XFlow Power problem

[swatson]

My recently built machine with secondhand engine/trans parts from all over, basically works, but has a fundamental problem

that spoils the enjoyment a bit.

 

I can blat hard for approx 5-10 seconds or so, then the engine limits (starts to pop etc) and starts to slow down. If you back-off on the throttle briefly then feed in the power again, its still not happy (just about keeps going, but no acceleration) after approx 10 seconds or so more, it all smoothes out and then Blatting can continue. My initial hunch, is that its fuel starvation due to incorrect float level (i.e the delay is time for the float chambers to re-fill) - any thoughts, before I take it for a Rolling road tune/diagnostic. (want to avoid the expense!)

 

Hopefully someone can give me some ideas on this one.

 

Spec :

1660 Xflow / mechanical Ford pump (from Caterham)

Twin 40's Jetted as per Caterham docs

 

Cheer

Steve

 

ps I've checked valve clearances, compressions, timing etc and all seem fine.

 

[gadrego]

Popping and banging suggests fuel isn't being burnt, which suggest either overfuelling or a problem with ignition. My money would be on an ignition problem. What type are you running?

[Peter T]

Sounds like fuel starvation to me, are you using the standard mechanical fuel pump ?

Is there a fuel filter in the line anywhere, this could be blocked. Do you run with a pressure regulator ?

 

Carbon Components from K9 Composites

 

[clive powell]

As it start's to misfire,cut engine,roll to a halt and take off a carb top,if its fuel starvation you will see from the fuel level or lack of it. And dump that fuel pump anyway before you get a pinhole in the diaphame and a sump full of very expensive petrol ie no bearing's left.

I know of 3 very expensive engine blow up's caused by them.

[andy couchman]

Check how tight the carbs are on the manifold.

 

They should be bolted up using either rubber or spring washers and you should be able to wiggle the carbs up and down a bit.

 

If you bolt them up rigidly, you get similar symptoms to those you have described.

 

How do I know?

 

The hard way...

 

Andy

[Bob_r]

check that you haven't lost a locating screw out of one of the carb venturi barrels - screws into the carb body from the outside and is held in place by a locknut.