390 - Vacuum tuning/timing question
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390 - Vacuum tuning/timing question
I set my timing, and fuel mixture using a vacuum gage last night to the optimum vacuum(highest that I could get) and kept resetting the idle screw to keep it right at 800 rpm. Once I put the air cleaner back on I then have an idle of 600 rpm ( 500-600 is the recommended idle with an automatic..in drive with brights on). My question is should I have done it the other way...that is set the timing and fuel mixture up at 600 rpm and THEN added a couple hundred rpm with the idle screw to compensate for the air cleaner? Guess I'll try it and see tonight if it makes a difference, but I just wondered if anyone else has a procedure they've used sucessfully.
I know this is an old time, low tech way of tuning but it sure made my 390-2v run a heck of a lot stronger, from idle through punching it at 75mph, by setting the timing, and fuel mixture using a vacuum gage instead of using my timing light and CO meter and strictly setting it at the recommended values (which I'd tried).
Got the details from here if you're interested in trying it:
http://www.sarcasmracing.com/wish/Tech/Tuneup/tune.html
Thanks in advance.
I know this is an old time, low tech way of tuning but it sure made my 390-2v run a heck of a lot stronger, from idle through punching it at 75mph, by setting the timing, and fuel mixture using a vacuum gage instead of using my timing light and CO meter and strictly setting it at the recommended values (which I'd tried).
Got the details from here if you're interested in trying it:
http://www.sarcasmracing.com/wish/Tech/Tuneup/tune.html
Thanks in advance.
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390 - Vacuum tuning/timing question
The filter element is brand new. The last one recently got soaked with antifreeze when the heater hose to the carb sprung a leak right under the air cleaner housing.
The heat flap in the air cleaner housing is open full time because I unhooked the spring that pulls it open to the exhaust manifold heat. The thermostat bulb mechanism is apparently busted as it won't close the flap (and override the spring) like it's supposed to when it gets heated up to 185 degrees(I tested it in an oven). I took it all apart and cleaned and checked it all before the test....to no avail.
I don't think it's all air cleaner..remember I'm putting it in drive and with the headlights on bright so that's sucking up some of those rpms too.
The heat flap in the air cleaner housing is open full time because I unhooked the spring that pulls it open to the exhaust manifold heat. The thermostat bulb mechanism is apparently busted as it won't close the flap (and override the spring) like it's supposed to when it gets heated up to 185 degrees(I tested it in an oven). I took it all apart and cleaned and checked it all before the test....to no avail.
I don't think it's all air cleaner..remember I'm putting it in drive and with the headlights on bright so that's sucking up some of those rpms too.
Post Fiend
Joined: Feb 2000
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From: Brea CA
390 - Vacuum tuning/timing question
In drive? Oh, I missed that, never mind…
About the procedure, I don’t think it will make a difference. Try it and let us know, note what your timing and mixture screws are set at before you readjust them.
Hey you like Triumphs? I used to have a ’71 TR6 and a ’78 Spitfire. TR4A's are cool!
Barry
About the procedure, I don’t think it will make a difference. Try it and let us know, note what your timing and mixture screws are set at before you readjust them.
Hey you like Triumphs? I used to have a ’71 TR6 and a ’78 Spitfire. TR4A's are cool!
Barry
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From: Oztralia
390 - Vacuum tuning/timing question
This procedure wont give the best economy.
You are only at first base ( best throttle response)
To achieve economy you need to lean it out to cause about a 50/75 rpm drop. This is especially true with holleys.
You are only at first base ( best throttle response)
To achieve economy you need to lean it out to cause about a 50/75 rpm drop. This is especially true with holleys.
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390 - Vacuum tuning/timing question
Sorry Barry, I was being lazy in my typing. I should have mentioned not only the air cleaner but also putting it in drive and having the headlights on bright whenever I mentioned the rpm drop.
I tried setting the timing and mixture at 600 and 800 rpm and it didn't seem to make a difference so I'll leave it where it was. It is better but I still feel like I'm getting the power and accleration that I should be getting from a 390. Certainly not the tire smoking power I see some talk about on these message boards.
I've had various Triumphs for the last 25 years and drive my 71 TR6 all over the country. Have gone from Portland, Maine to Portland, Oregon the last couple of years. Off to Minnesota this summer. The TR4A is my retirement project and I got the F250 as a Triumph support vehicle so I can haul frames, bodies, and various other parts around town.
Thanks
I tried setting the timing and mixture at 600 and 800 rpm and it didn't seem to make a difference so I'll leave it where it was. It is better but I still feel like I'm getting the power and accleration that I should be getting from a 390. Certainly not the tire smoking power I see some talk about on these message boards.
I've had various Triumphs for the last 25 years and drive my 71 TR6 all over the country. Have gone from Portland, Maine to Portland, Oregon the last couple of years. Off to Minnesota this summer. The TR4A is my retirement project and I got the F250 as a Triumph support vehicle so I can haul frames, bodies, and various other parts around town.
Thanks
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390 - Vacuum tuning/timing question
I'll try the 50/75 rpm drop thing as I continue to tweak the carb. Thanks for the help.
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Post Fiend
Joined: Feb 2000
Posts: 5,130
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From: Brea CA
390 - Vacuum tuning/timing question
Bud, if you’re not worried about getting the best mileage then I’d leave the mixture screws where they are. I do the lean drop method when gas gets over $2.00 a gallon in order to squeeze a few more miles out of the tank but the engine sure feels a lot weaker. This is with a 625 Carter, you might want to see how it affects your Autolite.
Wow, you really put the miles on your TR6! Guess you don’t follow the Lucas motto: “Get home before dark.”
I had a hard time keeping the carbs. in sync for any period of time, always needed fiddling. Also had the factory wire wheels that liked to come off the hubs. Can you still get Michelin Redlines? So your truck is the Triumph support vehicle, hey you need a TR250 to put in the back of your F250! Email me some pics if you get a chance.
Thanks
Barry
Wow, you really put the miles on your TR6! Guess you don’t follow the Lucas motto: “Get home before dark.”
I had a hard time keeping the carbs. in sync for any period of time, always needed fiddling. Also had the factory wire wheels that liked to come off the hubs. Can you still get Michelin Redlines? So your truck is the Triumph support vehicle, hey you need a TR250 to put in the back of your F250! Email me some pics if you get a chance.Thanks
Barry
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390 - Vacuum tuning/timing question
Never heard of the Triumph's wire wheels coming off...unless of course they mounted them wrong...have heard of that happening with MG's though, something to do with sudden hard stops. I initially had a problem with fuel contamination that drove me nuts messing with the carbs but once I got it figured out my carbs have held steady for a couple years. Ya gotta have a decent synchronizer and the uni-syn that was sold for years is not one of them. I got one for JC Whitney that is super. I'd thought about a TR250 and if I found a good one I would buy it...that'd be cool having a F250 towing a TR250..but I drive my cars everywhere so I don't know when that'd happen. They are roadsters afterall and I take that to heart. The TR250 is the car Triumph should have kept making...it's the best combination of styling and power that they ever came up with. So of course they made them for 1 1/2 years and switched to the TR6. Which I love but still the 250 was more of a classic.
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