the same adjustment order. It wouldn't run great if it was fubar from the jump.

If it was popping in the exhaust, that kind of supports a leaky exhaust valve - whatever the cause. An engine that sat 3 years could have lots go wrong... A tight valve guide with dried lube could cause trouble in a hurry. So could an inexperienced wrench adjusting lash on a running engine (your customer, not you). He could have loosened first and let the lifter pump up, then tightened and hung a valve open? Do it for long enough and the valve won't be long for this world..
Broken valve spring(s) would be another thing to rule out.

At any rate, I'd pull the rockers and valve springs from #6 and check to see if the lifter plunger moves and whether the valves can spin free in the guides. Using compressed air to hold the valves should also help find out if the valves are sealing in that cylinder.
 
Phreakish said:
Same firing order should be the same adjustment order. It wouldn't run great if it was fubar from the jump.

If it was popping in the exhaust, that kind of supports a leaky exhaust valve - whatever the cause. An engine that sat 3 years could have lots go wrong... A tight valve guide with dried lube could cause trouble in a hurry. So could an inexperienced wrench adjusting lash on a running engine (your customer, not you). He could have loosened first and let the lifter pump up, then tightened and hung a valve open? Do it for long enough and the valve won't be long for this world..
Broken valve spring(s) would be another thing to rule out.

At any rate, I'd pull the rockers and valve springs from #6 and check to see if the lifter plunger moves and whether the valves can spin free in the guides. Using compressed air to hold the valves should also help find out if the valves are sealing in that cylinder.
Click to expand...
My suspicions are a collapsed lifter? loose from the beginning and pounding on each other. But again I have to get back to it with a fresh brain. We kind of got on to it later in the afternoon and it was getting hot and we were of course burning our hands on the damn thing. I was watching him pretty closely and jumped in there a little bit myself just to make sure that what I was seeing was correct. We weren't doing anything crazy... We weren't in any rush to do something stupid. But again who knows from the beginning and we are human so there's always that. LOL..
 
That's the weak link: being human, LOL

A collapsed lifter would just be noisy though. Tightening the lask until it slows down signals the valve is hanging or there's suddenly a lot of resistance to rotation.

Could be a lot of things, but until you have some indicator of what it's more likely to be, everything about #6 is suspect. I'm not familiar enough with chevies to know how hard yanking the intake is to get at the lifters for a close exam, otherwise that might be the first thing I'd do. But checking springs, rockers, and stem tension/clearance are so easy they might as well just be ruled out right away.. At least that's how my tiny brain works.

Hell, could just be a burnt wire or plug or distributor problem! The noisy valve train may just be leading away from other potential causes - I know I've done it plenty of times.
 
It won't hurt to stop now and leak down the cylinders... It's easy and will clarify if there is a mechanical problem unless you have tight guides. Is it changing after it goes through a temp cycle?

JW
 
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Was it broke in b4 it sat 3 years? If not the cam is likely going flat. The miss on that cylinder and popping kinda confirms it. That could explain why anymore than 1/2 turn bogs it down. Hope not. Kim
 
My costumer found the girdle was to low and the rockers were hitting it...
Was back to running well, but still noisy..
I'll be able to look into it more tomorrow..
IMG950995.jpg
 
Head looks dry in the picture. Top end getting much oil?

Sitting 3 years, hydraulic lifters may have gone to **** (admittedly a long shot). Any suface rust that got swept up in the oil could plug the passages in them, plunger springs could get weak from sitting fully compressed for so long, etc.

SBC parts tend to be cheap, I might be tempted to just replace the lifters proactively.. Stupid tax for leaving a fresh engine to sit for so long ;)
 

Phreakish said:
Head looks dry in the picture. Top end getting much oil?

Sitting 3 years, hydraulic lifters may have gone to **** (admittedly a long shot). Any suface rust that got swept up in the oil could plug the passages in them, plunger springs could get weak from sitting fully compressed for so long, etc.

SBC parts tend to be cheap, I might be tempted to just replace the lifters proactively.. Stupid tax for leaving a fresh engine to sit for so long ;)
Click to expand...
I'm working on even a better solution...
I'm talking him into getting a Mopar..:thumbsup:..
 
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