OK, I'm at my wits end.....A plea to all you clever people who understand CVH engines........

I have aproblem with my car (westfield with a 2ltr Ferriday CVH, ported head, Piper 285C cam, Megajolt, twin weber 40's)....it blows back AF mixture at 5500rpm (irrespective of load) through the front weber (i.e. both barrels, up to this point it runs perfectly....


Engine has only just run in so I'm only just notcing this (noticed on a recent Rolling road).......

I've since tried replacing a follower, changing the valve springs, changing the oil (just in case the hydraulic followers were pumping), changing my VR sensor bracket to something stiffer, etc etc...but still my car is spitting back fuel air mixture at at 5500rpm (irrespective of load)....Just can't figure out what would cause this to happen out of both barrels of the front carb.....Also checked HT leads, plugs, timing, etc, replaced coil pack..........Carbs are in good condition all jets checked....

Clutching at straws, but if anyone has any theories on this, they would be most welcome as I'm about to torch the car!.......

The blow back is VERY specific to revs 5500rpm on the nose every time...........

Please feel free to ask questions.....

Many thanks....

Paul.

 

Sounds like a triggering fault... Can you see something supporting this in the datalogs?

 

I havn't noticed anything specific...but, I'll do some more loggin while under no load, and full load...this may give some clues.....Last time I took a data log, there was nothing obvious.....

 

May be a carb problem may be try swapping the carbs over to see if it changes sides ?
RON KIDDEL is the man for carbs 0208 340 5057.
He will know if anyone if anything to do with the carbs.
tabetha

 

Tabetha,

Thats not a bad idea....I think it would help to know if this is a carb issue / head issue / block issue / ignition issue....

Changing carbs is a pain, throttle linkage, throttle position sensor, etc...but that would tell me if it's carb related.....Cheers.

Paul.

 

Further to this....swapped the carbs around...no difference....

However, I now have a vid of this happening....What you see snorting out of the carbs is unburnt fuel / air mixture.....

Any suggestions on what the hell could cause this?.......

http://s34.photobucket.com/albums/d1...t=DSCF1479.flv

 

I saw this post when you first but posted but didn't really have anything constructive to add.

The only thing i can think to ask....is are you sure you aren't getting valve bounce at higher RPM?

The fuel is being physically blown out of the trumpets, can't think of much else it could be.