Timing a U20

Tech tips and how to's

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SLOroadster
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Re: Timing a U20

Post by SLOroadster »

Sounds like those SUs are tired, or something isn't seated correctly. If the rear is pulling more than the front carb, clearly its out of balance, or there is something lose allowing the carb to move or something odd like that.

Will
Sorry, I find modern engine swaps revolting. Keep your G, R, or U series in your Roadster!
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jasmith1975
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Re: Timing a U20

Post by jasmith1975 »

Circling back on this as I did some more fiddling and got things running pretty good. No more coughing or backfires. Idle holds steady at 900-1krpm, a little high but she seems happy there. Next is to finish the desmogging journey, remove all components and then plug ports. I have Dean's air injector plugs queued up although looking for a solution to plug the 3 ports in the carb manifold. After that, we'll address the dizzy with either a recurve or EI. Here's what I did:

1. Disengaged air pump by removing belt (didn't have to remove fan or shroud)
2. Pulled all vac hoses and capped connection points
3. Installed new vac hose from dizzy to front carb; only 7/32 available locally which is a little big at the carb - zip tied it for now
4. Retimed engine to 35 BTDC at full advance (3k rpm)
5. Resynced carbs and adjusted idle
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RustyBucket
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Re: Timing a U20

Post by RustyBucket »

Is there a check list of ports to plug-up and things to do on a ''69 1600 when doing a DESMOG ? Especially, addressing the calibration the dizzy with either a re-curve or EI ?

Thanks !!
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jasmith1975
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Re: Timing a U20

Post by jasmith1975 »

RustyBucket wrote: Tue Jun 29, 2021 7:59 pm Is there a check list of ports to plug-up and things to do on a ''69 1600 when doing a DESMOG ? Especially, addressing the calibration the dizzy with either a re-curve or EI ?

Thanks !!
All I did was locate the vac hose connections from the air pump, pulled and capped/plugged. Then I ran a new hose from the dizzy to the front carb. I left the smog system on the car, but removing the belt made it inoperable. I timed the engine to 35 BTDC at full advance (3k rpm) and seems reasonably happy. Not sure if the 1600 is the same as the U20 but when I finally remove the system, plugging the ports should include:
  • Plug 4 cylinder head air injector ports - Dean has a kit for this (#2208)
  • Plug 3 carb manifold ports (photo)- heard this can be accomplished with standard plumbing hardware
  • Plug upper radiator ports (photo)
As for the dizzy, I believe once you have a non-smog unit (either recurve or EI) it's a matter of timing engine to 16 BTDC. May need to adjust idle and sync carbs to fine tune. I'm far from being a master mechanic, so others with more knowledge may weigh in.
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Solex68
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Re: Timing a U20

Post by Solex68 »

There are a couple of recurve kits on ebay. Make sure you get one with springs.
Greg
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68 2000 U20
Always willing to help another Datsun Roadster owner
Pending installs: SS brake lines, Stan Stealth Dizzy
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RustyBucket
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Re: Timing a U20

Post by RustyBucket »

Thanks for the information !!

My first "69 SPL purchased ( here in Maryland) used in 1973 had not been tampered with , and only had the air pump and the few extra hoses- and NO Gas Vapor tank in the trunk.. ( The car was sold back in 1977 :-( )

Many Moons later, I have another "'late '69" ) purchased from Oregon) with a Vapor tank in the trunk and I think even more hoses.

The Left coasters must've required the extra bits out there ??

Question: What is the smog port on the radiator hose port in your photo? How does that work ?

Cam
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jasmith1975
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Re: Timing a U20

Post by jasmith1975 »

RustyBucket wrote: Wed Jun 30, 2021 7:40 pm Thanks for the information !!

My first "69 SPL purchased ( here in Maryland) used in 1973 had not been tampered with , and only had the air pump and the few extra hoses- and NO Gas Vapor tank in the trunk.. ( The car was sold back in 1977 :-( )

Many Moons later, I have another "'late '69" ) purchased from Oregon) with a Vapor tank in the trunk and I think even more hoses.

The Left coasters must've required the extra bits out there ??

Question: What is the smog port on the radiator hose port in your photo? How does that work ?

Cam
Apologies for the delayed response. I'm not exactly sure what those 3 smog ports do. All I know is there were hoses running from there to the smog/air pump system. Since I was disabling the smog system, I assumed (famous last words) these ports also needed to be capped.

How did you make out?
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Gregs672000
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Re: Timing a U20

Post by Gregs672000 »

I know theres a name for that... I believe it activates a thermo reaction valve and has something to do with making sure the engine doesn't melt down under certain circumstances. I'm not kidding l'm but it's not important with the smog system removed. You might check the U20 manual on line.
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RustyBucket
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Re: Timing a U20

Post by RustyBucket »

Greg,
Sorry to get back to you late. We have a son who's getting married soon, so there is a bit of "... runnning around with hair on fire".
I actually whimped out and took the engine block and head to a machine shop for them to go over it. Since the car is pretty much apart , I thought it would be "smart" to have a shop plane the head ( maybe) , deck the block, boil it, flux it, polish the crank journals , etc .
I'm looking for a shop that can go through a 5 speed I found on craiglist ( from Washington State) some ten years. - which is a problem since must machinist with the skills are retiring ..:-(
Smog line and Metal Fuel/Brake line runs are not documented or photographed enough for me.. I have to "SEE IT!"

Hope you got your car sorted out !
Cam
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RussellC
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Re: Timing a U20

Post by RussellC »

Cam,
You are welcome to come back down to DC and check out my de-smogged late '68 1600 once the dust has settled from wedding season. Congrats BTW!
Russell

Got her running, now need to do everything else...
1968 1600 "Custom" driver/project car
2018 Toyota 4Runner Limited 4x4
2012 Hyundai Genesis Coupe 3.8 GT
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RustyBucket
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Re: Timing a U20

Post by RustyBucket »

Hey Russell,
Hope you got your car inspected and road worth to be able to take the Mrs. for a ride with the roof down to look at the Autumn leaves soon.

I drop my motor off at a machine shop to have some work performed and in the "spare" time I'll attack the body and rocker panel rust :-(

Later Bubba!
Cam