Upgraded U20 Head Install

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CameronSF
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Re: Upgraded U20 Head Install

Post by CameronSF »

Hey Greg,
Thanks for checking in. So here's the latest and greatest - I opened the throttle bodies and got much better compression numbers. 185, 180, 175, 185. Compression is still a little low on the #3 cylinder which was the cylinder that dropped the seat. There was a small ding on the piston which may be lowering the chamber volume. I also was able to roughly sync the carbs enough to drive over to the local exhaust shop and have them weld on the flex pipe, 2" pipe through the frame rail, dynamax muffler and then 2 1/4" from the muffler back. The sound is pretty loud...I may need to add a glasspack to quiet things down a bit more but will drive it a bit before doing anything. I fabbed up a new throttle stand (my carb setup did not have one) from an old SU unit I got off ebay and tapped the valve cover vent to add an elbow and crankcase filter. I was still getting a lot of upper valvetrain noise so I decided to at least do a cold valve adjustment and set the valves to .006 / . 010 for the time being. I started it today and everything is still pretty loud but when I checked the valvecase vent it seems it has calmed down a bit...there is still what I would consider excessive crankcase pressure but I'm hoping the engine may have been a bit out of sorts from sitting for more than a year. Mr. SLORoadster Will has been really awesome with suggestions and feedback and has gracious enough to volunteer to come over tomorrow and help with syncing the carbs and tuning. I got a little backfire out of the carbs today and do not have a good uni-sync setup for the solex carbs so am looking forward to his help. When I came home from the exhaust shop I got some pretty decent pinging when I drove up my steep driveway (I had to make a run at it to get up and back in the garage) so I'm guessing they are too lean. I'll post an update after Will comes over tomorrow and we get some tuning time in.
Cam
- Cameron
San Rafael, CA

1970 2000 SRL311 #13184
1990 300ZXTT
2006 Infiniti FX35 DD
2000 Crown Vic 'Queen Vic' 24 Hours of Lemons ' racecar'
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Gregs672000
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Re: Upgraded U20 Head Install

Post by Gregs672000 »

Much better numbers, Good! Hope it all works out well!
Greg Burrows
'67 2000 #588
Tacoma, WA
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AidanDawn2000
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Re: Upgraded U20 Head Install

Post by AidanDawn2000 »

Maybe it just needed to be run and go through some heat cycles to be happy. Best of luck!
Oil a little low? Time to get a longer dipstick:)
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CameronSF
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Re: Upgraded U20 Head Install

Post by CameronSF »

Here's hoping some heat cycles and carb tuning are the fix! Fingers crossed!
- Cameron
San Rafael, CA

1970 2000 SRL311 #13184
1990 300ZXTT
2006 Infiniti FX35 DD
2000 Crown Vic 'Queen Vic' 24 Hours of Lemons ' racecar'
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SLOroadster
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Re: Upgraded U20 Head Install

Post by SLOroadster »

Headway was made this afternoon. The car had a host of issues, none all that difficult to solve. The cam timing was a tooth off, the intake valves were all too tight, ignition was at 28 degrees btdc, and the upper tensioner was WAY over shimmed , and had some screwy homemade anti drainback thing in it. We got all the mechanical stuff sorted out, carbs balanced, valves adjusted and took it for a spin. The carbs have massive amounts of seal drag on them and don't want to close and also don't want to idle. It doesn't help anything that the pilot jets are too small, the air jets are small and the fuel jets are larger than the airs. Above 5K or so the car pulls pretty well, but getting it to 5K takes some work. Once we get the jetting sorted out, this thing should rip. Also, I wonder if the carb bodies are the independent type that use the OA jet blocks? I'll have to remember to check that when changing the jets.

Will
Sorry, I find modern engine swaps revolting. Keep your G, R, or U series in your Roadster!
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Gregs672000
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Re: Upgraded U20 Head Install

Post by Gregs672000 »

SLOroadster wrote:Headway was made this afternoon. The car had a host of issues, none all that difficult to solve. The cam timing was a tooth off, the intake valves were all too tight, ignition was at 28 degrees btdc, and the upper tensioner was WAY over shimmed , and had some screwy homemade anti drainback thing in it.
Will
No problem for someone experienced with the U20, but it's a good thing you know that engine! Step by step. I'm interested to hear how the smaller exhaust seat theory works out...
Greg Burrows
'67 2000 #588
Tacoma, WA
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CameronSF
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Re: Upgraded U20 Head Install

Post by CameronSF »

Will was a huge help when he came over today. You can tell he's been working on these roadsters for 15 years! I would never have noticed the strange shims and anti drainback thingy in the tensioner. I knew we had to adjust timing and valves since I set them cold but finding the cam timing a tooth off was a big surprise as I was 99.9% sure I put the gear back on where it was originally. This leads me to wonder if it was always a tooth off as it never seemed as sporty as it should have been. I've got jetting in that Dave Premo originally recommended but its apparent we are off quite a bit and will need some tuning. With all of that being said I'm extremely excited to have been able to get the thing on the road again! There is a bit hesitation at throttle tip-in but at full throttle it seems to catch up but I think its still not quite right. Either way - Will's help was invaluable getting the throttles balanced and the mixture close for where its jetted. I'll report more as soon as we have a chance with different jets!
- Cameron
San Rafael, CA

1970 2000 SRL311 #13184
1990 300ZXTT
2006 Infiniti FX35 DD
2000 Crown Vic 'Queen Vic' 24 Hours of Lemons ' racecar'
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Gregs672000
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Re: Upgraded U20 Head Install

Post by Gregs672000 »

As I discovered, cam timing makes a huge difference in how the car runs. Despite cam tower shims, newer chains, decent gears etc, mine was several degrees off. During that time I was attempting to jet the carbs and run 40mm chokes and was never able to get good A/F readings consistently... there was always some area where I just couldn't get it right, usually over-fueling on top no matter what jets I tried, and a refusal to rev to redline. I did all kinds of things, including modifying the emulsion tubes themselves, until I gave up on the 40s and went to 37s, which improved overall running but it still wasn't right. The adjustable gear was the ticket for my engine, and at the moment it is only on "best guess" based on JT68s suggestions and my crude measurements. A dyno and some time to play is needed to get the most out of it, but it has run so damn good this summer it has not been a priority. However, that cam timing change made all the difference. The engine is significantly better, easy to drive under normal conditions around town despite the cam and modifications, revs to red line and still pulls, and gives great A/F readings everywhere. Modifying an engine requires tuning, and has to take into account all aspects of the entire system. I have no doubt that you will continue to find more power and drivability as you continue to fine tune it. For me, the final piece I suggest to you is the ol wideband A/F meter... no more guessing on jetting, you will KNOW if it's right. To me, next to the EI distributor (good for a stockish compression engine) the best money one can spend to improve a sidedraft carbed engine (Solex, Dellorto, Mikuni, Weber, etc) is the wideband. And if you are not sure your stock cam gear is going to give you proper cam timing, then the adjustable gear is a must.
Check you cam timing as close as you can. If OK, then do your jetting. If the cam is off, get the adjustable gear and try to get it right (JT can help there). Then fine tune your jetting if needed. It is not easy to check cam timing. I had to be pretty sure of my timing marks on the crank pulley as I had to set it up for the megajolt, so that made it a bit easier as I was fairly confident on what true TDC was, but it is still best guess, and the only way to know is to run her on a dyno, adjust the cam timing a degree or two, run it again and see what happened, and keep adjusting from there... time, money and patience.
Just my 2cents! Have FUN!!!!
Greg Burrows
'67 2000 #588
Tacoma, WA
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CameronSF
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Re: Upgraded U20 Head Install

Post by CameronSF »

Greg,
Thanks for the input! What sort of wide band are you running? I was thinking about that earlier and it sounds like a worthy modification. I've got the EI dizzy so that may be next on the list.
Cam
- Cameron
San Rafael, CA

1970 2000 SRL311 #13184
1990 300ZXTT
2006 Infiniti FX35 DD
2000 Crown Vic 'Queen Vic' 24 Hours of Lemons ' racecar'
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Gregs672000
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Re: Upgraded U20 Head Install

Post by Gregs672000 »

I have a glow shift version. A couple days/week or so ago I posted an Innovate one that was on Ebay as I recall, about $150 bucks plus install (which likely requires a trip to the muffler shop to have the O2 sensor bung welded into the collector, above a 90 degree angle to keep moisture from building up on it from condensation). Try this one, screaming deal I think... http://www.ebay.com/itm/Innovate-NEW-38 ... 0Q&vxp=mtr
This one looks to not need the "box" controller I have, so less complicated install or location. If I didn't already have one, I would probably get this. Some of the others allow data logging etc which is nice but not that necessary... you can monitor your A/F as you drive to see what its doing. It won't always be perfect with carbs, but you're looking for about the upper 13's to upper 14s for cruising (14.7 being "perfect"), mid 12's on acceleration (acceleration jets squirting for a time, then the mains take over, staying upper 12s to 14s with your foot in it). I can't tell you how helpful this is when setting the different circuits (pilots vs mains, plus accelerator pumps). Just driving around town at lower rpms you will be mainly on the pilots, then if you hit it you will see if you go too lean suddenly (might be pump jets are to small, not working, etc) or too rich (pump jet too big or duration too long), then what the mains are doing mid rpm (main fuel jet, too rich/lean), and then main air (mostly controls high rpm mix and kinda keeps the main fuel jet from over fueling)... that's a rough description, as the jets all influence each other so it's not just one or the other, but it gives a good idea of where to start. For example, she is great driving around town off idle and lower rpms (pilots are good, idle screws about right) and ok in mid range (main fuel is probably close), but goes too rich above 5000rmps for example, might try the next size up air jet and see what it does, etc. No guessing, no reading plugs, immediately able to see the results and feel how the car responds. Priceless.
Everyone has different views on what works well, specifically for our Mikuni carbed cars. Dave Premo has a theory that he works from with reports of good results; others have different theories or settings with also good results being reported... the A/F meter and how the car responds will tell you what works best for your car. No engine is the same, and yours now has a different head with changes to exhaust velocity, and that combined with which cam, intake filtering, exhaust header, exhaust size, ignition timing etc all contribute to what works best on YOUR car. I would say the octane of the fuel in CA also contributes, as well as sea level (my engine requires a bit of octane booster with CA gas in Shasta, as the gas there is 91 and my compression is 11.7 to 1... ok here in WA with well controlled timing and cooler weather and lower sea levels, but I don't hammer it in 4th gear at 2500 rpms with my cam and not expect her to complain!). Obviously, I love my A/F meter. If you read through all the trials and tribulations I posted trying to jet my engine you will understand!
Greg Burrows
'67 2000 #588
Tacoma, WA
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Gregs672000
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Re: Upgraded U20 Head Install

Post by Gregs672000 »

BTW, I have pretty much the same exhaust on my car (2.25 to the Dynomax, then 2.5 out, with the added Monza tip that kinda quiets things a bit and gives a richer sound. My carbs (currently with foam socks) are louder than my exhaust, so I won't change the exhaust until I make and install the cold air box again... if I ever get to it... but you might try the Monza tip and see if you like that.
Greg Burrows
'67 2000 #588
Tacoma, WA
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Gregs672000
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Re: Upgraded U20 Head Install

Post by Gregs672000 »

I also see you have a Rebello cam, which per Will is somewhat different if it is the same one he's running, so yet another reason to have an A/F meter to check your jetting, as it may not respond to typical jetting.
Greg Burrows
'67 2000 #588
Tacoma, WA
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CameronSF
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Re: Upgraded U20 Head Install

Post by CameronSF »

Thanks for the recommendations Greg. I'll take a look at that Wideband...seems like a worthy investment. I fired it up today and took it for another spin after installing a 'helper' return spring until I have a chance to get the correct throttle return spring. I think I may have gotten some of the permatex gasket maker on the throttle shaft which is gumming it up a bit. I'll drive it a while and see if it works itself out before taking it apart again.
Video of startup here...note fancy wheel and my custom console. (I still have the original but decided to install a double din I had laying around)

Second Solex Startup
- Cameron
San Rafael, CA

1970 2000 SRL311 #13184
1990 300ZXTT
2006 Infiniti FX35 DD
2000 Crown Vic 'Queen Vic' 24 Hours of Lemons ' racecar'
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SLOroadster
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Re: Upgraded U20 Head Install

Post by SLOroadster »

Gregs672000 wrote:I also see you have a Rebello cam, which per Will is somewhat different if it is the same one he's running, so yet another reason to have an A/F meter to check your jetting, as it may not respond to typical jetting.
His cam is much less aggressive than mine, mine was designed for Randy Carter's E Production SCCA race engine, but it made its power too early (they were looking for power at 9000 rpm :shock: ) Just looking at Cam's cam, I'd guess its closer to what a C cam would be, but I don't know for sure.

In doing the math, with 37mm venturis, it wants 148 fuels and 168 airs, so 150/170 will likely be a good starting point. I think the 60 pilots will be ok. The 137.5/135 combo that is in the car is really not right. I also think running a slightly longer dogbone will help the linkage work correctly as well. Another 1/4 inch would do wonders for things.

Will
Sorry, I find modern engine swaps revolting. Keep your G, R, or U series in your Roadster!
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Gregs672000
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Re: Upgraded U20 Head Install

Post by Gregs672000 »

I hear you on the jetting, but I do also know that Dave has been doing some experiments and research and coming up with what sounds like unconventional jetting that has worked well per others on this list, as well as on his car, while others disagree... All I know is that I trust the A/F meter and that every engine is different. How the jets interact with the emulsion tube is a bit of a "black box" kinda thing where even back in the day they were not always sure how things would work until they tried them. There may be more than one way to skin this cat so to speak. I think my original late version Mikuni A-11 carbs came from Nissan with a 135main and 140air on 34mm chokes, but who knows if that was just a standard "throw some jets in there" or if they had jetted them specifically for the typical U20. They worked, and I didn't make a jet change until I went to 37mm chokes.
Regardless, it should be fun to see how it all comes out!!! Glad you were able to help him Will.
Greg Burrows
'67 2000 #588
Tacoma, WA
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