67 tripower & clutch question

[Gary S.]

A friend recently purchased a 67 427/390 that has been converted to 435 tripower and I am clueless about these despite a couple of hours reading searches here.

1. His clutch linkage is adjusted to the very last set of threads on the clutch push rod and he still grinds a bit in gear. While he does have extensive maintenance and repair records going back over a dozen years there isn't any mention of clutch replacement. Years ago when i rebuilt my 66 Joe L (I think) suggested Luk clutch and throwout bearings for my L79. Are they still a "go to" clutch? The GM Heritage Center download says he should have a 14" flywheel and 11" clutch. Can a heavily worn clutch cause that much clutch rod positioning? I also very vaguely remember that there was a tall and short throwout bearing and one was appropriate for the Corvette but the other one was not. I cannot remember which is which. Any help on the clutch and throwout bearing?

2. The car runs really well with the tripower but the center carb (3660?) is leaking quite a bit at the fuel fill line going in to the carb. It looks like the entire fuel line assembly for the three carbs needs to be loosened in order to pull the large nut off and replace the gasket. Is that correct?

I am still searching and gathering information on this and I do appreciate the help.

Gary

[Larry M.]

Re: 67 tripower & clutch question

A friend recently purchased a 67 427/390 that has been converted to 435 tripower and I am clueless about these despite a couple of hours reading searches here.

1. His clutch linkage is adjusted to the very last set of threads on the clutch push rod and he still grinds a bit in gear. While he does have extensive maintenance and repair records going back over a dozen years there isn't any mention of clutch replacement. Years ago when i rebuilt my 66 Joe L (I think) suggested Luk clutch and throwout bearings for my L79. Are they still a "go to" clutch? The GM Heritage Center download says he should have a 14" flywheel and 11" clutch. Can a heavily worn clutch cause that much clutch rod positioning? I also very vaguely remember that there was a tall and short throwout bearing and one was appropriate for the Corvette but the other one was not. I cannot remember which is which. Any help on the clutch and throwout bearing?

2. The car runs really well with the tripower but the center carb (3660?) is leaking quite a bit at the fuel fill line going in to the carb. It looks like the entire fuel line assembly for the three carbs needs to be loosened in order to pull the large nut off and replace the gasket. Is that correct?

I am still searching and gathering information on this and I do appreciate the help.

Gary

Gary:

LUK and McLeod Street are both excellent choices. The problem with replacement clutches is that the pressure plate on many does not open up far to fully release the clutch, resulting is grinding.........especially into reverse. Friend may also have mismatched linkage pieces. You should check these as well. Archives have part numbers and dimensions, etc.

Intake is more likely the 400 HP intake and not the 435 HP intake...........as the 390 HP and 400 HP shared similar oval port heads. Part number will confirm. Can't help on the fuel leak, except to say do not use stainless tubing, only TWB coated steel. It seals better. Tri-power looks cool, but has its own special problems regarding leakage.

Larry

EDIT: Corvette C2 clutches are raised finger diaphragm type, and take the short TO bearing. Flat face diaphragm for passenger cars took the long bearing.

[Mark F.]

Re: 67 tripower & clutch question

Gary,

Comments on your #2: before disassembling the 9 fittings on your tripower fuel lines, try using your swagelok wrench to see if gently tightening them at the carb will eliminate your leak. When I reassembled my top end many years ago, I also had a leak @ the center - but it was at the flared end/seating surface of the fuel line going into the carb body.

Also, if you do have to eventually remove the entire fuel line "spagehetti" mess", try not to re-tighten down any one of those 9 fittings all the way at first (3 @ the carb and 3-each at each of the two brass blocks). If you lock one of those in place, that one segment will be stiff compared to the rest and the entire assembly of blocks and lines can get cockeyed - making leak-free alignment/tightening at other connections more difficult. PS - 3660 is the center carb for a non-K19 '67 tripower (K19 is 3888)
engine driver side.jpg

I changed my clutch, pilot bearing, pressure plate and throw out bearing around the same time - but I can't remember any issues or comments about short or long TO bearings and/or not enough travel adjustment - mine has been trouble free since then. If I can find my replacement TO bearing info, I'll let you know.

good luck!

[Harry S.]

Re: 67 tripower & clutch question

Have him check to see if the throw-out bearing in installed correctly. He can use a broach buster to go in through the clutch boot.

[Gary S.]

Re: 67 tripower & clutch question

Mark,
One of the takeaways from a search here as well as experience with my LT-1s Holley is to always install the lines, your description of spaghetti works, loose before tightening. I was hoping that there was a lot of transfer of my Holley experience to the 435 setup and that appears to be the case. The very first thing I did was try to snug it down with my flare nut wrench. It was snug. I'm going to start with the large line-to-carb gasket first. His carb is a 3660 and I noted but don't remember the left & right numbers. My reading here tells me that there is a love/hate relationship with the tripower.

Harry,
Now.i have to Google "broachtripper.

Larry,
Lines are definitely coated steel and not SS. No history on his part for properly or mismatched components

[Mark F.]

Re: 67 tripower & clutch question

Gary - good deal...and I love my 400 just wanted to save you some trouble - had you been able to stop the leak w/o undoing spaghetti...front and rear carbs on '67 tripowers are 3659 (regardless of K19 usage)

PS - Larry Mulder brought up an excellent point - more likely your friend has 390/400 oval port to oval port conversion.
Very easy to tell:
400 intake casting number is 3894382
435 intake number is 3894374

BTW - '67 400s are more rare than 435s anyhow - so he should be happy either way it goes!

[Gary S.]

Re: 67 tripower & clutch question

Is the scarcity of the 400 intake merely a conversation point or is there any preference - not that it will matter since he has what he has?

He does have the original Holley 4 barrel and I told him MY preference was a single 4 barrel vs the issues a search turns up. I can actually work with a 4 barrel.

[Ray K.]

Re: 67 tripower & clutch question

Gary,

It is not uncommon to see the clutch adjusting rod near the end of its adjustment, generally about 1/2" of threads remaining. If you have no further adjustment available, I would check for wear on other components, such as the cross shaft and its ball stud pivots. The clutch fork and the ball stud that it pivots on are both susceptible to wear over the years. If you decide to replace the clutch you could check those items at that time. Corvettes have always used the short throw out bearing approx 1 1/2" in length. Clutch diameter of 11" is correct for the 427 engine.

Ray

[Gary S.]

Re: 67 tripower & clutch question

Ray,
He is at the very last set of threads, even negative one thread perhaps. I followed the Chevrolet Service Manual adjustment procedure and that was a disaster - couldn't get it in gear with engine off. I took it back to its as delivered condition and it barely works. Looks like a potential clutch change is in the works once I follow the suggestions given on this thread.

[Mark F.]

Re: 67 tripower & clutch question

Is the scarcity of the 400 intake merely a conversation point or is there any preference - not that it will matter since he has what he has?

He does have the original Holley 4 barrel and I told him MY preference was a single 4 barrel vs the issues a search turns up. I can actually work with a 4 barrel.

Gary - "scarcity", "rarity" "1 of x" in this case are all just conversation points in my opinion. I just mentioned it for fun.
Plus, in your friend's case (and my bad for not saying the obvious earlier) - his tripower top-end conversion will not judge well with an engine pad presumably identifying it as a 390 (IL, IM, IQ, or IR suffix). If he has no intention of getting it judged, then he's got a cool-looking 400/435 style set of carbs and air cleaner on the other hand, 390 intakes are not all that rare, so if he ever wanted to go back to original configuration for future judging purposes, I think you're wise to tell him to keep any and all 390 parts he has.

[Gary S.]

Re: 67 tripower & clutch question

We've talked judging vs doing what he wants. He wants it to look original without worrying about real authenticity vs "looking" authentic. He's happy with the look despite his lack of mechanical skills and my lack of knowledge of BB & tripower

[Richard M.]

Re: 67 tripower & clutch question

Gary, I suggest you get some photos of the entire clutch mechanism from clutch fork to pedal rod. You can see most of it from the engine bay at different angles. You may want to et some accurate measurements of those pieces too. Even if you have to remove them. Much easier than pulling the clutch. But definitely check inside the bellhousing too and look for a bent spring clutch and the correct throw out bearing.

Parts could be worn as Ray said, or even wrong. If the fork or fork rod or cross shaft was the wrong part it could change the entire geometry. 1 wrong part and game over.

E.G. If the fork installed is a C1 fork, that moves the fork rod clevis at the lower/inner cross shaft lever further rearwad, resulting in the pedal rod clevis at the upper/outer cross shaft lever(where the pedal rod clevis attaches) too far forward. Hmmmmm!
Recent thread here with photos of both configurations....
https://www.forums.ncrs.org/showthre...133#post880133

Also, there were 3 different C2 cross shafts 63-67....SB, BB. I don't have the data at my fingertips but that could be a issue too.

Check these posts from John Hinckley and read the entire thread for more details from others.

Rich

https://www.forums.ncrs.org/showthre...aft#post592755

https://www.forums.ncrs.org/showthre...aft#post551649

https://www.forums.ncrs.org/showthre...aft#post188101

https://www.forums.ncrs.org/showthre...aft#post135501

https://www.forums.ncrs.org/showthre...ork#post625027