Upgraded U20 Head Install

[SLOroadster]

I'm looking forward to getting this thing sorted out. The engine feels really strong, but in need of a tune. I'm also curious if the math does indeed work out. It doesn't work for my engine with the 40s, but I have higher compression and far higher flow through the head (So much so that other math says my engine needs 50mm carbs, and Dave R will agree with that.) Speaking of the bleed tubes, I don't remember seeing any in the jet blocks now that I think about it. I'm 99% sure they were there, but I didn't happen to try and remove one to see what it was.

The WBO2 sensor is a great way to fine tune, but at this point just getting the driveability sorted out is the bigger challenge. At this point if the engine is below 4000 rpm it doesn't drive. It sputters and stalls and sneezes though the carbs.

Will

[Gregs672000]

Lean or plugged pilot system, assuming timing is right...

[SLOroadster]

Yes, lean pilot system, or it could be a lack of a heat shield, or both. With 60 pilots, it should be pretty close, but even opened way up it doesn't run any better. I have all my jets now so sometime this week I might be back down there trying again.

Will

[spyder]

I ended up with a bit larger pilot jets than the formula determines to solve low rpm driveablity. It helped with the transition from the pilot to the main jets. I also increased the accelerator pump orifice and it solved the sudden throttle opening stumble.

[jamesw]

The early style Type IIs require bigger pilots IMO because they are not homogeneous circuit carbs. I also noticed mine didn't idle well unless they were idling in the mid 11s. I confirmed this with my colortune sparkplug. A/F was saying 13s but the "flame" was too blue. Once at mid 11s the "flame" was the blue-to-orange that it should be.

HTH
James

[spyder]

The early style Type IIs require bigger pilots IMO because they are not homogeneous circuit carbs. I also noticed mine didn't idle well unless they were idling in the mid 11s. I confirmed this with my colortune sparkplug. A/F was saying 13s but the "flame" was too blue. Once at mid 11s the "flame" was the blue-to-orange that it should be.

HTH
James

Same here. When my engine heats up the idle leans out. Here it is idling cold, and it ends up mid scale when it gets hot.

[SLOroadster]

We made huge headway this afternoon. The car is now easily driven. Its lean on the top as I didn't have a set of 200 air jets, but it really seems to like the 160 fuels, the 220 airs are lean. Pilots appear happy with 60s 2.5 turns open (tried 62.5s but it wasn't as happy)

Will

[spyder]

Pulled out my paperwork to refresh my memory of what jet I use. 75 pilots, 185 fuel and 180 airs.

[AidanDawn2000]

75 pilots, 185 fuel and 180 airs.

I thought running bigger fuels than airs was a no no. Doesn't run too rich?

[spyder]

75 pilots, 185 fuel and 180 airs.

I thought running bigger fuels than airs was a no no. Doesn't run too rich?

Keep in mind, these are 50's and I do have a afr monitor. There is a minor leaning around 3500 rpm doing a full throttle pull but no pinging.

[AidanDawn2000]

75 pilots, 185 fuel and 180 airs.

I thought running bigger fuels than airs was a no no. Doesn't run too rich?

Keep in mind, these are 50's and I do have a afr monitor. There is a minor leaning around 3500 rpm doing a full throttle pull but no pinging.

Interesting. If I ever get a pair of 50s( ) i'll try it

[Gregs672000]

See, every engine and carb set up can be different, thus the use of an A/F meter...

[CameronSF]

Progress is definitely being made. The car didn't feel as good as when we had the 165/180 with 62.5 combo so I went back to 165/200 with the 60's and then 165/180 with the 60's but I think I'm going backwards. The good news is I fabricated a new dogleg that is a little longer so the throttle feel is better and just had the O2 bung welded into the exhaust. I'm just about to wire in the gauge itself...which leads me to a quick question: so I don't recreate the wheel is there a good spot to tap into switched power and the headlight switch in the glove box for dimming capability? I'd prefer not to go fishing around under the dash. Another question - my high beams are stuck on and the dash lights won't come on. Will mentioned it may be the relay on the driver side under the hood adjacent to the carbs. He mentioned the solder joint sometimes goes bad...is there a good way to test this or track down this issue?

[Gregs672000]

Afraid I can't suggest a good switched hot as my car was (wonderfully and thankfully) rewired by Curtis with an aftermarket set up. However, I am very glad you are going with a A/F meter... you won't be guessing what direction to go on your jetting! Over time and practice you will be able to figure out what system is doing what. Realize that you may be a bit rich at idle and slow speed running at times as these heads and the cams we run tend to be a bit dirty due to over lap etc. I idle in the low 13's upper 12's no matter what I do unless I make it really unhappy (lean) and the idle just sucks. As you test, be easy on the throttle at slower speeds and lower rpms and you will be able to see how the pilot system jetting is working. Mains (on my Dells anyway) come in above 3200-3500 rpms depending some on load, and of course at wide open etc (Note: Dellortos are different and have more slow speed fuel feed holes than Mikuni, which is what makes them perfect for my particular, rather sensitive engine, so your mains may come in earlier). The accelerators are self explanatory, and are usually on for about 2-3 seconds max at full pump. Gross adjustments are generally made with main fuels, finer adjustments with airs.
Have fun!!! You're gonna learn a lot!!!

[CameronSF]

Big progress today. Installed and fired up the wideband I purchased. Come to find out I was pegging the gauge lean at idle at 22.4. Haven't had a chance to take a spin but I backed out the mixture screws 3.5 turns and got it idling smoother at around 14...obviously needs different pilots! Is there a rough mixture screw turn/pilot jetting number correlation? I thought will mentioned it was about 1/2 turn for every 2.5 pilot jetting increase/decrease but I can't remember. Looking forward to getting this sorted out! Thanks again to everyone on this thread for all the help.