The V8 Owners Forum -

Hi guys,

I used to be on this forum a few years ago but then I put my planned V8 build on hold. Since then I bought a 4.7 ltr Porsche V8 to go in my Landy but for various reasons haven't got round to putting it in yet. Had my old 4cyl engine blow up a few months ago and now I am building a Rover V8 from the many rover bits I have lying around to replace it as can't afford to put the Porsche engine in.

ANYWAY... In the next month I will be starting up the engine for the first time (full ground up build, including new cam) once I have built the complex throttle linkage system and put the engine in. I plan to observe all the usual break in procedures but the issue is complicated because I am using a quad downdraft setup. The carbs are reconditioned DHLA 40 units from some company in America (many years ago) and *should* be jetted roughly to get started for a 3.5 engine. The chokes are 34 or 36 if I recall, but can check.

I need to ensure the engine starts easily and can be held around 2000 rpm. but the carbs are new and probably not setup. Has anyone got experience of these carbs that could give me advice on initial settings to get me started and through the break-in procedure?

Many thanks in advance.

Zander

Hi
I am no expert on these carbs, however you are presumably concerned with getting it started and then the 20 minutes or so to run in the cam, well you will be off load for this and running on the idle circuit, may be on the part throttle cruise bit. To be honest you really only want a mixture it will run on at whatever speed you can get it to run at at about 2K revs +-20% or so so it doesn't sit at one speed, well I recon you just pump the throttle to get it started and blip it to richen it enough until someone can set the idle screw to get it to run at 2K then tweak the idle mixture to get it to hold steady, any AFR from about 11.5:1 to about 16:1 should be able to do that the extremes aren't ideal but they would do.
best regards
Mike

Zander,

You need to contact Flyingphil of Muscle Sprout fame. He ran Dell'Ortos IIRC on his RV8. He's on here occasionally but more on Retro Rides.

Cheers,

Ian

kiwicar wrote:Hi
I am no expert on these carbs, however you are presumably concerned with getting it started and then the 20 minutes or so to run in the cam, well you will be off load for this and running on the idle circuit, may be on the part throttle cruise bit. To be honest you really only want a mixture it will run on at whatever speed you can get it to run at at about 2K revs +-20% or so so it doesn't sit at one speed, well I recon you just pump the throttle to get it started and blip it to richen it enough until someone can set the idle screw to get it to run at 2K then tweak the idle mixture to get it to hold steady, any AFR from about 11.5:1 to about 16:1 should be able to do that the extremes aren't ideal but they would do.
best regards
Mike

Many thanks for the advice Mike. It is good to know you think it should run ok for the cam break-in with little tunning. I have no personal experience with the carbs so don't know how picky they are about settings. I am sure I'll waste many hours tuning them later though! Out of interest (I assume you have these carbs or have had them before), have you found it is ok to sync them with those little carb synchrometers, or is a manometer setup required?

And thanks for the pointer Ian. I'll send him a PM.

Hi
I have very limited experience of this type of carb mainly on minis, and on a mates dolly sprint. However balancing them is like any other multi carb set up, get a rough balance using the syncro thingy (if you like gadgets) then use a piece of tube and a mk1 ear-hole to get it spot on, personally I would just use the piece of tube. My point is actually to do with the motor, wen running on fast idle/ running in off load the engine doesn't really care what the mixture is as 80%+ of the cylinder fill is exhaust gas from the previous cycle provided the plug can light off the 20% that is the fuel air mixture it will run.
Best regards
MIke

You could always fit the standard manifold until the cam is run in, then go to the quad setup once it's safe.