Hi folks,

I'm having a problem with the old X-flow, I can accelerate with the best of them and cruise all day at 70mph(about 3000rpm).

but if i increase the speed up to 80 or go up a long incline then the engine starts to bog down and feels very lethargic.

I've been looking for a crushed fuel hose but to no avail, my thoughts are this, could the float height in the twin 40's that i'm using be set to little at full droop?

I'll only be able to see if this is true in two weeks time as the cars in southampton at the father in laws and i'm not.

Many thanks in advance Dan.

Certainly sounds like classic fuel starvation. Could possible be float height set too low, but I'd also check

1) the filter built into the top cover
2) the needle valve itself (could be partialy blocked)
3) the fuel pump.

Also do you have the carbs correctly mounted with Misab plates and thackery washers to prevent vibration and fuel foaming?

[Edited on 15/11/05 by MikeRJ]

If you've got the Choke connected you could try pulling it on when its hesitant,
that might help identify if its running lean.

Dan,

I doubt if your problem is caused by fuel starvation, this is usually accompanied by a lot of popping and misfiring that doesn't seem to be happening in your case. From my experience with the crossflow, it does need a LOT of ignition advance compared with more modern engine designs. At tickover mine is best at 18 BTDC, rising to something like 44 BTDC at 3000 rpm. I don't know what ignition system you're using, but if it's a distributor check the centrifugal advance is working correctly.

May also be worth experimenting with main jets - I found 120 mains, 180 air correctors gave good results, an old fashioned check on plug colour will give a good indication here. Again, over leanness is usually accompanied by popping and backfiring through carbs, over richness can give a 'bogging down' feeling though.

ATB, Geoff.

Oh aren't we off topic here? I thought thought correction was discussed fully in George Orwell's 1984 and earlier in the work of the Spanish inquisition. . . . . .

Caber

General lack of power at high loads could be main jets to small but Gradual falling off of power under under load which recovers for short while if you back of the throttle for a few seconds indicates not enough fuel is getting through to the float chambers.

Check fuel pump delivery into a measuring jar
Blow out fuel lines
Blow out Carb float valves
Check filter Filter
Check tank vent Tank vent
Check float levels
Check idle main and air corrector jets are tight and clear

It might be an idea also to do a compression check -- burn't exhaust valves cause loss of grunt on hills.

[Edited on 15/11/05 by britishtrident]

quote:

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Originally posted by GeoffT
Dan,

I doubt if your problem is caused by fuel starvation, this is usually accompanied by a lot of popping and misfiring

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I once had a problem like this on an old cavalier sportshatch.
It had a recon weber on it and an asbestos heat gasket spacer thingy. In summer it was OK but in winter it used to ice up the carb venturi gradually losing power. I took the asbestos spacer out and it was fine until you stopped the engine and the heat then boiled off all the fuel in the float chamber.
I would check for iced up venturis perhaps maybe it's worth a look and easy done.

Had a similar problem on my way to SVA back in May, had left at 6AM to make sure I got there on time It was brass monkeys then . Got about 30 miles down the road and had the same symptons that you have .Pulled over and took off bonnet, couldn't see any problems, put bonnet back on after about 5 minutes and carried on . No problems after that, suspect carb was freezing due to having no pre heat system. Not had any problems since.

I remember steve m having this problem among the many he has encountered with the crossflow,after checking just about everything it turned out he was overcharging.

My money was always on set up of carbs

I had something similar years ago on a Sierra. It turned out to be a small piece of debris that got pulled onto the main jet when driven hard, restricting fuel. I think it was probably a bit of rubber from the aging fuel pipe.

Have also heard of someone's wire to the fuel pump being too thin and dropping the voltage to the pump too much. I would think the wire would get quite hot if this was the problem.

yep bob was right, we went all the way to exeter and back overcharging and the coil was basicley cooking itself over about 4k rpm

under that rpm the car was faultless