stromberg problems

olly_richman · Post by **olly_richman** » Sun Mar 15, 2009 8:54 pm

hi,
Just been tinkering with the range rover today, have sorted the cutting out problem (dizzy) the occasional almost dying problem (sticky needle valve) and now have the equally annoying backfiring through carb problem to deal with.

The range rover is fitted with a 1980 sd1 engine, BUT it is fitted with the strombergs from the range rover, It is running the later sd1 (1985 on maybe) standard stromberg needles. I have the engine timed up and it is running pretty smoothly until you go above 3k when it will backfire through the right carb (looking from front).

Not sure what to do really seems like it is running a little lean on that side (engine revs drop if you lift the piston slightly). I am waiting for my stromberg tool to turn up before I can start fiddling though.

Any ideas/help much appreciated,
Cheers,
olly

topcatcustom · Post by **topcatcustom** » Sun Mar 15, 2009 9:47 pm

Any chance you could have a weak inlet valve spring on cylinder 2/3/5/8? (I think the problem carb feeds those cylinders). It might be causing the backfire if it can't close the valve quick enough which will cause a problem at a certain speed- in your case 3k (if that is the problem!)

TC

RoverP6B · Post by **RoverP6B** » Sun Mar 15, 2009 9:55 pm

Hello Olly,

Your thougths I suspect are spot on Olly,...running too lean.

For the Range Rover, the needles will need to be much richer.

I have never used Stombergs, so I can't help with needle selection, but if you have access to the Range Rover workshop manual either at home of at your local Range Rover spare parts centre, the info on the required needle should be there.

Ron.

kiwicar · Post by **kiwicar** » Mon Mar 16, 2009 2:55 pm

Have you checked the diaphrams in the carbs? especially if it's already backfired once they are probably split (if they havn't been renewed in the last five years they will probably be split anyway) nine out of ten problems with strombergs are split diaphrams.
Onec you have checked out the diaphrams the next place to look is for blocked Idle and transition ccts (lots of very fine drillings in the body of the carb) you need these to be cleaned out and free of crud otherwise you will never get them working right. Where as the SU tends to drift out of tune and need constant tweeking to get the mixture right, the stromberg only needs adjusting when you change somthing, it is however very suseptable to any problems with the diaphrams (pin holes, splits, getting crinkled on assembly) and crud in the many drillings and passages, oh and the various choke arrangments are a good source of entertainment.
Mike

harvey · Post by **harvey** » Mon Mar 16, 2009 4:30 pm

topcatproduction wrote:Any chance you could have a weak inlet valve spring on cylinder 2/3/5/8?
TC

Or a worn camshaft, particularly the exhaust lobe on number 8 which wears away, so the exhaust gasses can't escape, and so they pop back through the carb the next time the inlet valve opens.

olly_richman · Post by **olly_richman** » Wed Mar 18, 2009 9:59 pm

Have ordered to B1EJ needles for the strombergs, have also worked out that the timing marks are out so when cyl 1 is at tdc the timing mark is lined up at 8deg(ish) BTDC. Tweaking this has helped somewhat with the backfiring, I know the needles in there arent correct for this setup because the engine was still pretty lean towards the middle/top of the rev range.
Diagphragms are new but as you say, could easily be damaged by backfiring, so will change them again.

Thanks for the help, will keep you posted, cheers, Olly.