Timing and Dieseling

[maxtwms]

I think were getting close to wrapping this thread up. Here's what I did over the weekend -
- Holley says there is not a choke valve needle in the 4175, so my last post was moot
- I added a gasket on either side of my thermal insulator (there wasnt one on either side when I bought it and assumed the insulator acted as one)
- Idle was off because of my inexperience with carbs.... I screwed in the choke stop screw so the secondary butterflies could close further allowing me to back off the secondary idle screw, therefore allowing the primaries to close further which gave me more adjustment for the idle screw.

Here are the results
- 12*btdc, 700rpm, 17inhg, zero dieseling (87 ethanol free)
- 10*btdc, 750rpm, 15inhg, dieseling (87 ethanol free), zero dieseling (93 premium)
- 6*btdc, 750rpm, 13inhg, dieseling (87 ethanol free), never got to try 93, possibly today

I adjusted the AF mixture screws each time to try and dial in the highest vacuum, this was usually around 1.25 to 1.75 turns out.
I also sprayed choke/carb cleaner around the base of the carb and vacuum lines with no affect. Forgot to check the intake manifold so Ill do that today too.
I can't tell if I have an air leak or just poor bearings on my pulleys...

Dampener came in so Ill try and put that on this week so I can actually find total timing (60* worth of marks) and quit this guessing game.

 

[maxtwms]

Im installing the dampener and I noticed in the dish of the pulley, there is an extra "weight" it looks like. Is this supposed to mount opposite the key?

 

[maxtwms]

Dammit, went to put the balancer on and I hit hard torque before it was seated. I have about a 1/4" left. I have a feeling I just didn't buy the right one. I got this one..
https://www.summitracing.com/parts/PFS-80000

After searching online, I'm still not sure wth I need to get. Mind you I have a 305... Any ideas or recommendations?

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[1987 GMC Jimmy]

I used a Dorman 594-009 from Autozone for my 305. Went on without a hitch, it appears well made, and it works fine. They carry them at the store so you should be able to pick on up tomorrow if you so desired.

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[maxtwms]

Nice! That's cheaper too.
The one I got just doesn't seem deep enough. I probably have 2" from the outer face to where I feel the crankshaft. I didn't pay attention when I pulled the old one off unfortunately.
Wife and kids are headed to the beach before I have to join em in 3 days so I was trying to knock a lot of this out in that time so I'm trying to make orders asap if I even have time. Thank you for the rec by the way!! I may have to do that

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[1987 GMC Jimmy]

I would have been hesitant with the Summit one myself. The dimensions of this other one are identical to OEM so there weren't any fitment problems. For me, it was quicker getting together than taking apart so you should be able to knock it out in a day tops. I did my water pump at the same time, too.

 

[1987 GMC Jimmy]

You going to Gulf Shores from north AL? Is the truck ready for that?

 

[maxtwms]

Ha I'm going to Destin but I'll be taking the Lexus ls460 for that. I rented my wife and kids a Toyota sienna to take. She drives a Lexus rx350. Both are 07 models. We're trying to replace hers with a Sequoia at some point but more space and in-laws are coming too so they're gonna chip in on the rental. Not gonna lie, I thought about taking the square

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[sparky11]

The champion sparkplug website says dieseling is caused by too hot of sparkplug.

 

[maxtwms]

Been a while on this thread but all is well with "Donald Truck" timing lights, vacuum guages, and internet's about vac advance, mech advance, base timing, timing curves, etc... For one thing... Get yourself an adjustable vac advance. Mine pulls 20 effing inches for some crazy reason and I'm dealing with it right now but whew! The best way to time your car I found was setting it at a safe 10 or so with a slightly snug but, driving down the road, giving it hell, and moving that distro a wiggle. Anyway, shameless bump to the top of the forum! KAG!

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[75gmck25]

I switched to Blueprint aluminum heads and a 213/217 cam, and when I tuned it for best AFR I found there was a fairly narrow AFR range where it did not diesel (I have a wideband). I am set with base timing of about 15-16 degrees, and 20 degrees mechanical. I run off manifold vacuum, which pulls the RPM up at idle.

I tuned for best vacuum, but then had to go about 1/2 turn leaner to get it to not diesel. Best vacuum was an AFR of about 14.5-14.7, but the best non-diesel idle shows more like 15.5-16.0 AFR.

Bruce