924Board.org

[the4ork]

just did a headgasket change, my first 924, but def. not my first headgasket...

got the thing running but it was slow as all hell, after several hours of tinkering (im pretty familiar with cis) i was unable to recover any power.

SO, did a compression test... 160-170 on the first 3 cylinders, then the #4 was at absoluely 0....

with all the spark plugs out, and just covering the whole with my thumb i cant even feel a breeze coming out of the cylinder! its almost like there are no valves at all

questions...

1. is this an interference motor? could i have bent A valve in #4?
2. looks like the valve lifters are adjustable, could this have anything to do with it? (seems way out there, but worth asking)
3. anyone else have any ideas?

sounds like ill have to pull the head again since i already have done it once it shouldnt be too bad. but the really crappy part is my daily driver was stolen this morning, no biggie ill drive the porsche, but its running on 3

so yeahhhh this sucks

[pocketscience]

No, the NA is non-interference.

Doesn't sound like you're having much luck... fingers crossed for ya!


G.
_________________
Whoever said you can't buy happiness forgot about Porsche!
81 924 N/A, GTS lights, Saratoga, interior, headers, Integral cam, EFI (sold)
95 993
69 911

[Imafordguy]

It is a non interferance motor.
I would suspect it to be a valve problem. How about the cam lobes? Rings?
Thieves suck! It really sucks to have your transportation stolen.
_________________
81 Porsche 924
84 Porsche 944(parting it)
66 Ford f100
66 AC cobra kit car(major project)
64 ford f100 (429 SCJ)
62 Studebaker golden hawk gt
61 baja bug (with bad opel 1.8, looking at ford 2.3 turbo to flovo)

[Paul]

The unburned fuel will dilute your oil and eventually cause damage to your bearings and cam.

Definitely check your valve clearance especially if you did not keep the lifters in order.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[the4ork]

I had the cam out to resurface the head and installed it myself... seemed pertty straight foward but what should I do now? should I pull the head or should I try something else? I just pulled the valve cover off to check the lifters out... grrrr

[leadfoot]

valve coil may have gone into bind and be keeping the valve open...
potential misalignment of the locating bushing near cylinder 4 with an unsealed head gasket...

if you place a compressor feed into your spark plug hole (as in leak down test) you should be able to trace where the air is escaping from.
Make sure the engine is at No 4 cylinder firing stroke.

i.e broken piston ring (hissing heard at the exhaust) , open intake valve in the air box, to side/back of engine (unsealed head gasket)
Stu
_________________
1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

[Rich H]

First thing - check the valves on 4 are moving. I'd expect it to be pretty obvious that t's not shutting - check the tappet clearances!
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[the4ork]

i hooked the compressor up to the compression tester hose and let the air on, the air is escaping through the exhaust, which means the exhaust valve is open, broken, or bent

[Rich H]

Or the tappet is miles out of adjustment and holding the valve open
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[the4ork]

explain, i only know hydraulic lifters

[Rich H]

There is a little screw that lives in the tappet that allows you to set the gap from the lifter to the cam, when the valve is shut there ust be a clearance between the lifter and the cam. If you mixed up the lifters when you rebuilt the lot chances are your tappet adjsutments will be out.

Turn the cam on number 4 until the exhaust lobe is pointing straight up. In this position the exhaust on 4 should be shut. Now using a 0.25mm feeler gauge try and slip it between the lifter and the cam. My bet is that you can't as it's holding the valve open. If you can't then wind out the grub screw a turn with a 3mm allen key (It will snap into position every turn as it has a flat on it.) and try again. To find the allen head you need to try the holes on both sides of the tappet one has a allen socket one dies not. Each turn is an extra 0.05mm or so.

If you have to wind it a lot then you might need to rethink the order of your tappets. the grub screw should always be well inside the tappet to avoind the chance of it fouling the tappet bore. There are different thickness screws designated by a number of lines scored into the none allen head end of the screw, from 0 to 4 lines, 0 is the thickest screw and 4 is the thinnest allowing for valve recession.

My bet is that you will have at least on valve with no clearnace (Exhaust on 4) and otheres with massive clearances.
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[ideola]

Just to clarify on Rich's explanation above, a "turn" on the grub screw is 360°. You will not be able to completely turn the grub screw in one motion using the allen wrench. You will have to make small incremental turns, and it will feel really stiff as you start to turn. You will only be able to turn about 60° at a time, so it usually takes about 5 or 6 mini-twists before the grub screw will snap back on the flat.
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erstwhile owner of just about every 924 variant ever made

[Arvidw]

@ideola, I hope you ment 360deg, the adjusting screw only has 1 flat side so it should be rotated 360deg when adjusting.

@The4ork, Here some pictrures to visualize what you are doing with the allen key





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Porsche 924 2.0 Kompressor 136.1wHp @ 5650rpm / 201.9wNm @ 3900rpm (dyno @ dp-engineering.nl)

[ideola]

[dannyboystaffs]

read my thread,i had same problem i think..no compression on cyl 3..turned out to be a exhaust broken valve..hope this helps you
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1984 porsche 924 lux guards red
1999 zx9r c1
1998 ford courier van
1998 bmw 328 m sport e36