took the mk out to drop one of the boys at his theatre group.

the engine is a 2.1 pinto on twin 45's, new (i'm supposed to be running it in). i was pulling out onto the duel carrageway from a standing start and with a determined use of the throttle... when i hit some gravel and traction was lost, the revs went sky high i did not see the rev counter as i was trying to change gear.

at the same instant there was a loud bang and and the carbs started back firing

i pulled over to the side the engine was running, it was back firing from one of the carbs, and it was running very rough with little power.

first thought was broken valve spring.

next plug failure, but that would not give a back fire.

the dizzy is tight and the plug leads are fine, so unless the belt slipped then the timing is fine..

i'm lost and don't know where to start...

this car is really getting me down.

any ideas lads??? please.

ditch

[Edited on 12/6/08 by ditchlewis]

Eew, don't sound good. Sounds like an engine strip to see whats gone wrong.

Don't get dispondant. Remember why you built it in the 1st place.

Hope it's easily fixable

well all is not totally lost i have a years guarantee on the engine.

the engine runs and there is no smoke.

the carb action is good and it is not sticking.

what are the main causes for a back fire through the carb?

timing?
sticking valve?

ditch

Sounds like a rev limiter might be a good investment...

does it back fire on every revolution and do you actually get flames or a puff of smoke, i had a similar sort of situation and on close inspection the inlet manifold gasket had ripped and it was taking air in by the block and not through the carbs, lead to various amounts of popping coming from the cylinder

just a thought.....

Valve stem snapped if you've bounced the valves?

just been out to the garage.

started the car up and there is a lot of black soot coming out the exhaust, a sign of running rich.

two weekends ago i had to replace the two front spark plugs, so i pulled the lead off the first and nothing, no drop in revs.

so i pulled the the second lead off and nothing again.

tried this on the last two plugs and each time the reves dropped off alot normal i Know

so the front two cylinders are not firing at all.....

the plugs i put in were not as good as those in before, so they may have failed.

do failed plugs cause back fires through the carbs?

am i being optimistic and infact it is broken valve springs or a stuck and bent spring?

ditch

1) Try swapping the plugs. I'm not hopeful, though.

2) do a compression test ...

yes david a rev limiter is on the list of things to do, as i'm incapable of containing my enthusiasm

will i see a broken valve if i take the cam cover off and rotate the engine?

ditch

I've just rebuilt my 2.0l and when I got it running it was back firing through the carbs initially.

After a RR setup John said the trigger wheel was reading about 8 degrees static advance which on top of the 14 degrees in the magajolt map equals way too much.

He also said the valve clearances were way out too.

Having sorted both these it's pretty much OK now although I still think the cam is too wild.

So from my experience I would say check your timing first.

my bet is youve bent at least one valve, not the end of the world as long as the pistons are still ok,

following on from David J's idea of a rev limiter.

is it possible to fit one to a car with carbs and dizzy?

ditch

I was expecting a post about inflatable dolls!

Before I fitted MegaJolt I had an Omex rev limiter - it's simple to fit. IIRC, it's 1 wire to 12v, 1 to chassis, and another to the coil. When you hit the limit it stops the coil discharging.

Has the cam belt slipped at all? -worth checking....

I would do a compression test too which will let you know if a valve or head gasket has gone.

Cheers

Mark

many thanks david, that one is filed in the list of important things to do

i'm not hopeful after all this that it is something like a broken plug. i think it must be a valve.

i only hope that the rest of the engine is ok

every one here at home thinks it's a great joke. i'm not laughing as it may be a few months till i have the money to carry out major works.

ditch

I'd whip the rocker cover off if I were you and investigate into the rockers etc.

will i be able to see a sticking valve if i take the cover off?

ditch

Yes you should.
I think head gasket between cyliders could be the case

looks like no escaping the head off route. this will really p~~ the Mrs off more time in the garage more money.

ditch

i have an omex rev limiter if you want one, u2u me

[Edited on 12/6/08 by omega0684]

My car has been apart more than together after passing, but that just makes me smile as I know every little detail of it!

Not like these boring modern cars (which ironically I also design, and still don't know all about)

have you tried a compression tes

Pull the rocker cover off - a bent valve will have loads of clearance , a broken one will have none - both dead easy to spot........but allso if you've broken a valve , as has been suggested , it wont want to turn over unless the top has been smashed out of the piston (you will have noticed that much damage going on , so a bit unlikely )

It could ( ) just be that the two cheep plugs have failled.

fits in with rev test.

That you have a mild or radical cam with some overlap - resulting in blow back into the carb from the two cylinders that are not working.

fits in with the symptoms and would be the best possible case . lets hope.

Paul

ps I am no expert so dont trust my opion.

cylinders 1 and 2 share the same carb - coincidence or not.

you need to take cam cover off and do compression test.

also check the carb for those 2 cylinders.