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View Full Version : 5% still risking gaskets after muffler delete?



1QuikV6
10-25-2004, 03:03 PM
Im having my 5% pulley put on as Im typing this and I just wanted to know if I can expect a noticeable difference over my stock 89 pulley. Also, I have deleted my stock mufflers but have left my resonator in place. Is that still too much backpressure and am I still risking my head gaskets?

David Neibert
10-25-2004, 03:35 PM
The head gaskets are going to fail pulley or not....IMO an extra 5% isn't going to hurt anything.

David

1QuikV6
10-25-2004, 05:33 PM
I was told the 89 pulley is about a 3% U/D anyway. is that right?

90blkbrd
10-25-2004, 05:51 PM
I was told the 89 pulley is about a 3% U/D anyway. is that right?

The 89 pulley is 0%. It's stock, unchanged. The 5% is 5% smaller in diameter.

This is how the pulleys measure out. A 5% and 10% were named that before the 94/95 cars came out and their names stuck.

94/95 3.250
89/93 3.135
5% 2.950
10% 2.850

David Neibert
10-25-2004, 05:52 PM
I was told the 89 pulley is about a 3% U/D anyway. is that right?

No it isn't...perhaps someone is confusing the 94/95 stock pulley, which is about 3% larger. So putting your stock pulley on a 94/95 would be overdriving it 3% from stock and putting a 5% on a late model is really overdriving it 8% from stock.

Most of the companies making pulleys, base their overdrive percentages on the early model blower pulley diameter. Just stay under 14 pounds of boost at 5500 rpms and it will be fine.

David

1QuikV6
10-25-2004, 06:04 PM
Well its not so much the amount of boost that I have noticed as it is how quickly I am getting boost. I did notice that this pulley does bury my gauge which I was not expecting. I reach 14-15psi by about 3000rpm. Id hate to see a 10% on my car. Although some people have said that a 5% tends to work better for a 5 speed car and the 10% is best on the auto. not sure of that truth either.

wezar
10-25-2004, 10:10 PM
You gotta lose that stock resonator and cats. Search on the topic and you will see that exhaust is choked at that point. If you are reaching high boost levels at 3000 rpms its the stock cats and resonator slowing down the exhaust flow.

Port your manifolds and add some high flow cats and a Magnaflow resonator.

If your engine is on the original head gaskets Dave is right in saying they are gonna blow anyway.

Another good topic to search on.


Good luck and

Robert Kohlman
10-26-2004, 01:39 AM
The stock resonator is the biggest restrictor in the stock system. The mufflers are actually not too bad. You need to ditch the resonator for a straight pipe or another muffler/resonator that has a larger diameter.

1QuikV6
10-26-2004, 01:06 PM
I want to ditch the resonator which Im going to do eventually, maybe next week, abd I want to delete the cats but there isnt a place around here that would do it for fear of me getting a citation for it.

86stang96
10-26-2004, 07:12 PM
I want to ditch the resonator which Im going to do eventually, maybe next week, abd I want to delete the cats but there isnt a place around here that would do it for fear of me getting a citation for it.


thats easy tell the shop that you want a test pipe and make it to where you can bolt it on so when you go to the track and where your cat bolts up.

1QuikV6
10-28-2004, 01:05 PM
Hmm, interestin' idea. Im half tempted to tell him to just bend me a new system with a side exit.