Oh my Holley

[magoo]

I must admit that I have disliked or even hated Holley Carbs for 35 to 40 years. Always finding them hard to adjust and bring to that perfect point of tune everyone talks about. Thinking it was the right choice, when I put the new motor in my 62 about 4 years ago I bought a new 650 double pumper. During those last 4 to 5 years and over 2000 miles I have tried to find happiness with this carb and I cannot. My new motor will be junk from all the test runs before I get this thing tuned. I originally bought a 350 passenger car crate motor for the pre 86 cars. Then installed a high volume oil pump, Comp Cams 268 Extreme Energy cam timing chain and gears. I reworked the ported and polished fuelie heads that were on the car and installed the Comp Cams springs from the kit. This left me with about 9.5 to 1 compression. I topped it off with the matching ported Vette aluminum intake, MSD ready to run vac advance distributor, MSD coil, and the new 650 DP. I bought the Holley pump cam and squirter kit, jets, and power valves. Tried every possible adjustment of the secondary throttle plates. Thinking the large ports were a problem for drivability I removed the fuelie heads and installed the stock 8.5 to 1 heads with 1.94 intakes and an Edelbrock Performer. This did help but it is just not right and the problem feels fuel related. I'm beginning to think I bought a bad new carb possibly one returned by a previous purchaser. I'm not here to trash a product or supplier, or anyone who has good luck with these carbs. After almost 45 years working on cars 20 in my own shop from the late 60's to mid 80's I may well be a Holley idiot. As a young man I always preferred the AFB, but before I spend the money to buy the other brand, lets talk. Thanks for listening.

Mike

 

[Hib Halverson]

It's difficult enough to diagnose carb problems via the Internet but when virtually no description of the symptoms is posted, it's impossible.

I can tell you that I have a Fuel Curve Engineering modified and self-tuned Holley 850 on my 460 in BBC in a 71 Coupe and it works fine. Lots of power and, considering the fairly aggessive mech. roller I have in the motor, it drives quite nicely.

 

[Kid_Again]

hmmmmm

which centrifugal weight springs did you install on the msd distributor? did you change the springs?

 

[magoo]

Thanks for the reply guys. The vac secondary Holley on my 68 also works fine so I know it's possible. Knowing how hard it would be to diagnose this on line, I really didn't include many symptoms. I guess I was just lookin for some other experiences to chew on. But since you guys are always willing to try, here goes. Sitting in neutral the car seems slow to respond to throttle. It doesn't cut out, but just isn't crisp. I would say similar to the timing not being advanced far enough. I don't use a lot of clutch slipping throttle to pull out but about the time the clutch is completely released the car may stumble which sets up a bucking situation where the clutch must be depressed again. Gear changes are jerky. These are all symptoms involving only the primarys. When pulling out and dumping the secondarys the car bogs down. does not cut out like no fuel, but bogs down and then will accelerate well. Mashing the pedal in high gear is the same, not a smooth transition from primary to secondary. Car cruises at highway speed just fine, no lean pulse or rich flood. When stopping quickly the idle will dip down like fuel is spilling in some way but float levels are right. The carb now has very aggressive green squirter cams, #28 shooter in pri. #37 shooter in sec. #67 pri. jets #74 sec. jets and 5.5 PV. Idle vac. is 11 to 12 inches. I don't remember exactly which springs are in the distributor. I think they are the middle ones. I know that I have 14 deg. on the crank, 36 deg. mech. by 2500 and 52 deg. total at 2500 with vac advance. I will try to provide any more info you need. And I sure do appreciate any help. In my years of experience I really don't claim to be Holley smart, but I know when something just isn't right. This wouldn't be so important if I was the only driver because I can deal with it all. Both of my kids learned to drive stick on this car with the old motor, and my daughter still likes to drive this one. Thanks

Mike

 

[GerryLP]

Mike,

Sometimes I am not patient, I don't make one-change-at-a-time, or neither keep track of all the changes that I would have made so far, so I have learned to go back to square one on the carb settings.

For example,

A Holly DP with 650 cfm flow list number 4777-6 has the following set-up originally (print the pages separately and join the right edge on page 1 to the left edge of page 2)

View attachment 14492

At sea-level, the carb should be set to the settings, cams, and nozzles as called-for here. For every 2,000 feet of altitude change a fuel jet size by one number [smaller number]. Maintain the same spread in fuel jets between the primary and the secondary sides of the carb -this is necessary, for typically, a DP won't have a power valve on the secondary side (even though there are metering blocks available to allow for a power valve in such set-up). The original pump cam set-up is just fine for everyday driving. If you encounter a stumble, then perhaps a cam set-up to start earlier on the throttle travel or faster with a more aggressive cam profile could solve the stumble. It is all a matter of trial and error.

Also, just accelerating the throttle without load will give you false results, so yes, you're going to have to take a drive after you make one change, AND ONLY ONE CHANGE, at-a-time. It is a pain in the you-know-what, but it is the most successful way to get your carb tuned perfectly.

I am in my 25th year and have worked with 7 different aircraft engine systems, and I still learn a thing or two in CAC almost everyday, so your experience resume is not necessary. We all have been in your shoes one time or another.

 

[porch dog]

a 350 sbc at 6k rpm requires lightly over 400 cfm. a 650 will run fat on a street car. you cant tune away cfm. on the streetrods i build i run a 390 cfm holley. this is for a driver. if it is a mild motor like yours i will step up to the 600 with 62 primaries, 50cc pump. if you can borrow a smaller carb and try it. good luck.

 

[GerryLP]

a 350 sbc at 6k rpm requires lightly over 400 cfm. a 650 will run fat on a street car. you cant tune away cfm. on the streetrods i build i run a 390 cfm holley. this is for a driver. if it is a mild motor like yours i will step up to the 600 with 62 primaries, 50cc pump. if you can borrow a smaller carb and try it. good luck.

Dog,

You are correct as far as for a daily driver, but I ran a 600, 650, 700, and 750 DP on my 68 block, Performer heads, the 268 cam, and 9.5CR, and the main difference I found was in the idle mixture screws turns, fuel jet changes, and the point at which I would get my best vacuum signal when tuning at idle. With the 600 and 650 I got better 1/4 mile time slips, and with the 700 and 750 I got better trap speeds on the slips. My best times were 14.6 seconds in the 1/4 mile at 5,000 feet of altitude (the general rule of thumb is to add [going up in altitude] or subtract [going down in altitude] by up to one full second in 1/4-mile times. Anyway, my point is that the Holly can be tuned very well and accurately.

Magoo,

I caught sight of your second reply where you mention your vacuum secondaries...the DP does not have vacuum secondaries...:confused, but anyway, if your carb does have vacuum secondaries, then they can be adjusted as well by replacing the spring resistance inside that funny looking cannister behind the choke and on the passenger side of the carb. The "Avenger Series" carb is easier to replace the springs, and it does run just fine out-of-the-box.

When tuned fine, the vacuum secondaries work well too. You see, the vacuum secondaries will open when the vacuum signal from the primary side reaches a certain point, so they basically self-adjust, and if the primaries can handle all the flow needed, then they will only open slightly [one way to look at it is by imagining the atmospheric pressure always trying to make its way into any space lower in pressure, so if the pressure can get inside through your primary side, then the vacuum secondaries won't be needed]. What you're trying to achieve is that the air gets inside as quickly as possible to improve your efficiency.

The DP basically ignores this, and you tune the amount of fuel it will receive when the secondaries are operating.

 

[JohnZ]

The DP basically ignores this, and you tune the amount of fuel it will receive when the secondaries are operating.

Correct - and that's what presents the challenge when tuning a double-pumper for normal street use - tuning that transition so it works as well at part-throttle as it does under full throttle. A vacuum-secondary Holley eliminates the need for most of that experimentation; a quick-change secondary spring kit is pretty much all you need (and a few jets) to set it up so the compromises are covered.

 

[Hib Halverson]

I'll had that most mech. secondary DP Holleys will not run very well on the street on engines with the mild cams typical of hi-po street use. My 460 has a fairly mild mechanical roller in it with not a lot of duration. The Holley 850 was calibrated on the primary side for an engine generating a much weaker vacuum signal. As a result, even with the tweaks the people at Fuel Curve Engineering (now defunct) did to the carb, I had to do a lot of modification and testing to get it to run nice at light throttle. Generally, I had to restrict the primary idle feed restrictions, I had to drill out the power valve restrictions and I had to jet down the primary main circuit. Once I did that then fine tuned the IFRs and the primary jets, I got that pup to run nice at light throttle as well at WOT up to 6800 rpm.

 

[Viet Nam Vett]

I removed my Holley 850 on my 502 after many attemps and money spent on Spring kits and Vac Sec covers Etc, recomended by Holley to get the sec to come on faster.

Wasted my $75.00 and got Zero change.

Went to the Barry Grant DP With Mech Sec... Problem solved. Much easier Carb to tune.

 

[magoo]

Well guys the problem is solved and we were all at least partly right. Over the weekend I decided the carb was coming apart completely and being completely and slowly inspected. Every passage, gasket, pump, etc. was to be removed, given a commom sense look and failure was not an option. I'll get right to the problem. I removed the float bowls and accel pumps and for the first time I removed the rubber flap type accel pump chamber check valves. The check valves had always looked fine and they were, but after pulling them out I wouldn't re-use them. Underneath them was a rough cast surface including some sharp protrusions. The common sense part of my inspection told me this was not a good surface for a check valve to seal on. Since I didn't really care if I ruined this carburetor or not, I used a die grinder first with a stone with a round flat end. Then glued an emery disc to the flat end of the stone, and finally polished the surface with compound. I had to remove a good bit to get a smoothe surface. I re-assembled the carburetor with all the original pumps, cams, squirters, jets, and power valve. It now works fine after several years and 2300 miles on the engine. You were all right that it should run with out of the box parts. And I still think I was right that I bought a carburetor that someone else returned. Through all of this and by my own fault I have weakened the threads in the secondary squirter. They are holding but are not strong. I emailed Holley tech service my story and asked if they could help me with a new body so I could now perfect my carb. They sent some type of canned reply telling me to adjust the accel. pump actuater arms by one full turn at a time til it cleared up and if that didn't work I may need a larger squirter. Been there done that. "Oh My Holley"
Mike

 

[Viet Nam Vett]

Underneath them was a rough cast surface including some sharp protrusions. The common sense part of my inspection told me this was not a good surface

Exactly my point.... Quality of manufacturing. That's why I shelfed mine and went to a BG..

 

[Kid_Again]

VNV almost got me to buy the BG 3x2's but i went with holley repop's and they work fine ( i was more interested in the classic look than tunability since i just drive the bb on the street)



....but for those of you who followed the MONTHS of problems i had with the original # match tripower holley's i bought at carlisle, some would say well, that's what you get with old holley's....frankly, the only lesson i learned was to not buy old junk....it's junk for a reason (except, of course, when I set up my table at carlisle, at which point i will emphasize the superior exterior quality of the carbs and provide a notarized statement that the carbs came off of a running car)

 

[KANE]

I must admit that I have disliked or even hated Holley Carbs for 35 to 40 years. Always finding them hard to adjust and bring to that perfect point of tune everyone talks about. Thinking it was the right choice, when I put the new motor in my 62 about 4 years ago I bought a new 650 double pumper. During those last 4 to 5 years and over 2000 miles I have tried to find happiness with this carb and I cannot. My new motor will be junk from all the test runs before I get this thing tuned. I originally bought a 350 passenger car crate motor for the pre 86 cars. Then installed a high volume oil pump, Comp Cams 268 Extreme Energy cam timing chain and gears. I reworked the ported and polished fuelie heads that were on the car and installed the Comp Cams springs from the kit. This left me with about 9.5 to 1 compression. I topped it off with the matching ported Vette aluminum intake, MSD ready to run vac advance distributor, MSD coil, and the new 650 DP. I bought the Holley pump cam and squirter kit, jets, and power valves. Tried every possible adjustment of the secondary throttle plates. Thinking the large ports were a problem for drivability I removed the fuelie heads and installed the stock 8.5 to 1 heads with 1.94 intakes and an Edelbrock Performer. This did help but it is just not right and the problem feels fuel related. I'm beginning to think I bought a bad new carb possibly one returned by a previous purchaser. I'm not here to trash a product or supplier, or anyone who has good luck with these carbs. After almost 45 years working on cars 20 in my own shop from the late 60's to mid 80's I may well be a Holley idiot. As a young man I always preferred the AFB, but before I spend the money to buy the other brand, lets talk. Thanks for listening.

Mike

Mike- I understand your pain.

I decided about 10 years ago that all my Vettes would be fuel injected. I too grew tired of messing with carbs.

I believe that EFI is much easier to tune than a carb- maybe even better from the maintenance standpoint. EFI will "tune" itself (advance, retard, usage of data on ambient air density and temp) and adjust for the optimum mixture.

Granted, the start-up cost is higher than a carb (parts, books, some tools), but I spend far more time driving my 1980 than I do working on it!