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tuning ?

Old 07-21-2014, 06:04 PM
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Engine: carb'd 357 vortec
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tuning ?

Hey fellas gott a car 92rs see my sig. That loves btdc as I guess most cars do. I stopped at 14dbtdc bur of course it loves more. I started tuning for vaccum and idle. Oh yeah how low is too low for idle? How far is too far for btdc? Right now the best I got it running is 750 rpm, 13-14in vac 14btdc, the prob I was having was only 10vac and no brake boostrr.
Old 07-21-2014, 06:12 PM
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Re: tuning ?

Originally Posted by budget builder
Hey fellas gott a car 92rs see my sig. That loves btdc as I guess most cars do. I stopped at 14dbtdc bur of course it loves more. I started tuning for vaccum and idle. Oh yeah how low is too low for idle? How far is too far for btdc? Right now the best I got it running is 750 rpm, 13-14in vac 14btdc, the prob I was having was only 10vac and no brake boostrr.
Do you have vacuum advance and is it connected to manifold vacuum??
Old 07-21-2014, 06:16 PM
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Re: tuning ?

Just tested at above parameters and now booster kick n going for test drive
Old 07-21-2014, 06:40 PM
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Re: tuning ?

Don't outsmart yourself over some "number" you think you're seeing.

THE ENGINE does not whup out a timing light, check some "mark", and decide how it's going to run accordingly.

THE ENGINE will tell you in no uncertain terms if it's unhappy with the timing; or more specifically, if it's less happy with any change you just made. It will also tell you in equally uncertain terms if it's HAPPY.

All you gotta do, is learn to listen to its language. Don't even have to SPEAK its language; just listen and understand.

"If it RUNS good, is IS good".

Make it run the best it can. At that point, you'll know you've got it just about right. (or at least, as right as it CAN be, given the curve that either your ECM or your springs weights & vacuum can are set up for)
Old 07-21-2014, 06:45 PM
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Re: tuning ?

Ok brakes worked a little they were ok at low speed but suck at higway speed emergency stopping but at least now I don't have to stand on them. At 14dbtdc the car diesled a litlle when shutoff I'm going to go to 16dbtdc and see if 1. Vac increases 2. Idle increases w/o turning screw 3. Dieseling stops. Then I'm going back down the road. My timing ligHt is almost toast I hope it lasts. Also is dizzy adv supposed to be connect to manifold vac on carb during these tests or am I correct in leaving it disconnected until after I get it all dialed in? Will post results

Edit. Just read above post. Ur right! It started dieseling so back to 16 or beyond.

Last edited by budget builder; 07-21-2014 at 06:48 PM.
Old 07-21-2014, 07:55 PM
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Re: tuning ?

Sorry for all the updates but getting frustrated. Ok, just drove on pavement and on grass.
Results: I nEed a timing tape. B/c I have no idea where the timing is but the enigine started diesling a little and was alittle hard to start so I backed off and adjusted the air/fuel screws and it decreased dramatically. I got. 19in vac and brake booster works but brakes (rear) still don't lok. The front completely lok on grass and feel good on pavement. The rear are still rolling. Driver side has new wheel cylinder the and brake shoes were cleaned. pass side wera adjusted. Both side were turned by hand with wheels on and were tight but not so far out that they stay loked (about .5 to .75 of a turn). Does the driving in rev and stopping thing really work? Thinking of getting new drums and shoes. But nothing really wrong with these (that I can see)

Last edited by budget builder; 07-21-2014 at 08:00 PM.
Old 07-21-2014, 08:03 PM
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Re: tuning ?

I have vaccum adv on dizzy. Dizzy is not connected to carb. All tests were conducted w/o dizzy connected. Even when 19in was achieved (no dizzy advance) connected. Carb manifold vacc is capped off

Last edited by budget builder; 07-21-2014 at 08:09 PM.
Old 07-22-2014, 07:15 AM
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Re: tuning ?

Use the vacuum canister on the distributor. That way you can retard the initial timing to about 8* (without vacuum) for ease of starting and once the engine fires up the vacuum canister (hooked to manifold vacuum) will advance the timing for better idle and cruising.

With the rear brakes have you replaced the rear rubber hose? As these cars get older these hoses will swell internally and block off the line. I had a front line go bad where I drove 40 miles to Ky Speedway for a drive the track special and on the way home I stopped at a light and one of my front wheels wouldn't release the brake pads fully which made the car pull to one side. Called AAA and had it towed home.
Old 07-22-2014, 07:28 AM
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Car: 91RS
Engine: carb'd 357 vortec
Transmission: 700r4
Axle/Gears: 3.42 posi
Re: tuning ?

I thought the brake lines in the back were steel all the way from the mas/cylin they are metal at the wheel cylinder. someone told me to check the proportioning valve I don't know how to check. and I cant find one for sale on rockauto, advance auto, autozone, or parts warehouse. and as far as the dizzy vac I will try that. and will post results.

Edit: forgot to say on grass; front lok rear don't, in reverse same thing. If I pull emergency brake lever up about 3-4in the brakes engage and the car screeches to a hault w/o touching brake pedal. If I let go of all brakes it will coast no brake dragging/locked from over adjusting. If I pull e-brake and hit pedal it THEN will stop like it should!

please help I will check when I get hom how to test prop valve? will check for rubber hose and since I already have the wheel cyl for the pass. side I will replace and bleed. by Wednesday.

Last edited by budget builder; 07-22-2014 at 09:01 AM.
Old 07-23-2014, 06:44 AM
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Car: 86 T/A - 70 Z28/RS
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Transmission: 700R4 - M22
Axle/Gears: G80, 2.73 - ZQ9 G80 4.10
Re: tuning ?

The rear rubber hose goes from the car chassis over to the axle and there is only one hose. It will look like this
http://shop.advanceautoparts.com/p/w...erm=brake+hose
Old 07-23-2014, 09:17 AM
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Engine: carb'd 357 vortec
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Re: tuning ?

thnks for info on rubber brakes line I found this;

https://www.thirdgen.org/forums/brak...lve-video.html

and here's some more info:

Made it home: jacked car up one side at a time the wheels are looser than what I adjusted quite a bit more. I had no problem taking off drum on either side Pass side wheel cyl had two baad stiff places in the plunger so I just changed it out re adjusted the brakes And bled, then re bled the driv side after readjusting brakes (remember I already changed that leaking wheel cyl.) drove around yard good improvement. From what I learned from reading the prop is working properly when the rear brakes don't lok. But still assist in even braking so I guess this is the best I can hope for with drums. Brakes do fEel better I just thought they should be locking up but from the video it seems that I might be having trouble out of the metering valve. I will keep digging! thanx fellas!
Old 07-23-2014, 06:26 PM
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Re: tuning ?

Problem solved: u kno if a person would slow down and double check maybe we would see and realize that on the pass side the brake shoes were rev'd. Meaning the big long pad was on the back and the small slim pad meant for reverse was on the front in the drive position. I reversed them,put them in the correct position and used a a stainless steel brush on all brake shoes and drums then readjusted both sides. And voila the difference is amazing. Don't git me wrong they are still stock but man does it stop! Thx fellas I guess I was just in too big of a hurry when I changed them. Now on to tuning this monster I need a 600cfm insteAd of this 750 but since ithis is all I have I guess I have to try to git it runnin right. Timing,vaccum,fuel efficiency,and power;oh my!
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