had my 215 oval ports freshened up this season, along with the rest of my engine. i needed guides real bad. my machinist installed bronze guides, i just put the motor in the car , filled all the fluids and the exaust guides are leaking. i did'nt even fire the car yet. can this be fixed or are the heads junk?machinist says he will install new ones and use sealer this time.i guess the exaust guides go thru water.
i'm really bummed out because these heads are fully ported with 2.25 /1.88 valves and have netted me 11.20's at 121mph. not to mention the 1200 dollars i have into them .any ideas? thanks ray

Originally posted by mr68:
had my 215 oval ports freshened up this season, along with the rest of my engine. i needed guides real bad. my machinist installed bronze guides, i just put the motor in the car , filled all the fluids and the exaust guides are leaking. i did'nt even fire the car yet. can this be fixed or are the heads junk?machinist says he will install new ones and use sealer this time.i guess the exaust guides go thru water.
i'm really bummed out because these heads are fully ported with 2.25 /1.88 valves and have netted me 11.20's at 121mph. not to mention the 1200 dollars i have into them .any ideas? thanks ray =
Ray,
Hopeflully whoever did the heads is aware the top part of the exhaust guide is larger than the lower side & drove it out the correct direction.
If not removing the guide the wrong direction will "broach" the lower hole & cause a water leak with the new guide.
It can be repaired but you will need a guide that is the larger diameter for the whole distance.
I had some a few years ago but cannot recall where I purchased them from.
If this is the problem email me & I will try to find where I purchased the guides from unless someone here happens to know??

Wolf, is it just the exhaust guides that are tapered? I took out an intake guide from a 1967 215 head and it was within .0002". I've read several places about the Big Chevy guides being tapered, but wondering if its just exhausts, or is it year specific?

Originally posted by Wooderson:
Wolf, is it just the exhaust guides that are tapered? I took out an intake guide from a 1967 215 head and it was within .0002". I've read several places about the Big Chevy guides being tapered, but wondering if its just exhausts, or is it year specific? =
Just the exhausts. They aren't tapered they are stepped, actually larger on the top
About 1985 or so GM in it's infinite wisdom actually switched ends on some heads so the larger part was at the bottom :confused:
The size difference is .004 as I recall which is just about right to still go through the head & do a nice job of "broaching" (read screwing it up) it to the larger size if you remove it or install it the wrong direction.

Ray,
I think that Perfect Circle / Clevite might have a bronze exhaust guide that is .002 oversize. I know they used to, but its been a while since we used one. We always use sealer (Permatex "Indian Head") on exhaust guides when installing them. Never have had one leak.

thanks for the reply gentlemen. i'm going to bring this information to my machihist today.
i'll bet he did'nt know about the stepped exaust guides. i'm very releived. thanks again, ray

There is something out there but I have lost the part numbers. In the old days we were running factory alum. heads. They would actually pound the alum around the guide so the guide was loose. The only fix was an oversize guide but I don't remember what it fit.

The guy at EPD who use to do most of the Pro Stock stuff said that if you ever pushed the guide out of a G.M. Aluminum Head to go drop them in the nearest trash can as they will never hold a valve job afterwords. However i'm sure the same isn't true for the iron heads. I think oversized valves or bronze liners would have been a better idea than changing the guides. A guy named Rothhammer (918-582-4773) here in Tulsa repaires heads all the time and i'm sure could answer any questions you might have about any repairs.

I just had a problem where I broke a valve guide in a big block head. It did some damage to the hole. My machinist said no problem. He drilled it and installed a sleeve and stock size guide. He told me I shouldn't have any problems as hes done them before. I haven't run the motor yet, but hopefully all is well.

Mike

talked with my machinist today. he said he knew about the stepped exaust guides and assured me he removed them and installed them in the correct manner. he again installed new exaust guides and this time he used a sealer that he says they use at navistar. they are being pressure tested this week , i should know by tues if they are ok. he said that this has only happened to him once before to only one guide and sealer corrected that guide. it makes me wonder why he did'nt install sealer to the guides in the first place. he will have to kiss the seats again so they will run in line with the new guides.thanks ray