LIFTER PROBLEM ?

[mike-b]

Hi All,
Symptoms, engine running but running rough, spits and backfires when put under pressure, i.e. right foot down more. Idle is rough, plugs not black or light grey.
I have noticed that if I watch any valve open then close fully and turn the crank say another 20 degrees thus making sure that valve is closed and not under pressure I can push the rocker ( rod end ) down a little. This is true to all valves EXCEPT the two valves for No.7 cylinder. At no time in two full turns of the crank will No 7 valves push down against the lifter when all the other valves will.

I think ( and could so very easily be wrong ) that No 7 lifters are not bleeding down.
Oil used is Halfords Classic 20/50.

Ideas anyone ? Thanks guys.

[ppyvabw]

Hi All,
Symptoms, engine running but running rough, spits and backfires when put under pressure, i.e. right foot down more. Idle is rough, plugs not black or light grey.
I have noticed that if I watch any valve open then close fully and turn the crank say another 20 degrees thus making sure that valve is closed and not under pressure I can push the rocker ( rod end ) down a little. This is true to all valves EXCEPT the two valves for No.7 cylinder. At no time in two full turns of the crank will No 7 valves push down against the lifter when all the other valves will.

I think ( and could so very easily be wrong ) that No 7 lifters are not bleeding down.
Oil used is Halfords Classic 20/50.

Ideas anyone ? Thanks guys.

Hi,

I'm sure you did, but did you set the tappet preload correctly?

[ChrisJC]

Sounds like those two valves may have had their valve seats cut in a little too much.

I once had some heads where the valve seats had all been recut by different amounts, so there was no way to get all the tappet preloads within spec.

Chris.

[mike-b]

Hi both, Thanks for the replies.
The preload was set thus:- I have adjustable push rods. The adjustable end on one rod was removed but still left loose, adjusting the adjustable end one "Flat" gave me a 6-thou longer unit, measured with digital calipers, 3 flats gave 18-thou, therefore one whole turn of six flats should and did give me 36-thou - a very near point to 40 and should be "good enough". All the valves were set this way and all the other 14 will push down against the lifter when the valve is not under load.
The valves were checked with a straight edge along their tops ( recon heads ) before bolting to engine, all level with each other, the heads from Paul at V8tuner and never a problem in the past with anything. Anyway valves were same height.
Oil & filter have been changed - classic 20/50. - and is good & clean. Everything works fine except both No. 7 valve lifters will not push inward when valve is not under load.

[ChrisJC]

It is a bit odd.

I have never managed to get lifters to compress once they are full of oil - I have had to dismantle them to get the oil out. Thus I have only managed to do the preload on new lifters, before the engine has been run. This makes me wonder if the two lifters are OK, and the rest are duff!!?!

Chris.

[mike-b]

Hi Chris, Thanks for that ..... and I think you have a point, it could be the other 14 lifters!!!!
Two are good & 14 useless or vice versa, either way it looks like lifters are the problem.
My biggest mistake was where I bought the engine, though it ran well at first then slowly but surely I have had problem after problem. I bought the engine from RPI, I wouldn`t buy the time of day from them now.
Checking the timing due to the spitting and farting I noticed ( by use of a "bung" in No.1 cylinder ) Ithe true T.D.C. mark was at 12 degree A.T.D.C. on the crank pully mark.
I agree with you .... it has to be the lifters.
Many thanks Chris, Mike