360 Help - Pre-cat Replacement/Headers

Hello all. I'm reaching out for some updated input on header replacement. I have read a lot of the older threads and know some of the options out there have been updated with air rails, heat shields, and so on.

My main goal is to avoid pre-cat failure risk while also improving sound and possibly adding a little more power. I will be keeping the factory cats and my Tubi muffler for now.

I do not want any CEL issues.

My questions are:

What experiences do you have and what do you recommend for my goals?

Any recommendations on brand?

Are header blankets really necessary or is that a gimmick?

Any pointers related to the install? (Plan to DIY)

Thanks everyone and the best to all of you in 2016!

 

I replaced my OEM headers with fabspeed headers and Capristo header blankets. No CELs. As to DYI, get the car at least 24 inches off the ground, remove the bottom trays. Use a new set of nuts, new OEM gaskets and new pipe clamps.

 

I've discussed this with my independent shop. Our plan is to take off the stock headers, cut out the honeycombs, flush and reinstall the headers. Labor estimate around $1,300. I've been told it shouldn't cause any CEL issues. I've already disabled the vacuum valves for the exhaust bypass - highly recommended if you haven't done it yet.

 

Thanks for the tips. Cheers

 

The cel issue has been talked about a lot. In my opinion (and experience with one car) it is more likely to get a cel with precat removal, than there is with messing with the main cats, due to the position of the o2 sensors. Getting a cel isn't the end of the world and there are various paths from there. I have fabspeed headers that are coated with white lightning... I think I posted some before and after temp readings awhile back... Didn't seem to me like blankets would be necessary - but again that's just two cents.

 

I broke down and ordered Fabspeed headers, blankets and O2 sensor extenders. Will probably be a few months until I have time to install and will do with oil and trans service. Going to try with OEM cats first. In the meantime my new alarm siren just came in so will be trying to get rid of LED.

 

I dealt with this question recently with my CS.

I reached out to rifledriver for his input. He said that he had only seen pre-cat failure in cars that were running poorly for other reasons. He also suggested that if I was to replace the headers, that he would go with the OEM Euro headers which don't have the precats.

Considering the weight that his opinions seem to enjoy around here, I decided to leave well enough alone. My car also only has 8k miles and runs flawlessly.

 

Yeah I read some of that. Chose the new Fabspeeds over used euro OEM manifolds that are prone to cracking. Hopefully I don't regret my decision!

 

It's been my understanding that the 360 manifolds don't fail like the 355 and 430

 

Silly question. The 1999 360 model year does not have precats.

Do you really need to install them?


Sent by incredibly fast electrons

 

No pre-cats in 1999 from what I understand so just smoke test for cracks. 360 is less susceptible to manifold cracking than 355 and 430 but it still occurs. I may be going overboard but I will be gaining a little better sound and power along with piece of mind.

 

did rifledriver mention how to deal with the CEL regarding the 2ndary air injection?
or there's no such a code as 2ndary air injection failure, so to speak

 

... If you get one you can turn it off with an ecu reprogram turning off the sensors (the range isn't alterable I don't think), you can electronically trick the sensor by managing the voltage, or you can mechanically alter the reading by reducing flow, using a mini cat, or relocating the sensor locations.

 

I've had this dilemma for a long time on my US sunroof 10,000 miles original paint modularwheel stickshift worthmorethan 300,000 united states dollars modena:

should I

1. cut open the existing header and gut the precat, welder, put back on , or
2. buy a used set of euro header and call it a day, obviously i need to deal with the possible CEL on the secondary air injection

 

1. Would probably trigger the cel too, since the sensors on US cars mostly appear to measure the precat efficiency. Not sure if you are asking me, but I have fabspeed headers and have the oem ones ready to put back on when/if I need to go back to stock.

 

I'd hate to flash the ECU to a non-OEM version

I'd rather have it flashed to a CS version. but most tuners won't do that or not able to, not sure why

 

Passing smog with the sensors turned off is a problem too

 

Thank you for supporting us! If you have any questions about the install, just let me know.

 

He didn't mention that part of the equation, but did say that he had seen a lot of parts damaged by aftermarket headers due to excessive radiant heat.

 

Mine is currently in a N.Denver shop getting Fabspeed headers, blankets, O2 extenders, heat shields, Hyperflow sport cats installed (along with belt change). I'm looking forward to find out the difference it creates. (Tubi Exhaust already installed before I owned it....)


I had been throwing a P0432 periodically. I'm curious to see if the new components eliminate the code....

 

Falcon Wing,

Hope your path here works well for you. I went with Agency Power headers (JetHot coated), Kinetix high flow CATS and FabSpeed muffler (I fabricated heavy duty muffler brackets), along with O2 extenders. Still got CEL. Had a shop in Jacksonville, FL modify the CPU code to eliminate the CEL, speed up the throttle response, and adjust air/fuel ratio, etc... that added 17 hp to the dyno. Came away with 347 rwhp!!!

 

thats exactly why I want to just gut the OEM ones. not to save money.

s

 

What kind of dyno and temp?


Sent from my iPhone using Tapatalk

 

I just dug up the dyno report, it was maybe two years ago when this was done with all of the new/modified exhaust installed. Steve was able to extract almost 19 extra hp and 11 FtLb.
The report does not show a lot, DYNO DYNAMICS DYNAMOMETER, performed by Mase Engineering (Jacksonville, FL). There is no ambient temp nor relative humidity.
Rear wheel readings:

Max 348.7 HP at 8020 rpm
Max 256.0 FtLb at 5220 rpm

The HP and FtLb gains were an added bonus for me as I was mainly after getting rid of the CEL for the exhaust and correct any issues with air/fuel ratio due to a freer flowing exhaust.

I might add... get your fuel injectors checked, cleaned and balanced and the car will run smoother and feel faster!!! RC Engineering in CA does a fine job!!!! Just a Happy Customer!!!