Bill Ball

Yeah, Tony, I'm on 30 lb injectors. I was lean on most of the BEFORE dyno runs, so there is a supply issue. Now, this is sampling after the new Random Technology cats, but my A/F meter agreed, not going into green on a bunch of the runs. I'm OK for daily driving, but need this fixed before any serious speed stuff, like open road racing.

Rick Carter

Bill,
Your A/F meter if narrow band pegs out about 12.5:1, if you want to run richer you need a wide band. Good to see more power you must be pleased.

Bill Ball

Right, Rick, we weren't getting into green at all on a few runs so we were way lean. 12.5 would be an improvement. Strangely, we had some runs that measured in the 11s, other in the 14s. Very erratic. The power increase was impressive, but I'm laying off until I get the A/F issues fixed.

Red UFO

Bump looking for pics!

Bill Ball

Pics of the X-over? Well here is one on another car. I have the same setup.

RDS928S

Here is my Motorsport ceramic coated x.

RDS

Robert_H

Bill,

It's good to hear of such improvements from a relatively easy swap out. I am glad to know that you have gotten some of your "sound mojo" back. I know you were not very pleased with losing the RMB sound.

Rob

SteveG

Personally I would go with the Devek. The Motorsports one has the O2s mounted on either side, so it does not monitor the two banks together; you can bung one off or wire two up thru the grommet, but you can't monitor both simultaneously, you can only hook one to the comp a time. Maybe that is an asset to some as you could narrow any malf to one bank. It comes with attachment bands/clamps and braided heat tape. You can weld it if you want. That would not be a "bolt on" in my book. This was for the '85: $700 + $53 S/H.

[edit] I forgot. There is no smog access on the Motorsports pipe!

cfc928gt

I wondered too about having the O2 sensor on one bank but since the injectors are a batch fire where they all fire at the same time for the same duration I don't think it really matters.

Mrmerlin

The second opening in the Motorsport pipe is for a an AF mixture reading device,

danglerb

Did all of that have to come off for a smog check?

Bill Ball

I think I could have kept it on for the check as it has cats, but I removed it anyway.

Bill Ball

Some updating here just for technical posterity...

The erratic and lean A/F readings I reported here were due to a faulty throttle switch. WOT was not tripping. I did not discover this until a long time later after the car ran real hot during a sustained high speed run.

The WOT portion of the switch retards timing and enriches fuel mixture to protect the motor under these conditions. Others have found that a weak solder point on the contacts for this portion of the switch can break. The WOT portion may still trip, but only at the very end of travel of the bellcrank and only if the cable is adjusted very snug.

Using a diagnostic tester I found mine was not tripping as it should at about 2/3rds throttle. In fact, it wasn't tripping at all. After I carefully snugged up the cable as tight as I could while making sure the idle switch portion worked, it would trip but only if I stomped hard on the gas pedal. That's not right but OK until I get under the manifold again. The switch can be opened and repaired, which probably is better than just replacing it as the solder joint appears to be an inherent problem.

Brian Felts

Is there a link to where these are for sale? IT looks like it would fit my 84 and would be a good start to a nice dual setup for an OB? Ideas?


Thanks
Brian

fabric

I don't believe Devek is making these anymore, and if they are, good luck getting one. Try here:

http://www.motorsportincslc.com/shop/

Also available from Carl at 928 Motorsports and Roger at 928s 'R' Us.

These are not exactly the same as the Devek, but are modeled on Louie Ott's original X pipe. 928 Specialists has a slightly different, modular design.