Semi race motor advice

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whitehause
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First Name: Tim

Re: Semi race motor advice

Post by whitehause » Thu Feb 21, 2019 6:14 pm

Is there a rule of thumb when replacing valve guides as far as depth? Got new guides from AR and an 8MM removal/install tool, but I can't find any mention of how far to seat them in the shop manual or CG's book. I can measure the stock iron ones, but I know that bronze can sometimes have a different requirement. I got the air hammer type tool, but I have a press I'll use to install them so I can accurately set the depth. The guides are not shouldered.
fp55scca
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Re: Semi race motor advice

Post by fp55scca » Thu Feb 21, 2019 9:02 pm

--Tim, I sent you this in an email, but I am posting here to open it up for general discussion.

--In GC's first book, he does not address valve guide depth. He merely notes that "guides are pressed from the inside out on removal, and from the outside in on fitting". Book #1, p. 46, fig. 5/12.

--In book #2, p. 166, 5.43, GC states that he uses a "case-hardened tool that locates on the shoulder of the guide and fits the guides to the height I want, without measuring." The assumption is that when the tool meets the face of the spring seat in the head, the guide is at the proper depth. GC does not mention the designation, or the source of the "case-hardened tool".

--If in doubt, measure the height of one of the old guides before removing. It should be noted too, that GC's guidance on p. 57, fig. 5/31 (to shorten guides flush with port roof) is no longer recommended. Doing so, significantly increases wear on the guide due the shorter length. Any benefit is not worth the trouble.
Jim Scurria
Norfolk, VA

1972 Fiat 124 Spider
1971 Spider - SCCA FP-24
1974 Fiat 124 Spider
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SimcaBertone66
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Re: Semi race motor advice

Post by SimcaBertone66 » Thu Feb 21, 2019 11:02 pm

Here is a fun , maybe useless factoid, with regards to valve guides, the chap that modified and flow bench tested the heads on all my TC engines, swears by no valve seals on the exhaust guides…..it's more oil, not less oil ..lol hey it's a race engine .. a bit of smoke when standing still …
Joe DeGasperis
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engineerted
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Re: Semi race motor advice

Post by engineerted » Fri Feb 22, 2019 8:10 am

Tim & Jim there is a drawing for the valve guide install tool in book#1 page 31 i think? I had a tool made up based on that drawing.
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1974 124 EProd race car
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fp55scca
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Re: Semi race motor advice

Post by fp55scca » Fri Feb 22, 2019 9:39 am

engineerted wrote:
Fri Feb 22, 2019 8:10 am
Tim & Jim there is a drawing for the valve guide install tool in book#1 page 31 i think? I had a tool made up based on that drawing.
-------------------------------------------------------
--Ah yes, so it does Ted! Thanks!

--Book #1, p. 32: provides drawings for both a valve guide removal tool, and a separate tool valve guide fitting. As suspected, the depth of the nose of the valve guide fitting tool determines the setup height of the guides. If any doubt, just measure the setup height of the old valve guides being removed.
Jim Scurria
Norfolk, VA

1972 Fiat 124 Spider
1971 Spider - SCCA FP-24
1974 Fiat 124 Spider
whitehause
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Re: Semi race motor advice

Post by whitehause » Fri Feb 22, 2019 12:11 pm

Thanks for all the replies! I'll just measure one of the old guides and use that as a "guide". :D I can mark all the new ones and press them in to that depth. Do you guys freeze them, lube them, both? I also got an 8mm flex hone to cross hatch them a bit for better oil retention as suggested in GC's book.
From the looks of the tool on page 32, it seems like 11mm is the depth he sets them at.
Last edited by whitehause on Fri Feb 22, 2019 9:23 pm, edited 1 time in total.
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engineerted
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Re: Semi race motor advice

Post by engineerted » Fri Feb 22, 2019 12:44 pm

I like to freeze the guides, lube the bore with anti seize and heat the head. put the head in the oven 250 degrees. Do you plan on pressing them in with a Hydraulic press? you will have to fab up some type of fixture to hold the head at the correct angle, (fyi intake and exhaust do not share a common angle). Close, something like 31 and 33 degrees. its in the GC book. I have pressed them in and hammered them in, both methods work well.
1978 124 steet car
1974 124 EProd race car
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mikehynes
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Re: Semi race motor advice

Post by mikehynes » Sat Feb 23, 2019 7:42 am

Take care to make sure you install the guides far enough into the head so that you avoid fouling the valve keepers/retainers on the valve seal.
Two '80 124 Spiders
Lots of X1/9s
Mike Hynes
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