Solex tuning for 18RG

**checksix** · 04-11-2016, 03:12 PM

Hi all,

It's been awhile since I last posted, but I know the help here in the past has been incredible. I just recently moved to the mountains in California. My home is at 6000 feet (1800 meter), and yes the car runs like crap. I was jetted on the rich side when I lived at sea level and the move made the car a really poor performer. Since then I've installed an Apex wideband O2 sensor. and have been changing jets to get a better running car (59 Austin Healey with an 18RG engine). As in the title, the carbs are Solex 40 ADDHE's. Currently running 110 mains, 65 idle and 180 air. The car now runs pretty damn good (no hesitation, no spit back just a nice pull), but since I can now see the mixture, I see room for improvement.

I have a perfect idle at low 14's at 1 1/4 turn out. A long hill pull shows mid to low 16's (ya, I went too lean from the 135 jets but a 125 is also too rich). Here's the conundrum...... When on the flat at a light throttle, I'm in the 12's. I'll probably move the mains to 115 as a 1st try to fix the pull on a hill, but I figure that may only fix the long hill pull, and the low throttle setting may be worse! I'm guessing the fix may be in the air correction jets, but I'm a novice with tuning these carbs and would like to hear from someone with experience so I can make a better guess at my next jet order. Other pertinent info. The floats are correct if you use the data in the 18RG manual using the method of measuring from the top the carb base to the fuel level (about 21 mm). I use a fuel pressure regulator set to 2 psi and have verified the pressure by having a gage in the car so I can see it at all throttle settings.

Thanks in advance!
Checksix
Woodfords CA

**73GTV** · 07-11-2016, 07:58 AM

http://www.mikunipower.com/PHH01.htm

I always state that if you are using original carburetors that there is a problem with the fuel metering block restricting fuel flow which can be mistaken for improper jetting. Just my suggestion.

**checksix** · 07-11-2016, 11:59 AM

Originally Posted by 73GTV

http://www.mikunipower.com/PHH01.htm

I always state that if you are using original carburetors that there is a problem with the fuel metering block restricting fuel flow which can be mistaken for improper jetting. Just my suggestion.

Hi Thanks for the help. I don't feel it is a dirtyness issue as the carb responds well to tuning inputs. When I rejetted, the carb fuel ratios followed an increase or decrease in jet size. I believe this is more about the ratio of size of the mains to the air correction jets, or something totally unrelated like a broken o-ring with the venturis etc (something I know NOTHING about). The carbs are not original, but I do know this model was used on the 18RG. I bought them new many years ago and they ran fine at sea level. This move to 6000 feet has shown they were probably weakly set up to begin with. I've made significant progress, and was trying to fine tune. I'll probably buy a bigger set of jets to fix the top end fuel mixture, and a different set of air correction jets, than the 180's I have just to see what difference they cause. I was hoping to get more specific advice before throwing money at it, but it looks like that is what I'll be doing.

Are there even metering blocks on these Solex? I know about them on American carbs, but I though the block was integral to the main carb body?

Checksix

**73GTV** · 07-11-2016, 12:42 PM

http://i306.photobucket.com/albums/n...ps9402ef3b.jpg

**checksix** · 07-11-2016, 01:50 PM

73GTV, thanks for the clarification. I saw that part as part of the accel pump assy. The good new is I had those off, as I replaced my pump diaphragms (were leaking). I also cleaned all the associated parts while there, and noted they were in excellent shape unlike those nasty ones you have a picture of. I've never posted a picture here, so assume you must use a photo sharing web sight, or I'd post back the schematic from my Toyota 18R book to clarify the part.

BTW I loved the picture of your car. LOOKING GREAT!

Checksix

**73GTV** · 08-11-2016, 08:48 AM

Old pictures of my former car, replica in progress.

The point about this metering block is that unless you take time to flush out the internal passages, dirt and grime will restrict that internal passage reducing flow during the initial acceleration which could cause your problems as time goes on. That is all.

Suggestion on how to correct this fault:

http://www.jenvey.co.uk/products2/tw...-40-48mm-tdsxx

**checksix** · 08-11-2016, 09:30 AM

I saw a similar one at foxinjextion.com. That one required the computer control typical of fuel injection (Megasquirt or similar). Since I have the wideband installed I'm partially along the way, but see this as a bit too rich for me as I'm retired and have limited funds to go play with.

I took her for another run today to try to narrow down what my next order will be. 115 mains and 160 air correction. Here's hoping. Will know shortly after they arrive.

**checksix** · 15-12-2016, 11:37 AM

In my last message I had moved down in the main jet to 115 and a 160 air correction. While the 115 mains ran ok, the 160 air correction jets was a BIG MISTAKE. Ran like crap. So I decided to go the other way on Air Correction and installed 200's. Great improvement. Ihis allowed me to move back to a 125 main jet. I am now mid 13's to low 14's AFR when under load (3rd, 4th or 5th gear up hill 60 MPH). However I am still running mid 12's when running on the level at 2300 RPM (60MPH). Even the slightest load gets me into the 13's. Going down hill I'm in the 11's.

I guess I'll be leaving it here as I have no idea how to get that low range up. Perhaps this has something to do with timing, so I'll be starting a new thread on the correct timing process for the 18RG.

Actually there is a member with a timing question, I will respond there to add insight.

Checksix