Valve Guide Loose in Head - Options?
Discussion
I dropped off the heads and discussed the issues with the engineer who didn't seem at all phased by the loose valve guide, but he did say:
- That's not a five minute job
- The new valve guide will have to be custom made
- You'll need to replace the Exhaust Valves as the stems have worn so much (I was only planning to replace the Intakes because they've all stretched so much)
- We may find the guides are within spec with new valves
- You should still get the heads skimmed (I hadn't planned to as the fire ring areas looked OK)
227bhp said:
Bloody hell, you must be expensive if you can afford those prices 
No not expensive or we wouldn't have a 10 week waiting list on modded heads! Been at it since 1984 and don't owe any money to anyone, lower running costs as, at 60, I am turning into an old fart 
I tend to spend my money on investing in the business as it is my pension ( as in I cannot see affording to retire!).Biggest investment lately was Dynocom rolling road in 2010, was a risk as recession biting hard but worked out ok as we paid it off in 2015.Superflow used engine dyno slow progress and proving expensive but three of us paying into the project. Just need to have an adaptor plate made to join MGB backplate holes and oil seal to dyno bellhousing. Might even test an engine this year at this rate
Peter
Hey, I worked out the quote tag as well
PeterBurgess said:
227bhp said:
Bloody hell, you must be expensive if you can afford those prices
No not expensive or we wouldn't have a 10 week waiting list on modded heads! Been at it since 1984 and don't owe any money to anyone, lower running costs as, at 60, I am turning into an old fart I tend to spend my money on investing in the business as it is my pension ( as in I cannot see affording to retire!).Biggest investment lately was Dynocom rolling road in 2010, was a risk as recession biting hard but worked out ok as we paid it off in 2015.Superflow used engine dyno slow progress and proving expensive but three of us paying into the project. Just need to have an adaptor plate made to join MGB backplate holes and oil seal to dyno bellhousing. Might even test an engine this year at this rate
Peter
Hey, I worked out the quote tag as well
Ok sit down, i'm pulling your leg, check out a company called Cutwell, you'll cut your reamer costs in half, they sell the measuring tools I mentioned and plenty of other gubbins too.
We used Cutwell to buy a 14 insert 8" milling cutter so we could get a finer finish to ensure Cometic head gaskets do not weep water! Bloody expensive exercise but finish is beautiful and so much faster than old flycutter, terrific metal removal speed, I reckon paying for itself in reduced milling time for each head and has improved productivity. Even had to have a one off drawbar made as old Milwaukee one imperial and new cuitter require metric drawbar!
Peter
Peter
PeterBurgess said:
We used Cutwell to buy a 14 insert 8" milling cutter so we could get a finer finish to ensure Cometic head gaskets do not weep water! Bloody expensive exercise but finish is beautiful and so much faster than old flycutter, terrific metal removal speed, I reckon paying for itself in reduced milling time for each head and has improved productivity. Even had to have a one off drawbar made as old Milwaukee one imperial and new cutter require metric drawbar!
Peter
I think their stuff is really good for the price. What machine do you use for head skimming?Peter
I use nothing but Cometic now, they make good gaskets, but yes the RA has to be right.
We have a Milwaukee H No2 vertical miller, circa 1948 for head milling. The Cutwell tool was the best price we could find and replacement inserts come up on offer bogof etc. Having said that it still cost about £1100 for the tool, adapter to the International taper, inserts and one off drawbar(fabricated locally), the miller only cost around £700 in 1987! Our large tool inventory is: Milawaukee vertical mill, Bridgeport universal milling machine with DRO, Harrison centre lathe, Ward 2C capstan lathe for valve guide manufacture, IDL for seat inserts and guide hole machining ( heads that have cast-in guides), Hobson engraver and a pillar drill.
Peter
Pic of a Milwaukee like ours.
Peter
Pic of a Milwaukee like ours.
ukkid35 said:
I dropped off the heads and discussed the issues with the engineer who didn't seem at all phased by the loose valve guide
Well I would be if a head that bad came to me. I can't immediately see a mechanism for a guide bore to get large enough for a guide to actually rock inside it. What usually happens is the overheated aluminium gets stretched a bit by the pressure of the guide or seat insert but that can't continue until the hole is bigger than what's inside it obviously as there's no pressure acting anymore. Maybe there is more to this than meets the eye and it's the guide that is faulty. As I said before, proper measurements first and save the guessing. Your photos make it look like the guide bore is like 1mm bigger than the guide but I would have said that's impossible.GreenV8S said:
Once it's loose enough for the guide to shift, can't it simply fret away?
If it is retained at the top by step or a large circlip then it may stay where it is and fret rather than drop. i have seen this before where a guide has been pressed out and this has galled / stretched the guide bore and the interference is compromised. In this case the guide dropped and wedged the valve open causing valve / piston contact..Dave
Mignon said:
Your photos make it look like the guide bore is like 1mm bigger than the guide but I would have said that's impossible.
Actually I think that's a fair descriptionI really don't think I have many options as there are no spare AJP8 heads
There were perhaps 2000 pairs made in total, and some of them are 4.2 and some are 4.5, I know they are different, but I don't understand what the difference is
In theory you can junk the AJP8 and fit an LS crate engine, people seem to budget about £8k and then spend twice as much making that work
I am not inclined to do that, and even if I were it would take me several years to be able to fund a conversion
Valve guide hole wear is very common in a lot of Triumph and BSA twin cylinder heads. The guides wear the holes oval, seems the head material is junk and the rocker arm action puts side load on the guide which 'kills' the head casting. Very careful hand reaming with adjustable reamer then make a guide to match, a labour of love almost, and a job we do in spare time to keep costs down. One wonders if it is a common problem in the TVR 'own' engines and to prevent catastrophic failure the guide was shouldered so it couldn't fall all the way through. Maybe the head material is too soft, maybe the head gets overheated and changes to a softer state which lets the guides move/guide holes wear?
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