"Slim line high flow racing cat"
Thread Starter
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
"Slim line high flow racing cat"
Just the politically correct wording for the "BIG PIPE". I have been toying with several ideas concerning the cat back system for my 85. I replaced the original cat with a high flow Magnaflow about a year ago. I was thinking about building my own cat back using the flanges off the old cat. Then I realized that I still had the restriction of the CAT. I didn't feel that the current pipes and mufflers were THAT restrictive and what I really wanted was to get a little more in the 1/4 mile. I could have gutted the old cat and bolted it back in, but I felt this would not be as smooth of a transation as the cat bows out and then back in.
So I cut off the flanges off the old cat, had some thin gauge material floating around the shop. A torch to heat the material and bend it around a pipe and then weld it up. I didn't want to bolt in my race day cat and leave the air tube hanging or wire it up out of the way, so I added a little piping to hook it up. Here is what I have:
And a end view...opening measures 4-3/8" x 2-3/4".
We will see what kind of difference this will make at the track. This will be a bolt in and out for the race day. The rest of the time will use the Magnaflow cat and keep the California air clean.
So I cut off the flanges off the old cat, had some thin gauge material floating around the shop. A torch to heat the material and bend it around a pipe and then weld it up. I didn't want to bolt in my race day cat and leave the air tube hanging or wire it up out of the way, so I added a little piping to hook it up. Here is what I have:
And a end view...opening measures 4-3/8" x 2-3/4".
We will see what kind of difference this will make at the track. This will be a bolt in and out for the race day. The rest of the time will use the Magnaflow cat and keep the California air clean.
Thread Starter
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
UPDATE - track trial
Okay last year the fastest I ran was a 14.1 after installing SuperRam runners and plenum. Before that it was 14.4. About a week ago I installed a set of March under drive pulleys. And Friday night I pulled the Magnaflow cat and installed the "BIG PIPE". No other changes.
First run as 13.613 @ 99.478 MPH. Broke out the rear end on the second run and shut it down. The third run was at 13.663 @ 102.395 MPH. So between the pulleys and the pipe I cut off .5 in the quarter and the bottom end is still stock pistons and cam.
The car pulled hard all the way thru the 1/4. Not to bad for a 22 year old car, automatic, 3.07 gears with 214,000 miles
Oh, the only other change which might have made a large difference is that my daughter in law gave me new Corvette tire valve caps with the C4 logo, they have to be worth 4 HP (1 HP per cap!).
First run as 13.613 @ 99.478 MPH. Broke out the rear end on the second run and shut it down. The third run was at 13.663 @ 102.395 MPH. So between the pulleys and the pipe I cut off .5 in the quarter and the bottom end is still stock pistons and cam.
The car pulled hard all the way thru the 1/4. Not to bad for a 22 year old car, automatic, 3.07 gears with 214,000 milesOh, the only other change which might have made a large difference is that my daughter in law gave me new Corvette tire valve caps with the C4 logo, they have to be worth 4 HP (1 HP per cap!).
Last edited by John A. Marker; Feb 19, 2007 at 02:39 PM.
