Upgraded U20 Head Install

[Gregs672000]

I would make sure your sensor has been calibrated just to be sure (mine has to be every once in awhile per manual). I would be surprised if it would require anything bigger than the 62.5s. Check your plugs and make sure you don't have a situation where one throat is not been properly fed fuel as that could potentially show up as a very lean mix on the meter.

[jamesw]

With Solex you want a richer idle in my opinion. I think if you are at 3.5 turns out at 14 afr you need bigger pilots - it's just direct cause and effect. I've never had to run bigger than 62.5 but I've never had a Rebello head job either

HTH
James

[CameronSF]

I agree James...will and I put in 62.5 pilots and I think that's when we got the closest. I plan on putting those back in and tuning from there.

[CameronSF]

THREAD BUMP! Reviving this old thread with some updates. I've been driving the car around rich every once in a while because home life got in the way of tuning. Recently I was able to devote a little time to trying to sort things out. I installed a new thermostat as I was half convinced mine was stuck open...it would never seem to get to the middle of the temp gauge. After doing that the car pegs to 180 nicely so I adjusted the valves again and brought out the protune to verify the cylinder balance. I ended up adjusting the balance between the two carbs slightly and 1, 2, and 4 are now much closer but 3 still is not pulling any vacuum. I did a compression check at hot and ended up dead on 160 for 1,2 and 4 and 150 for cylinder three. I'm stumped that 10 psi is causing such a vacuum difference. I also installed 65 pilots which made the car much happier in transition and was able to get the pilot screws down to 1.5 turns out where it is happy. The third cylinder is basically dead to the world at idle. I can pull the plug wire off and nothing happens. Convinced something died in that pilot hole. I may hook up my compressor and blow some air down pilot jet hole and screw adjustment hole...any downside to doing this? Also need to get my new wideband sensor hooked up. My first one burned out from being overly rich or something.

[Gregs672000]

Are you getting any smoke out the tail, as in burning oil? Otherwise, I would suspect a valve issue in #3. You mentioned you adjusted the valves, what lash spec and hot or cold? I tend to go a bit tighter than stock, 6in 8ex cold, comes out 8in 10ex hot. Also, 150-160 seems lowish to me... how did you test? Warm engine, throttle held wide open (hold it open with the hand throttle so you don't sit there and pump fuel in with the accelerators every time you push the pedal if you can), strong battery and several cranks?
Your sensor should not have died... warrantee time? You could have some gunk on the valves themselves from the rich condition, but it's hard to say... could be hanging up that valve from fully seating? Wouldn't hurt to run some cleaner. Yes, the idle holes are very small and the manual says it is easy to get stuff stuck in them. You can watch the fuel feed to the jet as I recall by removing some of the brass colored inspection caps that will expose the slow speed fuel feed holes just in front of the throttle plates, as well as the accelerator pump jet spot. Be careful to not loose the little washer when you pull out the jet, and they only go back in one way. Spraying carb cleaner down the pilot jet feed hole (look inside the carb with the jet out) should bring fluid to the idle holes (all done with the car off of course!) to make sure it's getting fuel. The idle screw itself is in front of the throttle plate. With it out, you should be able to see through the hole with a good flashlight. Move the throttle plate some if needed to see as they are quite close.
Hope this helps!

[CameronSF]

Hey Greg. No oil out of the tail to speak of. I went with .08 and .12 for the hot valve adjustment. The car was warm but it's possible that I didn't open the throttle enough...the last time around I got 185 on three cylinders and 175 on the third one. I have the type II solex carbs (if I remember correctly) that do not have the external adjustable float and kidney cover so I think you may be referring to a newer version. Regardless I'm going to spray some cleaner and air down the throat to see if it does anything. Of note is the #3 cylinder is the one I dropped the valve in and there is a ding in the piston which may account for slightly lower compression but I would be shocked if it's messing with the vacuum as much as it is. I'm a bit stumped. The innovate sensor went south on me - looks like from rich condition. It was all black and now I'm getting an error message from the new one. The exodus continues.

[Gregs672000]

Hmm, did you replace the valve? May have gotten bent? The ding will make no difference I'm afraid. The compression numbers look better and more typical. I believe you will have the same access to the holes etc that I described. There should be a screw cap in the center of each throat on top right in front of where the throttle plates are for this very reason. Also, if you pull out the pilot jet, you should see where the feed tube or channel is within the body of the carb for that circuit, stick the little flexible carb cleaner tube in there and spray away (watch your eyes!). The fluid should be very cleary flowing to where those holes are... I'm sure it's working or otherwise it would run like crap, but it might help confirm and/or clean out the circuit... couldn't hurt.

[Gregs672000]

BTW a leak down test will better tell you if that valve is not seating as well as the others. It doesn't sound like a ring issue. Something is not sealing as well in that cylinder. Sorry man. It's not terrible, but after having it fixed and given the expense and time, I'd be somewhat upset with the shop. Not much they can do unless you pull the head AGAIN, and it may improve over time as the parts work and wear together. Don't give up yet... make sure the carbs etc are all working well before going that route.

If you're still running rich, consider your float level as that influences that as well (thus the reason why they added externally adjustable float levels in later versions of the carbs). It may be expert consulting time... Dave Premo in CA or Dan Garrison in Oregon are good resources.

[CameronSF]

I was thinking of doing a leakdown test but don't currently have the equipment. The head was rebuilt by rebello with new valves, seats, cam, etc but the block was left alone as it didn't have any issues before. I'm going to tinker with some compressed air, carb cleaner, etc and will report back.

[Gregs672000]

Well, Robello certainly is known for good work... maybe it's more of a break in issue? What do they suggest?

[jamesw]

If you had a valve strike and bent valve on #3 you'd probably have the same on #1 - which you're not seeing. With 160 compression, you should be good to go.

Try a colortune sparkplug and see if you can get combustion in that cylinder if you squirt some gas in the carb throat. If you do then it's plugged jet or similar "no fuel" problem.

HTH
James

[SLOroadster]

I can't remember, do your carbs look like this (I can't remember)? These are early type 2 carbs. If so, you very well could have something going on with the accelerator pumps as the jets are in the venturi and are very small. That wouldn't account for lower vacuum on #3, but it might account for funky running.



Will

[fj20spl311]

I don't know if a "ProTune" measures, vacuum or flow. If it connects after the carburetor, its measuring flow.
Try opening the throttle on the rear carb until you get a measurement.
If you are measuring vacuum, try almost completely covering that bore to see if you get any vacuum.
I assume you looked for vacuum leaks.

[CameronSF]

Well color me stumped. I blew the carb passages out and sprayed carb cleaner throughout and no change. There was no valve strike on 1 as the strike was caused by a dropped valve seat that held the valve open. Thinking logically the issue has got to be related to the low vacuum on 3 but I cannot figure out why it is pulling such low vacuum but has good compression unless I have some massive intake leak which I cannot seem to locate. I can pull the number 3 plug wire and there is no change at idle - so that cylinder is dead at idle. It seems to come alive more at speed but something is still not right. I have even backed out the pilot screw all the way at idle to the point where it almost comes out and nothing happens. Frustrating.

[spyder]

I wonder if the pilot outlet is plugged.



I had trouble getting a smooth idle on mine until I linked the 4 intake tubes together. Blue pipe.