What did you do TO or FOR your Datsun today?(Roadsters only)

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redroadster68
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Re: What did you do TO or FOR your Datsun today?(Roadsters only)

Post by redroadster68 »

Replacing the rear shocks. Right rear had zero rebound. Left soft. Not sure age but rubber was in perfect condition . Used the ole zip tie method to compress for install. Far stiffer than old
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datsun510 1971 past
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redroadster68
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Re: What did you do TO or FOR your Datsun today?(Roadsters only)

Post by redroadster68 »

New fronts. KYB KG4528
New rears . KYB KG5447
datsun510 1971 past
Triumph GT6 1968 past
Austin Healey 100-6 1957 past
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redroadster68
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Re: What did you do TO or FOR your Datsun today?(Roadsters only)

Post by redroadster68 »

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datsun510 1971 past
Triumph GT6 1968 past
Austin Healey 100-6 1957 past
Infiniti G37Xs 2009 current
Datsun 2000 solex 1968 current
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redroadster68
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Re: What did you do TO or FOR your Datsun today?(Roadsters only)

Post by redroadster68 »

Just need to wait for all the snow to melt and test em out ! Only one of the old shocks was completely toast. One other was pretty soft .
Upgraded Sway bar next 😷
datsun510 1971 past
Triumph GT6 1968 past
Austin Healey 100-6 1957 past
Infiniti G37Xs 2009 current
Datsun 2000 solex 1968 current
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itsa68
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Re: What did you do TO or FOR your Datsun today?(Roadsters only)

Post by itsa68 »

Finally installed the new rear springs I had kicking around.
(Also, my worn seat belts were re-belted and installed last week, but no pics yet)
20210517_142816_small.jpg
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Ray B.
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Re: What did you do TO or FOR your Datsun today?(Roadsters only)

Post by notoptoy »

Nice progress!
"When all else fails, force prevails!" Ummm, we're gonna need a bigger hammer here.

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Re: What did you do TO or FOR your Datsun today?(Roadsters only)

Post by DCooke »

I was experiencing some pinging when accelerating from a stop. So, I changed the dashpot oil from ATF to MMO, wow, that really made a difference! Marvel Mystery Oil for the win.
Dave Cooke
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Gregs672000
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Re: What did you do TO or FOR your Datsun today?(Roadsters only)

Post by Gregs672000 »

DCooke wrote: Fri Jun 04, 2021 9:29 pm I was experiencing some pinging when accelerating from a stop. So, I changed the dashpot oil from ATF to MMO, wow, that really made a difference! Marvel Mystery Oil for the win.
Is it lighter or Heavier? I'm just curious as its an interesting way that an SU manages air/fuel ratio adjustments. It must slow or increase the speed of the piston rise.
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Re: What did you do TO or FOR your Datsun today?(Roadsters only)

Post by DCooke »

Gregs672000 wrote: Fri Jun 04, 2021 11:23 pm
DCooke wrote: Fri Jun 04, 2021 9:29 pm I was experiencing some pinging when accelerating from a stop. So, I changed the dashpot oil from ATF to MMO, wow, that really made a difference! Marvel Mystery Oil for the win.
Is it lighter or Heavier? I'm just curious as its an interesting way that an SU manages air/fuel ratio adjustments. It must slow or increase the speed of the piston rise.
I really couldn't tell visually which was thinner or thicker & I didn't look that closely or touch the fluid. Visually, they just appeared to be a different shade of red. I can go back and see if there's a telltale sign to see or feel the difference between the two. But on the performance side, there definitely is a noticeable difference, at least on my car. I used an eye dropper to remove the old ATF, so switching to MMO was a simple quick test that didn't required taking the domes off.

I agree, that changing the dashpot oil to another fluid does slow or increase the suction piston rise. Which in my experience was easily noticeable. While the engine idled the same with either fluid, with the ATF, the engine would give a quick ping with a puff of smoke after leaving a from a stop. I had to be careful to depart slowly or this would happen frequently after the motor was warmed up. Moving to MMO in the dashpot, I immediately notice a change & this ping/puff issue was now gone & I didn't have to baby the engine when leaving from a stop. It also seemed to be a bit smoother overall during higher speeds. Anyways, interesting to say the least & I'm glad I tried it. #easy
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Re: What did you do TO or FOR your Datsun today?(Roadsters only)

Post by Gregs672000 »

I'm gonna guess that it's delaying the rise of the piston slightly. The oil is in there to keep the piston from slamming up with the sudden and high vacuum change that occurs when you open the throttle plate and suck in a bunch of air before the fuel flow can catch up with it. Conversely however is the fact that you have a graduated needle that allows more fuel flow as the piston rises, so the lower the piston the less needle exposed/less fuel available. I'm thinking however that there's enough available fuel/flow with the needle down lower and the most important thing is to not suck in too much air. Since an SU has no accelerator pump it is interesting to me how it compensates, and it must be this very simple system controlled by oil viscosity. Pretty cool!
Someone with a wideband should document what happens with different oil viscosity... could be a useful tuning tool for those who are trying to dial in their SUS.
Glad it worked for you!
Greg Burrows
'67 2000 #588
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Re: What did you do TO or FOR your Datsun today?(Roadsters only)

Post by 70MTRoadster »

OK Greg and others....I have scientifically tested the differences on my U20 SU carbs from 10-30 Mobil 1, to 3 in 1 oil to Marvel Mystery Oil and MMO is the winner........again! this time, however, it is with an Air Flow Meter, your old one Greg. Each test was done with a warmed up engine and all three fluids started at a 10.9 idle. Starting from a stop and accelerating hard, full throttle, showed 10.9 with the Mobil 1 and 3 in 1 but 11.7 and up with the MMO. Seat of the pants says WOW....much faster accell with the MMO.


Acceleration was better the thinner the oil was with the MMO winning. From this I am speculating that we are over dampening our suction pistons. I have used 3 in 1 oil since the 70's, trying to approximate 10 weight oil which I think what is what Datsun specified??

Now, the interesting thing is that after I got the AF meter from Greg, I leaned out the mixture wheels under the carbs and thought I had a 14.7 idle mixture with both carbs balanced with a unisyn. So.....just like Greg's journey with his fuel injection, I need more testing in that why did my numbers change from 14.7 to 10.9? I will reajust to 14.7 at idle with MMO, then report back.

Scott
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1972 510 4 dr. vg30e/5 sp. ricky racer
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I drive a Roadster or 510 almost every day!