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

[rhodyguy]

I don't get how it could bow down that much.

[98101]

So the gaskets weren't leaking (at least at idle). It does seem that the right side of the engine is pulling harder than the left off of idle. So I think I need to adjust the linkage.

https://www.youtube.com/watch?v=wTxJsuCn5JQ

[type2man]

Check to make sure the linkage arms both come off the stops at the same time. You can do this by placing your finger where it comes of the stop on one side and looking at the other side. Also the linkage arm rods should have the same angle from the linkage to the carb base area, if not they will open at different rates. Also it sounds like it running on three cylinders, check the idle jets and pump jets. Try lowering the idle half a turn at a time on each carb. I think what might have happened is that one linkage arm came loose and moved over and is causing the high idle by jamming the linkage arm. Both throttle arms have to be resting on the stops at idle

[98101]

Check to make sure the linkage arms both come off the stops at the same time. You can do this by placing your finger where it comes of the stop on one side and looking at the other side.

Thank you! I tried this tonight and was able to detect that the right carb was coming off the stop before the left. The trick of feeling one while watching the other was the clue I was missing before.

I adjusted the linkage rod and got them much closer. And now the engine responds SO MUCH BETTER coming off of idle. Previously it was very rough when you just barely put your foot on the gas, and now it's great ... up until the next flat spot. I'm excited that I was able to make some progress.

I checked again with the air flow meters and observed it was much improved, but still far from perfect. I guess an experienced mechanic could get the linkage right without the meters. But for me they're fun.

Does anyone happen to know the wrench sizes of those CB Performance linkage rod lock nuts? Are they metric? I don't own many tools yet and I'm afraid of cornering them with my crescent wrench.

Also the linkage arm rods should have the same angle from the linkage to the carb base area, if not they will open at different rates.

Mine do not have the same angle, and I don't see how to adjust it. The angle on the right carb (the second photo) looks especially awkward to me.

Also it sounds like it running on three cylinders, check the idle jets and pump jets. Try lowering the idle half a turn at a time on each carb. I think what might have happened is that one linkage arm came loose and moved over and is causing the high idle by jamming the linkage arm. Both throttle arms have to be resting on the stops at idle

OK, I will look into this. It looks like I can still buy carb cleaner tomorrow.

As it arrived from previous owner, it starts instantly and idles at 800-900 when cold. When it's finally warm, the idle is way up there: 1200 or more.