I suspected last year that I was pushing thru the converter on the big end as I couldn't get more than 150 mph out of it. Adding boost and timing did nothing other than make it fatter (which makes no sense). Testing so far this year pretty much confirms it. At 12psi boost, I get 1100-1400 rpm drop on shifts. At 13.5 psi, rpm drops 800-900 on shifts. At 16 psi, it's down to 400-500 rpm drop. Finally, at 18 psi the rpm only drops 200-300 rpm. At 18psi it's going 150 at 7000rpm which translates to almost 19% converter slip. I've read that some cars like more slip, but 19% seems excessive. Talked to Lenny at UCC and he agreed. I'm currently running a 9" piece but he suggested stepping back to a 10" for better holding power on the big end. Got one ordered up and can't wait to see how it works!

Rob

 

Those number were looking ugly with the boost.

Less than 10% slip is good.

 

lenny is the man he will get you straight, and is an absolute pleasure to work with. great family too.

 

I would like to see the diiference. Remember no other changes just the convertor.

 

Did some more testing on the same converter at 19si boost. Raised the shift points and it responded with bigger rpm drops on shifts (around 1000 rpm), but still had 19% slip thru the traps. Went 155 mph at 7200 rpm. Very interested now to see what happens with a new converter from Lenny.

Rob

 

Lenny suggested the 10" to me also due to the holding power on the top end. I actually drove to CT just to meet him in person. He was great to deal with.

 

What's your rearend gear ratio.. And where you running 28 inch drag radials ??

 

3.27 gear with 325/50/15's

Rob

 

Have you been back to the track with the new convertor?
If so , what did it run?

 

Got the converter last week, but I'm not going to put it in just yet. I figured out with this converter if I raise my shift points to 7200 it doesn't slip as much on the shifts. Doing this got me an 8.85 at 155. The numbers still show a 19% slip thru the traps though. I'm going to keep playing with this one, then try the new converter at the end of the year.

Rob

 

Rob is your car mini tubbed? Them some big ole meats on there... I pulled my C4 today and am going to ship the converter to Lenny in the morning, Im getting about 24% slippage At 15psi the RPM's only dropped 300 RPM's. I hope I can get this converter turned around by NMRA columbus, Im sure he will, Lenny is awesome! It was a 3,600 or 3,800 , I cant remember, 10" he said he is going to drop it to a 3,200.


Jeremy

 

No mini tubs!

What was your shift point? Ever try shifting higher?

My new one is supposed to be a 10" 3600 stall, but tighter on the top end. I hope it works!

Rob

 

rob,
what was your old convertor-size/stall?

i am going to do a 400/10in conv but only a 2.73 rear and see how tight lenny can get on the top end.

can you pm the specs on your cam (cam motion right?) i am curious to what they suggested for mine.

i keep watching yours to see where you get with it.

 

Old converter (the one I'm using still) is 9"/3100 stall.

Cam specs:
LSA = 115.1
Intake Duration = 241.6
Intake Lift = .606
Exhaust Duration = 238.8
Exhaust Lift = .602

 

rob-how much rpm drop on the shifts are you getting now with the raised shift points?

how much did you have to raise the shift points to help with the slip?

 

I was shifting about 6800. Shifting at 7200 got me back to a 600 rpm drop (instead of 200-300). At 7500 I think it gets better, but need more testing to find out. Maybe this week I'll try again.

 

good luck with the testing...i am interested to see how the 10in does for you now?

 

Is there a link to your car rob? the build and some pics? Im puytting together a similar setup, but only one turbo.

 

Rob,

Nice seeing you go over 150. How do you get the 325/50's to fit w/o a mini tub? Do you just use a BFH or do you need a BBFH? I assume you are on a 10" wide rim with 6.5" bs.

Plus, everyone knows white cars are cool.

 

I'm actually interested in those twin Walbros,lol. What size are they? pics?