Rough Running Pinto

[Guest Newyorkers]

Hi guys need a bit of help on this one. Just re-built a 2 litre pinto with new short motor, the head has been skimmed and new valve guides added along with hardened seats. Thed head came with the car and was supposed to be running before it was dismanteled. Its fitted with a new dizzy and cap/leads. Ignition is a Bestek system, but have tried another dizzy. Rebuilt twin 40's and FR32 cam. Ok now the problem - clyinders 3 and 4 are down on power to the point where if you remove the plug lead it makes no difference to the running, put the lead against the block and there is a big fat spark. When the engine is switched off it makes a noise as if gas is slowly releasing through the carb.Have checked valve seats cylinders will hold fuel overnight. Any thoughts would be greatly appreciated.

[Guest russell555]

daft question no.1.... are you sure leads 3 and 4 are round the right way??

[steve_wilson]

are the plugs on 3 and 4 wet?

 

can you feel if the exhaust manifold on 3+4 are getting as hot as the others?

 

what have you set the valve clearances to?

 

long shot but have the valves be ground in well enough? bit too late to check now i guess but it's possible.

might be worth doing a compression test

[Guest Newyorkers]

Yep checked leads 3 and 4 even tried swapping them. no difference. Yes plugs are wet but not soaking, the manifold is definately cooler on 3 and 4. Turned the head upside down and filled with white spirit, they stayed almost full overnight.

[Guest Newyorkers]

set valve clearences to sierra manual

[Longboarder]

The only thing 3 & 4 have in common is they share a carb which you say has been rebuilt. I would look there first.

 

Nigel

[Bob Tucker]

I'm with Nigel....check that the balance between front & rear carb is set right.

Simplest test is to use a tube placed inside each throat & listen at the other end for identical hiss.

 

Describe the symptoms is it just at tickover, or does it misfire with carbs open a bit/lot?

[Guest Newyorkers]

I've swapped the carbs with the same result. It sounds rough at tickover and hesitant to pick up. Could the head be warped? ie as the piston comes up on 3 the compression is pulled out of 3 into 4.? checked gasket its fine rebuilt with new one anyway.

[Andi]

set valve clearences to sierra manual

 

 

 

 

Just a thought............

If you have a FR32 the clearances should be in,.25 ex,.30.

Andi

[Guest AWhite]

Compression test is definitely the way forward to make sure the valves are sealing ok. I doubt it would run on just 2 cylinders so that suggests the spark is firing at the right time on the other 1 or 2 correctly. They are wet so getting fuel as well.

 

Is the link between the 2 carbs OK. i.e. are they both opening by the same amount? Do you have another carb you can try it with to eliminate the webers as the problem?

 

Andy

[johnlrichardson]

Have you a pipe from the manifold to the crankcase breather

 

jon

[Guest Newyorkers]

Have you a pipe from the manifold to the crankcase breather

 

jon

 

No I dont have a pipe from the manifold to the breather, the servo vacuum is on 4. There is no "suck" on cylinders 3&4 through the carb but if you put your foot on the brake pedal and start the engine, the pedal sinks as though there is vacuum. I've a carb balancer and it shows no suck on 3 & 4.The only thing not changed is the camshaft!!!! it says FR32 on the end, but the cam was in the engine whitch I was told was working before the crash.

[Longboarder]

If you seem to say you have servo vacuum which is taken from number 4 runner but no vacuum at the mouth of number 4 inlet. That's hard to reconcile. You either have some vacuum or you don't. Can't be both. Except you could possibly have vacuum in the runner if the butterflys were fully closed and no suck at the mouth of the intake if they were sealing the carb completely and not opening at all. Are you sure 3&4 butterflies open when the throttle pedal is pressed, not just the lever on the spindle turning. Need to look down the intakes to confirm. When the carbs were stripped the butterflys weren't removed from the spindles were they. Could be wrongly reassembled.

If there really is no vacuum in the rear 2 intakes then the cam shaft might be sheared in half in the centre bearing housing and the rear half not be turning.

I'm clutching at straws and a wild imagination here!

 

Do a compression test!

 

Nigel

[johnlrichardson]

The compression test will have to be done with the butterflys fully open

 

jon

[Guest Newyorkers]

Hi Guys, thanks for all your help and sugestions, looks like we have found the problem with a knackered carb. Couldn't adjust the mixture. so a complete strip down and clean with new needle valve seems to have solved it.