Cmoney

I am having a engine built using 454 Mag rectangle port heads, the heads have a thousand hours on them. What is your opinion on the valve guides, should they be replaced with bronze guides no matter what?

I am asking because the guy doing the engine said he usally only changes the guides if they are bad. Does this sound right? I was always under the impression that the guides are a high wear part, please help me so I don't get hosed.
Thanks
C

Mbam

Don't replace them, use bronze liners.

formula31

Wow. I have always been under the impression that bronze guide liners were junk. Ive (any most the engine builders I know) say that if the wear on cast guides (clearance) is ok leave them alone. Otherwise replace with bronze guides. Never let them knurl the guides. Mark?

David Stotz

My engine builder does not believe in bronze giudes, especially if you are using other than stock rocker arm ratios.

Mbam

Boy, it has been a while since I really did any engine work, but we used to put bronze on even new heads. I wonder what the current wisdom is?

Make sure your builder has a dial bore guage to measure them, not just the wiggle test. Most of the time used guides are severly tapered.

Too much guide cleareance is ugly, the valve never hits the seat the same way twice.

I will be amazed if the guides are still good with 1000 hours on them.

Smitty

If it helps I just bought new Edelbrock aluminum heads and they have bronze guides. They came with stainless intakes and Inconel exhaust valves.

CIG3

Bronze liners will be fine for most applications. You have to open the guige up enough to get the taper out as Marc suggested. The fit is important. Should be cheaper than solid bronze guides also.

Cmoney

Thanks for the info guys.
But my question is, it possible for the guides to be ok even with 1000 hours on them. I find it hard to believe, but I don't have the experience to make that call. I don't want to tell my builder that he is wrong by leaving them, if he's not.

Whiteknuckle

I went to the same school as formula31. Oh well! Also, I would only expect bronze guides in aluminum heads. CI heads are a different story.

cstraub

Banging out BBC guides can be a nightmare since they are in or close to the water jacket and are prone to leak. OEM guides have taper and if not installed right can leak water. The alternative is to bore out the OEM guide and put a .502" OD bronze guide inside the old guide. This is the way I was taught. We never had any problems with leakage and the bronze gives excellent prevent wear resistance.

Is it possible the originals are ok, yes. Likely, no.

Chris