18 replies to this topic

[Grayedout]

Two different racing organisations.

Rasputin is racing under SEGTO and minipac is quoting NASA rules.

[rasputin22]

Problem is still backfiring through carb, everytime the throttle is pressed at idle or under load is when its worst. And occasionaly pops through exhaust.

I got hold of an AAU needle and tried it in the carb to little effect, slightly better performance. Tried an old HS4 with AAU needle. The idle and pick up was stronger but still backfiring as before and there was alot less rich smoke out of the exhaust. The throttle spindle was also heavily worn on this aswell. There was also little or no backfiring through exhaust now.

Did a compression test as thought a valve maybe bent and 3 cylinders went to 200 psi after about 3/4 engine turns and another made 180 psi so these seem good.

With the spark plugs out i turned over the engine to check spark at each plug and all had a good spark on them. They were also very black from the old needle running to rich, but seem to be clearing up a bit to how they should be. I did give them a good wire brushing to get some soot off.

Timing i have double checked at 12 deg advance without vacuum advance.

Checked electrical connections over especially to coil and all seem good.

I have fresh fuel.

I had a good look at the HIF while it was off and the upper inlet (overflow) and lower one next to fuel inlet (for lean off device) go straight to the same area of the carb the float chamber, but obviously at differing heights.
Everything seems to me to be correct, float at correct level, nothing out of place and secured correctly.

Only thing i am thinking about next is if the cam timing is out by the previous owner but i don't believe this as i drive it ok before i decided it was a good idea to take the thing apart.

It just now everytime i apply throttle from idle i get a big pop out of the engine. I have not tried to see if its lost any more power when driving as thottle linkage was not linked up.

[rasputin22]

Put the hif back on today with AAU needle and it still runs pretty awful with a costant almost backfiring. I changed all the manifold to carb gaskets. I also put an electrical fuel pump on and bypassed the mechanical just to make sure i was getting enough fuel flow.

I noticed that whilst running at idle, if i pulled off the vacuum advance and left the hole uncovered then the idle would pick up and reduce when put back on as though the mixture was rich, but everytime i blipped the throttle i would get a backfire.

I just can't work it out.

Just to make sure i have done this bit right, i have worked out that i have a non ballast coil, as its 3.5 Ohm across the LT coil and have it connected to battery via a switch and fuse box and no resistor/resistive wire.

I have just got some new HT leads, not that i think these are the problem. Plus i had another look at the spark plugs ad again they are very black.

[rasputin22]

Think i have figured it out. I found a kink in my fuel line masked by a grommet so that may be a good reason why its not running properly. Hopefully it should be sorted now.

Thanks for peoples help