Keep Dellorto DRLA 45s and Bosch 009? Options

[98101]

I suddenly find myself owning 1970 4-cylinder 2.4 with Web hot street Cam idles nicely and pulls hard at WOT. Part throttle response is not great, often with carbs coughing and even backfiring on trailing throttle. My use is mostly street, so I'd like to get this part throttle stuff sorted.

Here's pictures of the stuff that's in there now. I guess that's the infamous Bosch 009 with no vacuum advance and a PerTronix 1847A. The carbs are Dellorto DRLA 45s with short velocity stacks and these tall foam things that don't seal against the air cleaner housings. I'm willing to learn about the carbs but I don't have much confidence in the 009 for running nicely on the street. Please correct me if I'm wrong about any of this stuff.

Also from other threads I gather that switching to EFI such as MicroSquirt would cost $5K or so ... though I'm not ruling this out completely. Correct me if I'm wrong about that.






Is this kind of linkage OK?


Here's the idle you may have seen in another post:

https://www.youtube.com/watch?v=-AC53RRrXOU


Any help you can provide is appreciated!

--Michael in Seattle

[MarkV]

In your carb pic the vacuum advance port isn't capped off ??

I don't believe those ports are active on Dellortos. Mine were not.... I put rubber plugs on them but when I put a vacuum gauge on them I never got a reading.... I think the carbs have to be drilled for those to work.

[porschetub]

In your carb pic the vacuum advance port isn't capped off ??

I don't believe those ports are active on Dellortos. Mine were not.... I put rubber plugs on them but when I put a vacuum gauge on them I never got a reading.... I think the carbs have to be drilled for those to work.

Some carb sets come with only 1 port in the pair,can't remember if its the left or right one ,the 2 ex- Alfa sets I have are that way,if they ports are there they are drilled and will have vacuum....least mine are.
However I read on a UK forum some sets had vacuum ports on left and right ones as supplied new.
There are 2 hex screws on each carb below the height of the throttle shaft these for balancing maximum vacuum when tuning,I believe this is because the carbs never came with velocity stacks so couldn't be balanced with a conventional synchrometer.

Not sure this engine would idle as per the supplied video with blocked idle jets....seemed to run to smooth for that.

OP needs to pull a carb and see what he has...I think that's also a good starting point also.

[98101]

Not sure this engine would idle as per the supplied video with blocked idle jets....seemed to run to smooth for that.

In case anyone missed it, three things the engine seems to do well: start, idle, pull like a clydesdale at wide-open throttle. Poor running seems to happen at certain combinations of part throttle and engine load. The backfires might be most common after a hard run. Temperature is in the 40s (Fahrenheit) here, and the oil temp takes a long time to reach 170ºF.

OP needs to pull a carb and see what he has...I think that's also a good starting point also.

Thanks -- I'm reading the Dellorto Tech Book now about how to do that so I don't screw something up. I'm not clear whether I can easily check the main venturi size without removal.

The book suggested I should not trust the numbers on the jets, if they are even legible, as they may have been reamed. It suggested using jet gauges. I don't have those yet. Is this taking it too far?

I ordered the carburetor synchrometer from Pelican, part # PEL-TOL-STESK.

I ordered what I think are the same 3 1/4 inch air filters MarkV is using from CB Performance, their part #3301. A lady at CB Performance named Marieanne was knowledgeable and kept me from ordering the wrong filter.

Regarding the CSP linkage, she said CB Performance doesn't carry it. It looked like MarkV had no complaints about the same hex linkage I've got, so I may hold off on changing that.

No one suggested keeping the Bosch 009, or any reason not to get the 123 distributor I'm so intrigued with. I ordered the Bluetooth 123 distributor using the group buy code. I don't think I've changed a distributor before, so thinking I might seek help with this.

The roughness at part throttle and sensitivity to engine load make me want to experiment with vacuum advance, hence the interest in the configurable distributor.