incomplete combustion diagnosis

[4JGtootsie]

You have a fine old school engine.
I would simply begin with valve adjustments, good compression will greatly rely on good seating of the valves giving a tight seal, worry about worn piston rings and walls when you have already done all the other test.

The cylinder head gasket will be the next.
The third will be cylinder head check up (dismount head from block), take a close look of the valve condition, seats, guides and seals. Warpage and leaktest of the head should also be checked.

[janmike]

You have a fine old school engine.
I would simply begin with valve adjustments, good compression will greatly rely on good seating of the valves giving a tight seal, worry about worn piston rings and walls when you have already done all the other test.

The cylinder head gasket will be the next.
The third will be cylinder head check up (dismount head from block), take a close look of the valve condition, seats, guides and seals. Warpage and leaktest of the head should also be checked.

tnx! i really like this engine for it's simplicity and raw power (if i can manage to tame it ). your advise is highly appreciated sir, in fact i had it already on my long list of to do's. as of now i'm on top of my checklist and having it DIY. when it comes to your advise it's best i leave it to a professional - though i may still try to do it myself - but will see . Good thing for now is that i'm not experiencing white/black smoke (signs of internal engine problems), pinging, knocking or overheating (signs of wear).

Correct me if i am wrong please:

Idle Mixture screw - regulates the amount of gas flow? air(vacuum) flow? or both instantenously?

Which part of the carb countinously pours gas on idle - main jet or pilot jet?
where is it located in the carb?

TIA

[4JGtootsie]

tagat ko na dispatcha corolla liftback ko but i think the lowest screw is for air by pass and above it is Air fuel. You can do a lot of things to that engine pwede mo gawin 1800 by replacing the crankshaft from a 3t. Pwede rin gawin twin cam by replacing the head from a 2tg.

[janmike]

later nalang siguro un mods . more on efficiency at FC and objective ko muna . but tnx for the fyi parin.

Note:
i only have 2 adjustable screws in my stock 2bbl aisin carb. one underneath the throttle linkage (idle speed screw) parallel to the screw in the middle of the carb (idle mixture screw). so idle mixture = A/F mixture?

[red888]

about the a/f screw , yes that is the a/f screw ( pang idle mixture ) may i make a suggestion ? With the engine turn off, remove the screw all the way out of the orifice, then screw it back in slowly, taking note of how many times you turn the screw to fully seat the idle mixture screw.Divide this by 2, this gives you the ( rough ) number estimate of how many back turns of the screw you need to get to the mid way ( half open or close ng idle mixture mo). eto kasi yun theoretical na mixture nung carburator ( based on the screw ), from here you may need a vacuum gauge to fine tune the carburator.HTH ( btw, i got 13T engine, a bigger cousin nung 2T mo,and i do my own carburator overhaul, tuning)

[janmike]

it's been a while since i had a reply on this post. was able to learn a bit how carbs work in general within that period. however, though i managed to lower my fc i still have no response from my idle mixture screw. vacuum is good but i may have leaks internally since the engine don't stall when i close the top of the carb. will try to do your suggestion tonight then i'll go ahead with my rebuild on weekend.

[red888]

another test that u can undertake, is that while the engine is running, remove the idle mixture screw all the way, this should stall the engine. if not ,may problema un carburator.saka do u notice kung magalaw yun needle nung vacuum gauge mo ( normal should be between 15 - 17mm Hg ), this is one sign na may leak ka, pero not always.Kung intake manifold leak, look for signs of gasoline ( sa mga joints ) o un basa sya .