Engine sputters and chokes at part throttle

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On almost $3K for a complete rebuilt long block - that's really not bad if the builder does it right. I'd take that all day long. I have a CJ short block with the small chamber/large port heads in the machine shop now, and I expect to pay more than that. Granted, I'm doing screw-in studs and new forged pistons, but it'll be worth it.

$3K for machine work, clean and labor to rebuild is a good deal.
They're a very good engine shop. Their bread and butter is stock style rebuilds. Website says they've done over 60k rebuilds, and have a 36k mile warranty. I've had them do the 5.0 in my 95 GT and the 3.8 that went into my mom's pontiac. We daily drove those for years and never had any issues. This place lists $1996 for a stock style 351 cleveland long block rebuild. The $2990 price is for the upgraded one with a little more cajones. That price also includes a kit of gaskets to put the extras on the outside.

I figure I'll probably be in it for another grand after I add in the extras like fluids, plugs, motor mounts, a new water pump and fuel pump. It doesn't feel right to me to have those parts off already and go back putting 50yr old clapped out ones on a brand new motor.

And probably at this time, my dreams of a TKX will just have to wait. Its pretty much free to put back in the C6. The full TKX swap kit is just shy of $7k. There's not enough snow around here this time of year for that sort of snowballing.
 
Giantpune, rebuilding the heads is not a huge deal and can be done at the house. Bowes Machine Shop cleaned my heads, installed hardened seats, upgraded the valves and springs and got me ready for a quick install for about $800 or so for both heads. Since I am local, I am available to come over and assist with pulling the engine and reinstalling it. Also, I am ready to help if you decide to do the rebuild yourself. I rebuilt mine and it came out great in my opinion. Mine is a 351C 2v, and to tell the truth, it is new parts, measuring for correct specs, and torque specs. I did mine in a driveway during the winter with no garage, it can be done with basic tools and a little time. Btw, I think the block cleaning and the crank turning came to about $400 or so at Bowes Machine Shop, Mike Rivers (at Bowes) is a great guy and even installed my connecting rods to the pistons for me.

Tom
 
Giantpune, rebuilding the heads is not a huge deal and can be done at the house. Bowes Machine Shop cleaned my heads, installed hardened seats, upgraded the valves and springs and got me ready for a quick install for about $800 or so for both heads. Since I am local, I am available to come over and assist with pulling the engine and reinstalling it. Also, I am ready to help if you decide to do the rebuild yourself. I rebuilt mine and it came out great in my opinion. Mine is a 351C 2v, and to tell the truth, it is new parts, measuring for correct specs, and torque specs. I did mine in a driveway during the winter with no garage, it can be done with basic tools and a little time. Btw, I think the block cleaning and the crank turning came to about $400 or so at Bowes Machine Shop, Mike Rivers (at Bowes) is a great guy and even installed my connecting rods to the pistons for me.

Tom
I'm gonna take you up on that. The car is at my 2 post lift, so we can minimize rolling around on the ground. I was planning to try and get some pictures taken of everything, and get wires labeled and disconnected this week. Then if nothing comes up this weekend, start yanking that puppy out.
 

Hi giantpune

Pleass note that you have a engine that needs help. 80psi is no good on the one cylinder. The valve seals will find there way into engine pan and clog oil pump screen and finish engine. The first cocern seams to be remove oil pan to clean out valve seals and or rebuild engine. The way the Egr works is it only comes in during part throttle when hooked up. There is another issue is you have to have a maniflod that brings the EGR porting from exhaust crossover in the manifold. If the manifold has no provisions for this all the EGR is doing is acting as a spacer. The manifold I used was a edelbrock older performer with a one inch spacer ( it has smalle ports to 4V heads and has heatriser addition which you nesd in colder weather). Most people do the wrong thing and block off the exhaust heat riser with gaskets. The holley manifold may cause issues with out a spacer, I think the person was using it for this. The best carb results will be if you can fit a 3/4 to 1" spacer between manifold and carb. The timing will produce the highest vacuum about 18 inches but you may have to retard it a small amount for hot start. ( about 12 degrees) I have efi and run 16 degrees but I can crank without fuel shot prime when hot. ( turn Key ove imediatly no EFI pump shot). The carb setup I hated and I had a holley and couldn't stand the lag and tuning issues with carbs. The timming is a whole set of issues because you need the weakest springs for the advance wheights to bring timing to a curve thats all in by 2800 rpm (36 degrees total advance centrifugal is always safe and good. ( 16initial + 20 centrifugal= 36 total by 2800rpm mild engine). The carb will bogg unless there is no vacuum leak and correct pump shot ( and it will still lag just not as bad.). The EFI carb types when tuned up put it to shame. Even in 4th gear all it wants to do when you push the pedal down is go.
Hope this Helps
 
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The photo above (1st photo) isa an EGR valve, for sure. Those early EGR valves were supposed o hold vacuum, no slow bleed off by design. That said, most folks who wanted to alter its behavior either unplugged the vacuum line leading to it (and plugged the ported vacuum line, or installed a fabricated sheet of metal (preferably stainless steel) between the EGR valve and the adapter plate at the base of the carburetor. The quick play was unplugging the actuating ported vacuum hose, then plugging the hose so the vacuum advance would bot be adversely impacted.

The reality is the EGR valves on those early engines did not hamper the performance of th engine that much. In fact, because it was designed to quell the explosive burning of the Air/Fuel in the combustion chamber that it was possible for a previously quiet engine to begin to ping on light throttle acceleration once the EGR was compromised. The impact is so benign that on out 73 Mustang's 302 its EgR system is fully connected and operating as designed, as I know it has no real impact on the driveability of the vehicle. If I races the car on a track I would feel differently. But I do not track or race it, so it stays in working order as I know it does no real harm.

If an EGR valve is leaking where its pintle valve, where the exhaust gas is on one side, and the intake manifold A/F mixture is on the other side, the result will be a rough idle, and if stuck open too far it could even keep the engine from idling at all. Also, if stuck open too far the performance of the engine will be reduced, especially at lower levels of throttle opening. I rarely saw a leaking EGR valve's pintle valve, and when I did it was only enough to cause a rough idle. A new EGR valve corrected the issue.

When we first got our 73 Mustang Convertible about 2 1/2 years ago, it only has 19,000 some odd original miles on it. That is because one of its early owners had become very ill after buying it, and it was literally stored in a barn over 40 years. When we got it very little had been done. New tires and wheels as the original tires' sidewalls were cracked badly, and the recent buyer wanted the oem steel wheels replaced. It also had a new convertible top. And tune up also. Other than the plug, points, and condenser. and the tires, wheels, and top, everything else was in its original condition, well preserved, and unmolested. Well, so I thought. The engine had a little hesitation to it on light acceleration. I felt it was either a failing or leaking accelerator pump circuit issue, ruptured vacuum advance diaphragm, retarded ignition timing, EGR Valve behavior, or the float level in the carb was too low. I inspected the accelerator pump circuit and it was working properly, and the vacuum advance system was working with no diaphragm leaks. I then did a vacuum test on the EGR diaphragm and found it held a vacuum. I also saw the EGR valve's vacuum hose was delivering ported vacuum. The dwell was too high, which meant the ignition timing was a little retarded. I looked at the points and found they were fairly new, so I figured the points can lobes were never lubricated, causing the point rubbing block to wear too quickly. I applied a little bit of point lube to the lobes, reset the dwell angle, then adjust the timing, The hesitation remained. So, the last suspect was a low float level in the 2v carb.

Despite having low miles I decided to do a carb rebuild to make certain none of its passageways had a buildup of varnish from old, stale gasoline. I documented that on a YouTube video, of course, located at:

https://youtu.be/U-ETjhRqUwQ


I go into the float level issue in that video at 01:18:19 hh:mm:ss into the video itself. That was my first indication someone had rebuilt the carb previously, as the factory almost never sets their float levels as los as this one was set. My guess is someone set it that low to lean out the A/F mixture in an effort to get better fuel mileage. Hmmmph, and years later it bites me, it is not fair. But, it was easy enough to correct

The next hint the carb had been rebuilt is at 01:30:10 hh:mm:ss, where I begin to discuss the Power Valve. When I removed the Power valve I found someone had installed two gaskets. Most likely due to someone rebuilding it and not realizing usually two gaskets are provided that are slightly different. I fixed that, and the float level setting. Once back together the car ran great, no more off idle hesitation.
 

Hi giantpune

Pleass note that you have a engine that needs help. 80psi is no good on the one cylinder. The valve seals will find there way into engine pan and clog oil pump screen and finish engine. The first cocern seams to be remove oil pan to clean out valve seals and or rebuild engine. The way the Egr works is it only comes in during part throttle when hooked up. There is another issue is you have to have a maniflod that brings the EGR porting from exhaust crossover in the manifold. If the manifold has no provisions for this all the EGR is doing is acting as a spacer. The manifold I used was a edelbrock older performer with a one inch spacer ( it has smalle ports to 4V heads and has heatriser addition which you nesd in colder weather). Most people do the wrong thing and block off the exhaust heat riser with gaskets. The holley manifold may cause issues with out a spacer, I think the person was using it for this. The best carb results will be if you can fit a 3/4 to 1" spacer between manifold and carb. The timing will produce the highest vacuum about 18 inches but you may have to retard it a small amount for hot start. ( about 12 degrees) I have efi and run 16 degrees but I can crank without fuel shot prime when hot. ( turn Key ove imediatly no EFI pump shot). The carb setup I hated and I had a holley and couldn't stand the lag and tuning issues with carbs. The timming is a whole set of issues because you need the weakest springs for the advance wheights to bring timing to a curve thats all in by 2800 rpm (36 degrees total advance centrifugal is always safe and good. ( 16initial + 20 centrifugal= 36 total by 2800rpm mild engine). The carb will bogg unless there is no vacuum leak and correct pump shot ( and it will still lag just not as bad.). The EFI carb types when tuned up put it to shame. Even in 4th gear all it wants to do when you push the pedal down is go.
Hope this Helps
If you are rebuilding engine fix the liter bores with this kit
https://wydendorfmachine.com/kitb.html?kitid=2
 

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I've decided to pull the motor and have the full rebuild done. While i've been working on that, i noticed there appears to be a hole in the intake manifold that maybe shouldnt be there.

Either way, i was going to swap over to an edelbrock dual plane instead of this holley single plane. The edelbrock daesn't have a provision for an egr and i dont think going to bother with it.

Picture of the mystery hole in the intake is here. I will know more when i get the motor out and the intake off. https://7173mustangs.com/threads/the-snot-rocket-green-73-fastback.43098/post-434144
 
I've decided to pull the motor and have the full rebuild done. While i've been working on that, i noticed there appears to be a hole in the intake manifold that maybe shouldnt be there.

Either way, i was going to swap over to an edelbrock dual plane instead of this holley single plane. The edelbrock daesn't have a provision for an egr and i dont think going to bother with it.

Picture of the mystery hole in the intake is here. I will know more when i get the motor out and the intake off. https://7173mustangs.com/threads/the-snot-rocket-green-73-fastback.43098/post-434144
As long as your state does not require emission inspections annually or every so often you ought to be "fine." I say "fine" because even in states where cars over a certain age are no longer required to get emission control inspections, it is often still not lawful to remove or otherwise compromise the oem emission control systems. Different laws for different states. There may be federal legislation on that matter also. For off road use none of that matters. I just hate to see you wind up doing a lot of work only to find yourself having run afoul of some mundane Johnny Do Gooder legislation.

I know years ago California required annual emission control inspections, and for anyone found to have tampered with their oem systems the owner of the offending vehicle had to return the vehicle to its oem emission control to its original condition. Aftermarket parts were outright disallowed at that time (early 80s), and there was no upper limit re: how much a person was required to spend to get things back to original condition. That legislation caused a lot of grief for folks with high performance vehicles. Now the emission inspections in CA are done every two years, with some counties exempted. Also 1975 or older cars are exempted (whew!)... Depending on the state you live in YMMV.

Also, I have seen aftermarket performance parts that state they are compliant with CARB (California Air Resource Board) and/or EPA standards. I have also read that as of late if a vehicle passes the California emission test with aftermarket performance parts, they can be certified - as opposed to the 80s where such a car had an owner who got screwed over badly (but with headers they have to have a db level below a certain point). Anyway, I suggest before you make high performance modifications to your vehicle you make certain you will not end up running into trouble with your state/federal requirements - especially if you are subjected to routime emission control testing. https://www.sema.org/federal-regulation-aftermarket-parts
 
As long as your state does not require emission inspections annually or every so often you ought to be "fine." I say "fine" because even in states where cars over a certain age are no longer required to get emission control inspections, it is often still not lawful to remove or otherwise compromise the oem emission control systems. Different laws for different states. There may be federal legislation on that matter also. For off road use none of that matters. I just hate to see you wind up doing a lot of work only to find yourself having run afoul of some mundane Johnny Do Gooder legislation.

I know years ago California required annual emission control inspections, and for anyone found to have tampered with their oem systems the owner of the offending vehicle had to return the vehicle to its oem emission control to its original condition. Aftermarket parts were outright disallowed at that time (early 80s), and there was no upper limit re: how much a person was required to spend to get things back to original condition. That legislation caused a lot of grief for folks with high performance vehicles. Now the emission inspections in CA are done every two years, with some counties exempted. Also 1975 or older cars are exempted (whew!)... Depending on the state you live in YMMV.

Also, I have seen aftermarket performance parts that state they are compliant with CARB (California Air Resource Board) and/or EPA standards. I have also read that as of late if a vehicle passes the California emission test with aftermarket performance parts, they can be certified - as opposed to the 80s where such a car had an owner who got screwed over badly (but with headers they have to have a db level below a certain point). Anyway, I suggest before you make high performance modifications to your vehicle you make certain you will not end up running into trouble with your state/federal requirements - especially if you are subjected to routime emission control testing. https://www.sema.org/federal-regulation-aftermarket-parts
In my part of GA, they don't do any inspections.

Previous owner has already been up in here swapping intake, exhaust, and disconnecting half of the vacuum stuff. I won't lose any sleep about not hooking it back up.
 
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