Changing Lifter Spread (TFX 96)

Hi everyone,

I purchased my TFX 96 Hemi/Veney combo about two years ago totally green to how many variations to aftermarket Hemis there were. What I was sold was an old fuel motor that has been converted to run alcohol. 179 CC chambers and now 10.1 to 1 compression. The heads are 2.375/2.0 dual plug (one hole plugged) and the real limitation I am seeing is the 1.8 spacing on the lifters for future upgrades. (changing to newer, better flowing alcohol heads). Currently the motor is 526 cid 4.310 bore 4.5 stroke, and running a C-rotor at both 90 and 120 over.

After replacing the crank with a very nice Bryant and Fowler fixing some problems with the valve seats, I have a pretty solid motor, albeit older technology.

I'll never run with the pros, but have a few questions to help guide next seasons MX plan.

1. If I run this lower RPM combo, how less much power am I making compared the some of the bests heads out there?

2. Can I realistically have the exhaust lifter bore machined and bushed at 1.9 spacing and keep this block? Or is the 4.310 bore a problem too?

3. If I can do the lifter spacing to 1.9, will the cam have to be changed?

4 What would be the best head I could get into with the 1.9 lifter spacing

5. Or should I just sell and start over if I want to get into more modern heads?

The block is rock solid and hasn't been hurt yet and any changes are at least a year from now, wanting to get a long term plan together....

Thanks in advance for this and all the other advice,
Scott

 

first question is what class and how fast are you trying to run? I know of guys with roots f/c alky funny cars that can run 6.0s with the old "fuel" head set ups...I ran a roots on alky with bae old fuel heads and ran plenty 5.90's and 5.80's years ago. now if your trying to run a screw..... you gotta go to different heads because of valve size and port flow. also you are low on compression! 11.5 to 12.0 to 1 is where you need to be WITH a real good blower.

 

bruce is rite.get the comp.up I run the 4.310 4.5 stroke fuel heads and a roots 50% over and very happy with it.Dave

 

I am running outlaw stuff in a 25.2 door car. It can be as light as 2650 or 2900 depending on the race. If I can get 3.9anything and decent 6's, I'll be happy and be able to upgrade my license to "Pro Mod".

I went back and rechecked paperwork, with the new crank the compression works out to be 10.87 (forgot about the recalculation going from the 4.25 stroke to 4.50 stroke and the shorter rods). The head gasket is .072 now, would be able to get to over 11.0-11.2 with a thinner gasket..

Sounds like I might not be too far off from a decent combo..... at least for now.

 

what overdrive are you running and what blower?

 

C rotor at 90 over and 120 over. Does not have the bluprinting or Cantrell coating this year. Might do that in the next couple of years.

 

I was thinking the same thing that the static compression was too high. I ran 11.32-1 on a roots and then ran the same on the screw. I then changed to 10-1 on the same motor and went quite a bit faster. Not sure if the extra static would help any based on what I ran into. That's on a wedge motor though so I don't know if that's a good comparison to a Hemi. Will is right on changing the overdrive. We ran 92% over all year and got the combination close to working good and went to just 97% over on a C and it blew the tires away like we were on ice. Not what we were expecting for such a "small" change. That "small" changed turned it into an animal. I'd recommend getting a good controllable baseline first and then do small changes or steps one at a time.