The 82 GMC I need some help!!!

[Squarebod]

I have an 82 Shortbed been playing around with it for a year now so here it goes.
I took a 350 out of an 82 RV 207 cast block.
Went straight to the machine shop had the block bored .030.
Machinist said I had a desired crankshaft so he polished it up for me.
Also installed new 12cc valve relief dish pistons. Stock rods.
Running a comp Mutha Thumper roller cam pn-12-601-8 to be exact. (Did not degree due to not even knowing about that I am a newbie as most would say but I am loving this project)
Double roller timing chain
Dart 180cc intake 64cc SHP series aluminum heads with .015 gasket and .028 deck clearance from block
Holley strip Dominator single plane
Assualt racing distributor 65k coil.
Holley 750 dp 4160 with conversion block 70pri jet 73sec jets 2.5 power valve
Th350 2500 b&m converter
3:42 gm12 bolt Spartan Locker


Here's my problem truck idles great in park outstanding throttle response then I drop it in gear and it just falls on it's face dies instantly doesn't sputter it's dead soon as it loads it idles about 1000rpm right now. I do have one soft spring and one medium spring in my distributor (a little trick I read don't know how it affects ((newbie))) is that a bad idea what springs should I run with an automatic or does it matter I only make about 6hg of vacuum at idle. Is it my carb do I need different jets or PV. What's a good timing for this setup got it 10 degrees initial and 36 total is timing my mistake?!?!

Please help me out thanks in advance. My 355 thanks you too haha

[mud.man.rj]

I'm not sure on your cam but that's low vacumn, especially with that intake, can see why you would lose your fuel signal, timing seems about right or ball park, from anything that I have ever learned the offset springs is a Ford thing, I usually run 2 mediums to start with, maybe go back to the heavier or at least 2 medium springs to start with, it's definetly not pulling fuel in at idle, maybe a vacumn canister would help.
I did have a similar problem years ago with a new big brand name 2,500 stall convertor that didn't stall at all and was locked at idle with a fairly conservative build and w make it stall at idle, temporarily swapped a stock convertor in just to try it and solved the problem, hard to tell online but that intake with that low of vacumn isn't going to help for sure. Does your distrib run a vacumn advance
Maybe someone else has a few more ideas.
Mudman.

[gmachinz]

Good Lord take that 2.5 PV out and put a stock 6.5 in there to begin with-then use a vacuum gauge hooked to an intake port and with the dist vacuum dis-connected the adjust your dist timing to the highest reading-then re-connect the vacuum line and test drive it. Dont make any other changes until you do that then list the result

[Squarebod]

Thanks for the help. I pulled my front bowl threw in my original 6.5 power valve and tried your test my distributor plugged and every port on carb except where I hooked up my guage my distributor is right where it wants to be lose vacuum both ways but I peak at 5.5-6 hg vacuum also lose vacuum when I adjust idle mix screws. So isn't my 2.5 PV the right choice that was what I was told by Holley to run because I'm running at such low vacuum? I'm new and I trust sites like these usually more than some tech guy behind a phone. Thanks. Oh yeah still dies when I put in gear with the 6.5 PV seems to be somewhat flooding or loading putting the 2.5 back in that's how I got rid of that problem in the first place. But anything is worth trying.

[geezer#99]

You got no initial timing.
At that 1000 rpm idle you’re already well into the mechanical timing.
Likely are right close to 2 degrees initial.
You need to get your idle down to 750 and then set your initial at 20.
Get a helper to hold it in gear or do the juggling act. Increase the initial a bit and then turn down the idle. Keep doing that until it will idle at 750.
20 is likely just a starting point. At your elevation you might need more. Don’t worry about recurving the dizzy until you find what initial your motor likes. Keep bumping it up until it’s hard to start. 2 degrees less than that will be right. Make sure you plug off the vac pot for your initial settings.
Here’s a link on setting your timing.
http://www.badasscars.com/index.cfm/...d=76/prd76.htm

[gmachinz]

To require a 2.5 PV means something isnt right with that setup. What octane rating fuel are you using? Pump gas? 64cc heads I'm guessing you're running about 10:1 at least.

[Squarebod]

Well guys I found the problem, and it hurts my pride a little to admitting this but it was low transmission fluid. I initially filled it after I broke my cam in. But it was a Gallon low so I filled it and it went right into gear and had a nice choppy idle around 500-700. Then I noticed my output shaft was leaking some where in the center by the u joint almost like it's cracked. I got a spare tho I'll have to pull clean and inspect and install but I drove it anyway and let's just say my face lit up like Christmas and so did my tires haha thanks guys this is my first time posting on this site, of I've spent hours upon hours on here. So thanks guys I'll post some pics of my project it's still a project so don't bash on my I'm not done building my dream. Merry Christmas to you all

[Squarebod]

Now I can get it in gear I can play some more I'm running 91 octane when at what point should I run higher my CR I may not be correct but based off my numbers I'm running 9.62:1
She does run and drive good now and she is fast even with my grocery getting gears I just need this automatic as a temporary i have a m22 4sp and will install different gears then too so your input will be helpful when that time comes but again thanks and Merry Christmas

[Squarebod]

I'm still curious to what could be wrong gmachinz I just assumed my cam was the result in the low vacuum I wouldn't mind one bit improving vacuum cause I just took a drag and my brakes are completely **** and hard as a rock. I got a canitster somewhere if I can find it would that help?

[gmachinz]

Ok-glad you found the problem! I forgot you mentioned running aluminum heads so compression tationisnt as much of an issue w/64cc heads as i had thought at first. Theres really no free lunch with high vacuum if you have a cam with a lot of duration. To solve your brake issue imo I'd suggest swapping to a manual disc brake MC like those offered from wilwood for example. Vacuum brakes require more vacuum than what your cam will build-vacuum can or not

[mud.man.rj]

Good point on the power to manual brakes, will help a lot w the vacumn signal and when you switch to the M22 will help also, nice project.
Mudman.

[gmachinz]

I'd use a 1.25" bore MC and stick with your stock lines-possibly add a rear prop valve to dial the rear brake bias down a bit.

[Squarebod]

So wilwood is not cheap but it would be nice to get rid of that pesky booster that's always there and in the way. How big of a difference is there with manual vs vac booster/hydro boost Im willing to work the cash on brakes something you don't wanna go cheap on my opinion but are they as good as an assisted brake setup cause I was thinking on getting a hydro boost system but I don't want to replace my vac boost with all the plumbing of a hydro boost plus I had a hydro boost system fail me once left me with nothing but a e brake. I have zero experience with manual are they as good is my big question.