Carburetor ??
Thread Starter
|
Tuned
Joined: Jun 2006
Posts: 363
Likes: 3
From: Graham WA
Carburetor ??
I have recently pulled my 86 4X4 460 to clean up the oil leaks and put a straight up timing chain set in. I also removed some of the polution stuff to see how it would run without it.
It idles beautifully now. However, when I first hit the throttle it will sputter and maybe cough and then accelerate fine. I'm thinking that the 600 cfm holley may not be giving the engine enough fuel from the accelerator pump and it leans out with a sudden throttle opening.
Do I need larger or smaller shooters in the holley? It has a 1 year old holley 600 cfm model 4150 double pumper and it's a manual trans.
What else could cause the symtom?
It idles beautifully now. However, when I first hit the throttle it will sputter and maybe cough and then accelerate fine. I'm thinking that the 600 cfm holley may not be giving the engine enough fuel from the accelerator pump and it leans out with a sudden throttle opening.
Do I need larger or smaller shooters in the holley? It has a 1 year old holley 600 cfm model 4150 double pumper and it's a manual trans.
What else could cause the symtom?
Last edited by E30tdf; Dec 30, 2006 at 11:40 AM. Reason: speeling
Freshman User
Joined: Jun 2006
Posts: 36
Likes: 0
From: north west pennsylvania
in your opinion how much improvement was there with changing the timing set without any other mods? im looking at digging into mine this weekend to see if that has been done already when my father had it rebuilt in 98 or if they just put on a stock replacement. he removed all the emissions crap too back then. now i can only use it less than 5000 miles a year with the new laws. however if i drive 1000 a year im doing good thus far it seems.
Thread Starter
|
Tuned
Joined: Jun 2006
Posts: 363
Likes: 3
From: Graham WA
You will notice an increase in torque right away with the straight up timing set. I can't quantify how much, but if you put it on a dyno it is measurable I'm sure . I also had my distributer recurved. I forgot to mention that in the original post.
Has anyone else had similar issues as mine (leaning out on throttle response) after pulling the thermactor system (air pumps)? I'm still running an EGR.
Has anyone else had similar issues as mine (leaning out on throttle response) after pulling the thermactor system (air pumps)? I'm still running an EGR.
Thread Starter
|
Tuned
Joined: Jun 2006
Posts: 363
Likes: 3
From: Graham WA
Well gentlemen, I got out the vacuum guage again and started checking vacuum again and I learned something (new for me at least).
The vacuum reading is not the same at every available port on the holley 4150. On my engine I had attached the vacuum line for the distributer to the lower port which was pulling 5 lb. more vacuum than the port near the top of the carb. The lower vacuum was 15 lb. The higher reading was 20 lb.
Consequently, I had too much vacuum advance on my distributer as set up. Moved the line to the upper port and things got a lot better.
I still may need some larger squirters to get the stumble fixed completely.
The vacuum reading is not the same at every available port on the holley 4150. On my engine I had attached the vacuum line for the distributer to the lower port which was pulling 5 lb. more vacuum than the port near the top of the carb. The lower vacuum was 15 lb. The higher reading was 20 lb.
Consequently, I had too much vacuum advance on my distributer as set up. Moved the line to the upper port and things got a lot better.
I still may need some larger squirters to get the stumble fixed completely.
Junior User
Joined: Apr 2003
Posts: 88
Likes: 0
Besides the larger squirters you might want to go to a more aggressive accel pump cam. Find yourself a book on Holleys and do some research. You might even want to consider a 50cc accelerator pump kit. I used to run a 600 on a built 400 and had it tuned to the point where the off-idle pickup was as good as fuel injection. I run a built 460 now with a 770 Truck Avenger but the tuning principles are still the same. A 600 on a stock 460 should be adequate.
Trending Topics
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Originally Posted by DeanG
Besides the larger squirters you might want to go to a more aggressive accel pump cam. Find yourself a book on Holleys and do some research. You might even want to consider a 50cc accelerator pump kit. I used to run a 600 on a built 400 and had it tuned to the point where the off-idle pickup was as good as fuel injection. I run a built 460 now with a 770 Truck Avenger but the tuning principles are still the same. A 600 on a stock 460 should be adequate.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Thread Starter
|
Tuned
Joined: Jun 2006
Posts: 363
Likes: 3
From: Graham WA
I had already purchased the acceleator cam packet, but have so far only tried one new combination.
So Bear, what do you think is going on? From your signature, it would appear that you are up on all these problems.
So Bear, what do you think is going on? From your signature, it would appear that you are up on all these problems.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Generally vacuum leak (which you found already) or the accelerator pump linkage is not adjusted properly causes almost all this type of problem unless it is a timing issue. Having manifold vacuum to the dist. vacuum unit at idle can cause this.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Originally Posted by E30tdf
Thanks Bear! I like this forum and the people here show a lot of knowledge and class. Us WA fellas will have to get together sometime.
Thread
Thread Starter
Forum
Replies
Last Post
krazyness
1973 - 1979 F-100 & Larger F-Series Trucks
23
Sep 29, 2016 07:56 AM
forestgreen
1967 - 1972 F-100 & Larger F-Series Trucks
4
Oct 29, 2015 04:14 PM
Jnissen04
1967 - 1972 F-100 & Larger F-Series Trucks
8
Apr 15, 2014 11:14 AM