Engine Bogging

Jamieg285 · June 13, 2006, 04:25:18 AM

Following the weekends carb swap and timing adjustment I appear to have developed a bit of a bog problem.

I did notice it on the test drive, but thought I would give a couple of days to settle and see what's what.

On this mornings run it showed itself to be a definite problem, the first real 'acceleration' provided a small backfire, but there was general hesitancy on any application of throttle.

My guess is the timing is wrong. (Guess we should have test driven before changing the timing.

) I've looked around, and the advice given is to start at 8-10* advance, with 32-37* total. I'm going to try and pick-up a decent timing light with a degree dial, and try adjusting it back.

From memory - it was at about 8*, and we moved it to about 6* - Can anyone confirm that?

55starchief · June 13, 2006, 05:07:11 AM

Sounds more like fueling than timing. What fuel pump you running? as it might not have enough flow rate for that new carb

Jamieg285 · June 13, 2006, 05:11:07 AM

AFAIK it's a stock pump.

Wouldn't flow rate affect top end, not initial acceleration?

FUBAR · June 13, 2006, 05:25:08 AM

Quoting: Jamieg285

From memory - it was at about 8*, and we moved it to about 6* - Can anyone confirm that?

That is correct yes.

55starchief · June 13, 2006, 05:27:41 AM

Quoting: Jamieg285

Wouldn't flow rate affect top end, not initial acceleration?

might be a little to rich at the bottom end mate if its bogging there, sounds like the carb isnt adjusted correct.

Jamieg285 · June 13, 2006, 05:32:18 AM

Done a bit more research - it might be the vacuum on the wrong port (it's on timed, but might need to be on full)

55starchief · June 13, 2006, 05:35:54 AM

Quoting: Jamieg285

Done a bit more research - it might be the vacuum on the wrong port (it's on timed, but might need to be on full)

Ah ok didnt realse you had vacuum advance on the timing

Jamieg285 · June 13, 2006, 05:39:15 AM

Quoting: Jamieg285

Done a bit more research - it might be the vacuum on the wrong port (it's on timed, but might need to be on full)

But now I'm not so sure - conflicting advice.

I think I'll still look for a timing light, and try the different ports anyway.

55starchief · June 13, 2006, 05:43:16 AM

I really dont think its timing,

All my years tunning nitro motors has taught me that Bog is caused by fueling and jetting. We dont have ignition on these little motors but get settings wrong and the motor dies real quick

Incursus · June 13, 2006, 05:44:45 AM

I thought we did the timing at the weekend?

Jamieg285 · June 13, 2006, 05:57:00 AM

Quoting: Incursus

I thought we did the timing at the weekend?

We did, but I'm not convinced it's right - don't forget we sort of guessed based on the figures for the 305 and 350's, and that was the stock settings. Being as the engine isn't stock any more, that may not be the right settings either.

All the advice I have seen says go for 8-14 initial.

F Body · June 13, 2006, 07:43:34 AM

Quoting: Jamieg285

All the advice I have seen says go for 8-14 initial.

14

seems on the high side ?

Jamieg285 · June 13, 2006, 07:49:17 AM

Quoting: F Body

14 seems on the high side ?

I think it depends on your cam. I'd expect to go for 8-10 realistically.

55starchief · June 13, 2006, 08:17:18 AM

Quoting: Jamieg285

I think it depends on your cam. I'd expect to go for 8-10 realistically.

also what fuel your running. The higher the octane the more timing you can run and the more power you make

****edit****

Also you could find that the cam is +/- on the install depending how it was built. Desktop dyno showed that running 5 d retard on the cam would pick up 15hp on my motor