tuning help needed

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fishy68

fishy68

Tyr Fryr's Inc.
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Ok guys I don't know what big blocks like but I'm sure there are some here that do. What's going on is a fellow moved near me and has a Challenger with a 440 in it that sounds mean but is a slug and has asked me to help him get it running better.

He helped build it about 15 yrs. ago and said they put in 10.5 to 1 rated pistons but didn't deck the block or check the height they sat at so it may only be about 9.5~10 to 1.

Has a 284/484 purple cam.

Has 906 heads with a little bowl work and a 3 angle valve job.

1-7/8" full length headers with full length 2-1/2 exhaust.

An old Direct Connection aluminum dual plane manifold, not sure what it really is, i.e. part number or ??, it just looks like a low rise aluminum dual plane.

750 vac. secondary Holley.

Has a factory dist. with a MSD 6al.

2500 stall and 3.55 gears and 27" tall tires.

I think I remembered all the specs he told me but if I missed something let me know and I'll find out.

In my opinion it should run real good but I guarantee after riding in it the thing would be lucky to turn 16's.

Ok now the question. What do you guys like to see for a max timing on something like this? I checked it and right now it's 12 degrees at idle and 38 total all in by 3000. I think it probably needs some more initial timing but what do you think? Also what total timing do 440's usually like? And if any of you guys run a 750 vac. sec. carb on a dual plane intake on a 440 what jets are you running? How about a plug suggestion and what gap??

Oh yeah, I put a vacuum gauge on it and it pulled 11~12 inches of vacuum at idle.

Thanks for any help you can give. Tracy
 
Tracy,
Everything sounds right and the 440's like 38* total so thats right on. The 750 VS carb should be enough with everything else he has.
What it sounds like is happening is the secondaries aren't opening. I generally drill and modify the 750 VS holley carbs before I use them. I drill the power circuit to 32 and the idle circuit to 78 and jet the carb to 82/88 with either a 4.5 or 6.5 PV depending on what the engine vacuum is. I take the vacuum pod off and drill the brass bushing out or remove the check ball. Usually a 1/8" drill takes the bushing out. Make sure that the vacuum port that operates the secondaries isn't blocked off as most that come from the factory use a cork gasket thats too large and it closes the vacuum port hole, and makes the diaphram inoperational. I also take the metering plate out of the rear and replace it with the metering block that you can change the jets in. By doing this and setting the idle mixture screws at 1 1/2 to 1 3/4 turns should get it real close. Also too get a diaphram spring kit and change the diaphram spring to the short yellow one and if necessary change the diaphram as they tear when removed. This will make the carb run on a 2 bbl like normal and if needed when floored will run like a dp without the sag or bog.

Also check the fuel pressure and make sure that he has enough or anything that you do won't make any difference.

Doing these mods to the carb has showed a .5-.7 gain in performance at the track, so it works and works well.
 
I think it's just a mismatch. The intake is more than likely similar to a factory iron, but with the holley flange. The cam is too large, the static ratio too low. the advance curve too slow, the headers too large. I understand the ideas Bobby's given you on the carb. I wouldnt do a damn thing to it except male sure it's been rebuilt fairly recently is it's not new. You do not want to remove the check ball as this is what makes the vacuum secondary work properly. Without it, you've created a manual secondary carb with no secondary accelerator pump and without steep gearing and a loose convertor, it's a disfunctional mess. I would change to a jet plate metering block, but it's not imperative for that combo. I've never seen any issue with the cork gasket except installation error. They are not subjected to enough suction to pull the gasket out if it's installed in the right spot. In any event, take a cylinder pressure reading. What vacuum does it pull in gear, and at what rpm is it idling at?
 
I had a Charger with a .030 over 383, 906 heads with 3angle, with 484 cam, 750 VS Holley,Performer intake, 10:1 compression, headers, 2800 stall, 4.10 gears, 28"tires, 10 inches of vacuum. That car would absolutely haul buddy!

If the compression test turns out fine I'd have to say something is up with the carb or lack of fuel. I ran a Holley electric pump with regulator to keep the fuel flowing for the motor. Other than that I'd say more stall and gears. Didn't really answer any questions but I know the motor ran very well.
 
moper said:
I think it's just a mismatch. The intake is more than likely similar to a factory iron, but with the holley flange. The cam is too large, the static ratio too low. the advance curve too slow, the headers too large. I understand the ideas Bobby's given you on the carb. I wouldnt do a damn thing to it except male sure it's been rebuilt fairly recently is it's not new. You do not want to remove the check ball as this is what makes the vacuum secondary work properly. Without it, you've created a manual secondary carb with no secondary accelerator pump and without steep gearing and a loose convertor, it's a disfunctional mess. I would change to a jet plate metering block, but it's not imperative for that combo. I've never seen any issue with the cork gasket except installation error. They are not subjected to enough suction to pull the gasket out if it's installed in the right spot. In any event, take a cylinder pressure reading. What vacuum does it pull in gear, and at what rpm is it idling at?
Click to expand...

I was thinking the same thing about the intake myself but since I haven't seen one wasn't positive I was right. So you think that's a big cam for a 440? I know it's pretty big for a small block but I thought it wasn't all that big for a 440 even if the compression is the least I think it is which is 9.5 to 1. Of course if things aren't matched up with it it wouldn't run right. It's gonna be about 2 weeks before he has another day off that we can get together so that'll give me time to get a secondary block with changeable jets and I'll do a compression test also to see what it is. I was planning on mod'ing the dist. for less advance so we can get the initial timing up some more and I have a lighter spring to put on it so it'll come in quicker. Right now it pulls 11~12 inches of vacuum idling in gear at about 750~775 rpm.

Thanks for the tips Moper. Tracy
 
mullinax95 said:
I had a Charger with a .030 over 383, 906 heads with 3angle, with 484 cam, 750 VS Holley,Performer intake, 10:1 compression, headers, 2800 stall, 4.10 gears, 28"tires, 10 inches of vacuum. That car would absolutely haul buddy!

That's real close to this build except yours was 57 cubes smaller so this one should run good too.

If the compression test turns out fine I'd have to say something is up with the carb or lack of fuel. I ran a Holley electric pump with regulator to keep the fuel flowing for the motor. Other than that I'd say more stall and gears. Didn't really answer any questions but I know the motor ran very well.
Click to expand...

I'll do the compression test when we get back together in a couple weeks. I am also going to look the fuel system over good. He said he put a HV Holley mechanical pump on it when he rebuilt it but that was 15 yrs. ago. He's only put about 15,000 miles on it in that time but sitting is bad on stuff too you know so it is possible it's not maintaining fuel pressure. I'll check that also. Thanks, Tracy
 
Fishy, I think you're going in the right direction with checking the compression and fuel system, and fuel pressure. I don't think that cam is to big, mind you I wouldn't go any bigger, your vacuum readings aren't that bad. I'd dump the intake, it's old school and go with an Edelbrock RPM and your timing is about right but you could bump your initial up 2 deg's. I'd wire the carb secondaries closed after you've done a "to the floor in all gears" run then do another one and see if there's a difference. The way that 440 sits it should haul *** but can be inproved. You might also try to get your hands on a "demo" 750 with mechanical secondaries, it might surprise ya but then I've never been a big lover of vacuum secondary carbs.

Terry
 
demon seed said:
Fishy, I think you're going in the right direction with checking the compression and fuel system, and fuel pressure. I don't think that cam is to big, mind you I wouldn't go any bigger, your vacuum readings aren't that bad. I'd dump the intake, it's old school and go with an Edelbrock RPM and your timing is about right but you could bump your initial up 2 deg's. I'd wire the carb secondaries closed after you've done a "to the floor in all gears" run then do another one and see if there's a difference. The way that 440 sits it should haul *** but can be inproved. You might also try to get your hands on a "demo" 750 with mechanical secondaries, it might surprise ya but then I've never been a big lover of vacuum secondary carbs.

Terry
Click to expand...

I know a new manifold would be a big improvement but I kinda doubt he'll spring for one cause things are tight for him. I think he just wants me to get it running the best it can with what it has and leave it at that for now. Even with the old school manifold it should run a whole lot better than what it does. We took it out to the back road where I run mine to test it and I have an approx. 1/4 mi. marked off there. It barely hit 85 mph in the 1/4. Just felt very sluggish all the way through the range. Actually felt more like a stock 318 than a modified 440 to me.

Thanks for the tips, Tracy
 
fishy68 said:
We took it out to the back road where I run mine to test it and I have an approx. 1/4 mi. marked off there. It barely hit 85 mph in the 1/4. Just felt very sluggish all the way through the range.
Click to expand...


I took my Dart to the track one time and was only going around 85 mph through the traps and it was sluggish and not RPMing very well. Turned out that I did not have my throttle cable ajusted right and the secondarys were not opening all the way. Don't know if that is it or not but it is easy to check any way.

Good luck.
 
moper said:
I think it's just a mismatch. The intake is more than likely similar to a factory iron, but with the holley flange. The cam is too large, the static ratio too low. the advance curve too slow, the headers too large. I understand the ideas Bobby's given you on the carb. I wouldnt do a damn thing to it except male sure it's been rebuilt fairly recently is it's not new. You do not want to remove the check ball as this is what makes the vacuum secondary work properly. Without it, you've created a manual secondary carb with no secondary accelerator pump and without steep gearing and a loose convertor, it's a disfunctional mess. I would change to a jet plate metering block, but it's not imperative for that combo. I've never seen any issue with the cork gasket except installation error. They are not subjected to enough suction to pull the gasket out if it's installed in the right spot. In any event, take a cylinder pressure reading. What vacuum does it pull in gear, and at what rpm is it idling at?
Click to expand...


I don't understand your reasoning here that the carb would be a disfunctional mess. Most holley 750 VS carbs don't even start to bring the secondaries on till well past 3,000 rpm's with the check ball in place, and may never have them fully open. The reason I say this is the amount of vacuum that the carb would see with the tiny hole in the bushing that might be all of .015 isn't sufficeint enough to operate the diaphram, or the restriction of the check ball. Further more almost every 750 VS carb that I've seen in the last few years that weren't gone into before had the gasket problem on the secondary vacuum port to operate the diaphram. Some even had a paper gasket that totally blocked the port altogether which doesn't allow the secondaries to operate any.

As for the carb becomming a manual secondary carb without the pump shot couldn't be further from the truth. Everyone that I've done has operated as it should. I've done these same modifications with the 750 VS on my truck and on others and never had a dissatisfied customer. And none of the vehicles had steep gears or high stall converters. The secondaries don't come on immediately but start to open at 1800 rpm's and aren't fully open until 5,500 rpm's or more depending on the spring that is used. The secondaries don't come on til the engine vacuum falls far enough to pull the diaphram open. So to say that it becomes a manual secondary carb isn't true. But this does allow the engine to get up in the rpm range before the secondaries start to open, making a crisper or sharper throttle response.

Also to you have to have your foot on the floor for the carb to operate this way. Needless to say that most of the time it won't be on the floor, and the carb will operate like a normal 2 bbl. until the vacuum falls enough to open the back 2 bbls.. By removing the check ball or bushing will bring the sec. on quicker when the engine really wants it or needs it.

You can do to it anything that you want, but if it isn't working right now what do you have to lose. Or better yet if you have a DP carb put it on first and see if it doesn't pick it up or make the engine respond better. If it does then the secondaries aren't comming on fast enough. If not and you don't want to do anything more to it or take the chance that it may work, then you or who every owns the car will have to be satisfied with the way that it is.


Moper, You and I have had disagreements before and we may have to differ here too. But hey were still buddies, and anytime you get a group of people together you'll always have differences of opinions. It's just human nature.
 
huh..very interesting have a fella i know with a similar prob...bored 30 440 new pistons around 10:1 mildly ported 915's 2200 torque converter , fresh 750 holley,3:55's..idles great 12 degrees initial 38 all in ...take it out and give her some....omfg..i can run faster than this car....pings and generally runs like dog crap...any suggestions warmly received??? should i put it to sleep???
 
dust-u said:
huh..very interesting have a fella i know with a similar prob...bored 30 440 new pistons around 10:1 mildly ported 915's 2200 torque converter , fresh 750 holley,3:55's..idles great 12 degrees initial 38 all in ...take it out and give her some....omfg..i can run faster than this car....pings and generally runs like dog crap...any suggestions warmly received??? should i put it to sleep???
Click to expand...

Hey Dust, why don't you start a new thread for this engine and see if you can find out at what RPM its hitting 38 deg's and some idea about the cam if possible also manual or vacuum carb and vacuum at idle.

Terry
 
i would be willing to do that....but i do not know how..I would ...however like to get to the bottom of that 440 running so badly though...lots and lots of money in that car...and ...honestly (i am a smallblock guy) that big incher should blaze the hides off that car.... btw the cam is a .509 unit..
 
On the camshaft, it's got 241°@.050 IIRC.. that's a fairly large cam with a bit of overlap... A consequence of the oldschool design. Not a lot of life, big duration. By comparison, most modern stuff in those lift ranges will have 10° or more less duration at .050.

Bobby,
Sorry but I disagree with you on this one. And so does Holley among others. No offense, but it's an oldschool way of trying to tune secondary timing without buying the right spring package and it simply makes for more problems. The check ball and smaller orifice makes the secondaries open smoothly as air flow increases. It's the airflow that pulls the fuel out of the boosters. If you pull the ball and enlarge the passage the secondaries fall open creating a lean stumble as the blades snap open, and it continues until the airflow picks up and the fuel gets pulled thru the boosters properly. If it's a race car, and the stall is high, and the gearing is such that the engine can pull enough air to get proper flow thru the boosters, then it's not going to hurt anything. On a street car, where the carb size is a big deal abd gearing and convertors are mild it makes it a turd. Of course, you could add a ton of squirtor or jet and bandaid a problem you created. But VS carbs have smaller acc pumps and adding jet simply means there is more fuel available earlier... then it goes rich. Note how Holley and every other carb maker using thier design installs a 50cc accelerator pump for the secondaries on a double pump carb. Or you could keep your foot out of it so you never open them. But it's simply the wrong way to run a vacuum secondary carb to get performance or economy. BTW, what opens them is not vacuum created by piston movement as read under the throttle plates... Something that is strong enough to "suck in" gaskets... but the difference in pressure from atmospheric that occurs right at the booster in the venturi. It is less than atmospheric presssure, but nowehere near "0". That same principle controls the fuel pulling up thru the boosters, which is why the orifice is placed so high in the carb throttle bore. Drilling the orifice means a faster developing pressure differential... more area for the air flying by to pull on. Hence the earlier opening secondary or slamming open without the check ball. When the carb is running right, you shouldnt feel the secondaries, and by adding the right spring, they can be made to open cleanly and as early as 1500 depending on the engine it's on.
 
The issue that your talking about happening has never happened with any engine I've ever had the carb on. And on my street vehicle with a stock converter and a 3.08 gear, and the truck would blaze the hides at will, pulled the race car for many years and never a issue there either. The old truck also was getting 17 mpg with a regular 3 spd. auto. trans. and 13 mpg towing. Thats as good of fuel mileage that I'm getting with my late model Dodge Ram with a OD. So I guess that I'm wrong when it was better than a newer vehicle and had more performance. I guess I'll have to keep being wrong then. And we'll agree to disagree.
 
Burntorange70 said:
I took my Dart to the track one time and was only going around 85 mph through the traps and it was sluggish and not RPMing very well. Turned out that I did not have my throttle cable ajusted right and the secondarys were not opening all the way. Don't know if that is it or not but it is easy to check any way.

Good luck.
Click to expand...

I'll check that too. Thanks
 
dust-u said:
huh..very interesting have a fella i know with a similar prob...bored 30 440 new pistons around 10:1 mildly ported 915's 2200 torque converter , fresh 750 holley,3:55's..idles great 12 degrees initial 38 all in ...take it out and give her some....omfg..i can run faster than this car....pings and generally runs like dog crap...any suggestions warmly received??? should i put it to sleep???
Click to expand...

Dust-u I'd say look back at the responses I got and check those things since your buddy's car is doing basically the same as my buddy's car.

BTW: Is your buddy running 92 or better gas? With that much compression he'll need to. My buddy is running 93 and I never heard it spark knock.
 
i dont think the 440 my buddy has is suffering from a carb issue...swapped it out with a brand new barry grant that was on a sweet running 440... still laid down... and pings and farts etc...like i said 12 degrees initial and 38 all in but i do understand getting the 38 to stay steady is a problem...I honestly believe the cam may be either severly retarded/advanced....everything else appears ok...this is a "fresh" motor...any ideas????:read2:
 
dust-u said:
i dont think the 440 my buddy has is suffering from a carb issue...swapped it out with a brand new barry grant that was on a sweet running 440... still laid down... and pings and farts etc...like i said 12 degrees initial and 38 all in but i do understand getting the 38 to stay steady is a problem...I honestly believe the cam may be either severly retarded/advanced....everything else appears ok...this is a "fresh" motor...any ideas????:read2:
Click to expand...

If the timing is erratic I'd check the dist. bushing in the block. If it's worn it'll let the dist. shaft wobble and make timing erratic. That happened on my 360 and I replaced the bushing and it was rock solid afterward. If the bushing is not worn it must be a problem in the dist. What dist. is it? You may want check to see it don't have a bent shaft cause that'll make things erratic. If the cam wasn't degreed in it's possible it's off also. Awhile back I had 4 different brand timing sets and a day of nothing to do and I installed each one on an engine and checked the cam timing and found one was 4 degrees retarded. 2 were 3 degrees retarded, and the last was 1 degree retarded. None were advanced. I'd check the dist. first since the timing is erratic and get that fixed and see how it does.
 
yup...gonna head down the cam timing road....i am pretty sure the dist was/or is new...but will try a known good unit...
 
took the motor apart....strongly suspected a timing issue...get this... double stamp on lower timing gear...motor was outta time...corrected the issue...took it out...blazes the hydes.....at will...like it should...Guess we can thank cloyes for outsoursing ...Is anything made in america anymore????
 
dust-u said:
took the motor apart....strongly suspected a timing issue...get this... double stamp on lower timing gear...motor was outta time...corrected the issue...took it out...blazes the hydes.....at will...like it should...Guess we can thank cloyes for outsoursing ...Is anything made in america anymore????
Click to expand...

Good deal Dust. Still haven't got back together with my buddies to work on his. Hopefully he makes it back over before it gets blazin hot this summer.
 
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