After 10+ plus years of racing my TA alum block, I felt with over 1000 sub-10 sec. passes I should do a complete freshen, but did not want to not have the race car down for long so I built a "clone" using a 4.1 production block to the same 800+ RWHP specs.
Having built many 4.1 street and strip production block engines I wanted to also prove, or dis-prove, how reliable it would be?
The race car is ~3500#'s and the turbo is a 70mm BB feeding well-ported TA alum heads, forged internals w/2 steel center caps. We also converted the car from 116 octane to e-85 with the production block.
It was tuned on a chassis dyno and had over 50 high 9 sec passes.
Friday night I was testing for an event on Saturday and the first pass was at 16 psi and all was good with a 10.3 @130 MPH. The second pass with the same settings it left the line like the first but was shocked when it hit the rev limiter at 7500 and of course slowed down, but picked up speed when shifted into third?
The data log gave an indication of a converter issue, but actually the sprague failed and this has happened in years past but not at WOT? In a TH 400 this will give you another "neutral" so the RPM will immediately spike.
Car drove on the trailer but was not happy. The block did its best to hold all together, but the crank is bent, SFI balancer trashed, 2 rods twisted and the threaded holes for no. 3 main cap are cracked.
In all my years of street and strip performance cars, this is my worst disaster of all time.
Over the past year, I have built about a dozen 4.1 builds, street and strip, 4 of them I used personally, and the worst issue has been a couple head gaskets.
In none of the 4.1 engines have we seen have issues with the block, head surface, oiling or lifter valley.
Compared to the 109 block, or the early 3.8 blocks, we just do not buy the comments of how weak or problematic these 4.1 blocks are?
Any production V-6 block should survive 6-700 HP when built properly, but this is not a guarantee, especially when something extraneous like I just experienced happens.
I just installed a fresh 4.1 so it will be running this weekend [with a new, improved sprague in the 400!] so I can continue my path to find out just how hard we can push a production block to determine a reasonable and reliable HP level!
Having built many 4.1 street and strip production block engines I wanted to also prove, or dis-prove, how reliable it would be?
The race car is ~3500#'s and the turbo is a 70mm BB feeding well-ported TA alum heads, forged internals w/2 steel center caps. We also converted the car from 116 octane to e-85 with the production block.
It was tuned on a chassis dyno and had over 50 high 9 sec passes.
Friday night I was testing for an event on Saturday and the first pass was at 16 psi and all was good with a 10.3 @130 MPH. The second pass with the same settings it left the line like the first but was shocked when it hit the rev limiter at 7500 and of course slowed down, but picked up speed when shifted into third?
The data log gave an indication of a converter issue, but actually the sprague failed and this has happened in years past but not at WOT? In a TH 400 this will give you another "neutral" so the RPM will immediately spike.
Car drove on the trailer but was not happy. The block did its best to hold all together, but the crank is bent, SFI balancer trashed, 2 rods twisted and the threaded holes for no. 3 main cap are cracked.
In all my years of street and strip performance cars, this is my worst disaster of all time.
Over the past year, I have built about a dozen 4.1 builds, street and strip, 4 of them I used personally, and the worst issue has been a couple head gaskets.
In none of the 4.1 engines have we seen have issues with the block, head surface, oiling or lifter valley.
Compared to the 109 block, or the early 3.8 blocks, we just do not buy the comments of how weak or problematic these 4.1 blocks are?
Any production V-6 block should survive 6-700 HP when built properly, but this is not a guarantee, especially when something extraneous like I just experienced happens.
I just installed a fresh 4.1 so it will be running this weekend [with a new, improved sprague in the 400!] so I can continue my path to find out just how hard we can push a production block to determine a reasonable and reliable HP level!
