Dead cylinder in 1972 2002tii

[OriginalOwner]

Here's another idea for "the problem."

 

Twice now on my '74tii the head gasket "let go" between cylinders 3 & 4.

 

SO, how about a tiny piece of Pablo's head gasket "let go" just enough in the right place to cause the problem on cylinder #2 ??

 

Cheers,

 

Carl

 

Edited August 23, 2023 by OriginalOwner

[Mike Self]

Based on what the borescope look told you, I'd definitely vote for a leakdown test  before pulling the head. 

 

You'd feel pretty silly if the problem turned out to be a stuck valve, or one that's either misadjusted, or not closing fully due to excess carbon buildup.  You can make a tool to pressurize the cylinder...

 

I had a friend make a fitting to pressurize the cylinder from the metal base of a spark plug, a length of copper tubing and a valve stem with the rubber scraped off.  Tube was soldered to the spark plug base and the valve stem, and then hand screwed into the cylinder.  Worked just fine...

 

mike

 

 

[TobyB]

Quote

 

I don't have the facilities/tools to do a leak down test

Sure you do-

 

a spark plug, some tubing, and a can of compressed air from Orifice Depot.

As Mike says, knock the porcelain out of the spark plug, figure out what size

tubing will jam in there good-n-tite, adapt that to your can of compressed air,

and then install the plug shell in #2.  Roll the engine over until #2's on compression stroke,

(tdc is best) and then wedge the tube in, hook the can up to it, and give it a squirt. 

Have friend listen at tailpipe for hissing.  If none, check at intake with throttle plate open,

then check at oil filler.

 

It'll be one of the three.  

 

THEN you can decide how to dive in

 

t

 

[Pablo M]

11 minutes ago, TobyB said:

Sure you do-

 

t

 

Ok! Will try it. 

[66Vette]

You can find cheap leakdown testers ($30) on Amazon.  I don't have any experience with them (maybe another member does). They will have all the fittings and at least give you a relative reading which you can compare a good cylinder to the bad cylinder.  All you need is a source for compressed air.

[Pablo M]

4 minutes ago, 66Vette said:

.  All you need is a source for compressed air.

Actually I have a couple air brush compressors and a compressed co2 tank. I’ll look for a fitting for my hoses. Thanks. 

[Pablo M]

New update:

 

Checked compression, definitely no compression at #2.

Bought leak down tester and tested #2. Bad exhaust valve. You can hear it clearly in the exhaust pipe.  We rolled the car back around in 4th gear and doesnt look like the valve is closing fully. 

 

Cue me looking at FAQ posts about R&R heads, lol. teardown starts tomorrow.

 

I'm going to try to manage scope creep, but do want to replace the valve springs with HD springs, new head bolts and washers, chase the threads. Anything else in the head I should replace?  I'm not changing the cam.

Edited September 2, 2023 by Pablo M

[Son of Marty]

Yes pull the head replace that valve and check the others closely, no need for new head bolts and washers on a m10 and there's no advantage to h/d valve spring with a stock cam they will just increase cam wear and nothing else. spend your money having the head  gone over checking the valve guides and surfacing along with the valve cover, replace everything that shows wear, do it right and do it once.

Edited September 2, 2023 by Son of Marty

[tech71]

New guides if required to fit Viton valve seals, they be better.

Limit scope creep outside of the cylinder head if you want but spend what's necessary to totally spiff up the head.

72 Tii? is that an E12 or 121Ti head? no matter, spend the cash and have it pressure tested.

Keep the stock springs, look closely at rockers, rocker shafts and eccentrics

Edited September 2, 2023 by tech71

[TobyB]

Quote

doesnt look like the valve is closing fully. 

Can you figure out why?

 

Is the rocker loose, with lots of slop?

 

2002 valves seldom stick in the guides, so something smells like a denizen of the deep, here....

 

t

once had a blue shop towel cause these symptoms...

[Pablo M]

3 hours ago, Son of Marty said:

Yes pull the head replace that valve and check the others closely, no need for new head bolts and washers on a m10 and there's no advantage to h/d valve spring with a stock cam they will just increase cam wear and nothing else. spend your money having the head  gone over checking the valve guides and surfacing along with the valve cover, replace everything that shows wear, do it right and do it once.

Aren't head bolts TTY, or one time use? That's what I've read. An 02 friend suggested HD springs since I'll be driving it pretty hard once it gets sorted. Intent is a canyon/track toy. He also suggested staying with stock cam. 

2 hours ago, tech71 said:

New guides if required to fit Viton valve seals, they be better.

Limit scope creep outside of the cylinder head if you want but spend what's necessary to totally spiff up the head.

72 Tii? is that an E12 or 121Ti head? no matter, spend the cash and have it pressure tested.

Keep the stock springs, look closely at rockers, rocker shafts and eccentrics

Definitely feel the scope creep within the head itself makes sense, good housekeeping sort of thing. Its a 121 head. 

Rocker on that valve was loose too, more play than any other. 

57 minutes ago, TobyB said:

Can you figure out why?

 

Is the rocker loose, with lots of slop?

 

2002 valves seldom stick in the guides, so something smells like a denizen of the deep, here....

 

t

once had a blue shop towel cause these symptoms...

The rocker is definitely loose, more play than any other. Lots of carbon buildup from looking at it through the borescope so I suspect carbon preventing it closing, or maybe it slightly bent. Are the guides prone to wearing eccentrically, ie ovalizing? I thought I read that somewhere. 

I did stuff the intakes with blue shop towels when I replaced the intake runners and plenum recently. I'll pull that off first to make sure lol. But it never ran right. I replaced the plastic intake runners and plenum with metal ones from a '74 chasing vacuum leaks.

[TobyB]

Quote

Aren't head bolts TTY, or one time use? That's what I've read. An 02 friend suggested HD springs since I'll be driving it pretty hard once it gets sorted. Intent is a canyon/track toy. He also suggested staying with stock cam. 

Nope.

That trend didn't start until the mid- 80s at BMW, later with other makes.

The bolts are 100% reusable, and they don't age out.  As long as they're not damaged

(rust, usually) they're likely better- or at least, more consistent, which is what matters-

than anything you can buy today.

 

HD rockers are not needed until you get well into the 7k range, and are running a taller and 

steeper cam than stock.  And if you stay with the stock cam, you won't be making much power over 6500.

(but the M10 responds very well to a bit more cam)

 

Yes, the guides do ovalize, from the off- center force from the rocker tips, but sticking is unusual.

Getting bent, however, does happen IF they stick.  

 

Kinda up to you if you want to chase that valve further- carbon buildup COULD do it, and you might be

able to clean it up, but pulling the head off's probably going to be quicker and more conclusive.

 

t

 

[Pablo M]

Thanks @TobyB  appreciate the clarification. 
I’d been told the tii motor doesn’t respond well to a cam, I thought because of the mechanical kfisher. 

[Mark92131]

1 minute ago, Pablo M said:

I’d been told the tii motor doesn’t respond well to a cam, I thought because of the mechanical kfisher. 

 

That's correct, the Kfish has a fixed "fuel map" and can't be adjusted without tricky modifications, so unless you are building a race car and plan on having someone modify the pump, stick with the stock cam.

 

Mark92131

[Pablo M]

Well, pulled the head and clearly I have an exhaust valve issue.