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My 440 is a slug, please help. #471559
09/18/09 09:27 AM
09/18/09 09:27 AM
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Gator73 Offline OP
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Like the title says, my 71 440 runs like a slug and has very little low end torque. It doesn't even want to spin the tires with 3:55 gears. We have a few theories on why it may be lazy but wanted to check here for some additional ideas. Here is the background on the engine. This was a bone stock 71 440 that has been in my 74 Roadrunner for years. It ran great when the engine was put in the car but over the years, the stock AVS would dead spot and no amount of tuning or rebuilding would fix it. Since there were some other small issues to address on the engine, we decided to remove it and replace the cam, timing, chain, carb and intake. Used a Crower 267HDP (220 and 223 @50 with 478 and 486 lift 112 lobe separation angle). On went a Holley Street Dominator and a new Edelbrock 800 Thunder Series AVS. It should be noted that we are using stock 73 HP Magnum exhaust manifolds. The car starts, idles,and runs nice and doesn't even really have any lope at all from the cam. The timing is set at 11 initial and doesn't ping. It bogs a lot when you step on it from a stop. Air door has already been adjusted some but hasn't cured the problem. So, anybody got any ideas? Is the Street Dominator killing off the bottom end in this combination despite the fact that it is generally known as a good low-end intake? I think the AVS carb should run pretty good on a stock-type engine and not be too much. The cam is also pretty mild and should not make a dog out of it. We have a Weiand Action Plus we can try to see if that brings back some of the low end but it is so dead I don't know what will help. A 440 like this should melt the tires. Any help would be greatly appreciated.

Re: My 440 is a slug, please help. [Re: Gator73] #471560
09/18/09 09:48 AM
09/18/09 09:48 AM
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Brookeville, Md
Mr.Yuck Offline
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what's your total timing? you mightwant to try 38* at 2400 rpm. Unhook the vac advance and lock it in. Don't worry too much about int timing. Then adjust the carb until you get the best vacuum reading. You can try adjusting the pump shot as well. what notch do you have it at now? What stall is in the car?
Also you say you adjusted the air door...how about the choke flap? I had one that like to suck shut on me, I wired it wide open. I'll probably start a holley vs eddy debate but do you have access to a 750DP? if so barrow it and see if that helps. I have found the holleys to be more responsive. That said the 800 thunder should be enough to get the tires loose. Just sounds like you have to work the tune some.


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Re: My 440 is a slug, please help. [Re: Mr.Yuck] #471561
09/18/09 09:56 AM
09/18/09 09:56 AM
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Smithville .Ontario,Canada
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fastback383 Offline
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There is a post on here about the bog from the Edelbrock carbs you might want to read. Read past all the BS and typical bickering here about switching to a Holley and it might help you some. It's a start. It sounds like that is only part of your problem. Good luck, Dave.


https://board.moparts.org/ubbthreads/show...e=1#Post5428740


Re: My 440 is a slug, please help. [Re: Mr.Yuck] #471562
09/18/09 10:02 AM
09/18/09 10:02 AM
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Gator73 Offline OP
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I knew someone would ask about the total timing. My friend is working on this car and I don't have that info but I can get it. There is no stahl converter in the car and I was advised that the cam was mild enough that stock would be OK. I hear you on the DP. I have thought about trying a Holley if we can find one to see how it compares. Any thoughts on the Street Dominator as the culprit?

Re: My 440 is a slug, please help. [Re: Gator73] #471563
09/18/09 10:06 AM
09/18/09 10:06 AM
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Brookeville, Md
Mr.Yuck Offline
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No the Street Dom is a good intake. It shouldn't be causing the problem. I'm guessing it's a timing and carb tuning problem. The only reason I mentioned a holley is if you have a buddy that has one or any carb know to work you could check it on your motor.

Re: My 440 is a slug, please help. [Re: Gator73] #471564
09/18/09 10:06 AM
09/18/09 10:06 AM
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Yep, read all about the Edelbrock 750 and its problems. The Performer 800 and the 800 AVS are supposed to be much better carbs. I have an 800 AVS on another car and it works pretty well. There seems to be something about this particular combination that isn't working. More tuning and perhaps parts swaps.

Re: My 440 is a slug, please help. [Re: Gator73] #471565
09/18/09 10:10 AM
09/18/09 10:10 AM
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Yeah, I wouldn't think the SD would be causing the problem given the rave reviews it gets. Maybe it just works better on hotter engines rather than my relatively stock combo. Anybody ever use a SD on a stockish engine and have low end issues? I agree that changing carbs to a known good one regardless of the brand could elimiate a lot of guess work. I'll have to beat the bushes to see if I can scare a good candidate up.

Re: My 440 is a slug, please help. [Re: Gator73] #471566
09/18/09 10:13 AM
09/18/09 10:13 AM
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Overland Park, KS.
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Joshs68 Offline
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Initial timing is very important! ask a carb shop if you want a second opinion. What is the total timing? I would give it more initial. try for 15-18* initial with a total of 35-37* should be plenty.

Re: My 440 is a slug, please help. [Re: Joshs68] #471567
09/18/09 10:30 AM
09/18/09 10:30 AM
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Indiana
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I agree with Josh. Initial timing is very important in a street car with a larger than stock cam and an auto.
You wrote that you have 11 degrees initial timing, now once you know what your in gear (foot on brake, engine at running temp) vacuum reading is, you have a base line.
Then I would suggest bumping the initial timing up to 15-18 degrees (since you have a larger than stock cam) and retune your in-gear vacuum to the highest number at the same rpm as you had with the 11 degrees. If your vacuum reading went up, then the motor wanted it. Then you would want to recurve your distributor for your total timing and then test drive the car. If you gained in gear vacuum, then you will gain bottom end response too if the carb is tuned correctly. That 800 Edy should be fine for your setup. Get the timing correct first and then finish tuning the carb.


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Re: My 440 is a slug, please help. [Re: Gator73] #471568
09/18/09 10:35 AM
09/18/09 10:35 AM
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Woodinville, WA
Viol8r Offline
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Quote:

Yeah, I wouldn't think the SD would be causing the problem given the rave reviews it gets. Maybe it just works better on hotter engines rather than my relatively stock combo. Anybody ever use a SD on a stockish engine and have low end issues? I agree that changing carbs to a known good one regardless of the brand could elimiate a lot of guess work. I'll have to beat the bushes to see if I can scare a good candidate up.




You will lose a little bit of bottom end with the SD vs. the RPM (or dual plane). A few things jump out at me. Not enough compression, no stall, not enough initial timing, and the wrong carb.

Re: My 440 is a slug, please help. [Re: Viol8r] #471569
09/18/09 10:47 AM
09/18/09 10:47 AM
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Lincoln Nebraska
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fix the timing and the bog in the carb. EDIT all oe AVS's are emissions era carbs & you might get an eddie strip kit & some flat metering rod caps & richen it.

Last edited by RapidRobert; 09/18/09 10:51 AM.

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Re: My 440 is a slug, please help. [Re: RapidRobert] #471570
09/18/09 11:06 AM
09/18/09 11:06 AM
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That cam isn't very big , looks like a modern version of the stock 440 magnum cam .

What distributor do you have on this ?

If the air door is set to loose you'll get a big bog .

Re: My 440 is a slug, please help. [Re: JohnRR] #471571
09/18/09 11:34 AM
09/18/09 11:34 AM
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Gator73 Offline OP
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It is a mild cam and Crower tech support indicated that a stock torque converter would be fine. There are members on here who have recommended the 271HDP and have utilized a stock converter in a heavy car and had great results. John, the distributor is a stock Mopar replacement unit from a parts store that was bought years ago (not a Mopar Performance unit). It was recurved some time ago and has one heavy spring and one light spring. It seems to be working find. I have thought about replacing it with a known good MP unit to see if that would help.

I do understand that all carbs may need tuning to get optimal performance but I would think the Thunder Series AVS would run pretty good right out of the box. The air door has already been tightened some. Any other 800 Thunder Series users out there who have had to make major adjustments on the air door on a mild combo? Just trying to get an idea of how much tuning this carb needs out of the box. As many have said, it probably needs more timing and once that is sorted out, deal with the carb tuning. I already have the calibration kit for the 800 AVS so we are ready if it needs different parts.

Re: My 440 is a slug, please help. [Re: Gator73] #471572
09/18/09 11:42 AM
09/18/09 11:42 AM
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New Mexico
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If you do all that others have suggested and are not happy with results, advance your cam timing about 5 degrees. it's all about cylinder pressures!!

Re: My 440 is a slug, please help. [Re: dmerc] #471573
09/18/09 12:25 PM
09/18/09 12:25 PM
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Pendleton NY
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terzmo Offline
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what's the compresion?

Re: My 440 is a slug, please help. [Re: terzmo] #471574
09/18/09 12:37 PM
09/18/09 12:37 PM
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Grand Haven, MI
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what kind of vaccuum are you pulling at idle?

did you do a compression test?

if you have a lot of vacuum at idle (13+" In gear), changing the stock orange step up springs (5" vaccuum) to the pink or natural (7 or 8") will help a lot with a lean bog at tip in.

also, there's 3 holes on the acc pump lever to adjust the volume of the pump shot, closer to the carb the hole is, the bigger the shot. play around with that adjustment as well.

do you have any vacuum leaks?

if your compression test shows low, did you degree in the cam? If it's installed slightly retarded (say, 112 ICL instead of 108) the later intake closing point will cause the cranking compression will drop, and low RPM torque will be reduced.

Last edited by patrick; 09/18/09 12:40 PM.

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Re: My 440 is a slug, please help. [Re: patrick] #471575
09/18/09 01:36 PM
09/18/09 01:36 PM
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Ontario, Canada
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Is the vacuum advance hooked up?? and is it on manifold vacuum! unhook it and forget it for now.
ALL initial tuning should be done with vacuum advance unhooked and capped!!!!!!!!!!!!!!

Re: My 440 is a slug, please help. [Re: Dodgem] #471576
09/18/09 02:36 PM
09/18/09 02:36 PM
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This is a higher mileage engine and the compression was checked before going into this. The cylinder pressure varied amongst the cylinders and ranged from a high of 145 to a low of 130. I thought I posted about these numbers and whether they would be ok, but I can't seem to find the post. Anyway, from what I gathered on other similar posts, my compression while not great was not all that bad. I believed the engine to be in good enough condition that it could take a mild cam along with the new timing chain, intake, and carb. All advice on timing including vacuum readings will be considered and we'll see how much additional it can take. I believe the pump shot is still in the stock position and we can play with that some too after the timing is figured out. It doesn't have any off idle stumble under moderate throttle or anything like that, just bogs when you try to open it up. This car runs great and could be driven all day long but just simply has no guts.

Re: My 440 is a slug, please help. [Re: Gator73] #471577
09/18/09 03:18 PM
09/18/09 03:18 PM
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Woodinville, WA
Viol8r Offline
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This combo is just not a barn burner, sorry my friend. An 8.5:1 iron headed, stock bottom, no stall 440 is just not going to feel real quick. Especially with a single plane intake and too much carb.

There is good chance those pistons are way down in the whole with a early 70's block. I am guessing 6.5:1 dynamic compression.

I would cut .040" off the heads, get a dual plane, go to a 750 Holley, headers, that will wake her up.

Re: My 440 is a slug, please help. [Re: Gator73] #471578
09/18/09 04:17 PM
09/18/09 04:17 PM
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Thigh-Gap Junction
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Have you checked your vacccuum advance diaphragm lately? It should run fine at 11B initial, assuming the damper hasn't slipped. I think I'd fatten it up a bunch to see if it helped. That's what others are saying when they say double-pumper, they just don't realize it. I had a '67 New Yorker with a similar combo and I had to fatten up the AVS I was using a ton, but then it ran great. At 4500lbs it ran 15-flat in the 1/4-mile and chirped the tires on the 1-2 shift. That was with a Performer intake, HP manifolds and full dual exhaust. The cam was similar to the factory HP.

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