1970 429 SCJ

Hello everybody, I'm new to the forums and I'm here because i have a problem. I really hope somebody can shed some light on my situation. This is a DEFCON 2 emergency.

I have a 1970 ALL STOCK, except the carburetor ,429 SCJ. I have it in a 1969 Mustang with a C6.

Short story: it runs pig filthy rich. It's really bad.

Long story: After finally installing the 429, i had a really nice, lightly used BG 750 DP carburetor laying around that i used and worked like a dream on a 383 stroker i had before. I used that and it fouled literally everything. No matter what adjustments i made, it smoked me out.

I went out and got a brand new Holley 600cfm from Advance Auto. Put that on, ran just as rich. AA was nice enough to take back that carburetor.

So i finally purchased a QF 750 DP (67200). Smokes me out and bogs like a chimney. When i go to shut my engine off, it tends to "diesel" and i hate that it does that. I know its doing that because i have probably fouled up those cylinders so bad and it's igniting any extra fuel getting sucked in.

Please.... I'm 27, i have had this car for 10 years and i just brought this down from my parents house last summer and i have busted my ass getting all this put together for this summer just to be held back by this. I live in a small town in Tennessee and I have literally nobody here around me who i know who has any knowledge of this. It's just me. I need all the opinions i can possibly get. I feel like I'm going to destroy this engine if i keep messing with it and making things worse. I'll take all the constructive criticism you all can give.

Thank you.

dragkid wrote:Hello everybody, I'm new to the forums and I'm here because i have a problem. I really hope somebody can shed some light on my situation. This is a DEFCON 2 emergency.

I have a 1970 ALL STOCK, except the carburetor ,429 SCJ. I have it in a 1969 Mustang with a C6.

Short story: it runs pig filthy rich. It's really bad.

Long story: After finally installing the 429, i had a really nice, lightly used BG 750 DP carburetor laying around that i used and worked like a dream on a 383 stroker i had before. I used that and it fouled literally everything. No matter what adjustments i made, it smoked me out.

I went out and got a brand new Holley 600cfm from Advance Auto. Put that on, ran just as rich. AA was nice enough to take back that carburetor.

So i finally purchased a QF 750 DP (67200). Smokes me out and bogs like a chimney. When i go to shut my engine off, it tends to "diesel" and i hate that it does that. I know its doing that because i have probably fouled up those cylinders so bad and it's igniting any extra fuel getting sucked in.

Please.... I'm 27, i have had this car for 10 years and i just brought this down from my parents house last summer and i have busted my ass getting all this put together for this summer just to be held back by this. I live in a small town in Tennessee and I have literally nobody here around me who i know who has any knowledge of this. It's just me. I need all the opinions i can possibly get. I feel like I'm going to destroy this engine if i keep messing with it and making things worse. I'll take all the constructive criticism you all can give.

Thank you.

Getting the distributor curve right to go along with needed 14 degrees initial timing will help.
Probably won't cure it all though.

I currently have it set at 12 btdc, if 14 helps even just a tiny bit I'll do it. I just have this feeling that fuel is being sucked in from somewhere else, maybe the secondaries? Would it be okay to turn the secondaries in more than what the primaries are at? I'm afraid I'm going to make it too lean. I have 6.5 psi to the carb also. The crazy part is, my vacuum gauge says im at 10 hg of vacuum, but it will increase only when i mess with the idle screw, but if i mess with the fuel idle screws, it dosent move at all...

I owned a 70 SCJ also and after the original 780 cfm Holley went bad I temporarily put a 650 cfm Holley I had good for driving around but not so much for speed, Finally bought a new 850 cfm Holley I forget what jets it had stock but other than some minor tuning it worked great. Are you sure you are only putting 6.5 pounds of fuel pressure to the carb??? Sounds like it's getting more pressure than that. I ran a mech. fuel pump and an old 6 psi electric pump to help with vapor lock and high rpm lean out. Good luck.

I will triple check the PSI on it just in case. I have a brand new holley blue, holley carb regulator and a aeromotive fuel pressure gauge on a russell carb line. I was just out there messing with it and i started it up, it was going well and then my belt just shredded all to pieces. Looks like I'm packing it up for the night until i can get one tomorrow.

1: Fuel pressure is too high.

2: float level. When sitting on level ground the fuel should not run out the sight plug unless you rock the car. If it is glass set it where you have to rock the car to have fuel touching the glass. If you can see fuel on the glass it’s too high. Set it with the car idling.

3: needle and seat is not sealing.

4: busted float is holding the needle open.

5: you are correct about messing stuff up running it that way it will wash down the rings and excess fuel will thin down the oil. Check the oil level before you go any farther to. E sure this hasn’t already happened.

Good luck.

I just ordered some new VR1 10W30 earlier today, i will get a new Motorcraft filter tomorrow and i will change everything out before i start it up again. The sad part is i just did that oil change a month ago and it's already black as night. Haven't even driven it yet. Thats how bad it was fouling up. I'm going to wait until i change the oil and belt to try again.

dragkid wrote:I just ordered some new VR1 10W30 earlier today, i will get a new Motorcraft filter tomorrow and i will change everything out before i start it up again. The sad part is i just did that oil change a month ago and it's already black as night. Haven't even driven it yet. Thats how bad it was fouling up. I'm going to wait until i change the oil and belt to try again.

If your engine oil was so contaminated with gasoline, it completely lost it's lubrication qualities and even though you installed a new carb, that probably was in good working condition, the gas/oil mixture in the engine will blow by the piston rings, fouling the spark plugs. Hopefully, your engine bearings didn't score, and possibly the cylinder walls. I have seen this happen before. Always check a new carb for proper float level. These are shipped and they get tossed around. Floats can get out off adjustment very easily. Changing your oil and filter will help, but check the oil pressure with a manual gauge.

I doubt you’ve done any damage with that little Of run time. On the bright side the gas in the oil will clean the inside of the engine a little. You’d have to give it hell with a lot of gas in the oil to do damage to the crank and rod bearings. The lifters will start to rattle first.

Pull your spark plugs and look at them.  You can't tune it if all the plugs are fouled and black...

rharden wrote:

dragkid wrote:I just ordered some new VR1 10W30 earlier today, i will get a new Motorcraft filter tomorrow and i will change everything out before i start it up again. The sad part is i just did that oil change a month ago and it's already black as night. Haven't even driven it yet. Thats how bad it was fouling up. I'm going to wait until i change the oil and belt to try again.

If your engine oil was so contaminated with gasoline, it completely lost it's lubrication qualities and even though you installed a new carb, that probably was in good working condition, the gas/oil mixture in the engine will blow by the piston rings, fouling the spark plugs. Hopefully, your engine bearings didn't score, and possibly the cylinder walls. I have seen this happen before. Always check a new carb for proper float level. These are shipped and they get tossed around. Floats can get out off adjustment very easily. Changing your oil and filter will help, but check the oil pressure with a manual gauge.  

I checked the floats prior to installing, made sure everything was set to spec. I have a manual gauge installed, oil preasure is at 60 psi @ 800-1,000 rpm.

stanger68 wrote:I doubt you’ve done any damage with that little Of run time. On the bright side the gas in the oil will clean the inside of the engine a little. You’d have to give it hell with a lot of gas in the oil to do damage to the crank and rod bearings. The lifters will start to rattle first.

I have maybe 30 minutes to an hour of run time while revving it no more than 1,800 rpm. I thought the same thing about it cleaning out the engine a bit considering the gentlemen i bought it from said it sat under a cover for 20 years, it still had oil in it, i drained that out so there may have been some left in it.

cletus66 wrote:Pull your spark plugs and look at them.  You can't tune it if all the plugs are fouled and black...

I'm not even gonna doubt they are black. I'm just going to go purchase new plugs. That's what I'm not looking forward to is changing plugs considering how tight those shock towers are to the block. Would you recommend a specific plug? Maybe a colder plug? I have Motorcraft plugs in it now.

dragkid wrote:

cletus66 wrote:Pull your spark plugs and look at them.  You can't tune it if all the plugs are fouled and black...

I'm not even gonna doubt they are black. I'm just going to go purchase new plugs. That's what I'm not looking forward to is changing plugs considering how tight those shock towers are to the block. Would you recommend a specific plug? Maybe a colder plug? I have Motorcraft plugs in it now.

Just look at them before you spend a dime.

Do you have a modern electronic ignition, or the stock points type? This makes a big difference in the quality of the combustion cycle.
So you have checked and set the float level to the correct setting. Next, turn your idle mixture screws all the way in, then back them out 1 1/2 turns each....this is a baseline setting for these, you may have to expiriment with this a little to get it just right.....but be aware that farther out you go on these, the richer its going to get at idle.
Next, check that your carb has the correct power valve, and that it is not blown or ruptured, as that will be a source of internal fuel leakage if the rubber is torn or damaged.
Also check and set the accelerator pump linkage to the correct setting.

dragkid wrote:

stanger68 wrote:I doubt you’ve done any damage with that little Of run time. On the bright side the gas in the oil will clean the inside of the engine a little. You’d have to give it hell with a lot of gas in the oil to do damage to the crank and rod bearings. The lifters will start to rattle first.

I have maybe 30 minutes to an hour of run time while revving it no more than 1,800 rpm. I thought the same thing about it cleaning out the engine a bit considering the gentlemen i bought it from said it sat under a cover for 20 years, it still had oil in it, i drained that out so there may have been some left in it.

If that engine just sat for that long, it would not surprise me at all if some rings are stuck abd just not working.anymore.

rmcomprandy wrote:

dragkid wrote:

stanger68 wrote:I doubt you’ve done any damage with that little Of run time. On the bright side the gas in the oil will clean the inside of the engine a little. You’d have to give it hell with a lot of gas in the oil to do damage to the crank and rod bearings. The lifters will start to rattle first.

I have maybe 30 minutes to an hour of run time while revving it no more than 1,800 rpm. I thought the same thing about it cleaning out the engine a bit considering the gentlemen i bought it from said it sat under a cover for 20 years, it still had oil in it, i drained that out so there may have been some left in it.

If that engine just sat for that long, it would not surprise me at all if some rings are stuck abd just not working.anymore.

I turned the crank by hand before purchasing it and checked the cylinders with a borescope, i still seen the cross hatches in each cylinder with no scorn marks. Before installation i did a compression check and the cylinders check out at 148-151psi. I figured they were okay.

Where in small town Tennessee are you from?

jasonf wrote:Where in small town Tennessee are you from?

Wartburg, Morgan County

Cranking pressure on a stock 429 SCJ should be around 190-200 psi. Compression ratio on a stock one should be 11.3 to 1. No way it would run properly on today's pump gas.

rmk57 wrote:  Cranking pressure on a stock 429 SCJ should be around 190-200 psi. Compression ratio on a stock one should be 11.3 to 1. No way it would run properly on today's pump gas.

I must have been doing something wrong then. I have all types of different fuel choices here, 100%, E85, 93,97, 110, jet fuel, feel free to tell me what would work best.

I'm not postive but didnt the original 429 SCJ 780 Holley have holes drilled in the primaries? Are the mixture screws doing anything? How much of the idle transfer slot is showing?

I would run 97. 93 has nowhere near the octane level needed when that engine is at operating temp.

30+ years ago I had a 1970 Ranchero with a factory 429 SCJ in it and it would diesel on if I didnt stall the engine with the clutch. It would also ping a bit when the engine got hot with 12 degrees timing

and that was with chevron 94.

Randy

rmk57 wrote:  I'm not postive but didnt the original 429 SCJ 780 Holley have holes drilled in the primaries?  Are the mixture screws doing anything?  How much of the idle transfer slot is showing?

I would run 97. 93 has nowhere near the octane level needed when that engine is at operating temp.  

30+ years ago I had a 1970 Ranchero with a factory 429 SCJ in it and it would diesel on if I didnt stall the engine with the clutch. It would also ping a bit when the engine got hot with 12 degrees timing

and that was with chevron 94.

Randy

Randy,

I wish i had the original carb that came with it, i would have just rebuilt that and used it instead. I would have to check out idle transfer slot when i get home. The mixture screws do something yes. When i close them all the way, the RPM just increases, but dosent shut down on me, which i find odd. What timing do you reccoment I set it to? Would 14 be sufficient? Maybe 15-16?

dragkid wrote:

rmk57 wrote:  I'm not postive but didnt the original 429 SCJ 780 Holley have holes drilled in the primaries?  Are the mixture screws doing anything?  How much of the idle transfer slot is showing?

I would run 97. 93 has nowhere near the octane level needed when that engine is at operating temp.  

30+ years ago I had a 1970 Ranchero with a factory 429 SCJ in it and it would diesel on if I didnt stall the engine with the clutch. It would also ping a bit when the engine got hot with 12 degrees timing

and that was with chevron 94.

Randy

Randy,

I wish i had the original carb that came with it, i would have just rebuilt that and used it instead. I would have to check out idle transfer slot when i get home. The mixture screws do something yes. When i close them all the way, the RPM just increases, but dosent shut down on me, which i find odd. What timing do you reccoment I set it to? Would 14 be sufficient? Maybe 15-16?

If you screw the idle air mixture screws all the way in and it doesn’t kill the engine. You can stop trouble shooting you found the problem. The carb is leaking internally.

stanger68 wrote:

dragkid wrote:

rmk57 wrote:  I'm not postive but didnt the original 429 SCJ 780 Holley have holes drilled in the primaries?  Are the mixture screws doing anything?  How much of the idle transfer slot is showing?

I would run 97. 93 has nowhere near the octane level needed when that engine is at operating temp.  

30+ years ago I had a 1970 Ranchero with a factory 429 SCJ in it and it would diesel on if I didnt stall the engine with the clutch. It would also ping a bit when the engine got hot with 12 degrees timing

and that was with chevron 94.

Randy

Randy,

I wish i had the original carb that came with it, i would have just rebuilt that and used it instead. I would have to check out idle transfer slot when i get home. The mixture screws do something yes. When i close them all the way, the RPM just increases, but dosent shut down on me, which i find odd. What timing do you reccoment I set it to? Would 14 be sufficient? Maybe 15-16?

If you screw the idle air mixture screws all the way in and it doesn’t kill the engine. You can stop trouble shooting you found the problem. The carb is leaking internally.

So you're suggesting the $500 Quickfuel Carb i just bought has an internal problem? My BG 750 did the same thing, but that carb is like 8-9 years old and it ran beautifully on my 383 i had. The engine i had in my 69 before was a 347 stroker and it had a Demon 750 on it, i regret every day selling that carb with the engine. It was such a great carb and never had issues with it. I have not spared a single dime putting this car together and i seem to be taking 2 steps forward and 3 steps back.