Tried to hollow out Precat = FAIL

wish2345 · 06-30-2009, 01:18 PM

i got all the bolts off the manifold and the three on the bottom and that damn precat would not come off the manifold. Is there something i am doing wrong ?

*Derrick2k2SE* · 06-30-2009, 01:37 PM

If its rusted on you may just have to force it. There are no other fasteners or clips. Just make sure you actually have all the bolts out and soak it with some PB blaster or WD40.

BE CAREFUL NOT TO GET ANY OF THE MATERIAL IN YOUR EYES!

*max929* · 06-30-2009, 01:39 PM

BUMP....perfect timing....I'd also love some advise from those who have done this before.

e-subliminal-2 · 06-30-2009, 02:57 PM

i KNOW from pervious advice that this is a complete PITA. the whole process is, Only thing id say is spray some lubricant(wd40 as reccomended above) and try to pry it off.

Ahmad_1290 · 06-30-2009, 03:01 PM

Are u taking off the whole manifold? When i did mine, i just unbolted the precat from the manifold. You'll have to take off the heat shields before though. Once you get all the bolts off, give it a tug and it should fall right out. Oh and make sure you disconnect the o2's

nismowolfe · 06-30-2009, 05:25 PM

I have done this as well in maybe 2 hours tops and I agree with the above except I used a pry bar to help me separate the cat from exhaust pipe behind it.

*mannetti21* · 06-30-2009, 05:35 PM

Quote:

Originally Posted by Derrick2k2SE

BE CAREFUL NOT TO GET ANY OF THE MATERIAL IN YOUR EYES!

I don't know if its coincidence or related, but I was replacing my alternator and kept getting it in my eyes.....2 days later I woke up with bilateral pink eye. Pink eye FTL, bilateral pink eye FTMFL

Grand_hustle17 · 06-30-2009, 05:43 PM

is there any proven power difference when doing this???

HotshotVQ35 · 06-30-2009, 07:07 PM

maybe, but why go thru all the hassle when you can get obx headers for cheap..

Quote:

Originally Posted by Grand_hustle17

is there any proven power difference when doing this???

PatKeo6373 · 06-30-2009, 08:50 PM

Quote:

Originally Posted by HotshotVQ35

maybe, but why go thru all the hassle when you can get obx headers for cheap..

ya why destroy your cats when u can sell them for good money and pick up the headers

dustey · 06-30-2009, 09:51 PM

WD-40 isnt going to do anything. WD = Water Displacement. You dont need to displace any water.

Liquid Wrench or PB Blaster is the way to go. Spray it on, let it soak in for a while, and go at it.

*Derrick2k2SE* · 06-30-2009, 11:04 PM

Quote:

Originally Posted by dustey

WD-40 isnt going to do anything. WD = Water Displacement. You dont need to displace any water.

Liquid Wrench or PB Blaster is the way to go. Spray it on, let it soak in for a while, and go at it.

WD is good for a LOT more than water displacement. I've been using it for different things for close to 30 years. True, there are better products for penetrating rust but it WILL work and everyone has WD40 near by.

To say it won't do anything is just false.

BTW I'd actually recomend WD40 for this since it requires laying on your back and spraying up a few inches from your face. I don't mind getting WD40 in my eyes and face. PV blaster in the eyes is another story.

*foodmanry* · 06-30-2009, 11:21 PM

You need to pry it out....it fits inside with a lip on the edge. It is a VERY tight fit....

hotstartup · 07-01-2009, 12:53 AM

2 hours to get this done? sounds like not long enough. lol

Mu_036sp · 07-01-2009, 01:07 AM

I may be doing this, or getting obx headers in about a month.

wish2345 · 07-01-2009, 07:10 AM

Are there 2 precats ? one on each manifold ?

*Derrick2k2SE* · 07-01-2009, 07:16 AM

Yes, there is one on each manifold.

wish2345 · 07-01-2009, 07:19 AM

do both of them usually go bad or just the front one ?

*Derrick2k2SE* · 07-01-2009, 08:55 AM

They should wear out pretty evenly but when a cat fails it can happen quick. If the element inside cracks it can melt and cause a blockage.

If you're going to do this I'd recomend doing both at the same time. That way you keep an even exhaust flow between the cylinder banks.

**E55AMG2** · 07-01-2009, 12:05 PM

PB Blast is the best for getting at rusty bolts.

*Child_uv_KoRn* · 07-01-2009, 05:47 PM

Hammer!

or rubber mallet if you're faint of heart :P

dingoes · 07-01-2009, 06:33 PM

I replaced my 3 way cat (it sits behind the radiator) I looked it up on this web site - http://www.courtesyparts.com/

This is what I did to replace it. The day before, I sprayed PB Blaster on the bolts that hold the cat to the manifold. The cat sits very close to the exhaust ports so the cat gets so hot it fuses itself to the manifold. I removed the O2 sensor at night then drove it, (the next day)took all the exhaust bolts off the following morning. Be careful you can twist off the bolts they are small. After beating on the cat with a hammer, small sledge hammer, air hammer, I resorted to a 35lb pry bar .. that did the trick. Once it was off it was very easy to get the new one on. It's getting the old one off .. that's the hard part.

dingoes · 07-01-2009, 06:37 PM

I just wanted to add .. I don't know how the car gets as good of gas millage that it does and produces he HP having to breathe through all the converters. I bet it would get 50 more HP without them!

*LA02MAX* · 07-01-2009, 08:43 PM

Quote:

Originally Posted by dingoes

I just wanted to add .. I don't know how the car gets as good of gas millage that it does and produces he HP having to breathe through all the converters. I bet it would get 50 more HP without them!

I wish...I would have had headers by now.

*KRRZ350* · 07-01-2009, 08:47 PM

Make sure you have all of the bolts out on the top, trust me there is one that is very hidden! Some go in from the top IIRC.

I had to use a crowbar once it was broken loose.

wish2345 · 07-02-2009, 07:15 AM

i got the two nuts off the top where the studs are . i was able to get all 4 bolts out but broke 1. That may be my issue but didnt look like it was causing it to stay on. I may just have to remove the entire manifold and precat and a whole.

A33Black · 07-02-2009, 08:07 PM

Quote:

Originally Posted by Derrick2k2SE

BTW I'd actually recomend WD40 for this since it requires laying on your back and spraying up a few inches from your face.

I don't mind getting WD40 in my eyes and face.

PV blaster in the eyes is another story.

WD in my eyes =

I usually put on

, or at least try to remember to..

But seriously, be safe and throw on some goggs too, regardless of the product..

*KRRZ350* · 07-02-2009, 08:14 PM

Quote:

Originally Posted by wish2345

i got the two nuts off the top where the studs are . i was able to get all 4 bolts out but broke 1. That may be my issue but didnt look like it was causing it to stay on. I may just have to remove the entire manifold and precat and a whole.

Sucks to have to drain the coolant, but if you have to do it that way it's best to pull the rad & not just the fans, actually I think it's required anyways, so pull the rad first.

Grand_hustle17 · 07-03-2009, 07:06 AM

Quote:

Originally Posted by HotshotVQ35

maybe, but why go thru all the hassle when you can get obx headers for cheap..

im waitn fo somebody to sell their hotshots

*Derrick2k2SE* · 07-03-2009, 09:29 AM

I've done two header installs without taking out the radiator. You can just pull the top hose and remove the cooling fans. You just have to catch the small amount of coolant from the top hose. You can slide a piece of cardboard in front of the radiator to keep from hitting it.

e-subliminal-2 · 07-03-2009, 10:30 PM

Excuse my late post but 2 hours of work compared to $400.00 on obx headers. Cheap sure but with this economy we're not all banking.

Also isn't the point of headers to delete your cat and cause for easier exhaust flow? i'm not saying you're getting the same hp if you gut your cats as you would if you bought obx or cattman headers, but i'm sure there are some hp gains considering you're making less restriction..
Correct me if i missed something.

*Derrick2k2SE* · 07-03-2009, 10:36 PM

You'll probably get a little gain. The precats are part of the reason for headers. The other part is that the stock manifolds are very restrictive.

Grand_hustle17 · 07-05-2009, 11:42 AM

Quote:

Originally Posted by e-subliminal-2

Excuse my late post but 2 hours of work compared to $400.00 on obx headers. Cheap sure but with this economy we're not all banking.

Also isn't the point of headers to delete your cat and cause for easier exhaust flow? i'm not saying you're getting the same hp if you gut your cats as you would if you bought obx or cattman headers, but i'm sure there are some hp gains considering you're making less restriction..
Correct me if i missed something.

+1 i so agree... IIRC is that stock manifolds arent really that restictive

*Derrick2k2SE* · 07-05-2009, 12:42 PM

These are the stock manifolds. The one on the left pinches down to about the size of one exhaust port where all three come together. The one on the right is almost twice the size at its narrowest point.

The flow through these will be uneven and restricted. Especially when you add other exhaust and intake mods.

Grand_hustle17 · 07-05-2009, 02:43 PM

......... you showed us lol... i would still like some knida test though (preferably dyno but hell with it)

*Derrick2k2SE* · 07-05-2009, 06:12 PM

It would be cool to see a dyno with Good precats vs. hollowed precats vs. headers on the same car.

When you figure that hollowing out the precats is basicaly free, any gains would be good.

I'm afraid the sound might be pretty bad though. I guess we'll see when he finally gets it done.

Grand_hustle17 · 07-05-2009, 06:16 PM

Quote:

Originally Posted by Derrick2k2SE

It would be cool to see a dyno with Good precats vs. hollowed precats vs. headers on the same car.

When you figure that hollowing out the precats is basicaly free, any gains would be good.

I'm afraid the sound might be pretty bad though. I guess we'll see when he finally gets it done.

to see that on the same car would be heaven... i wouldnt mind just seeing a dyno of gutted cats, everybody knows the ball park numbers for a I/H/E maxima, so if its just a few HP less, i think ill have to jump for it, in that it is free

*Derrick2k2SE* · 07-05-2009, 06:27 PM

A before and after dyno would be cool.

It'a almost free. You'll probably want to use new gaskets. I think there may be crush gaskets in there somewhere but I can't remember. It's been 4 years since I did the headers and had it apart.

You'll also want an o2 simulator to avoid a CEL. Those are pretty cheap though. I'd still consider it free compared to headers.

boost4age · 07-05-2009, 08:00 PM

Quote:

Originally Posted by Derrick2k2SE

I'm afraid the sound might be pretty bad though. I guess we'll see when he finally gets it done.

yeah i think the sound will be pretty bad also, this was done to a honda civic and it didnt sound the same after. it was almost like you could here the exhaust being pushed through

Grand_hustle17 · 07-05-2009, 08:50 PM

Quote:

Originally Posted by boost4age

yeah i think the sound will be pretty bad also, this was done to a honda civic and it didnt sound the same after. it was almost like you could here the exhaust being pushed through

4cyl and 6cyl have completely different sounds, but if anyone looking to modify headers and dont expect sound increase should just stop in their tracks