Carburetor + Transmission Question

[patriotgames65]

Hi there. Hoping someone can give me some insight to a couple of concerns I have going at the present time. I'm just a dumb welder, so please use lay-mens terminology if responding. And thanx in advance for the help/input.

I recently purchased a 79 GMC High Sierra in fantastic shape but with all the general things that go wrong on a 30 year old truck. When it comes to u-joints and such, I'm good to go. Get much deeper, and I bog down.

Ok, the truck was originally equipped with a 400(vin # decode) but now sports a swapped in 350, at least, I've identified the heads as 882 series heads but have not been able to id the block as of yet. # stamped on pass. side head under the Alternator does not correspond with any decoding info I have been able to locate on the web.

Motor is equipped with an Edlebrock 1406 series carb, Edlebrock intake, run of the mill rusty as hell headers and farm boy dual exhaust with generic glass paks. Additionally, the truck has a 4 inch lift and 33x12.50/15's.

This truck will be seeing duty as my daily driver and of course, I would like to find the best power/economy ratio that I can achieve. My 1st question is this, what would be the best metering kit to put into the 1406 to lean it up a bit, but still maintain a respectable amount of power? Any Edelbrock experts out there?

2nd question: When accelerating from a stop, when the transmission shifts, it shifts into 2nd very quickly. I would say within 2-3 seconds of appying the accelerator. Then the transmission winds up considerably, and I have to "feather" the accelerator to get it to shift into 3rd. I know that it could be any number of things, but my question is, what would be the first thing I should check, second, etc. etc. short of cracking the tranny?

Again, sorry for the long post, and thanx for any help you can give.

Kevin

[wyattglock]

I would check the vacuum line that runs from the intake to the modulator on the passenger side of the trans and make sure it is not dried and cracked. If that is good, I would probably replace the modulator with a new one. If you get a decent adjustable one, it should come pre-adjusted for roughly a factory style shift. There is a set screw inside the modulator that you can adjust the shift points with if you want to tweak it a little.
Good luck with getting the carb setup, I have always just used the stock setup on an Edelbrock 1406. Of course, with a right foot that feels like a chunk of lead, tuning really doesnt matter for gas mileage in my case.

BTW, awesome looking truck!

[patriotgames65]

@ wyattglock

Ok, thanx, you confirmed what my research was leading up too. I'm none to experienced with Chevy's, and the last Ford I had was a 68 Cougar XR7 with a wee 302 and that was, umm, nearly 30 years ago! Been building Harleys for the last couple of years, so, I have a basic understanding of mechanical things but no practical experience with truckx.

Thanx again!

Kevin

[wyattglock]

No problem! I have been helped by a lot of guys on this site also, I only hope what little I may know can help someone else. Good luck with the truck!

[bhummell]

eldebrock has a kit for its carbs around 60.00 dollars. has the jets and metering in it.I did one this summer for a customer .droped it 2 jet sizes in the main jets with leanest rods that were in the kit. did not change the rear jets. the 1406 is jetted common so it will work on most anything it is put on.
I do not care for them. they tend to be hard on gas . i had one on my pontiac and pulled it installed a quadrajet off my race car. with 66 jets. diffrent primary rods . and cv secondary rod went from 10 mpg to 18 mpg.

if you want to set up your current carb i can get the part numbers of the parts that i used. also when i had that carb apart floats were off by alot and not even in sinc.


on your trans which trans is it. depending on it being a turbo 350 or 400 the 350 use a cable to modulate the shifts. were the400 uses vacume and the governor.

[James McClure]

I spent 33 years working for Chevy as a dealer mechanic and rebuilt thousands of 350 transmissions. That being said, the 350 downshift cable is just that, a downshift cable. It does not "modulate" shift points. The only reason it has a downshift cable is to make downshifts more positive and faster to lesson slipage. The shifts are all governed by a "ballancing" act between the shift modulator and the governor. Most often shift errors can be traced back to the shift modulator or the vacuum circut to the modulator. Second would be the governor driven gear "apple coreing". The driven gear gets it's center torn out, it should be flat or straight accross. To check the governor, pop the cover off (left side of trans near the back) pull the governor straight out and look at the gear. Next, turn the governor gear up and hold the fly weights in and look thru the slots in the shaft, let the weights (1 at a time) fall free. You should see the internal valve move up and down. If the gear is apple cored it means the governor bore in the trans case is to tight, usually caused by dirt, bad fluid or a serious over heat. Lastly would be a valve body problem, but this is really rare in both the 350 and the 400. Hope this helps. I'm not trying to knock anyone here. There are some misconceptions about the purpose of the downshift cable on older transmissions since the 700's came out equiped with a detent cable instead of a shift modulator. jim

[patriotgames65]

That's why I LOVE this site, there's a ton of info here and it's all mine for the asking. Will be wrenching this weekend dusk to dawn, will take all into advisement Thanks much!

[bhummell]

Originally Posted by James McClure

I spent 33 years working for Chevy as a dealer mechanic and rebuilt thousands of 350 transmissions. That being said, the 350 downshift cable is just that, a downshift cable. It does not "modulate" shift points. The only reason it has a downshift cable is to make downshifts more positive and faster to lesson slipage. The shifts are all governed by a "ballancing" act between the shift modulator and the governor. Most often shift errors can be traced back to the shift modulator or the vacuum circut to the modulator. Second would be the governor driven gear "apple coreing". The driven gear gets it's center torn out, it should be flat or straight accross. To check the governor, pop the cover off (left side of trans near the back) pull the governor straight out and look at the gear. Next, turn the governor gear up and hold the fly weights in and look thru the slots in the shaft, let the weights (1 at a time) fall free. You should see the internal valve move up and down. If the gear is apple cored it means the governor bore in the trans case is to tight, usually caused by dirt, bad fluid or a serious over heat. Lastly would be a valve body problem, but this is really rare in both the 350 and the 400. Hope this helps. I'm not trying to knock anyone here. There are some misconceptions about the purpose of the downshift cable on older transmissions since the 700's came out equiped with a detent cable instead of a shift modulator. jim

i agree but also in my 35 years as a mecanic. i have seen cable out of adjustment cause the above problem on a turbo 350 more than once.
and if i have missed something { which is useally the case } i have not seen a indication of what trans it is.