Timing and Dieseling

[maxtwms]

I really appreciate this. I know I've read all these on here before but when it becomes my problem the ideas seem to hold more weight. I owe 9/10 of my knowledge of these engines to this site alone so again, thank you. I'll replace that one plug wire tomorrow and retard the timing and see where my vacuum is after it warm up and I plug the choke port. I could totally imagine the manifold leaking. While we're at it.... The intake doesn't look aftermarket. If I were to replace it, what should I look for?? I know it's a pretty open ended question but I just don't know. But keep inind I want to eventually replace this 305 with a 350 so I'm trying to find compatibility with my bolt ons..

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[1987 GMC Jimmy]

Okay, I thought you were running a Quadrajet. You’re running a Holley 4175, right? The carb warping is not going to be a concern with this so I’d strike that from the list. You still have the base gasket and intake gasket to concern yourself with, though. The most ubiquitous spreadbore aftermarket intake is going to be an Edelbrock 2101. It’ll work on anything from a 262 SBC to a 400 SBC. Also, you mentioned at the beginning that you don’t have a fuel filter. I just wanted to make sure you realized that this model has an integral filter like a Quadrajet.

 

[maxtwms]

Okay, I thought you were running a Quadrajet. You’re running a Holley 4175, right? The carb warping is not going to be a concern with this so I’d strike that from the list. You still have the base gasket and intake gasket to concern yourself with, though. The most ubiquitous spreadbore aftermarket intake is going to be an Edelbrock 2101. It’ll work on anything from a 262 SBC to a 400 SBC. Also, you mentioned at the beginning that you don’t have a fuel filter. I just wanted to make sure you realized that this model has an integral filter like a Quadrajet.

Yea I was looking for an inline filter until I took the 4175 apart and found the internal one. All is well there. I also bought the 1/4" spread boar gasket to attach to the intake. I feel like I'mma replace everything but the engine before I get this running right. Still mad that I let my brand new plug wire melt on the manifold. I should ask while I'm at it.. the EGR valve is the one between the manifold and exhaust right? There's a tube coming out of it like a dipstick.. I can remove that solid line right? That going to affect vacuum? Should I plug it? See pic of silver cylindar between starter and manifold

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[1987 GMC Jimmy]

The EGR valve sits on the passenger side of the intake manifold at an angle next to the carb. What I see in this picture is the EFE valve. If you want to cancel vacuum going to that particular valve, you need to move that rod by hand to open the valve and tie it open. Then you can remove vacuum.

 

[Rusty Nail]

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"If I raise the idle by advancing timing"

This is flawed at the roots. You simply must eradicate THIS manner of thought.

Your heart is in the right place but you're not thinking about it correctly.

87 is barking up the right tree. Vacuum that low with timing that high is what Blue calls a Clue.

Anything built upon that poor of a foundation is destined to fall.
Raise vacuum with the base idle screws, not distributor advance. Timing is set AFTER the carburator is tuned properly, not in lieu of.

I think you have far too many "hard" numbers or adjustments in mind and now you question why it doesn't operate how you want it to. It's kind of like potty training a puppy...especially concerning forty year old street trucks. You have to work WITH IT , don't get angry because it continues to piss in the house after only two days of bad training.
It's unique in it's own way and worn out or in and suffered through all manner of terrible previous owners before it found you.

Start fresh. Ask it what it likes and offer suggestion and try new things until you both reach a mutual agreement.

You're going about this all wrong, it's obvious. Raising the idle by advancing igntion timing is fatally flawed from the onset. You are yelling at the dog after it peed inside because it didn't have to go when you wanted it to.

That's no way to train a puppy...

Hope this helps!

P.S.
VERY IMPORTANT to make sure the thermostat is open when attempting these adjustments or none of them will EVER be right.
EVER.

See what I did there? It's like potty training a puppy.

 

[CSFJ]

Was the balancer ever replaced after it was diagnosed as slipping?

 

[maxtwms]

Great analogy to the potty training! I appreciate that. To clarify, I wasn't necessarily trying to raise the RPM by adjusting timing. I was only suggesting that that is a symptom Ive noticed. I have always read to put the carb in a reasonable starting point (mixture screws turned out 1.5 turns, transfer slots showing square, etc.) and then get the timing for the motor to run about 750RPM, then adjust the carb for vacuum, then hook up the vac adv and set total timing to about 35btdc. But I digress - I agree that I'm going to have to stop engineering things on paper and assuming they should work because "thats what the manual(internet) says" and just realize this thing is it's own beast. Man, I can't wait to drive this thing one day!

 

[maxtwms]

Was the balancer ever replaced after it was diagnosed as slipping?

No. I figured I have it reigned in for the moment to get timing down. The truck hasnt moved from the carport in over a month... Only been cranked the past few days at idle and maybe a few throttle punches so it should still be relatively accurate.

 

[Obwonkonobe]

I'd look for an aluminum edelbrock dualplane, they're pretty solid if the pass the straight edge test. As far as testing your current intake for leaks. I've heard that if you spray carb cleaner around suspected leaks you can hear the motor rev because it well suck it in near a leak, but I'd be careful where I spray, maybe use some card board to shield the exhaust

 

[CSFJ]

No. I figured I have it reigned in for the moment to get timing down. The truck hasnt moved from the carport in over a month... Only been cranked the past few days at idle and maybe a few throttle punches so it should still be relatively accurate.

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[Honky Kong jr]

What could possibly go wrong when that outer ring flys off?????

 

[maxtwms]

Yep, just fixing 6 things to fix one. Ill get to it. Cash and other findings along the way are leading me different directions ATM.

Just ordered this one. The implied facepalm hurt me.
https://www.summitracing.com/parts/pfs-80000

Do I need any kind of special tools or can I just rent them from Advance if thats the case?
Im covering a lot of ground here.. I might need to rename the Thread lol

 

[1987 GMC Jimmy]

You need the balancer puller/installer. It looks like a metallic bird foot. I got the Dorman balancer from Autozone. I think it was cheaper than that one, they had it in stock, and it’s done well. It actually looks like it was made right.

 

[maxtwms]

Wow... I might have found the problem, or a least a contributor. By sheer luck I noticed in a video that I'm supposed to have a check valve needle under the discharge nozzle in the carb. I didn't know it was there and must have lost it during cleaning and rebuilding if it even existed in the first place from the PO.

I'm not sure but it may contribute to extra gas being pulled in, making my idle higher even at correct timing and might also contribute to the run-on... Please tell me I'm on to something here..?!

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[1987 GMC Jimmy]

My stance is anything helps, but there are bigger factors at play that cause run-on, high idle, etc. It may have some impact on the idle speed, but more fuel just muddles the AFR. Air is the key to idle. That’s why the engine idles up super high when you pull th line off the brake booster. As far as the dieseing goes, generally carboned up piston tops, poor gas, too far advanced timing, or excessive heat cause that. I think the balancer could be a problem, too, depending on how far gone it is.