Holley 4160 carb tuning questions

[WisconsinCutlass]

Very informative and helpful. I was thinking because I was running rich after the secondaries opened that openeing it sooner would help. Like the bog was happening before the secondaries opened. If that makes sense. I was planning on going up a few sizes on the Accel pump to see what happened. It has a 31 in it now and I think the next size I have is a 35. I also have the pump cam set. Can't remember what color is on it currently. I think either orange or pink?

 

[vanrah]

Good Evening all; Pm me with your name of if ya don't mind let us all know? My phone # is all over this site 6o8 75two 59two5 (? why do people do this?) call me if you like? You can take it off the car & bring it down if that idea suits the timing better? Give us some details about the engine like size, compression, cam, heads, intake & distributor. Car weight & rear gear too. Just off the top of my head the squirter #31++ seems big? I want to know about your timing curve?? Do you know? Back to squirters, it's possible that you are emptying-exhausting the acc pump stroke it too soon with that #31 nozzle & the secondary diaphragm hasn't let the butterflies open yet??? Just a shot in the dark! Anyway you're more than Welcome to give me a call & or a pm.
More snow (I know bad word) possible next week YUK. Ole' Bob.

 

[Mike T]

After giving it some thought, I believe the best thing you could do right now is to pull the acc pump cam on your carb off and see which hole in the cam the holding screw is in. Be sure you can tell which hole in the cam the scew was tightened into. Also, the screw should be through the upper hole in the carb linkage plate.

The cams will have either two or three mounting holes and be numbered on one side of the cam. The number one hole always sets the cam in the most advanced position. ie the pump comes on sooner. If your cam is in the number two or three hole, change it to number one and see if there is an improvement. If the cam is in the number One hole already, its time to move to the next step.

As Vanrah says above, the .031 nozzle might have enough flow to empty the accelerator pump too soon. However, the fact that your afr ratio still shows lean when the secondaries come in indicate its still not getting enough gas to stop the lean condition. Squirters for the 4160 carb get bigger in increments of one, two or three thousandths per step. after your .031 comes .032, .035 and then .037. If it were my problem, I would jump to the .037 squirter and try them. That's a 17% increase in size, which should be big enough to supply enough gas without flooding the engine.

Your afr will tell you if the lean condition lessens or goes away.

A pair of squirters from Jegs is about $13 usd. That's a pretty cheap way to see if your problem goes away.
The next step would be a Acc Pump Cam. I would go with blue in position one.
After that it would be the next size up acc pump.

Please post what you do and how it works. THX.

 

[MrSony]

After giving it some thought, I believe the best thing you could do right now is to pull the acc pump cam on your carb off and see which hole in the cam the holding screw is in. Be sure you can tell which hole in the cam the scew was tightened into. Also, the screw should be through the upper hole in the carb linkage plate.

The cams will have either two or three mounting holes and be numbered on one side of the cam. The number one hole always sets the cam in the most advanced position. ie the pump comes on sooner. If your cam is in the number two or three hole, change it to number one and see if there is an improvement. If the cam is in the number One hole already, its time to move to the next step.

As Vanrah says above, the .031 nozzle might have enough flow to empty the accelerator pump too soon. However, the fact that your afr ratio still shows lean when the secondaries come in indicate its still not getting enough gas to stop the lean condition. Squirters for the 4160 carb get bigger in increments of one, two or three thousandths per step. after your .031 comes .032, .035 and then .037. If it were my problem, I would jump to the .037 squirter and try them. That's a 17% increase in size, which should be big enough to supply enough gas without flooding the engine.

Your afr will tell you if the lean condition lessens or goes away.

A pair of squirters from Jegs is about $13 usd. That's a pretty cheap way to see if your problem goes away.
The next step would be a Acc Pump Cam. I would go with blue in position one.
After that it would be the next size up acc pump.

Please post what you do and how it works. THX.

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neato

 

[lilbowtie]

Been following your post. I hate giving carb tuning advice because there are so many variables and set-ups. You have the best tool being the AFR. You need to have a good understanding of the carb and what is taking place. You have been given some great advice and that along with some common sense will take you all the way to a great tune. As Mike said make sure your timing is optima for the cam (mine loves 40) and once you set your throttle blades to the correct transfer port setting don't be playing with it. My car is crisp from any rpm, even idle

 

[WisconsinCutlass]

Thanks for all the advice. I think what I need to do is start over before going any farther. I don't have a timing light but I have a friend that does so I will ask him to come help me with that. I have never checked the transfer slots are sets correctly so I'll start there. Then move to the squirter size and cam. Then move on to the secondaries. I get over anxious at times and forgot to do one thing at a time. Unfortunately like Bob said Wisconsin weather sucks and we got 6 inches of snow yesterday. It'll be awhile before the car leaves the garage again. Last Wednesday it was 60 degrees and I went golfing. Wisconsin weather sucks.

As for the engine I can tell you what I was told about it. It was in the car when I bought it.
Oldsmobile 350 from a 72 Cutlass
Ported, polished, 5angle valve job heads. They are olds 7A heads
Edelbrock performer rpm cam, lifters, spring, intake kit.
Cam specs : http://www.edelbrock.com/automotive/mc/camshafts/oldsmobile.shtml
Harland sharp roller rockers
Petronix hei distributor
Flat top hyperutetic pistons
1-3/4" long tube headman headers into dual 3" exhaust
3:73 gears
200-4r trans
Weight- no idea?
Rear tire size 275-40r17
It sounds good!! Looking forward to getting running great and for some warm weather.

 

[WisconsinCutlass]

Took my carb off yesterday to check the transfer slots. They looked set correctly to me. I then put the vacuum secondary spring back in it that I started with. I also looked to see what size metering plate is on the secondary side. It had number 21 on it, quick search and I found that'd be a 75 jet. When I get to putting the metering block on that side that's where I'll start for jet size. Was going to switch to the blue squirter cam and apparently lost it. Went with brown instead. Hopefully it'll be warm enough this week to get the car out.

 

[olds307 and 403]

I assume you have flat top forged pistons, nobody makes hyper pistons for the Olds 350. For timing, I find the Olds V8 like very aggressive timing with 20 degrees at idle or more and as much vacuum advance as it will tolerate. I have found 36 total for the track but 38 to 40 feels stronger on the street, bring it in before 3000 RPM with the vacuum advance unhooked and the line plugged, remember you are adjusting base and total centrifugal advance. If the vacuum advance is adjustable, try full advance and back off as necessary. The cam has high duration but is a generic, fairly lazy design, it should help part throttle a lot with aggressive timing. My 88 Brougham weighs 3750 pounds, with a bucket seat car with less options should shed a few pounds. Follow the Holley experts for tune on your carb.

 

[Mike T]

Greasemonkey, If you look at the curve for the brown cam you will see that it is not as aggressive in the early stages as the blue cam. The brown cam, as I have had it explained to me, is for racing applications with big engines and lots of valve overlap (which can contribute to weak cylinder charging at low rpm). While it may help some for your application, I don't think it will be enough to completely solve your problem. The blue cam comes in "heavy" much earlier and gives more of a gas shot quicker than the brown. I really think that, along with the other recommendations, will resolve your issue.

Please let us know how things progress.

 

[WisconsinCutlass]

Oh it's been awhile. Had 8" of snow in April then a week ago 6" of rain in 2 days. My car is in a detached garage in the back yard and I have to drive through the yard to get the car out. Wasn't going to happen with how wet it was. Monday I finally got to working on this pile again. Everytime I touch this car I seem to find a new problem. Anyways It used to be I would start the car and I'd have to hold the gas a little bit to keep it running for about 30 seconds and then I could use the manual choke till it warmed up. Monday I couldn't get the car to start and stay running without staying on the gas pedal. Once it started to warm up it finally idled. I noticed the car was idling at 12-12.5 AFR in park so I leaned the idle mixture. To 14.0 when I put it gear to get out of the garage the AFR spiked to 17.0. So I put it back in park and put the mixture back. Did some googling and found this could be caused by a vacuum leak. Checked the couple vacuum lines I have and didn't see anything unplugged. Did the test with spraying starting fluid around and it seems my intake manifold gasket has a leak at the middle runner on both sides against the block. Does that make sense? Also while the car was idling I pulled the choke cable and absolutely nothing happened. Didn't make a single difference in idle speed or anything. What do I do next? Fix the intake manifold leak and see what happens? Thanks for all the help because I'm starting to get impatient with this car. I'd just like to get it on the road and be able to trust it.

Forgot to add the bigger squirter and blue pump cam did seem to help while idling didn't get a chance to see what it did while driving. Still seems to me a 35 squirter is way to much for my engine.