Bizzare lfter problem

UKFIVEO · 02-06-2001, 10:04 AM

After a high speed run on an airfield (154mph), a lifter noise suddenly began, we have isolated it to number 7 intake and replaced the lifter- the noise continues!
We ran the engine with the valve cover removed and you can quieten the lifter by tightening it until all is quiet....for about 3 seconds. Then the tap returns.
All the valvetrain seems ok, pushrods etc and we are pretty much foxed. Any ideas?
Thanks from a very wet England

90GT: TFS, E-303, GT40, 1.6 FRRP Roller rockers, Paxton SN89 5lbs pulley
11.87 @ 115- quickest in the UK

Chevyguy · 02-06-2001, 01:17 PM

Have you verified proper cam lift on that lobe?? That sounds like a flattened lobe which is highly unusual with roller lifters. Did you see any sign of distress on the lifter you removed?

Could it be a wrist pin or rod bearing on #7 instead?

------------------
Frank W
90 5.0 LX coupe Stone stock soon to be daily driver
74 Chevy Laguna Type S-3 305 apart in garage, getting a 454 to put next to it
www.chevellepages.com/folingo

UKFIVEO · 02-06-2001, 01:26 PM

The lifter seemed to be fine and we compared it to all the others, no excessive wear.
You can quieten it for a few seconds and then it becomes noisy again. I did suffer a lean condition at the same time resulting in number 3 and 4 plug tips melting. Maybe this gives anothr clue.
Thanks for the reply.

Chevyguy · 02-06-2001, 01:34 PM

Maybe a damaged roller bearing on that rocker arm?? Any piston damage would not be affected by tightening the rocker arm.

It's fun breaking stuff isn't it

UKFIVEO · 02-06-2001, 01:41 PM

We also tried swapping two rockers over and the problem remained with number 7!!
It really is proving a tricky one.

I have a Novi 2000 on order, lets see what I can break with that!!!!

93CobraR · 02-06-2001, 02:52 PM

The rocker might need to be reshimed. So what are you doing with the old blower? Wanna sell it to me?

------------------
87 GT, 4 inch cowl hood,17x9 Cobra R's/255/45's,GT-40 heads,long tubes headers,h-pipe,Flows,BBK cold air, Mass air,70mm MAF, 1.7's, 1" spacer,underdrive pulleys,Pro 5.0, King Cobra, Adj. fuel Reg., Lakewood Lift Bars,50/50's,subframes, 4.10's.
Best time 13.012
Best MPH 104
Best 60' 1.816

Visit my site at:
http://www.geocities.com/cobrar93_2000/MyPage.html

UKFIVEO · 02-06-2001, 05:35 PM

We have just tore the motor apart again, the lifter is fine, the lifter bore is ok as well. However my Twisted wedges were made in '97 (the motor was built in '99 and has done only 4000 miles) and have iron guides, we think we can detect some play on this particular guide (no7 intake)
Could this be my problem and are the symptoms typical of the known TFS problem?

macx · 02-08-2001, 11:13 PM

just aa s.w.a.g. - have you checked very carefully to make sure the rocker stud isn't pulling up? maybe compare height to the others or something

Chevyguy · 02-09-2001, 10:07 AM

The TFS heads should have screw in studs??
Can't imagine one would convert to press in studs from the non adjustable bolt on rockers. I am really curious to find out what happened to this motor

------------------
Frank W
90 5.0 LX coupe Stone stock soon to be daily driver
74 Chevy Laguna Type S-3 305 apart in garage, getting a 454 to put next to it
www.chevellepages.com/folingo

UKFIVEO · 02-10-2001, 04:49 AM

I have taken the plunge and torn the motor down now, no 7 intake valve guide is very worn, that valve shows signs of wear also.
The (loc wire) head gasket shows evidence of failure around no 8 cylinder, water has got in and corroded the aluminum in the groove quite badly.
So I need the head welded, the groove re-cut, new guides installed and all the machining done, sucks big time!

ps They are screw in studs

02-06-2001, 10:04 AM	#1
UKFIVEO Registered Member Join Date: Aug 1999 Location: England UK Posts: 7	Bizzare lfter problem After a high speed run on an airfield (154mph), a lifter noise suddenly began, we have isolated it to number 7 intake and replaced the lifter- the noise continues! We ran the engine with the valve cover removed and you can quieten the lifter by tightening it until all is quiet....for about 3 seconds. Then the tap returns. All the valvetrain seems ok, pushrods etc and we are pretty much foxed. Any ideas? Thanks from a very wet England 90GT: TFS, E-303, GT40, 1.6 FRRP Roller rockers, Paxton SN89 5lbs pulley 11.87 @ 115- quickest in the UK

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02-06-2001, 01:17 PM	#2
Chevyguy Backyard Mechanic/Chemist Join Date: Feb 2001 Location: Acton MA USA Posts: 435	Have you verified proper cam lift on that lobe?? That sounds like a flattened lobe which is highly unusual with roller lifters. Did you see any sign of distress on the lifter you removed? Could it be a wrist pin or rod bearing on #7 instead? ------------------ Frank W 90 5.0 LX coupe Stone stock soon to be daily driver 74 Chevy Laguna Type S-3 305 apart in garage, getting a 454 to put next to it www.chevellepages.com/folingo

02-06-2001, 01:26 PM	#3
UKFIVEO Registered Member Join Date: Aug 1999 Location: England UK Posts: 7	The lifter seemed to be fine and we compared it to all the others, no excessive wear. You can quieten it for a few seconds and then it becomes noisy again. I did suffer a lean condition at the same time resulting in number 3 and 4 plug tips melting. Maybe this gives anothr clue. Thanks for the reply.

02-06-2001, 01:34 PM	#4
Chevyguy Backyard Mechanic/Chemist Join Date: Feb 2001 Location: Acton MA USA Posts: 435	Maybe a damaged roller bearing on that rocker arm?? Any piston damage would not be affected by tightening the rocker arm. It's fun breaking stuff isn't it

02-06-2001, 01:41 PM	#5
UKFIVEO Registered Member Join Date: Aug 1999 Location: England UK Posts: 7	We also tried swapping two rockers over and the problem remained with number 7!! It really is proving a tricky one. I have a Novi 2000 on order, lets see what I can break with that!!!!

02-06-2001, 02:52 PM	#6
93CobraR Registered Member Join Date: Oct 1999 Location: Cincinnati, Ohio Posts: 1,575	The rocker might need to be reshimed. So what are you doing with the old blower? Wanna sell it to me? ------------------ 87 GT, 4 inch cowl hood,17x9 Cobra R's/255/45's,GT-40 heads,long tubes headers,h-pipe,Flows,BBK cold air, Mass air,70mm MAF, 1.7's, 1" spacer,underdrive pulleys,Pro 5.0, King Cobra, Adj. fuel Reg., Lakewood Lift Bars,50/50's,subframes, 4.10's. Best time 13.012 Best MPH 104 Best 60' 1.816 Visit my site at: http://www.geocities.com/cobrar93_2000/MyPage.html

02-06-2001, 05:35 PM	#7
UKFIVEO Registered Member Join Date: Aug 1999 Location: England UK Posts: 7	We have just tore the motor apart again, the lifter is fine, the lifter bore is ok as well. However my Twisted wedges were made in '97 (the motor was built in '99 and has done only 4000 miles) and have iron guides, we think we can detect some play on this particular guide (no7 intake) Could this be my problem and are the symptoms typical of the known TFS problem?

02-08-2001, 11:13 PM	#8
macx Registered Member Join Date: Oct 1999 Location: Gordonville MO USA Posts: 448	just aa s.w.a.g. - have you checked very carefully to make sure the rocker stud isn't pulling up? maybe compare height to the others or something

02-09-2001, 10:07 AM	#9
Chevyguy Backyard Mechanic/Chemist Join Date: Feb 2001 Location: Acton MA USA Posts: 435	The TFS heads should have screw in studs?? Can't imagine one would convert to press in studs from the non adjustable bolt on rockers. I am really curious to find out what happened to this motor ------------------ Frank W 90 5.0 LX coupe Stone stock soon to be daily driver 74 Chevy Laguna Type S-3 305 apart in garage, getting a 454 to put next to it www.chevellepages.com/folingo

02-10-2001, 04:49 AM	#10
UKFIVEO Registered Member Join Date: Aug 1999 Location: England UK Posts: 7	I have taken the plunge and torn the motor down now, no 7 intake valve guide is very worn, that valve shows signs of wear also. The (loc wire) head gasket shows evidence of failure around no 8 cylinder, water has got in and corroded the aluminum in the groove quite badly. So I need the head welded, the groove re-cut, new guides installed and all the machining done, sucks big time! ps They are screw in studs