351 cleveland hesitation and slow.

Help Support 7173Mustangs.com:

Joined
Sep 12, 2015
Messages
5,905
Reaction score
971
Location
SW Ontario
My Car
1971 Mustang Mach 1, M code, 4 speed.
This is a great thread. Lot's of good info and points to consider.
Looking at the pictures, I notice your distributor vacuum canister is pointed way too far to the driver side, but that only suggest the gear in relation to the #1 wire is off. The distributor can be re-stabbed to put the canister in a better spot.
I also notice my absolute pet peeve and that is gear clamps on the fuel lines. Please change these to correct clamps if not already done. Gear clamps are good for temporary use or non-critical applications only. Besides they just look UGGLY!!
Clearly something is off and it's a matter of elimination, one thing at a time.
There has been lots posted on timing, carb set up etc., so "search" is a great resource.
I too went through something similar, but my issues where distributor curve and carb set up for MY engine. What worked on my M code, might not be what you need on your engine.
Good luck and I hope you get it sorted soon.
 
Joined
Jul 27, 2021
Messages
741
Reaction score
537
Location
East Texas
My Car
1971 Mustang Mach 1 M code 351 4 speed
This is a great thread. Lot's of good info and points to consider.
Looking at the pictures, I notice your distributor vacuum canister is pointed way too far to the driver side, but that only suggest the gear in relation to the #1 wire is off. The distributor can be re-stabbed to put the canister in a better spot.
I also notice my absolute pet peeve and that is gear clamps on the fuel lines. Please change these to correct clamps if not already done. Gear clamps are good for temporary use or non-critical applications only. Besides they just look UGGLY!!
Clearly something is off and it's a matter of elimination, one thing at a time.
There has been lots posted on timing, carb set up etc., so "search" is a great resource.
I too went through something similar, but my issues where distributor curve and carb set up for MY engine. What worked on my M code, might not be what you need on your engine.
Good luck and I hope you get it sorted soon.
A lot of people have no idea what a major difference a distributor recurve can make, especially on the later muscle cars with low compression engines, which has especially slow advance curves and the timing was always a bit too retarded from the factory.
 
Joined
Sep 12, 2015
Messages
5,905
Reaction score
971
Location
SW Ontario
My Car
1971 Mustang Mach 1, M code, 4 speed.
A lot of people have no idea what a major difference a distributor recurve can make, especially on the later muscle cars with low compression engines, which has especially slow advance curves and the timing was always a bit too retarded from the factory.
Indeed, recurving makes a huge difference most of the time imo. As you too have a 71 M code ( funny thing is I just noticed that, dhhh!), then what I came up with for my engine is probably similar to what your engine likes; Stock distributor, 14 degrees initial, 20 (10L slot) on the crank and 4-6 on vacuum can, ported, with 1 heavy stock spring set slightly loose and 1 lighter Mr.Gasket 925D spring set just snug. I'm all in around 3K and with my carb settings (Holley670) it pulls like a train.
That's getting a bit off the original question, but...........
 
Joined
Sep 14, 2021
Messages
15
Reaction score
2
First off thank you again for the comments. I have a picture attached of the cam specs. Also the the rear gears are 2.75 and froma previous post the torque converter is a 1500 rpm stall. The distributor is Mallory unilite electronic conversion distributor. The harmonic balancer was supposed to be a new balancer but I can replace if you think necessary. I will check the TDC again by marking the balancer but I used both a piston stop and a Top dead center indicator. Does anyone need anymore info? I feel like 71projectjunk comments are spot on. Like I said before this is my first Ford project ever so I'm kinda running blind but with the way the drive train is set up it should really better than it is. Thanks again and keep the comments coming cause spring is coming and I want to lay some black marks in front of the house, Lol!
 

Attachments

  • 20211022_153341.jpg
    20211022_153341.jpg
    101.8 KB · Views: 13
  • 20220215_230649.jpg
    20220215_230649.jpg
    168.5 KB · Views: 14
Joined
Jul 27, 2021
Messages
741
Reaction score
537
Location
East Texas
My Car
1971 Mustang Mach 1 M code 351 4 speed
That cam is 219 degrees at .050, that is really at the threshold of needing a converter. Comp cams says you can use a stock converter, and you can, but a 2200-2500 stall would not be a bad idea. Now, do not go changing converters yet. First thing is to get some gears in the rear end. I would put in 3.50 gears in the back, which is a middle of the road compromise between in town and highway driving. The RPM's will definitely be higher at highway speeds but the car will behave completely different from a standstill and at low speeds in first gear. If you do a lot of highway driving you may want to go to 3.25 gears, but there will be a reduction in acceleration, conversely if you do mostly in town driving you could go to 3.70's and get even more acceleration, but 3.50 is a good compromise gear.

Depending on how experienced you are in working with rear ends you could just buy a set of 3.50 gears and install them on your 3rd member. I am not experienced enough, nor do I have the tools to correctly set up the back lash or anything else on the gears, so I would buy a fully assembled 3rd member with a trac lok. In fact I just bought a 3.50 3rd member for my car from Quick Performance for $820 plus shipping:


Since I did not have a trac lok unit, and you probably don't either, it just made sense to buy a complete unit with everything installed and ready to go. You just need to remove you axles and driveshaft, unbolt your 3rd member and drop the new one in. If I had a trac lok unit I would have just rebuilt it and put in the gears, well I would have had someone that knew what they were doing assemble the 3rd member, and then put it in, LOL. If you do not have a trac lok, by the time you buy the trac lok, the gears, and the installation kit, and pay someone to correctly assemble it, you will probably have close to $800 into it anyways. Please be aware that the third member weighs about 90 pounds and is a bitch to put in by yourself if the car is just on jack stands on the floor. I am not looking forward to doing this by myself...
 
Last edited:

jspears

Active member
Joined
Aug 3, 2018
Messages
30
Reaction score
4
Location
USA
My Car
73 Mach 1
I used a powerbond on my 2v cleveland, it was dead on when I degreed the cam. I am using pretty much hemikiller's timing specs as well as using vacuum advance off manifold vacuum. engine idles cool and my 0-60 is 5.3 seconds.
 
Joined
Sep 14, 2021
Messages
15
Reaction score
2
If #1 cylinder (front one on passenger side) is truly at tdc and you show 22.5 degrees, it is an indicator that the outer ring has slipped on the harmonic balancer. If that is the case, then you need to replace it. That would cause a lot of your problems. Depending on the brand and finish they start out around $100 for a 351c and go up from there.
Is there a way to tell if this is truly what happened?
 
Joined
Sep 8, 2018
Messages
1,674
Reaction score
611
Location
Ross, Ohio
My Car
71 Sportsroof Bright Red.

Is there a way to tell if this is truly what happened?
If number one cylinder is at tdc then only two things could cause the timing mark to be off. The first and most common cause is that the the damper outer ring has slipped on the rubber. The second cause would be that the harmonic balancer key sheared or was not installed, and the balancer has slipped on the crankshaft.
I would once again bring number 1 to tdc making sure it is on the compression stroke - thumb over spark plug hole- and then using a piston stop rotate the crank until it stops, make a mark on the balancer and then rotate in the opposite direction 'til it stops marking the balancer once more. The center between these two is your tdc mark. If it is not on 0 or within 1 degree or 2 at the most you got problems with the balancer.
 
Joined
Sep 14, 2021
Messages
15
Reaction score
2
Ok cool. Since the discussions of rearends has come up Im not sure which one I have and the tag non readable. So at a quick glance is this an 8 inch?
 

Attachments

  • 20220216_232829.jpg
    20220216_232829.jpg
    291.4 KB · Views: 9
  • 20220216_232900.jpg
    20220216_232900.jpg
    197 KB · Views: 9
Joined
Jul 27, 2021
Messages
741
Reaction score
537
Location
East Texas
My Car
1971 Mustang Mach 1 M code 351 4 speed
That looks like a 9" rear end. Here is a good article on how to id the Ford 9":
 

Hemikiller

Well-known member
Staff member
Moderator
Joined
Jul 12, 2010
Messages
3,666
Reaction score
932
Location
Killingworth, CT
My Car
71 Mach 1
65 coupe
The harmonic balancer was supposed to be a new balancer but I can replace if you think necessary. I will check the TDC again by marking the balancer but I used both a piston stop and a Top dead center indicator.

If you're confident that you have found true TDC, mark the balancer and then mark it again at 10* increments in the BTDC direction. Reset your timing and test drive the car. If makes a huge improvement, then buy a new balancer.
 

machphil

Active member
Joined
Feb 23, 2018
Messages
27
Reaction score
16
Location
Illinois
My Car
'71 and '73 Mach 1's.
Ok cool. Since the discussions of rearends has come up Im not sure which one I have and the tag non readable. So at a quick glance is this an 8 inch?
This IS a 9 inch. An easy way to remember is a deep well socket WILL fit directly onto the bottom two mounting bolts of an 8" housing. If it is a 9" housing, the casting around the pinion juts down in front of those bottom two bolts and you have to use a 9/16" universal socket or a box end wrench. The deep well socket will never go on the bottom two nuts of the 9" housing.
 

machphil

Active member
Joined
Feb 23, 2018
Messages
27
Reaction score
16
Location
Illinois
My Car
'71 and '73 Mach 1's.
Ok cool. Since the discussions of rearends has come up Im not sure which one I have and the tag non readable. So at a quick glance is this an 8 inch?
Looking at that frontal view of your rear end, it IS a 9" housing. Sorry, I should have zoomed it better the first time.
 

machphil

Active member
Joined
Feb 23, 2018
Messages
27
Reaction score
16
Location
Illinois
My Car
'71 and '73 Mach 1's.
I have a 1973 Mach 1 with a 351 cleveland and c6 auto. I just completed a Restomod on the car after having it for almost 20 years. The car started life as a 2-barrel but I changed to a 4-barrell with the correct 73 4 barrel heads, I know its yucky open chambers. Anyway with this new motor refresh it was bored .030, Edelbrock Performer 4 barrel intake, a mild cam, and a Holley 670 cfm carb. So the issue is that the car starts and runs but is very draggy or slow with hardly any responsiveness in the throttle till 2000 rpm. Once its there the motor responds better and really responds at 3000 rpm, problem is that's 80 mph which is hard to find a road in the Ozarks to drive it on at that speed, LOL! So this is my first Mustang build and is my 30 year National Guard retirement present, from wife. I'm not really sure how it is suppose to respond but it really seems like there is something wrong. Any thoughts on what to try would be greatly appreciated. Thanks!
I have owned a '73 Q code since May of '76. When working on that particular year you must understand several peculiarities about the car. First, the 4v engine was an 8.0 to 1 compression motor. If you used the dished pistons and then the large combustion chamber 4v heads you won't have high compression. That must be taken into consideration with the camshaft selection. Your overlap is 110 degrees and I believe the overlap on the factory 4v cam is 112. Again, a drop in dynamic compression. The cams were also retarded 4 degrees. I believe this was to accommodate the high rpm capability of the heads, but some will say it was for emissions. The narrow overlap will also lower idle vacuum and change the response of your carburetor at tip in and up to when the engine begins its power range. Factory they did have a 3000 rpm jump in power and with the lower compression the factory installed a 10" converter on the C6 transmission. That torque converter was about 2800 rpm stall. With the size of your cam you could advance it 4 degrees to increase the low rpm dynamic compression. Piston to valve clearances should be checked before firing. I loved the way the Motorcraft 4300D spreadbore functioned in the Cobra Jet package. Ford knew what they were doing when they packaged that and the Vette owners of the day swore that my engine couldn't be factory stock, but I would pop the hood and it was, right down to the carb, exhaust manifolds, and mufflers. I was running a factory 3.25 gear and it was open. I later installed a traction lock.
 

MaddMike

Member
Joined
Nov 28, 2021
Messages
16
Reaction score
3
My Car
1971 Mustang Mach 1: 351 C (modified), FMX trans (modified), 9" 3:25 traction lock rear gear. I have owned this car 44 years, since I was 17.
My motor is a '73 351C I added 4bbl Edelbrock. I had he same issue - when I stepped on it from a standing start it moved but it seemed to need to catch up with itself and once the R's went up it took off. Otherwise it ran fine. For me it was only a matter of re-jetting the carb.
 
Joined
Sep 14, 2021
Messages
15
Reaction score
2
Ok cool. Since the discussions of rearends has come up Im not sure which one I have and the tag non readable. So at a quick glance is this an 8 inch?
Found it finally the tag reads as follows. The last four numbers on the bottom row are 95 but the last 2 digits we can barely read but look like 10.
 

Attachments

  • 20220221_172554.jpg
    20220221_172554.jpg
    8.2 MB · Views: 11
  • IMG_2202.jpg
    IMG_2202.jpg
    691.3 KB · Views: 9

Hemikiller

Well-known member
Staff member
Moderator
Joined
Jul 12, 2010
Messages
3,666
Reaction score
932
Location
Killingworth, CT
My Car
71 Mach 1
65 coupe
WES-T is actually a 69-70 axle tag code, 73 should be WES-T1. However, with the 3DB build date (1973 - April - 2nd week ), it looks original as long as that precedes your build date by a reasonable amount.

WES-T is a 2.75 gear ratio, 28 spline 9" axle with a 2 pinion differential unit. 951 is the plant code.
 
Joined
Sep 14, 2021
Messages
15
Reaction score
2
WES-T is actually a 69-70 axle tag code, 73 should be WES-T1. However, with the 3DB build date (1973 - April - 2nd week ), it looks original as long as that precedes your build date by a reasonable amount.

WES-T is a 2.75 gear ratio, 28 spline 9" axle with a 2 pinion differential unit. 951 is the plant code.
Are the better axles 31 spline? I will likely be getting a third member to replace the gear ratio any good recommends as to where to purchase? Would prefer a posi.
 
Joined
Sep 14, 2021
Messages
15
Reaction score
2

There are two links here the first was using a TDC indicator to find the stop. The second video shows the timing in relation to the TDC indicator, to the distributor location, to the harmonic balancer. It appears my previous post was wrong. It looks like TDC is at 12 degrees on the Harmonic balancer. I need a recommend on what to do next. Also theharmonic balancer is a Moroso balancer bought new. Do I need to somehow check something to verify I need another balancer or do I put it all back together and get a timing light on it? Second video below.

 
Top