GMC .... is better!

[ianjpage]

Well Saturday was a very productive day (sometimes rather a pain though) for me & Deano.

As most of ya know the GMC been running flat and cr*p lately, well last monday dean dropped one of the manifold fixings for teh exhaust on teh GMC as he (along with the guys at astrosafari) believed the CAT to be blocked - well they both right - drove it round the estate and it was a differnt animal - loads of power and no flat spots - so we confirmed the cat was blocked.

Come satuday, we decided the best plan of action was to punch the insides of the cat out, therefore making it a straight through piece of pipe to solve this issue (money is uber tight at the mo hence cant afford a replacement).

Well.......the "header" bolts (bit between the manifold section and Y pipe) came out all ok (bar one that was a bit stiff) but the cat -> back section studs / bolts - what a fricking PITA - one sheared off totally, one rounded and one you couldn't get to.......took me and dean a good couple of hours of fiddling to get the bolts off and then getting the CAT setion out - what a nightmare as well.

You'd think with a van you would have loads of room to simply take the small, relatively straight section of pipe forwards over the trans x member, but no - you have to go backwards, twisting it over and over to remove it...got it out in the end....

Had to cut through the pipe just behind the cat as the outlet wasn't exactly straight - just as well as there loads of crap in the cat - few mins with big hammer and metal pole and the cat innards were no more

Then we coonected the Y pipe back up and fired her up to check all ok (and to see what it sounded like) - OMFG it was loud and reverberating...way too loud to drive like it sadly

Then the fun of fitting the bits back together (cat section -> cat -> rear box) - ended up needing to take the whole back box and piping out (again twisting and turning over the rear axle) to cut a slot in the stud area's to releas the presure to remove the studs to allow us to bolt them back together again - got it all back under there, Tin can, jubille clips and band clamp around the cut section, bolted back in and works 100% perfect.

The van now feels a totally differnet beast - loads of power and acceleration and the gear changes are super super smooth now so all in all a definate sucess (oh and the van sounds a bit meatier(?) now as well )

HUGE HUGE thanks to Dean for the help @ weekend, wouldn't have done it without ya mate - also big thanks & to Ryan for his band clamp and fire putty

Going to price up the parts needed now (brakes, idler arms, track rods etc) and see how much it comes to but i think i will repair rather than replace the truck now, although i may end up getting a cheap run around but all depends onthe ££££

[Incursus]

What about the MOT?  or is the Van old enough  to not require a CAT?

[ianjpage]

Quoting: Incursus

What about the MOT? or is the Van old enough to not require a CAT?

meh we'll find out when it has MOT next month lol!

[F Body]

Quoting: ianjpage

meh we'll find out when it has MOT next month lol!

Just make sure the engine is really warm before the test

[Roadkill]

All in a days work !

[v8mad0]

Top work chaps

[philoldsmobile]

yank engines normally run clean enough to get through without a cat - the numbers wont be stunning, but it should be fine - its euro and jap market engines like mine or shifty's that produce much higher BHP / liter that wont usually pass without one.

to give you an idea on how much more relaxed yank engines are,

astro, 200bhp / 4.3l - 46bhp / liter
IROC  240bhp / 5.7l - 42bhp / liter
LS1    286bhp / 5.7l - 50bhp / liter

Alfa    190bhp / 2.5l - 76bhp / liter (original map, with software update now 220)
FTO  200bhp / 2.0l - 100bhp / liter



the higher state of tune leaves an engine that is naturally a little dirtier, so the cat has more work in cleaning up the exhaust on a higher tuned engine. Don't forget, if the tester looks underneath, there is a cat still present, its just a shade more free flow than normal.

[HardRockCamaro]

Cats were only required from Jan 93 onwards weren't they?

The previous requirement should be passed easily.
The IROC has had the cats removed in the past and it sails through emissions tests...

[Roadkill]

Quoting: HardRockCamaro

Cats were only required from Jan 93 onwards weren't they?

(The GMC's a 97, IIRC)

[FUBAR]

Glad this seems to be much better

[ianjpage]

Quoting: FUBAR

Glad this seems to be much better

... just gorra price and buy other bits now....

[ianjpage]

Quoting: Roadkill

(The GMC's a 97, IIRC)

yup

[philoldsmobile]

Quoting: HardRockCamaro

Cats were only required from Jan 93 onwards weren't they?

yup.