440 Engine Guru's Help

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jms.racing

jms.racing

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Conroe , TX
Hey guy want to get a second opinion besides my own on this problem . I recently purchased a 75 Dart with a 440 in it . The guy i got it from was not much of a car guy and actually took the car in on trade , its obvious he did not maintain it very well , heck it might not even be a 440 maybe stroked , valves out of adjustment , 6 burnt wires , fowled plugs , carb was trashed , all the grounds mounted over paint , electric fuel pump mounted upside down and no relay or fuel filter , IT WAS BARLEY RUNNING WHEN I PICKED IT UP. Since then i have fixed all of the above. The problem is the car is acting like its missing or pre detonating the engine has a vibration , the guy i got it from says its a pump gas motor but im really not for sure , the cam specs are as follows

Bullet solid flat tappet lift 645/630 - dur @ .050 267/272 - 109 lc on 106 cl
Heads 440 Source Alumimun Stealths ported
Mopar single plane

I did a compression test on all the cylinders with the carb off , plugs out , battery charger on , also fogged all the cylinders with a couple drops of 5w30 oil . All of the cylinders pumped 178 to 185 ( does that sound like pump gas numbers ) anyone have a similar combo pumping those numbers running pump gas

I thought maybe flat lobes but you would think the compression test would not be so close ? or bad valve job but compression check would show ?
I checked the valve spring pressures 140 seat 400 open ?
I have had the timing set at 32 to 40 total with same results
Fuel pressure at 6.50
I put a vacuum gauge on it and the needle is bouncing from about 5 to 10 lbs , This would seem to point me towards a vacuum leek , so sprayed carb clean everywhere and nothing ?
Could the ignition be causing the the bouncing vacuum and the rough running ?
it has a MSD 6al / blaster coil and some sort of electronic distributor

Or is it maybe just more compression than pump gas.

Any help or insight would be greatly appreciated .
 
Are those compression numbers dry or with oil?

What Carb? Whats the flow rate on the Fuel pump? Is it keeping up or over powering the carb? Have you checked the plugs since you replaced them?
 
Compression check done with two drops of oil in each cylinder and then followed with an air hose. Carb is one of my 950 HP series complete with the Dr modification. Compression test was done with engine cold. Have not check the plug yet since everything else has been repaired good idea I will check them this Sunday any other info would help guys.
 
Fuel pump is a holley red with #6 push lock all the way with a regulator set at 6 3/4 psi , does this while idling also , hoping it might be an ignition issue .
 
I picked up a GTX while down south visiting ,,, years back, well it ran good going on the trailer. on way back home, stopped to see a car friend, he wanted it, i sold it. he was racer. ran good on I 35, till he got it up to full speed, 90 and more, had a vibration coming from the engine.

he torn it down, the 400 had one six pack rod, rest reg 440 rods!!!!! Ha ya never know what you are buying!????
 
185 is about the limit with pump gas, but you also have aluminum heads. That makes 185 likely a good number. Not sure why you would put oil in the cylinders before a compression test if you don't have numbers without oil. That vacuum reading is probably normal with a large cam. Mine only idles at 5.5".

Throw in some fresh plugs and known good cap and wires and run it again. Do another compression test when warm without adding oil. Does it miss all the time or only at idle, cruise full power?

All the time is easier to chase down. Spray a splash of water on each header tube and see which one is cold.
 
jbc426 said:
185 is about the limit with pump gas, but you also have aluminum heads. That makes 185 likely a good number. Not sure why you would put oil in the cylinders before a compression test if you don't have numbers without oil. That vacuum reading is probably normal with a large cam. Mine only idles at 5.5".

Throw in some fresh plugs and known good cap and wires and run it again. Do another compression test when warm without adding oil. Does it miss all the time or only at idle, cruise full power?

All the time is easier to chase down. Spray a splash of water on each header tube and see which one is cold.
Click to expand...

Dry compression was about 165 / 170 this was cold also , it does its constant idle and cruse , Im afraid to give it a wide open blast especially if there is a chance of pre detonating , good ideal on the water thing never thought of that. See yall are helping .
 
Have you done a cylinder drop test? Unplug a wire one at a time and see if it changes?

How old is the fuel?

As I understand large cams like more initial timing. So 40 may not be enough.

On the distributor, have you looked it over internally to make sure its not messed. Does it have a vacuum advance?
 
dano said:
Have you done a cylinder drop test? Unplug a wire one at a time and see if it changes?

How old is the fuel?

As I understand large cams like more initial timing. So 40 may not be enough.



On the distributor, have you looked it over internally to make sure its not messed. Does it have a vacuum advance?
Click to expand...

No vacuim advance , cylinder drop test I will try , as well as pull dist and inspect .
 
if it's that cam and 185 cranking with the starter, I'd say it's probably too high for pump gas once it's running. It also sounds like it's been stroked. IMO you need to pull a head and get some basic info and measurements.
 
moper said:
if it's that cam and 185 cranking with the starter, I'd say it's probably too high for pump gas once it's running. It also sounds like it's been stroked. IMO you need to pull a head and get some basic info and measurements.
Click to expand...

I was thinking the same thing , most of the other motors I have built that have that kind of cranking pressure was around 12.10 comp , plus it didn't make much since to put that big of a cam in a pump gas motor , plus I think it should bleed off some cranking pressure, if it was stroked that would make a little since , I'm going to throw some race fuel in and see what happens as well as check some thing other have mentioned , Thank to all for the input great help .
 
my engine is 197 average cold cranking, 11.5:1 with iron heads, 260*/260* @ .050 flat solid, runs fine all day with 37* total advance, on 93 pump gas. if U think it is detonating do not go more than 36* total advance. maybe the damper outer slipped-rare for mopars-try race gas. vibration may be the engine/damper/flywheel out of balance-some folks are confused about the correct mopar combos.
 
Not a pump gas engine with that cam and those cranking compression numbers. I'd say it is at least 12:1 compression. Either dome pistons if it is a 440 or flat tops if it is a stroker. You might be able to see the top of the piston if you look thru the spark plug hole. Just depends if you can get your eyeball in the right location to look in there.
 
I see several possibilities here.
Firstly at idle
1) that cam has in the neighborhood of 100 degrees of overlap. Perhaps more. So for sure it will idle"rough"
2) the bouncing vacuum gauge needle, if a steady bounce may be normal, but if it's intermittent, it's a problem, and may be pointing you to the direction of the miss.There can be only one reason for that; a pressure spike is moving into the manifold from a cylinder.That means an intake valve problem.
3)The lack of vacuum advance at part throttle puts a severe handicap on the engines willingness to take throttle.
Without a well tuned PT timing system there are basically two times that an engine can have the right timing; 1) full load/WOT/ sometime around the torque peak, and 2) Possibly at idle.Of course this has almost nothing to do with your problem;jus saying.
Then at speed
You didn't say when the miss is occurring, but your first paragraph infers that you were driving it and possibly hard. So if that is right, missing under load is often bad plugs. Bad could be because they are carbon fouled, or overheated or cracked insulators. The CDI can easily light just about anything at idle to when it switches, somewhere around 3000 rpm. But after the switch it does just about what the standard system does, allbeit slightly hotter So a bad plug is still a bad plug.

So heres my 2cents; 8 new wide-gap plugs, and back up the timing to 30/32 and go for a new roadtest. If it's cured, maybe you can sneak in a lil more timing, but maybe bring it in a lil later.And figure out what killed the plug(s), and cure that,before it happens again.Ima thinking the fastest thing to kill a plug is wrong time spark, and second fastest is wrong fueling.

I once watched a guy build a Polaris triple(three cylinder) snowmobile engine.After melting it down in less than a mile, I watched him build it again. And melt it down again. In less than a mile.In frustration he finally asked for my opinion. I showed him the slugs and the plugs, and asked him if he knew why they looked like that. He did not. I pointed him to the Mikuni carb tuning guide. After a third rebuild,and a fresh load of fuel, he jetted up the carb for the current temperature and altitude, and had no more problems.
Two-strokers operating at temps that can vary from freezing to 30 or 40 below, are sensitive that way................................
More useless info, I know.
 
Thanks for posting up all of yalls thoughts , I'm going to put a bore scope back in the engine the headers make it hard to get the right bend , also I have never put my foot in it I'm afraid something might break right now until I get bugs worked out , they vacuim gauge isn't a crazy intermediate bounce it's more like it's flutering.
 
UPDATE
Finally got some time to try what we have been discussing , pulled plugs looked a tiny bit lean no damage all looked about the same , pumped all the fuel out of it , thru some 110 race fuel in it and bam fired up and responded way better , idled better , smelt better actually wanted to run , but noticed right off the bat there was a little knock / rattle coming from the front plus oil pressure was about 20psi idling , brought the rpms up about 1000 more just to check pressure did not rise at all , let off and it rattled more , shut it down at that point / ugh crap , come to the conclusion that they where trying to drive it on pump gas and that it had been pre detonating the whole time , this would ex plane the vibration , the missing , and the bottom end going out with oil pressure dropping , Cant really blame the guy I got it from he had no clue and was not a car guy at all , I got a great deal on the car even with the motor bad LOL , My only hope is that the 440 block can take this abuse and there is not enough damage to the block so i can give it the loving that it needs , Anyway motors coming out , Thanks to all that helped with advice .
 
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