Tuning '89 power problem

[H105Daz]

Hello people,
I have an '89 GF that has a power problem, runs fine upto and around 4000 rpm, then tails off badly. Symtoms include bad pinking, blackish smoke and lack of power. It has original distributor with correctly functioning bobweights new points (cassette) new rotor arm, dizzy cap and leads and plugs (NGK) and a new dry type coil. Now, would the installation of a quality electronic ignition sort out this problem for me or is it something else?
Has standard exhaust, K+N type pan filter in oem filter housing, carb is a DATR with uprated jets (115/135 I think) .. I dont think its the new type coil causing the power drop as it did the same with the old oil type I had in before. The power and accelleration up to 4000 rpm is good, but overtaking can be a lottery! Would a Lumenition kit eliminate the huge power loss I'm experiencing at higher revs..? at £200 I'm willing to give it a go, but I dont want it fitted to find its something else.. Thanks in advance.

 

[jimbro1000]

The problem is most likely to be ignition timing or a blockage/air leak in the carburettor.

The fact that it runs fine at lower revs would suggest that the primary circuit is working in the carb but the secondary circuit has a problem. The pinking and smoke is pointing to fuel as the culprit. Check the cam timing is correct though as this can cause problems too.

If it is ignition timing at fault then you don't need a lumenition kit to solve it but you probably would solve it in the process of fitting the kit.

 

[H105Daz]

The secondary throttle is definately working because you can hear it ... but unsure if there is an air leak between the carb and inlet manifold tho, would that cause this much power loss? Maybe it might be worth trying to time it up via the flywheel marks this time..?

 

[jimbro1000]

I wasn't doubting that the secondary throttle was operating mechanically rather I was questioning if the fuel was flowing properly. It is very easy for the tiny fuel circuits to become blocked with debris. And as for an air leak causing that much power loss? Definitely - if the stochiometric ratio is out you'll find the power is massively reduced. Obviously it depends on the air leak - where it is and how big it is.

If the engine has been timed up incorrectly then it will run like a dog with lots of power low down and nothing at the top (or vice versa). Fortunately it is a non-interference design so no danger of valve to piston contact.

 

[H105Daz]

If the engine has been timed up incorrectly then it will run like a dog with lots of power low down and nothing at the top (or vice versa). Fortunately it is a non-interference design so no danger of valve to piston contact.

:doh: Surely this would have been spotted when timed and tuned on an anilyzer tho....

 

[jimbro1000]

That assumes that it was timed correctly to start with (the old Fiat SOHC is notorious for multiple timing marks) and that the timing has skipped a tooth (more than possible).

 

[H105Daz]

Damn this thing lol ... destined for Ebay I think..:idea:

 

[H105Daz]

Hi again..
car seems really torquey low down now, which feels nice however I purchased a new cylinder head as I'm sure the one on the car has leaky guides as it belches oily smoke on startup and I wanted to get work done without being without ol' faithful on the road for long!
As for head work, what is the average price I should be looking at for the usual treatment .. ie skim, standard valves and valve guides replaced etc?
luckily, its only eight valves then
Cheers Daz

 

[jimbro1000]

Depending on how generous your engineering shop is it could be as little as £75 with some of the prep done by yourself and keeping the original guides. Getting the head stripped down and the valves removed isn't difficult as long as you have a spring compressor. The cost of replacing the guides is likely to be down to getting replacements.

The cost actually comes from reshimming the vales. Once you've reseated the valves you'll probably find the original shims are just fine. You'll need to make a tool to depress the bucket so you can slip the shim out or improvise.

 

[H105Daz]

Hey Jimbro,
yer removal of the valves etc will be done by myself, I was more concerned about the valve guides which may have a bit of slop causing the oil ingress to one or more cylinders via the cam box. Freezing the head aids removal, but how you do that and the other bits without having three pairs of hands I'm unsure.

 

[jimbro1000]

Looking around on the internet I think you'll be looking at between £30 and £50 per pair of guides - so another £120 to £200 on top of the basic skimming.

 

[littlephil]

you can get your old valves re sleeved by some engineering garages. A lot cheaper than a set of guides

 

[H105Daz]

Hmm need to do some research then ... Malvern Rebore didn't seem much cop last time I took my block to them, so does any one know any reputable headworkers in the West midlands area?
cheers for replies.