Inliners International Forums General Discussion Engines Gmc 270 timing and tdc

Hi!

I am trying to get a gmc 270 to run alittle better.
As of right now it runs, but i feel something is not quite right, the symptoms are:
Very low power, occational backfire under load (especially at wot) poor mpg..
The engine does not make any strange noises, just seems to respond slow.

My first thought is to check out the timing, and here are my questions for you tech guys:
Which is the no 1 cylinder, the one closest to the radiator or the one closest to the rear?
I have a peep hole on the drivers side bellhousing, is this for finding tdc and setting the timing or are there other places to check?
What is the firing order for a gmc 270?

Thank you in advance,
Fred

#1 is in the front.
The pointer in the peep hole will line up with a round/ball mark on the fly wheel at the #1 firing position. There is another mark for TDC.
All inline sixes have the same firing order 1-5-3-6-2-4 Well as far as we are concerned.
Have you had the engine long? Has it been sitting a long time? Check the fuel filter and lines. Check the compression and look at the plugs to see what they tell you. Check ignition timing. If the problem isn't here you'll have to dig deeper. Distributer, coil and carb.

Thank you!

I have not had the engine long, bought it and a car from a gentleman who was as in experienced with gmc straight sixes as i am.

The thing is that he has labeled all the sparkplugwires 1-6, and placed the 1 on the actual number six cylinder.
Is it possible that the engine is 180 degrees off? would it start at all if this is the case?
i have converted the car to 12v neg ground, changed coil.

All new fuel lines from gastank to pump, new filter between tank and pump.
fairly new filter between pump and carb. (this is extra due to a formerly dirty gastank, i have had the tank cleaned out)

The 1 port carter w1 carb is bad, thinking of going with a repro 4bbl alu intake and holley 390 cfm and a th700 transmission.
Do you think the 390cfm is a good choice?

The 390 will do fine. Mine has a 500 and it doesn't need it.
It can be 180 out but the exhaust valve would be open. Make sure the plug wires are in the right order on the cap. You could be a tooth off on the distributer. The rotor turns clock wise. Here is a handy article. LINK

Good luck!

Update:

Thanks a million for the info.
Turned out that wire #3 and #2 were at the wrong place on the dist.

Just switched places, started right up and i instantly got a big grin om my face.
Engine runs like new, unbelievable what torque it produces!

Gonna check out vacuum and mess with timing now that i know that wiring is as it should be.

Great! Have fun with it.