Holley jetting

[Jack21]

Running a Holley 700 DP. Motor is 351W +.030, 9.5:1 CR, TFS's out-of-the-box heads, Perf RPM intake, Comp Cams Hydraulic Roller 224/224. Typical street Cobra motor.

Stinks and burns your eyes when running in garage, even with door open so I know it's running way too rich with out-of-the-box jetting. Primary jets are #69's. I'll drop it two steps at a time and likely go to one of the local emissions check places to check my AF ratio till I get it dialed in.

Off the top of your head, what jet sizes have you used on combos like this?

[jwinkler]

I'm running a 650dp on mine (10.7:1 351@.060), with the stock 67s in front, a 35 shooter, and a 4.5" pv (if memory serves - may be a 6.5"). A friend with an identical motor except for a 750 vac-sec carb was running 72s up front (at the time, non-adjustable secondaries), so I actually put 72s in when we finished the motor, which ended up being *way* too rich. With the 72s, I'd get a stumble at about 4000 before I opened the secondaries (does anybody else notice a distinct point in pedal travel where the secondaries open on a dp?) which went away when I jetted down up front. Plugs are barely on the lean side of just right right now. I still have a stumble under 2000 rpm, so I'm guessing I need to mess with the shooter or the whole pump cam/diaphragm thing, which I'm not overly eager to do at the moment.

Definitely an interesting topic to me - maybe Don and DV will chime in. At one point I emailed Holley tech, but only got a worthless "every motor is different, blah, blah, blah" response.

JLW

PS - Rob's car (with the 750 on an identical motor) still has bigger jets up front, and doesn't run richer. Combining our vast carb-tuning and fluid dynamics knowledge (which unfortunately, simply proves that multiples of zero are still zero), we came up with a theory as to why that should be:

Given that a 650 will pull less air than a 750 at any RPM, then the vacuum signal at the jets will be bigger for the 650, meaning that a given jet will send more fuel at that RPM on the 650 than on the 750 due to the bigger vacuum signal.

Any chance this is reasonable, or did I just give everyone a good Tuesday laugh?

[Double Venom]

JW,
You're not going to like my response. With my experience over the last 5 years or so, the way I fix a holley is take it off and punt it as far as I can!

I've given up! We thought we moved up and even tried Barry Grant carb's. Now that was another sotry to tell.

Maybe Don can give you some insight with a better perspective.

I wish you all the luck in the carb-kingdom!
DV

[bigmike]

I have used Holleys and fought the jetting for over 30 years. What a pain!!
Last spring I changed my neighbor's Lone Star (427 s/o, 750 cfm) to use a Holley accessory called "adjust-a-jet". It goes between the fuel bowl and metering block, and uses NO JETS AT ALL. A large adjustment screw, readily accesible at the top of the carb is calibrated so that a certain # of turns = a certain jetting. A chart is provided by Holley, and it is a snap. His worked so well that I put a pair on my Holley 750 (428 CJ), and can tune to a given altitude or track in seconds. They run about $180.00/pair from Summit, Jeg's, or PAW.

[jwinkler]

I'm not sure that's the whole story - isn't it really true that you just couldn't find an Edelbrock intake for a V-10?

JLW
(Who doesn't drool over the Edelbrock RPM Pro-Flo EFI setup - HONEST! )

[Don]

Don & DV:

If not Holley, what carb and size would you recommend ? Have a 351W, .030 over, Crower 280 cam , MSD 6A , MSD Billet Distributor, 9.5:1 compression, Edelebrock performer intake, Ford GT40 heads 1.94 intake, using a Holley 600 carb. Don built the engine and it runs just great !

[dscott]

DV, I bet I can kick my Holley farther than yours! I don't use the Holleys much anymore. We use them on most of the race engines we build just because racers want the changability and of course you can get great big Holleys. Many of the Carbs we build for the racers run on Methanol or Ethanol so major mods are necessary which the Holley will accomodate. For the street I use the Edelbrock carbs. The 600 on engines up to 350hp, 700 on engines up to 425hp, the 800 up to 475hp. Over that we usually go to the Holley dp. We have dyno tested both carbs on probably 25 different engines and found the same results in all cases. They produce the same hp. I like the Edelbrock because it is very reliable and forgiving. We have had to change metering rods and jets for the higher elevations, which is very easy to do, besides that they run about the same in any weather or humidity. I've probable sold about 150 of the Edelbrocks over the last few years and haven't had a single call on any of them. I have had nothing but problems with the Holleys for along time. Constant jet changes, blown power valves, leaking bowls, sticky needle and seat. I always carried a small hammer in the car for the needle and seat problem. You do lose the "Holley look" on your engine but for reliabilty I'm sticking with the Edelbrock.

JLW, Your theory is correct on the 650 and 750 Holley carbs. The 650 will draw more fuel.
Don

[Jack21]

Wow! Now that's a reaction.

DV, you must an EFI convert. Don, I've owned one Edelbrock carb, and it went into the trashcan.

20 - 30 years ago, that's what most people said about Rochester Quadrajets. Into the trash. Bolt on a Holley and it will run. And that's exactly what I did, and it worked.

One would think that the Barry Grant Demon carbs to be an improvement over Holleys.

Althouth my experience is mainly Pontiac & Oldsmobile, some 289 - 302 Fords, my engines have always ran well with Holleys.

Not that they don't have quirks and problems. If you get a cold casting, it will never run right. And the metering block surface on the throttle bodies will warp and have to be milled flat, and accelerator pump transfers always eventually leak, etc., etc. Holley's got a new one to cuss about now. Instead of cork gaskets, they have sealing type gaskets now I swear they epoxy on. Nearly destroyed the carb trying to get the metering block off.
Then spent 4 hours with an exacto knife & laquer thinner getting the shredded gasket off the parts.

I thought this question would be an, "Oh yeah, we always use a #65 on those". Save some time dialing it in.

This Holley may not have a permanent home atop this motor. EFI seems like the way to go here, and I'm no stranger to programming computers.

Anyone favor any particular EFI system for warm street 351W's? Holley Pro-Jection, Edelbrock, Accel, OEM Ford?

[dscott]

Jack21, I've used several of the Holley systems with the latest being the digital. The old systems were a bear to tune and they never covered the rpm range well. The new system worked well on the dyno after we created a new fuel map. The ones they supply are very generic and need major mods. I spent many hours on the dyno tuning with a laptop. The engine went to Miami Cobra and I know he had to tune it further for the street. As far as I know it is working well. I have used the OEM ford port injection, the GM throttle body, GM tuned port. All of these systems worked well with the stock engines. I've never tried a modified engine with the OEM injection. I'm still a carburetor man, there's something about the sound of a 4 bbl opening that makes my blood run!

Back to the Holley carbs, We've tried just about all brands of modified Holley carbs from Barry Grant to Pro-systems, to Bowlus, to C&S. They all charge big bucks and the gain is very minimal. We modify all our own Holleys at about half the cost with a better gain. We had one C&S that a customer paid over $1000 for. We took a simple Holley with some minor mods and gained 5hp with a savings of about $500. If you get the Holley Carb book it discusses all the mods necessary that most of the aftermarket companies use. The Edelbrock carbs have 2 metering rods and jets that are held in with one small screw on each side. No gaskets, no pulling the top. a 5 minute change. No power valves to blow. I'm sure there are people that love and hate the Edelbrock. I have just had such good luck with them I'm staying. I'm not against Holley but for the street, reliability and trouble free running mean alot to me. Many of the people I sell to couldn't even find the carburetor let alone fix one.
Don

[Double Venom]

Don,
I've got a 35 yarder on my last holley double pumper! Right between the cornstalks!

Fellas I can't say enough bad things about Holey, and gawd knows I used to love them so---35 years ago!

I just can't find the pwer valve, metering rod, jet combo that will work anymore. Either so lean we burn plugs out in days, or less, or we flood the plugs out, burning so rich you can't stand to be around the car when.

We use edelbrock, simple bolt on....maybe....just maybe.... play with the idle circuit, and hit the street/track.

If you're racing hard, then maybe it's time for a holley, for street and play, throw it on the shelf! Sorry Holley. This is strictly my personnal opinions, and experiences.

Nope, we don't sell any manufacturers carbs, but I damn sure have to warranty them on a customers car!
DV

[jwinkler]

Don and DV - since you've got dyno time with Holleys and Edelbrocks, I'm guessing you like the overall curve better with the Edelbrocks.

Also, knowing that dyno runs are highly susceptible to environmental elements and other factors, could you guess (or tell us what you've seen similar motors do) as to what Jack's and/or mine would pull on the dyno (I'm guessing with the 700cfm carb) or if they might merit the 800? I'm betting you've built similar motors.

Finally (if you've read this far!), in your opinion, how close do the dyno simulations come to what you've seen on the engine dyno?

Per Vizard and other books, even a 351 is adequately carb'ed at 600 cfm, but I've just got a nagging sense that to hit the higher RPMs, it needs a little more, so I've been toying with the notion of moving up from my 650 dp (originally looking at a Holley vac-sec 750, since that works well on my friend's car).

Thanks for any info

JLW
(details:
10.7:1, Edel RPM heads, torkerII intake, CompCams 282s cam (236/236@.050, .528 lift))

[dscott]

JLW, I think the 750 would be more than enough for your combo. We have found that the dyno programs are pretty close to the real thing. We normally get within about 20hp from the dyno programs. They are usually a little high. Not knowing the valve sizes on your heads I can only guess at the horsepower but that is similar to the combo's I use. With the Edelbrock 2.02 heads and a good hyperutectic piston such as Keith Black, a good MSD dist and box, the Performer RPM manifold, comp extreme energy cam, and a 750 carb, we usually get between 395hp and 415hp. There are so many other variables it's hard to say. If you want to give me more details on your engine I may get to a closer guess.
Don

[jwinkler]

More details on my motor? No problem! Anecdotally, an engine identical except that it has a Holley 750 vac-sec in a Pantera (don't know if the different exhaust systems between the Cobra and Pantera would make a difference) pulls hard all the way to a 7k rev limiter. I haven't had the guts to try that anywhere yet, but it hits my 6k limiter without a fall-off.

Anyway, here are the details:

'74 block @ 0.060 overbore
KB-151 hyper pistons
CompCams 282s (single pattern 236@.050, .528 lift - lots of P/V clearance)
Torker II intake
Edel 6025 heads (RPM with the 2.02/1.6 valves)
Holley 650 dp (67 primary, 78 secondary)
Mallory ignition system (HyFire IV/c box, ProMaster coil, and Unilite dist - out-of-the-box advance curve, and don't know what that is)
The only accessories it drives are the waterpump, alternator, and PS pump
With the KB-151s and the 60cc heads, compression is calculated to be 10.7:1

The simulator I used shows power peaking at 6k - if you think an Edelbrock 750 would let me spin it to 6500-6800, without the stumble on tip-in I've currently got, I'd be thrilled!

Thanks,

JLW

[dscott]

JLW, Here goes, this is just my opinion and experience. The cam you are using should make peak hp around 5300 to 5500 rpm. To take the engine any higher is a waste and a danger unless the bottom end has been beefed up with good rods, balanced, etc. I never run my engines over 6000 with a stock lower end. Ideally when racing (I'm sure DV can confirm) you want to find your peak torque which is probably around 4700 rpm and have your shift point at 500 rpm above that. Many racers have found this difficult because they feel they are short shifting out of the power band but usually the et's increase. If you try and rev above the 6000 rpm you can get into valve float. Also the power drops dramatically at the higher rpm with the cam you have. You need a pretty wild cam to make your hp at the upper end. The problem you have may not be in the carb. If the valve springs are not designed for the pressures at the higher end you may be getting valve float. What rpm are you having the problem? But then again things change at those rpm's so carb jetting may be it. I have used the 750 Edelbrock with great results on your engine combo. But like I said I don't rev any higher than 6000. I would check your cam card, it should give you a good estimate of the power band.

The stock 650 carb probably has a 6.5 power valve. At the higher rpm you may be making that much vacumn and closing the power valve. If this happens it's the same as decreasing your jets by 8 sizes which can cause a lean condition. This is definitely dangerous because you can melt pistons if you are too lean. You could try a larger power valve and see if that helps. I also think a 650 carb with your combo is too small. The 750 would be better.

Don

[Double Venom]

Damn...

You would think Don and I are partners and not competitor's!

I agree with absolutely everything he has said. Have I told you, Don makes all my rebuilt/custom motors?

He is so right about the power band too! You may think you are still pulling power, "it is not"! Once you go over the torque band you are wasting time! This is the hardest thing I had to learn on the drag strip. I absolutley knew the car was still pulling all the way to the rev limiter--6,800+ rpm.

Dyno showed us the max torque was right around 5,500. Do you know how hard it is to force a shift 1,500 rpm short when the nose is still in the air and your helmet is kissing the back of the seat!?

I mean, I have to actually force myself to shift, my hand, my butt, my brain says "not yet-not yet!" My times slips and speed say, "Told ya so!"

I've actually turned my tach in the dash so that the 6,000 rpm mark is straight up at twelve o:colock.

If you can get "her" on a dyno, it will be worth every penny of it. Take a Holley and an edelbrock with ya. Run at least two runs, then make up your own mind.

DV

[cobrashoch]

DV and dscott- My tuning expierences with Hollys is very close to yours. Years ago I helped a dyno tune shop that tuned muscle cars and hot rods. While I don't throw the Holleys away the word we always used on Holleys was Rich>to rich. It was hard to tune that out of them. Big Mikes adjust a Jets is one of my personal secrets (not anymore) that I was planning to use on a dominator or a 950 for my bomb. They require air bleed work though. A Holley is really a big end carb only.

When Barry Grants Demons first came out about 2 or 3 years ago the folks I trusted said they weren't there yet either. That has changed lately so I'm told , by the same sources above. So maybe a king demon will go into my pressure box first. Word to the wise, don't use a used demon, so I'm told.
Anyway , the demons I have tuned lately are much more stable(less finikey) than Holleys. A demon MUST be tuned however. I to like Edelbrocks carbs (Carters?) and for the costs, they will work very well and really don't need that much, even box stock. Have you two looked at the Carter versions of the Edelbrock carbs. (really vice versa) They really are much better built, even though parts are harder to get, they are a bit better runners.

So a question to you guys- Either of you know of a throttle body setup of fuel injection that works in a pressure box of a 500+ cu/in motor? So far I have scared everyone to death except Kinser(very expensive)and Rons fuel injection. (home of the flying toylet bowl thats really a port setup) I plan on running 7 to 11 lbs of boost, nothing to wild here. The Hot wire Holley setup is junk, not a option. In posts above you guys eluted to the new, greater holley setup. So is it now a option?

DV-The torque thing is soooooooo true! My advice on drag racing though is to dump the tach. It will cost you a motor sooner or later. Use engine throttle stops for your launch and a shift light together with a rev limiter. You will go faster too. PS- if your front wheels are up in the air much you are loosing E.T. Better to spin the rear wheels a bit, and you will get bigger speed numbers to. Somehow, somewhere, I think you allready know this though.

cobrashoch

[dscott]

I can't really answer your fuel injection question. The latest system I used was the Holley 4di system that was supposed to be good to 400hp. It worked good but took time to tune on the laptop. The port system that Edelbrock has looks impressive but I have never used one. Sorry I couldn't help more.
Don

[wilf leek]

Sorry guys, can't add anything to your discussion on EFI systems, I'm one of those guys who can't resist the sound of secondaries opening up.

Have used both Holleys and Edelbrocks now. Love the look of a Holley, hated the constant fiddling to keep it right, plus never stopped the fuel leaks, and also carried a hammer for the needle valves.

Now have fitted an Edelbrock (aka Cartr, aka Weber) 800cfm carb, so easy to set up, only one (secondary) jet size away from "box" on my stroker 351W. No fluffs, no hesitations, no flat spots, just pure pull from 1000rpm to 6000 rpm.

Only thing I can't do is floor it completely (i.e open the secondaries fully) from under 3000 rpm - then I will get some "bogging", but I can live with this, and on the track it's not a problem, as I keep it "on the boil" over these rpm's, on the road I shouldn't be doing it anyway.

One last thing - in hard right handers the carb floods. Getting over this by dropping the fuel level slightly (have fitted the high flow needle valves to compensate for this). Really no problem on the road, and you have to be pushing pretty hard on the track to make it happen.

I'm a convert!

Wilf

[Double Venom]

I'm printing every word of this out. This is exactly what I try to explain to the "newbies".

Holley's name is so synonymous with "fast cars", they just think they have to have a 750 CFM DP or their car just wont run! Ohh the headaches I (we) have endured.

Ron, just a side note - Suspension tuning stage of the DV's:
1. Left front would come up hard, with little pulling of the right
2. suspension, suspension, suspension -- pulled both front
wheels evenly
3. Suspension, etc., now both wheels are really pulling- wheelie
bars installed and used!

4. Suspension, suspension, etc., Removed wheelie bars, front
wheels will "normally" stay planted- normally

Best 60' time to date is a 1.51 !!! Wa-Hooo!
DV

[cobrashoch]

Option five- left front goes up slightly, right wheeley bar makes contact first, 1.40 60 footer maybe ?(depents on frame/suspension) Sounds like you are having fun, I can't wait to get my iron into the mix. I generally concur with your holley advice to.
cobrashoch