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Username Post: Holley 4160 Tuning        (Topic#356462)
93 Suburban 
Member
Posts: 113

Loc: ON, Canada
Reg: 08-22-05
05-17-19 04:47 PM - Post#2766625    

I am helping out a friend with an '82 El Camino, trying to get it running a bit better. It has a LG4 305, Holley 4160 carb (maybe a 600?), with long tube headers and dual exhaust with cats. Otherwise it is pretty well stock. I set the timing on the car (seemed to run okay with about 10-12 degrees initial) and took it for a run. It seems to be fine at lower RPM low to medium loads. At full throttle/heavy loads it bogs when you punch it and has no power. Once it reaches high RPM than it starts to pull okay (no tach, so not sure on the RPM but it's not too long before it upshifts). Running WOT I am getting lots of fuel smell from the catalytic convertors (that rotten egg smell form rich mixture) and the tailpipes are sooty.

I am thinking that it may be running rich when the secondaries open, and then once the engine builds enough RPM the mixture leans out a bit and it makes more power. So, I was thinking that the vacuum secondaries are opening too soon and it likely needs a spring kit to tune it? The pump shot seems strong and the bog is too long to be related to that (IMO).

Anyone have any other ideas why it would have no mid range power at WOT but pulls okay at the upper end?


1976 Chev Chevelle Malibu Classic 2-dr



 


Shepherd 
Frequent Contributor
Posts: 1765

Loc: Lake George, NY
Reg: 11-11-15
05-18-19 05:45 AM - Post#2766652    
    In response to 93 Suburban

tough to diagnose from here, but if it has vacuum secondaries th may be opening too soon. That will cause a considerable bog.



 
93 Suburban 
Member
Posts: 113

Loc: ON, Canada
Reg: 08-22-05
05-24-19 05:57 AM - Post#2767009    
    In response to Shepherd

Thanks for the help. I did some more work on the car and noticed that the timing is advancing very slowly. It has about 34 degrees all in, but it doesn't happened until about 3800 RPM. That seems a little high doesn't it?

I was thinking of getting a vacuum secondary spring kit for the carb. Maybe also checking the jetting. What is a good starting point for a stockish 305 and a Holley 600 for jetting? I am not sure what Jets are in there now.

Any other advise is appreciated.

1976 Chev Chevelle Malibu Classic 2-dr



 
raceman6135 
Senior Member
Posts: 925
raceman6135
Loc: Calgary, Alberta, Canada
Reg: 11-04-02
05-24-19 07:44 AM - Post#2767012    
    In response to 93 Suburban

If you're getting gasoline smell and sooty pipes, I would tend to think that there is too much fuel and/or not enough air -- perhaps the secondaries are not opening at all.

Test the vacuum secondary pod by removing it from the carburetor, pressing up on the linkage, and place your finger over the vacuum port on the pod. The linkage should remain retracted into the pod; if it doesn't remain retracted, that means that the vacuum diaphragm is faulty and the pressure of the spring is returning the linkage to the 'secondary throttle closed' position.

If the vacuum diaphragm is working properly, when you remove your finger from the vacuum port, the linkage should extend down to its normal, resting position.

As for jet size, I would start with whatever size is stock for your list number of carburetor. Look up the size on this PDF from Holley:

https://documents.holley.com/techlibrary_carb_nume ...



Edited by raceman6135 on 05-24-19 07:46 AM. Reason for edit: No reason given.

 
Shepherd 
Frequent Contributor
Posts: 1765

Loc: Lake George, NY
Reg: 11-11-15
05-24-19 09:35 AM - Post#2767017    
    In response to 93 Suburban

I run my sbc at 15 initial, 35 total at 3k, unless you had high numerical gears in the rear, 3800 is too late, shoot for around 3k. Of course every combo somewhat different.



 


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