Hello & Strombergs
Posted: Tue Jul 17, 2012 11:23 pm
Hi all,
Back on here after a while, onto my second Elan "George" a 69 DHC S4 SE. What a lovely thing he is too. After owning quite a few serious modern performance cars it's a relief to go back to a proper sportscar! Just had a great drive in my "new" S4 and I still believe no one has made a better sportscar for the road, especially British roads!
Anyway, I've got a couple of questions I hope you can help with. I've been pouring over the archives but can't quite see the answer I'm looking for.
I bought my car fully restored from a specialist and it's in top condition, everything (and I mean everything) has been rebuilt. The car has however only done a couple of hundred miles since then so it needs a shakedown, which is part of the fun eh.
I've had quite a bit of experience tuning various cars from 50's-90's but this is my first look at Strombergs. The car has a set of 175 CD-2's according to the dashpots.
First of all I disconnected the linkages and saw the carbs were out of sync, so out with my trusty SK and they are now perfectly balanced at idle and up to 3000 rpm. The car will now hold a good steady idle at c. 900 rpm and will start from cold ok too. However, the idle is not as good I expect it could be.
So, out with the dual colortunes on 2 and 3 cyl. No. 2 cyl plug was sooty and 3 sooty and wet. The rich condition was confirmed with the colortune showing both were running rich at idle and of course number 3 more rich than 2. Rocket science eh!
Revved up, number 2 leans out and appears to be close to spot on off idle - it goes blue with tinge of yellow at a cruise condition, and yellow with sharp acceleration, quickly settling back to blue shortly after. Good, good.
Number 3 off idle is clearly running too rich as up the rev range it needs leaning out slightly and is mostly yellow.
So in short, at idle both carbs are running rich, but front carb is rich at idle but ok off idle, rear carb is rich at idle and off idle.
This is where I lack the next level of information on how to correct this condition. From what I am reading it doesn't sound like you can adjust these 175 CD2 Stromberg's like an SU. I see there is a tool available to adjust the needle, and I read of these air bleed screws on the RHS of the carb body near the temp compensator, but what is the correct procedure as it seems that mixture adjustment should not be touched, just all parameters base lined ie jet height, needle location, float height - ? There is a diaphragm involved here too?
Do I need to go to the full hog of removing the carbs, checking the jet height, float level etc condsidering the carbs have been rebuilt or is there some way I can make a small correction to address the issues above?
I have two books coming sometime in the next few days which will undoubtedly help, but some advice from the experts on here would be appreciated as of course books don't address specific issues.
Cheers
Back on here after a while, onto my second Elan "George" a 69 DHC S4 SE. What a lovely thing he is too. After owning quite a few serious modern performance cars it's a relief to go back to a proper sportscar! Just had a great drive in my "new" S4 and I still believe no one has made a better sportscar for the road, especially British roads!
Anyway, I've got a couple of questions I hope you can help with. I've been pouring over the archives but can't quite see the answer I'm looking for.
I bought my car fully restored from a specialist and it's in top condition, everything (and I mean everything) has been rebuilt. The car has however only done a couple of hundred miles since then so it needs a shakedown, which is part of the fun eh.
I've had quite a bit of experience tuning various cars from 50's-90's but this is my first look at Strombergs. The car has a set of 175 CD-2's according to the dashpots.
First of all I disconnected the linkages and saw the carbs were out of sync, so out with my trusty SK and they are now perfectly balanced at idle and up to 3000 rpm. The car will now hold a good steady idle at c. 900 rpm and will start from cold ok too. However, the idle is not as good I expect it could be.
So, out with the dual colortunes on 2 and 3 cyl. No. 2 cyl plug was sooty and 3 sooty and wet. The rich condition was confirmed with the colortune showing both were running rich at idle and of course number 3 more rich than 2. Rocket science eh!
Revved up, number 2 leans out and appears to be close to spot on off idle - it goes blue with tinge of yellow at a cruise condition, and yellow with sharp acceleration, quickly settling back to blue shortly after. Good, good.
Number 3 off idle is clearly running too rich as up the rev range it needs leaning out slightly and is mostly yellow.
So in short, at idle both carbs are running rich, but front carb is rich at idle but ok off idle, rear carb is rich at idle and off idle.
This is where I lack the next level of information on how to correct this condition. From what I am reading it doesn't sound like you can adjust these 175 CD2 Stromberg's like an SU. I see there is a tool available to adjust the needle, and I read of these air bleed screws on the RHS of the carb body near the temp compensator, but what is the correct procedure as it seems that mixture adjustment should not be touched, just all parameters base lined ie jet height, needle location, float height - ? There is a diaphragm involved here too?
Do I need to go to the full hog of removing the carbs, checking the jet height, float level etc condsidering the carbs have been rebuilt or is there some way I can make a small correction to address the issues above?
I have two books coming sometime in the next few days which will undoubtedly help, but some advice from the experts on here would be appreciated as of course books don't address specific issues.
Cheers