Technical advice on bad machine work

Buick Bill ,
Yes,,,I can see the gall mark on the valve stem,,,,and your rockers look fine .
They didn’t cause the valve to hang up ,,,,too tight clearance will usually do that .

Tommy

 

i really didnt think it did . but ,im mainly just wanting to make sure i dont have to tear it apart again .the bad thing is the shop , or me cant say this is the cause .and now its fixed . as someone commented working on cars is the nature of our hobby . and im retired so im happy to have something to do every day . but re-do every day is getting old . they are going to ream the guides out a bit more this time . but in real life the clearance shouldnt need to be any wider than factory specs ! im not really happy about brand new sloppy guides ! i spent some time yesterday trying to find if there was another shop in the medford ,or. area that could would surface the rockers . the only other shop i could find open for buisiness said they send them to sacramento . machineing is another on the list of dead or dying trades . i started to drive to redding ca. but its 150 mi each way . so, i talked my self out of the trip !

 

Some of the older valve resurfacing machines also had an attachment for refacing rockers. I had one years ago, but my current one doesn't have that feature. You might ask around to see if there are any older guys with one in their workshop as most commercial shops no longer use them. Car clubs, especially antiquers can be sources of clues.

 

Hmmm, I can see @buick bill grinning when he listens to the "your head is done" voicemail messages the shop leaves for him.

I'd be tempted to stick his 848 head up their ass.

 

im trying to be pissed . but yall are making me laugh !!......

 

Sometimes you can be a victim of “ Stacked tolerances”. Especially today, with cheap parts. Your new guides could have been a bit over sized and/or the reamer dull on installation. The final reamer could have been dull also, and didn’t cut the hole big enough. Add to the fact that the new valve stem might have been at maximum plus tolerance. This combo could have contributed to not enough clearance and causing the valve to stick. Maybe?








Bones

 

Bill ,
Don’t worry about clearance,,,,factory clearance is correct .
In all likelihood,,,,they,,the shop,,,,had it too tight .
I don’t understand why some shops have to have things zero clearance .
A friend many years ago got his block back from being bored,,,,,put it together and fired up .
It started slowing down after about 10 minutes,,,,almost seized up .
He tore it down and two cylinders were trying to gall up .
Had to take back and re hone the block,,,,,polish , smooth the skirts on those pistons .
It was great after that .
Everything requires a little bit of clearance,,,,,to work smoothly .

Tommy

 

I have found new 1 piece valves with as much as .005" runout. I always check the valve/ seat contact with Prussion Blue. I had several valves stick in a 216 Chevy ( several bent pushrods resulted) . When I removed the head I found found a sticky substance all through the intake ports; the ethanol gas disolved the glue in the fuel pump diaphagm and carried into the intake. I rebuilt the fuel pump with an ethanol safe kit. No problem.

 

Hey, Bill;
The old head that had partial fixes done to it, is called... Repair. In the past, what needed fixing got replaced, what didn't, got cleaned up. Nothing wrong w/that process, esp iffen it's a lack of funds, or a need to get things done to use again quickly. Or even that's all that was needed to make it serviceable. As long as that process is explained, agreed to ahead of time, & of course, charged accordingly. There are terms that unfortunately are used interchangeably, but now have actual (legal) meaning when it comes to defining a type of fix.

One major problem w/bad machinework, is that it almost never gets told about, which includes naming the place & do-er, so repeat f'n's to others are almost guaranteed. & some shops go from ok -> lousy, for any # of reasons, but w/o prior notice to either current or prospective customers... ;( . Glad this shop is straightening things out. As you mentioned, too bad it wasn't on the 1st try.
Marcus...

 

I have like 3 shops I totally trust, one has a guy who does heads and nothing else but heads.

 

Why ' reka ?

 

Why Knott?

 

pronounced yrikr . got the head back yesterday . nearly done with the installation . AGAIN...........im adding heat to the intake this time .im sure the cold intake didnt contribute . but i guess it cant hurt . the best excuse the shop could come up with is its running rich . and the gas is washing all the oil off the stem/ guide . RIGHT..............im running a 3/8 copper tube from one header to the plate i made for the bottom of the intake . it should warm things up a bit . cant hurt anyway if you look at the pix you can see that there is a black carbon ? in the combustion chamber . zero smoke from the exhaust . maybe better atomization will help . i just hope the contact between the valve and piston did no perm. damage . if it warms up , ill know soon . 20% here this morning . so , im in no hurry to head outside !!

 

Page 45 here

https://www.mahle-aftermarket.com/m...orkshop/schadensbroschuere_englisch_final.pdf

I'd put a series of pencil lines across the seat 90° or so apart on the valve and valve seat pair that are actually going to be living together. Then manually spin/oscillate the valve as if lapping the valve and seat. It provides a decent indication of valve seat concentricity, valve's seat runout accuracy, location of actual "seat" on valve face and valve seat (there are specifications for that too) , etc and etc. I think it may even be a bit more sensitive than thick abrasive lapping compound. It also doesn't leave the matte gray permanent witness mark that offends machine shops proud of their ground finishes.

I pretty much always include a series of solvent test when the head is assembled, expecting to pass.

Assembled Spring pressure can definitely hide concentricity issues of parts not checked by other means.
There are reports over on SpeedTalk by engine builders that vacuum testing sometimes is not a very strict test. It finds big problems, but may "pass" assemblies that could/should be better.

The valve guide> seat concentricity in a running engines gets pushed out of whack by thermal expansion and uneven temperatures around the seats and guides. The theory that high mileage Aircooled VW. valve breakage is result of the extreme temp differences in the head make a lot of sense.
That does not mean room temp concentricity can be ignored.

 

im embarrassed to admit ive already mounted the head without double checking their work .they SAID all the guides were reamed again a little looser . i believe that the valve was defective or damaged .thats the only thing that makes sense in my mind . they said it was vacuum tested . and some how it does look like it was making full contact at the time of failure . i watched the seat tested and it was right so what else could it be . i guess by not double checking i will be more to blame than them ! only a dumbass does the same thing repeatedly and expects different results . i represent that statement !!.oh well . i need the practice . .....

 

I have to agree with this comment. Pass the word out when asked for advice on a machine shop in your area.
Vic

 

well its runnig again . for how long ! .. scared straight , it took forever to get oil up top . so many bad thoughts . but it got there . turkey/football break . we will see how it looks in the morning !!

 

i got some heat to the bottom of the intake yesterday. i didnt think it would make a difference but my thermo. says it heats up to over 100% almost right away . that should end any atomization problems i cant tell any change in the way it runs. ran good before ,runs fine now .im not sure what could cause the high carbon build-up im seeing . i guess i will have to find a carb. if the head holds up this time !

 

For the last few years I drive 100 miles round trip to a shop with a $300,000 Newen single axis head machine..Because of it's accuracy guide clearances can be tight with no seizure issues. Of course the machinist still needs to pay attention..I had several valve seizures with local shops because they were sloppy with runout even with larger guide clearances

 

150 mi. round trip 6 times ..............................so far ! their excuse is the guides arent getting enough oil , or the carb is to rich , washing the stems