340 rear main choices- race motor

-
Fishracer66

Fishracer66

Lap, not 1/4 mile times!
Joined
Jan 17, 2014
Messages
95
Reaction score
14
Location
Scappoose, Oregon
My Barracuda vintage race engine (7000 RPM 340 T/A block ) has a leaky rear main seal, so I have it on the engine stand, pan removed and ready to replace. The problem is, what to replace it with?

Timkin 5414 from Summit $44.97 (the most expensive, maybe)
Felpro BS 40245 from Summit $10.97 (Says "not intended for race applications".....)

Superformance SPF9340 from Mancini Racing, $26.95

Dvorak DVO 23340 "Red Seal" (no price listed on their website, but is probably $30-40)

http://dvorakmachine.com/rearmainseal.shtml

Amazon.com shows a Cometic C5683 for about $30 or so.

I am sure I can also just order something from NAPA, but I am unsure about the quality.

What says ye in A-Body race land? I am tempted to go with the Dvorak part, since they have a special "no leak" version.

What else is there that will be good for a race engine?

Thanks;

Mike
 
It will be interesting to see the outcome of your thread. I've had mine replaced twice by the builder and it still leaks. Good luck
 
If it absolutely can't leak I use rope. It does take a little power away but you don;t get leaks.
Given you're road racing - what do you have for crankcase evacuation? Have you done a leakdown at all to make sure the ring seal is still good?
 
I had a leaking rear main seal that I attempted to fix 4 times with no success until I did this.

I found that magnum small block engines have a slightly smaller crankshaft rear main seal diameter making the magnum rear main seal clamp tighter on a non-magnum crank.

Also, the magnum seal is the orange material which remains more pliable over time.

This is what I did to finally fix this irritating leak 5 years ago with not a drop since.
 
moper said:
If it absolutely can't leak I use rope. It does take a little power away but you don;t get leaks.
Given you're road racing - what do you have for crankcase evacuation? Have you done a leakdown at all to make sure the ring seal is still good?
Click to expand...

I have both valve covers ventilated into a cross over pipe with a couple of breathers on it. There is almost no air coming out of those vents, so I don't think it is a pressure issue. My engine builder was concerned that I am using an old crank (that used the rope) in a new block (that uses the new type seals). Here is a picture of the system.
 

Attachments

  • Barracuda Engine.jpg
    62.3 KB · Views: 261
Do you find any oil on the outside of the breathers? You may not find much at idle, but things can cause crankcase pressure at higher rpms.
I didn;t know that about Magnum cranks... That also migh be an idea...
 
No, there is no oil on the breathers at all. I did not put any oil on them, figuring that the engine would do that itself, but they are still clean, inside and out.

I have been road racing this car for 20 years now, and never had this issue before this last build with the MP 4 bolt main block. Busy cleaning all the "Right Stuff" off the pan and gasket area of the block today......
 
My 1970 stock type 340 block and crank was rebuilt in 1994 by me with the basic fel pro neoprene seal that comes in the kit set, and with a 10" deep baffled pan and 7 quarts of 10-30 no leak, shifting at 7000. fel pro has a performance R. A. C. E. set 2714. at the last build did u change the block + crank? is it an original T A block or moparperf T A replacement, and how are the oil directing grooves in the crank? maybe the pan gasket is leaking. did u put sealant between the #5 main cap and block to the left and right of the seal? I would not use rope
 
New MP block, with an old forged crank. I did not build the motor, it was built by a guy that was a Mopar engine expert here in the PNW. He has since passed..... My assumption is that he did everything right.

The pan is an 7 qt aluminum Charlie's unit, and does not use gaskets. It uses a liberal amount of "Right Stuff" instead.

Thanks for the FelPro part number, I will look into that.
 
You must log in or register to reply here.
-

Back
Top