Don Terrill’s Speed-Talk

Looking at fitting Bronze guides in an aluminum head. It needs to be done, however the guides available are what I would consider to be "at the limit" as-delivered.

The valve stem is 0.310" diameter, and the guides, as delivered, before installing, are 0.313" diameter as per the supplier. This would give, assuming that the guides are truly .313", 0.003" clearance in the guide. Recommended clearance is 0.0013" to 0.0022", per Del West.

Can I expect the bronze guide to crush down that much on installation? Or is it time to buy bar stock?

Why don’t you install guide liners and then hone them to size?
The other plus of doing it this way is that your Correction valve job will remove far less material which means the valve(s) will sink less so you will drop off less flow and compression.

Who's guides are you using ? What heads are they ? I just looked at a couple of manufacturers and all of the 5/16 guides they show are .509 id so you can size them wherever you want ?

They're LS 862 truck heads, the guides and seats both will need to be removed and refitted due to a LOT of welding being done. The press fits will be significantly distorted after welding and straightening. Once new seats and guides go in, titanium intakes and stainless exhaust valves will be fitted. The new Ti intakes have a 0.310" stem diameter.

The guides are from Straub Technologies, they're local-ish to me and have LS-specific manganese bronze guides at a good price. I also found them from SI valve, and PBM. Straub actually went out and measured a guide for me when I called.

Not sure who's guides Chris is selling. The ones I see in the PBM catalog are either .309, .310 or .3109 ? They don't really list one as being for the LS heads. I don't have one here to measure and I am not sure if they have somebody at the warehouse that can measure them that accurately.

Part of the issue is if you look for an LS specific guide it will be larger because the LS valves are 8mm which is a touch larger than 5/16 Stock LS guides measure .315 and the valves are about .313

I really don't think you will find a guide that can just be pressed in and not fit to the valve.

I think you're right Bill.

I've found some guides from a Jaguar that are the correct length, OD, and are a .312" ID, but I'd rather be around .309 when they go in so I can ream and hone or just hone, if they're close.

I might just buy some bar and make some. They're not difficult, any machinist who pays attention can get a 7x hole straight and true off the drill with modern tooling.

Xnke wrote: ↑Mon Sep 13, 2021 3:46 pm I think you're right Bill.

I've found some guides from a Jaguar that are the correct length, OD, and are a .312" ID, but I'd rather be around .309 when they go in so I can ream and hone or just hone, if they're close.

I might just buy some bar and make some. They're not difficult, any machinist who pays attention can get a 7x hole straight and true off the drill with modern tooling.

What about the ones from PBM ? It looks like the P5512's would work. If you aren't in a terrible rush I can get one in a few days with my next order and measure it for you. What size stem are your exhaust valves ? SBI has a bronze replacement for the LS but it is .315 id. Might be what Chris is selling.

I have a set of new 5/16" bronze guides I was going to use in a set of aluminum bowtie heads, never did. Let me know if you need them.

BillK wrote: ↑Mon Sep 13, 2021 4:12 pm

Xnke wrote: ↑Mon Sep 13, 2021 3:46 pm I think you're right Bill.

I've found some guides from a Jaguar that are the correct length, OD, and are a .312" ID, but I'd rather be around .309 when they go in so I can ream and hone or just hone, if they're close.

I might just buy some bar and make some. They're not difficult, any machinist who pays attention can get a 7x hole straight and true off the drill with modern tooling.

What about the ones from PBM ? It looks like the P5512's would work. If you aren't in a terrible rush I can get one in a few days with my next order and measure it for you. What size stem are your exhaust valves ? SBI has a bronze replacement for the LS but it is .315 id. Might be what Chris is selling.

That one from PBM is the one I was looking at, the P5512. I'd be appreciative if you were able to measure one, although I think PBM will sell directly, if I remember correctly.

Just curious ... what is the O.D. of an LS guide ...?

Walter R. Malik wrote: ↑Tue Sep 14, 2021 8:32 pm Just curious ... what is the O.D. of an LS guide ...?

.500 -.501

Xnke wrote: ↑Tue Sep 14, 2021 8:30 am That one from PBM is the one I was looking at, the P5512. I'd be appreciative if you were able to measure one, although I think PBM will sell directly, if I remember correctly.

I dont think PBM will sell to you if you dont have an account. I will put a couple on my next order and gladly measure them. Might be a few days.

Call PEP in Vegas. they should have it.

Bronze guides need to be undersize, then honed after installing.

I've found they always banana shape.

If you ream after installing the hole gets elongated most of the time

Xnke wrote: ↑Tue Sep 14, 2021 8:30 am
That one from PBM is the one I was looking at, the P5512. I'd be appreciative if you were able to measure one, although I think PBM will sell directly, if I remember correctly.

Just wanted to let you know that I ordered a couple. Should have them Tuesday and I will let you know what they measure.