Thanks for the info Wes. I'm getting ready to fire up the rebuilt motor in the Trans Am and going to stay with R12 on the AC.
CK5
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Wes's Burb build/update/maintance
- Thread starter Wes Harden
- Start date
Took the burb out for some wheeling innthe Hualapai foothills near Kingman.
Been sitting mostly since unBB24, other thanbthe fan clutch failure repair, done in September, i popped a air filter, and topped off the oil.
Has travel to and from moab, trails and coupke errands in Havasu, basically 3k miles.
Shots from trip.
Been sitting mostly since unBB24, other thanbthe fan clutch failure repair, done in September, i popped a air filter, and topped off the oil.
Has travel to and from moab, trails and coupke errands in Havasu, basically 3k miles.
Shots from trip.
Brush on the trail was pretty over grown.
Got this little owie. Hadvto be from brush.
Got this little owie. Hadvto be from brush.
That’s just wrong - it’s against the rules to damage a one year only ochre colored trim piece…
Brush marks are some of the worst.
My Dad used to call oakbrush, "yeeper bushes " because of the sound that they make dragging over the fenders.
Been tinkering with the timing Sunday and today.
I bought an Ac Delco oem GM number 93440806 distributor in June 2019, and just dropped it in and went.
Having a detonation issue, I think, I hear a rattle when accelerating from the tail pipe.
Began by checking the advances both mechanical and vacuum. Before Sunday I was using ported vacuum, for vac advance.
Sunday int
initial base timing, 550 rpm 15°
Mechanical adv @2k rpm 32°
@2.8k rpm 34°
Switching to manifold from ported at idle,
rpm did increase and went to 36°
1st change.
I wanted to limit the total amount of advance the vacuum can could give.
I went through my bucket of parts. I have several HEI distributors to rob parts from.
Comparing cans i noticed the slot opening for the rod were different lengths.
shiny is from my dist, grungy is from parts bin.
As you can the slot is much smaller. Fortunately that grungy can is good so I installed it.
Base timing @550 Rpm 15°
With vacuum advance timing @550 rpm 24°
Base timing at changed to 12° with Vac Adv 20.5°
Went for a short test drive. @ 5 mile on streets. Up hill from lake to house, 25 and 35 mph, trans in drive. I felt the power was a little smoother, but truck wasn't really working hard. More to do I could still hear the rattly noise.
Today
1st was to change the mechanical weight springs,
Used 1 heavy and 1 medium.
Base timing no vac @500 rpm 9°
Change base timing @ 500rpm 12°
Advance @1500 rpm 18°
@2000 rpm 23°
@2450 rpm 25°
@2750 rpm 27°
@2800 rpm and up 28°
Mechanical advance is adding 16° total. Spoke with Bent77 after this. Mark thought my base timing a little high and vacuum was still to much. I was thinking I need more mechanical advance, and agreed the vacuum was still advancing to many degrees.
I changed the springs to 2 mediums, and I slipped a piece of vinyl tubing over the vacuum can rod. The purpose of the tubing was to limit rod travel further.
The tube removed 1/32-1/16 to the rods travel.
Results
Base timing @500 rpm 12°
@1500 rpm 17.5°
@2000 rpm 23°
@2500 rpm 27.5°
@3000 rpm 29°
connect Vac @700 rpm idle 20°
total combined @3000 rpm 32°
Time for a road test. Got to highway, accelerated from a stop to 55, held 3rd gear to 50, then shifted up to overdrive. Still could here some rattling. Stopped to fill up, Sundays wheeling and my tinkering used 26 gl. I decided to retard the timing at gas station, left the dist just loose enough I could move.
Drive home seemed a little better.
Back in the shop I checked my adjustment,
Base timing @500 rpm 10°
reset base timing @500 rpm 8°
with Vac adv connected @700 rpm 17°
total timing 3000 rpm + 34°
Then dinner was ready so road test tomorrow.
Bent was right on with reducing the initial timing suggestion. I think it will be miles better.
springs in for ground are the original from the 93440806 distributor pretty weak and malformed. The black, heavy, and gold, light are from a kit.
HEI Tach tap tool
I bought an Ac Delco oem GM number 93440806 distributor in June 2019, and just dropped it in and went.
Having a detonation issue, I think, I hear a rattle when accelerating from the tail pipe.
Began by checking the advances both mechanical and vacuum. Before Sunday I was using ported vacuum, for vac advance.
Sunday int
initial base timing, 550 rpm 15°
Mechanical adv @2k rpm 32°
@2.8k rpm 34°
Switching to manifold from ported at idle,
rpm did increase and went to 36°
1st change.
I wanted to limit the total amount of advance the vacuum can could give.
I went through my bucket of parts. I have several HEI distributors to rob parts from.
Comparing cans i noticed the slot opening for the rod were different lengths.
shiny is from my dist, grungy is from parts bin.
As you can the slot is much smaller. Fortunately that grungy can is good so I installed it.
Base timing @550 Rpm 15°
With vacuum advance timing @550 rpm 24°
Base timing at changed to 12° with Vac Adv 20.5°
Went for a short test drive. @ 5 mile on streets. Up hill from lake to house, 25 and 35 mph, trans in drive. I felt the power was a little smoother, but truck wasn't really working hard. More to do I could still hear the rattly noise.
Today
1st was to change the mechanical weight springs,
Used 1 heavy and 1 medium.
Base timing no vac @500 rpm 9°
Change base timing @ 500rpm 12°
Advance @1500 rpm 18°
@2000 rpm 23°
@2450 rpm 25°
@2750 rpm 27°
@2800 rpm and up 28°
Mechanical advance is adding 16° total. Spoke with Bent77 after this. Mark thought my base timing a little high and vacuum was still to much. I was thinking I need more mechanical advance, and agreed the vacuum was still advancing to many degrees.
I changed the springs to 2 mediums, and I slipped a piece of vinyl tubing over the vacuum can rod. The purpose of the tubing was to limit rod travel further.
The tube removed 1/32-1/16 to the rods travel.
Results
Base timing @500 rpm 12°
@1500 rpm 17.5°
@2000 rpm 23°
@2500 rpm 27.5°
@3000 rpm 29°
connect Vac @700 rpm idle 20°
total combined @3000 rpm 32°
Time for a road test. Got to highway, accelerated from a stop to 55, held 3rd gear to 50, then shifted up to overdrive. Still could here some rattling. Stopped to fill up, Sundays wheeling and my tinkering used 26 gl. I decided to retard the timing at gas station, left the dist just loose enough I could move.
Drive home seemed a little better.
Back in the shop I checked my adjustment,
Base timing @500 rpm 10°
reset base timing @500 rpm 8°
with Vac adv connected @700 rpm 17°
total timing 3000 rpm + 34°
Then dinner was ready so road test tomorrow.
Bent was right on with reducing the initial timing suggestion. I think it will be miles better.
springs in for ground are the original from the 93440806 distributor pretty weak and malformed. The black, heavy, and gold, light are from a kit.
HEI Tach tap tool
Last edited:
8* initial is where I always start.
I have very few examples of running dist/carb, but it seems that the GM curves were usually late bringing in the mechanical advance (emissions? mountain gas?) and lighter springs usually pleased the butt dyno.
I was always told 2* and then 2* per 1000’
But is hard for me to test that being as 5000’ is the lowest elevation I’ve ever seen
10 is a good number. They seem to be lazy under that that. I also lean pretty hard on timing, so 12-15 before vac advance is where I start
Pretty sure I used these https://www.summitracing.com/parts/fel-7733pt2/make/chevrolet in 1993
emission tunes with egr, used more base timing and ported vacuum advance. Which is what I have known my whole career. My only real high hp engine had an Accel dual point in it, no vac all mechanical. Malory Unilite was newish and $$$, or magneto were the other options.
I figured out the vac can numbers. The 1st 3 are the last 3 of GM part number. The last 2 are the amount of advance. So shinny one is 20°, and grungy is 10°
I wish I had the deck height written down. I think it may be less than .020" more like .015-.018
Under 9 comp ratio I shouldn't have a detention issue.
I never did when this engine was in front of a manual trans in a different truck. Gas was better then and regular 91 not 87.
Under 9 comp ratio I shouldn't have a detention issue.
I never did when this engine was in front of a manual trans in a different truck. Gas was better then and regular 91 not 87.
yes block is decked,and bored .030, align honed, rotating assembly balanced.
