holley 670

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forcedfedmopar

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So, not an A body but still a mopar. Ive been racing my pick up for the past year with the eddy on it and tuned it the best I could. Truck went a best of 9.74 at 76MPH in the 1/8th. It always had a terrible BOG off the light. 2.45 60FT best ever. Usually consistent 2.48-2.5.

Now everyone at the track told me to go get a holley and throw the eddy away. Being a novice at carbs I did what I was told. An opportunity came my way and I traded some work for a holley 670 street avenger with electric choke and vacuum secondary's.

I promptly put it on, set the float levels, mixture screws to highest engine vacuum, set idle and fast idle, and im off to the track. :blob:

My 60ft dropped to a 2.42. the BOG is less than before but still there slightly. My 330 times are slower and the 660 is now a 9.99 at 73MPH!

vehicle;83 D150 short box 2wd
engine; 77 400. single plane, headers, SMALL hemi grind cam
trans; 727 stock stall (12-1400)
rear; 8.75 3;55

So recap, truck goes slower with holley, I lost top end. WHERE DID IT GO AND HOW DO I FIND IT?

Thank you.
 
your so called friends just dont want to take the time to learn the AFB style. i could tell you how to tune an AFB style, but not a enough space here. but start like this. change only a jet OR a rod. NEVER change both at the same time. start with the jet first. remember a little is a lot. a change of .003 is a change that will be seen. and a .003 dia change on a jet is more change than a .003 change on a rod. try making the float lever 5/16 " the stock is 7/32". if at idle the fuel pores out the discharge nozzle go back to 7/32". and give the change testing time before making more changes.
 
I think you have a 80670 carb?

If that's the case, you should have a .031 primary pump nozzle? That should be plenty with a "regulation" single plane intake plenum volume.

With that said, the as delivered #65 primary jet may be lean for you, especially on a big block? That carb should have a "plain" secondary opening spring also. Although I'm not sure how early/late the hesitation is, I think I'd try at least a "yellow" spring to bring the secondary's in a little earlier.

I'd be remise if I didn't ask what your timing is set at. I hope you're pushing the initial as high as you can without knock/ping issues along with not running the total too high...34/36*. If you're running anywhere near stock timing numbers.....just throw out my carb suggestions. Timing first, then carb adjustments...it's gotta be done that way.
 
OldmanRick said:
I think you have a 80670 carb?

If that's the case, you should have a .031 primary pump nozzle? That should be plenty with a "regulation" single plane intake plenum volume.

With that said, the as delivered #65 primary jet may be lean for you, especially on a big block? That carb should have a "plain" secondary opening spring also. Although I'm not sure how early/late the hesitation is, I think I'd try at least a "yellow" spring to bring the secondary's in a little earlier.

I'd be remise if I didn't ask what your timing is set at. I hope you're pushing the initial as high as you can without knock/ping issues along with not running the total too high...34/36*. If you're running anywhere near stock timing numbers.....just throw out my carb suggestions. Timing first, then carb adjustments...it's gotta be done that way.
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Thank you for the suggestions! I actually went the other way with the springs with no positive results so i will be trying lighter springs next. I read somewhere that they were opening too soon, but the more i think about it you may be right.

The accelerator nozzle is a 31. And i found that the red cam on position 2 made the best out of the bog situation.

The inital timing is the most i can run with it still being easy to start. I havent actually checked where its at but it IS the most it can run without pinging and gives the best results in the 1/8mile.
 
were you using a 750 eddy carb and switched to a 670 holley
 
I would invest in a timing light since you are trying to dial it in for best performance at the track, then you can also dial it back at little for the street if needed and know exactly where the timing is set at every time. A $35 light at your local parts store would be good enough for that. And then tune the carb as oldmanrick suggested.
 
duster360 said:
I would invest in a timing light since you are trying to dial it in for best performance at the track, then you can also dial it back at little for the street if needed and know exactly where the timing is set at every time. A $35 light at your local parts store would be good enough for that. And then tune the carb as oldmanrick suggested.
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I do have a timing light. I just haven't checked it since ive played with it at the track. I had initial timing at around 14* last I checked. But have changed it since. I will start by changing the secondary springs to lighter ones to see if opening sooner helps.

Thank you for your help everyone! I am not new to carbs, but ignorant. I spend my days with fuel injection stuff.
 
teringer said:
were you using a 750 eddy carb and switched to a 670 holley
Click to expand...

Ya know, I honestly am not sure what was on it, I thought it was a 600 but could be mistaken. I will have to double check now. Do you think a 670 is not enough of a carb for the 400?
 
In my opinion, for your application, the 670 is not too small when tuned correctly. Your shift point is probably in 5500/5700 range i would think, and that should feed it pretty well considering in the 1/8th mile you'll spend little time at peak rpm.

With the improvement in 60' times, and the loss of 3mph, which is considerable, you're losing mid/upper range performance. One of the reasons why I suggested a little earlier secondary. Without going crazy, it's actually a lot harder to get a vac. sec'd Holley into bog range vs a "air door" style carb.

I should have mentioned this earlier.....Your truck is super nice. :thumleft:

Good Luck
 
I don't know anything about a 400, but with it being a heavy truck, a short track, that convertor, those 3: 55 gears, and being concerned with your 60' times, I'd swap to a dual plane intake.

What RPM are you shifting ?

How are you coming out of the hole ? Power braking or just slamming it from a dead stop ?
 
If this is a more race oriented vehicle, then I would change almost everything....almost nothing in your combo matches to make this thing go fast (no offence). As far as the carb, yes it is a little small, and again, if this is race oriented I would have gone with a double pumper for ease of tuning (preferably a 750).

With that said, you will need to tune the carb to get it to work well whether or not it is new or used (I'm assuming used since you traded work for it)...and if it is used you might have even more work ahead of you because who knows what the previous owner did to it.

I would start by going to a test and tune night, getting a base line, then jet for the best MPH. As far as the bog, that would be in your pump cams and shooters more than likely.

Very nice looking truck by the way :)
 
flyfish said:
If this is a more race oriented vehicle, then I would change almost everything....almost nothing in your combo matches to make this thing go fast (no offence). As far as the carb, yes it is a little small, and again, if this is race oriented I would have gone with a double pumper for ease of tuning (preferably a 750).

With that said, you will need to tune the carb to get it to work well whether or not it is new or used (I'm assuming used since you traded work for it)...and if it is used you might have even more work ahead of you because who knows what the previous owner did to it.

I would start by going to a test and tune night, getting a base line, then jet for the best MPH. As far as the bog, that would be in your pump cams and shooters more than likely.

Very nice looking truck by the way :)
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The truck was not built or intended for racing. I have much faster vehicles that I run in other classes. But for the street tire class im having a lot of fun messing with the pickup. Which by the way started last year at a staggering 10.54 at 67MPH! So ive made progress!

SO, it turns out after researching a little bit that I indeed did have a 750 eddy on it not a 600 as I thought. So I guess that would likely explain my loss of top end. :banghead:

That being said is it worth messing with the holley to get it to perform the way I think it should or is it a lost cause and I should go back to the eddy and start tuning on that unit?

This is why we do research before swapping parts! Let me be an example to the rest of ya!
 
70 DUSTER CRATE said:
I don't know anything about a 400, but with it being a heavy truck, a short track, that convertor, those 3: 55 gears, and being concerned with your 60' times, I'd swap to a dual plane intake.

What RPM are you shifting ?

How are you coming out of the hole ? Power braking or just slamming it from a dead stop ?
Click to expand...

Ive found the best method is going up on the brake to around 1000 and letting it go from there.
Im not "concerned" with my 60ft times, but its is an indication of the bogging issue. I don't mind coming out slow and picking it up on the top end.
Im shifting right around 5k give or take 300rpm. MY 1-2 shift is tricky. it really depends where im at on the track. We have a "patched" area that I try to avoid, because when I shift on it, the a$$ end kicks out on me.

Last year the guy that was my nemesis was driving a 77 vette. He would 60ft in the 1.8s but I would always run him down on the top end. he was trapping around 74-76 so it was ALWAYS a race! I haven't seen him this year but I want to be ready, I thought if I could get it to 60 a little better and improve the top end I would have him whooped.
 
I applaud you for running the street bracket with your truck. Many don't realize how competitive, or how much fun it can be. Let's face it, vehicles like this are not efficient by racing standards, but well tuned and consistent can compete very well.

If it was mine, I'd play with the Holley for a while. Your MPH range at 4500lbs will put you just either side of the 300hp range, and that ain't half bad with a low comp 400 with a few bolt on/in's.

How much do you really get out to the track with it? I assume you can do some "street" testing. Kinda like I used to do. :D

I really have only responded to the carb swap, and would like to see you get the most out of it vs any combo changes at this point. Just a nice ride to enjoy at the track.
 
OldmanRick said:
I applaud you for running the street bracket with your truck. Many don't realize how competitive, or how much fun it can be. Let's face it, vehicles like this are not efficient by racing standards, but well tuned and consistent can compete very well.

If it was mine, I'd play with the Holley for a while. Your MPH range at 4500lbs will put you just either side of the 300hp range, and that ain't half bad with a low comp 400 with a few bolt on/in's.

How much do you really get out to the track with it? I assume you can do some "street" testing. Kinda like I used to do. :D

I really have only responded to the carb swap, and would like to see you get the most out of it vs any combo changes at this point. Just a nice ride to enjoy at the track.
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Thank you. The street class has been alot of fun for me regardless of how slow the pick up is. (I won the class last year). The series I'm running in has a race about once or twice a month, next being may 3rd. My work is located on a nice 1/4 mile stretch in an industrial park so I get plenty of street tuning done. I don't usually take it to test and tunes because its so dang slow. I will try playing with the jets and secondary springs to see if I can improve it.

It appears to have a #5 power valve. According to mu in gear warmed up vacuum (12.5-13) I should be running a 6.5. A buddy of mine suggested going to a 4.5. Your thoughts on this?
 
forcedfedmopar said:
It appears to have a #5 power valve. According to mu in gear warmed up vacuum (12.5-13) I should be running a 6.5. A buddy of mine suggested going to a 4.5. Your thoughts on this?
Click to expand...

No need to lower it, that's for sure. As far as the race track, you'll have little to no vacuum at wide open throttle, so you'll be good there regardless.

PV tuning is all about part throttle acceleration/performance. The farther apart you're cruise vacuum is away from the PV opening rate, the more throttle opening you'll need for enrichment. Every combination will be somewhat different, but if you feel any lag or the need for excessive throttle when partially accelerating from cruise speed, raising the number will generally help with that.

Most subscribe to the "half" method, and that's certainly a reasonable place to at least start. My personal preference on engines producing middle of the road vacuum has always been to be a little closer then 1/2. As a example.....11" idle/14" cruise, I'd generally run a 8.5" PV.
 
You probably know this since you've been racing, I'm just getting into this and if I have it right, here is something guys might forget about.

Got this from Holley. SAYS:
Check your clearance at .015" at WOT.
And then it says Make sure that the accelerator pump arm is being acti-vated the moment that the throttle begins to move.

If you powerbrake, you may already be in your pump, so you need to back it off so you'll have more pump shot.

Also if your carb. is a street avenger, it could be 10% smaller than the advertised rating. Some Holley techs will tell you and some won't. So what do you believe. There are two ratings, wet and dry.
Forcedfed--Would like to hear more about you racing your vette buddy !
And thanks for the tip, OLDman RICK !
Hope this helps.

ACCELERATOR PUMP SYSTEM
The accelerator pump system consists of three main components:
the pump diaphragm, the pump cam and the pump nozzle.
This is the carburetor system that is most responsible for having
good, crisp, off-idle throttle response. Its purpose is to inject a
certain amount of fuel down the throttle bores when the throttle
is opened. By accomplishing this purpose it acts to smooth the
transition between the idle and main circuits so that no stumble,
hesitation or sluggishness will be evident during this transition
phase.
The first adjustment to check is the clearance between the pump
operating lever and the pump diaphragm cover’s arm, at wide
open throttle. This clearance should be around .015". The pur-
pose for this clearance is to assure that the pump diaphragm is
never stretched to its maximum limit at wide open throttle. This
will cause premature pump failure. Once this clearance has
been set take a good look at the pump linkage and work the
throttle. Make sure that the accelerator pump arm is being acti-
vated the moment that the throttle begins to move. This will
assure that pump response will be instantaneous to the move-
ment of the throttle. These adjustments can be made by turning
the accelerator pump adjusting screw that is located on the
accelerator pump arm together with the pump override spring
and lock nut.
The amount of fuel that can be delivered by one accelerator
pump stroke is determined by the pump’s capacity and the pro-
file of the pump cam. The period of time that it will take for this
pre-determined amount of fuel to be delivered is affected by the
pump nozzle size.
 
a little update, I went to the track Saturday and did some test and tune. Started off with 65primary and 68 secondarys.

Put the soft white spring in, seemed to help a little.

Went up to 76 primary's and 78 secondary's. Truck is much happier, got back up to 75 MPH. Plugs are starting to show signs of a richer mixture, engine is running cooler also. Next week im going to go to 78 primary and 81 secondary with a new set of plugs. Definitely going in the right direction.

The bogging situation is almost completely gone now. its actually spinning off the lights now instead of bogging. (which results in about the same 60ft LOL

Thanks for everyones suggestions and input.
 
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