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383 hesitation

7K views 47 replies 4 participants last post by  jaw22w 
#1 ·
I have been lurking a long time, but this is my first post.
I have just installed a new 383 from Skip White Performance in my 1927 T roadster and am having some small problems.
Specifications: Long but maybe helpful

Car:
2280# with driver
3.55 rear gear, (Frankland quick change)
26" rear tire
TH350C w/ 2500 stall

Engine:
440 advertised HP using 93 octane premium pump gas
383 SBC
Flat top forged pistons w/ 2 valve relief, 10.8-1 CR
210CC procomp aluminum, 64cc, 2.02/1.6
Howards roller cam:
Lift: w/1.5 rockers .530/.545 (1.6 rockers installed)
Adv dur: 286/294
dur @ .050: 233/241
LSA: 110
Procomp Hi-rise air gap intake
QFT SL-750 carb vac.2ndary
jets 72 front 82 rear
idle air bleed 70/39
hi speed bleed 31/31
pri nozzle 35
needle and seat 110
power valve 6.5
HEI ini 24*, mech 10* total 34* no vacuum advance
Autolite 5224 plugs @ .035
1-5/8 lake style headers into 2-1/2 exhaust in front or rear tires
10-11" Hg @ idle

PROBLEMS:
ROUGH IDLE: White says not to use the vacuum advance. Motor seems to want more advance at idle. Why not use the vac adv to increase the advance at idle.
BUCKING OR SURGING at cruise speed. ???????
HESITATION at hit of throttle. ??????? bigger squirter????

I think I have searched out and read everthing to do with timing on this site. This has been very helpful, but I have had the timing all over the place and have not been able to eliminate the surging or hesitation. It must be in the carb. I am not a very good carb tuner. I know there are a lot of very knowledgable people participating in ths forum. I would appreciate any help you guys can give me Thanks in advance.
Jim
 
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#36 ·
the adjustment bolt is between the upturned end of the rod and the can. The bolt is parallel to the long portion of the vacuum rod. As the vacuum comes in and the upturned end of the rod moves toward the can, the bolt contacts the upturned end of the rod and stops its movement, thus limiting the amount of advance. I hope this makes sense. I have attempted to post a picture, but was unsuccesful. I will work on it.
 
#40 ·
Posting photos: http://www.hotrodders.com/forum/how-post-pictures-videos-hotrodders-com-210091.html
Edit- just saw you figured it out.

Pump free play at WOT:

Basically, you want zero play at rest, foot off the gas pedal.

With the throttle opened wide open, there has to be about 0.015" play so the pump diaphragm isn't damaged from the linkage over-traveling.

The adjustment is made using the small bolt/spring that contacts the pump arm and a feeler gauge (see below). This photo is one that shows the feeler, etc. good, but the adjustment bolt and nut are upside down plus don't look to be original (shouldn't be slotted). Assembled correctly, the adjuster nut, bolt, and spring should look like the second photo.

Holley's instructions on the shooter and cam are on page 6 and 7, here.



 
#46 ·
Custom10, I brought up the vac adv question because White performance told me not to use it. I wanted some confirmation from some of the expertise I knew was on this forum. I have always run my circle track race motors at 34* total with no vac adv and the advance numbers seemed very high to me with vac adv. This new motor was a large investment for me and I didn't want to burn it up. I have seen the results of too much timing in race motors. UGLY!
 
#48 ·
Update: I jetted the carb up to 76 on the primary and changed the primary nozzle from .035 to .040. It was nice out today, so I took the roadster for a ride. These changes got rid of the hesitation and the bucking or surging. Don't know which change helped, but the car runs like a raped ape now. Again, thanks to Cobalt327 and Custom10 for all the help. I am very happy with the results.
 
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