Classic Mustang Problems

[fordguy67]

Hi.

I have a 1967 mustang that has a "Mild" 351W (with edelbrock 625cfm carb) mated to a B&M C6 Transmission (which has a 2,000 RPM stall converter).

My first question is:
The engine idle speed in "Park" must be astronomically high otherwise when I put the car into any gear, it will die. Is this due to the stall converter? I was under the impression that 2,000 RPM was just slightly over stock... Anyhow, it seems like the engine has to idle at ~2200 RPM before putting into gear, at which point the tires chirp and the engine drops down to 900 RPM. This seems like it is VERY hard on the transmission. Any help here would be a GREATLY appreciated.

My second question is:
The engine is very hard to crank over. I'm using a stock (brand new) starter which sometimes will crank the engine, and sometimes it will not. When it fails to crank, it sounds like the starter is "free wheeling" (its the only thing turning and not the engine). This seems to be more prominent when the car is cold. I've already had the starter bench tested and it tests ok. It's almost like the starter teeth aren't always engaging the flexplate teeth. Is this an offset problem, or is it a matter of too high of a compression ratio (10.25:1)? Thanks!

ME--->

[351wStang]

Since you have a higher compression ratio you may need to upgrade to a mini-starter. I have a mini-starter on my 351w and even with the blower it started my motor just fine every time. Your idle problem sounds like a possible vacuum leak. The problem is not the stall converter. We need more information to properly diagnose this problem. What is your timing set at? Is it vacuum or mechanical advance? If its vacuum advance how large is your camshaft? Once you get the car in gear and running how does it run out on the road and under load/acceleration? My first guess would be a vacuum leak, but there are a number of possibilities. Try spraying carb cleaner around all vacuum fittings, the base of the carb, around the intake, ect. Loose intake bolts or a manifold vacuum leak can cause similar problems. Tell us all you can about your problem and any related info about your combo that you are willing to share may be of some help as well.

[fordguy67]

Thanks for the quick reply. I will have to get a Mini Starter and see if that fixes the starting issue.

The engine combo is as follows:

KB 10.25:1 Flat Top Pistons
Crane 282/292 Camshaft Kit (Hydraulic)
Ported/Polished OEM Heads (Stock Valves/Springs)
Pete Jackson Gear Drive (Set at 0 degrees)
1.7 Ratio Comp Roller-Tip Rockers
Weiand Stealth Intake
Edelbrock Performer 625cfm Carb
Ford Distributor w/Ford Electronic Ignition & Vacuum Advance

Transmission Combo:

B&M C6
TCI Saturday Night Special Converter (2000 RPM)


The car runs fine once in gear although I do have to "2 foot" it at stop lights as even at idle in first gear it wants to die. I don't want to raise the idle anymore than it already is as it is so high. The car used to be a stick shift car and seemed to be much quicker than it is with the C6-- it seems to be bogged down with the automatic-- although it does shift very hard.

The car used to have an 8" rear end with 2.79 Open Differential and 3spd. Manual tranny when the car had a 289 in it. When I put the 351 in, it twisted the drive shaft like a pretzel. After putting a HD driveshaft in, it broke the 8" rear end. Then I put in a 9" with 3.50 gears and a locker. Then the 3spd. tranny broke. That's when I put in the B&M C6.

Obviously I am losing more HP/TQ through the C6/9" combo, but the it should be negligable with the 3.50 gears I put in right?

Anyhow, I guess I should try hunting for a vacuum leak?

[351wStang]

How much base timing and how much total timing? Have you verified that the timing is advanceing? Couldnt find that cam so I'm not sure there, but are the stock springs enough or do you get coil bind? Bent pushrods could make the engine run poorly and may explain why you have to idle it so high. You say the car used to be a stick shift car with open diff 8" & stock d/s. Did the hard to start problem as well as the need for high idle come only after the C6 swap? If so then there is something wrong with the install for sure.

[fordguy67]

I can take a look at all the valvetrain this weekend.

I was told by a mechanic that there could be a serious problem with the transmission itself. The engine's rpm should not drop by half when put into gear, this indicates something in the transmission is putting an abnormal load on the engine. The main suspect at this point is the torque converter, at least that's what I'm told. I was thinking about a 3,000RPM stall to replace the 2,000RPM I have now. Does this sound right, or not like it could be the problem?

[351wStang]

The stall speed will not affect the motor at idle, that should not be the problem. However I do agree that something may be fishy with the trans. Since its a B&M tranny I figured you bought it new and in that case it should be fine. Did you buy it used? Is the torque converter used? Something definatly sounds fishy. The converter could be way to tight I suppose, as in its not allowing the proper amount of slippage at idle. Do you have a stock converter you could try by chance? It would rule out an issue with the converter. I know those things arent cheap, I'd hate to buy a new one and it not fix the problem. Where did you buy the trans and converter from?

[351wStang]

The stall speed will not affect the motor at idle, that should not be the problem. However I do agree that something may be fishy with the trans. Since its a B&M tranny I figured you bought it new and in that case it should be fine. Did you buy it used? Is the torque converter used? Something definatly sounds fishy. The converter could be way to tight I suppose, as in its not allowing the proper amount of slippage at idle. Do you have a stock converter you could try by chance? It would rule out an issue with the converter. I know those things arent cheap, I'd hate to buy a new one and it not fix the problem. Where did you buy the trans and converter from?

The correct stall speed for you will depend on a number of things. A link to your camshaft would help. Also the weight of the car will be a big factor here. Remember when shopping for a torque converter that two different converters with the same stall speed will act different even in the same car. The amount of torque produced by your engine will also factor in to your stall speed.

[fordguy67]

The transmission was bought new (I drove to B&M in CA to pick it up). The torque converter was bought new as well, but I have heard of stuff being bad right out of the box.

I don't have any other converter, but I have my eye on a converter on Ebay that would be inexpensive to try.

It's been a long time since I've put in the cam, but I believe it was this one http://www.cranecams.com/?show=brows...tType=camshaft
(I guess I wass off on the duration)

I am estimating weight at 3300lbs. Since I have not had the engine dyno'd I would estimate the torque at around 400ft.lbs.

It would appear I have a lot of work to do on the car still. I am going to take the transmission out (again) this weekend. But first, I'm going to call B&M tomorrow and see if they think it could be the transmission.

Sigh. This car is making me nuts.

[351wStang]

Thats a blower cam. Its not optimal for your combo but it will work. Since your car is pretty light and you have a decent amount of torque, also useing that cam, I would suggest a converter with a stall speed around the lower 3000 range, nothing over 3500 for sure.

[72' Stang 351 H/O]

Uhh 3.50 gears for a mild 351 W. My dad's stock 351 C comes with 4.10 gears.I suggest you get some bigger gears.

[fordguy67]

4.10 Gears? I can't even drive over 55MPH as it is with 3.50 Gears without staying at about 3,000RPM. If I had overdrive maybe, but not with a C6.

[fordguy67]

I just bought a 3,000RPM Stall Converter off of ebay. I'll try to get it installed next weekend and let you know if it was the problem.

[351wStang]

You do have the metal plate/spacer that goes between the engine/tranny installed dont you? If not then the converter may be pushed back against the pump causing your strain when starting and could cause big problems for the tranny. There are two different kinds of plates for the large and small bellhousings. If you do not have this plate you can order one from www.summitracing.com that will fit either bell. Good luck! Be sure to keep us updated, hope the converter fixes your problem.

[fordguy67]

I'm using the plate from the manual transmission I had in there. Is it possible the automatic plates are thicker?

[351wStang]

No, the only difference in the plates is the starter location. If your starter bolts up then you have the correct plate.