Chuff Chuff Chuff

#1
Good morning to one and all, my resent thread ( running rough) got to the position of the car all back together and running, and i would like to thank all members who helped and gave advice. however its still got problems!!!
to recap car is p6 2000 tc 1972, original problems was a badly cracked exhaust manifold, valve gaps all over the place, very low compression on number 4 cylinder, and sticking jet on front carb.
The manifold has been repaired,valves all now set correctly, head has been checked and all valves lapped in etc, sticking jet now working as it should. every thing re built as per the manual with all new gaskets etc, carbs balanced with no air leaks that i can find.
However i still have that awful CHUFF CHUFF on idle !! , rev past the idle and it sounds ok and indeed seems to drive ok, after a about 50 miles or so, checked the plugs and all were about right.
An other problem just noticed, is that i have an oil leak from rear of the head, ( o ring ?) really have had enough now! it was a new o ring and fitted with care, so now as a minimum the head has got to come off again.
Any further advice would be great before i pull all my hair out.
Regards Steve.
 

sdibbers

Well-Known Member
#2
It’s really trying your patience isn’t it? I would suspect a couple of things. Try spraying some carb cleaner or easy start around the intake manifold and the flexible joint between the carbs and the manifold while the engine is at idle. If you see a change in idle speed you may well have an intake leak.

The O ring leak is very annoying, is there a chance the head gasket moved during refitting the cylinder head? That could be responsible for both the oil leak and the chuffing sound.
 
#3
HI Steven, thanks for your thoughts on the problem, next day i will be able to look at car is weekend, i have checked out the carb and inlet side of things with carb cleaner and no change in idle, but will try again at weekend, I am going to examine the manifold very carefully when its off to check there are still no small cracks ect, re check the valve gaps, and another compression test, from the sound of the car i am starting to think i may have an exhaust leak from around the manifold.
your point about the gasket moving slightly and causing the oil leak could be about right, more care needed next time.

regards Steve.
 

harveyp6

Well-Known Member
#4
your point about the gasket moving slightly and causing the oil leak could be about right, more care needed next time.
Did you coat the O-ring with Hylomar gel (not silicone)? If not, do that next time, it holds it in place, and lessens the chance of leaks.
 

cobraboy

Well-Known Member
#5
from the sound of the car i am starting to think i may have an exhaust leak from around the manifold.


regards Steve.
I know nothing about 4 cyl Rover engines, but I do know that exhaust leaks can mimic all kinds of mechanical noises, look for cracks as well as obvious leaks.
 
#6
Thanks Harvey and Cobraboy, not knowing any better I did put the o ring in dry, I will be getting some Hylomar gel as recommended ready for the next attempt, and the more i think about it i am leaning towards a possible leak/crack/non sealing gasket on the manifold, but before pulling it all apart again I intend rechecking the valve gaps and compressions.
Regards Steve.
 

Demetris

Well-Known Member
#7
A leaking / noisy exhaust manifold will become louder with the engine under load.
I am not exactly sure what you mean by chuff - chuff - chuff. If it is uneven exhuast note, a sort of misfire, only at idle, you can try and measure the %CO at the exhaust. Anything below 2% means that it runs too lean, hence the misfire.
Oh, and something too obvious, but it does no harm to ask. Are you sure that it's not the belt?
 
#9
Thanks Demetris, my Chuff Chuff is an uneven exhaust note which you can hear and feel at idle, it is more than likely still there when driving, but not as easy to detect,
I have read that a weak mixture can lead to an uneven exhaust note, but on checking my plugs, they seem just about the right colour, I have tried enriching the mixture quarter turn at a time but it makes no difference to the exhaust note, just seems to choke up the engine( black sooty plugs).
I do not have a CO2 tester at home but will pester my local friendly garage to test for me.
I have already run the engine with the belt off, ( not to check the exhaust note ) but to see if my alternator or water pump bearings are rumbling,
but no change, my wife is always saying the engine is very noisy , anyway I intend starting from the top and checking every thing again when off work next week.
Thanks to all Regards Steve.
 

Demetris

Well-Known Member
#10
From your description i think that we can rule out the weak mixture.
If the tappet clearances are still correct (sometimes they tend to close up a little on the first runs right after a head rebuilt) then you can can get back checking compressions, or preferably having a leak down test if possible.
 

sdibbers

Well-Known Member
#11
That makes more sense on the description of the noise.

The slight misses that cause that noise can be commonly caused by three things. Lean mixture or the spark plug gaps being too small or a weak spark
 
#12
just tried a leak down test, only to find the second gauge ( pressure loss gauge ) just sits on its stop!!, however i connected up each cylinder in turn and listened for any leaks etc, 1,2,and 4, all produced a very slight loss of air out of the top of head, ( very hard to hear, but definitely there) no leak from exhaust tail pipe, no air in bubbles in coolant, but number 3 cylinder produced a very loud hiss and loss of air, coming from around the top of the head I traced the leak to coming out of the number 4 cylinder plug hole, when i put my thumb over the plug hole air started pouring out of the rear carb !!.
First lesson learnt , -- dont buy a cheap tester of E BAY
Second lesson, well im not sure what is going on.
Regards Steve.
 
#13
I think that inlet valve on number 3 doesn't seal. Check again the tappet clearance on this one, and if it is not closed up completely, then you have to pull the head again.
Before fitting the head, did you pour some petrol down the inlet and exhaust ports, to check if all the valves seal as they should?
 
#14
HI Demetris, all tappet clearances are as per the book, and no I didnt pour petrol down the ports prior to fitting, ( foolish of me ) but having had the head stripped and checked, valves cut in etc, by a engine machine shop,
Compression test last week, I got 175 on number 3, how can this be possible with what sounds like such a bad valve?
Regards Steve.
 
Top