Best exhaust for an 87 Grand National?

[johnstonmark]

Thanks everybody for your comments. Lol I guess size doesn’t matter

 

[69hurstolds]

Well, it does, after a certain point. If the exhaust is too fat, it won't help you scavenge well and you can hurt performance. I'm in the camp with everyone else- 3" duals if the engine is slightly warmed over, or the 4" single that motorheadmike suggested. I wouldn't go over those sizes, personally. It WILL give you more exhaust noise, but too much will just suck donkey balls. So the advice given previously is good to heed.

 

[olds307 and 403]

Yup. Built right with a good muffler it works mint.

Natasha was in her first trimester taking videos on a very hot August day:

Nice, that sounded good👍, I was expecting it to sound like loud *ss.

 

[motorheadmike]

Nice, that sounded good👍, I was expecting it to sound like loud *ss.

The secret is a huge turbo... aka. pre-muffler muffler. A 3" single is another good option for a mild build... just strangely more expensive from RJC.

 

[1 RARE T]

Its truly a balance of performance, a quality installation, look of quality, and sound your looking for. GN's (I.M.O.O) came stock with duel exhaust, and should remain this way to get the true unique sound. With that being said, no more than 3" AT MOST. Anyone who puts a 4" exhaust on a GN knows nothing about engineering, performance tuning or takes pride in the quality of their work, because you will have to either modify or hack your car to do the install. CONGRATULATIONS on your purchase and I wish you the best with your decision!

(personally, whatever you do decide to go with, I would look for a quality stainless steel exhaust to ensure a great look for years to come)

Wow.

 

[motorheadmike]

Wow.

Some people's children, eh?

---

We've seen this chart kicking around for about 20 years.

The thing is it only accounts only for horsepower, not torque. Torque being the turbo V6's strong suit, and a very different animal than HP in the power band (air mass being moved). Theoretically a Buick V6 making double it's factory HP at 490hp is making double the torque at 710ft/lbs. That's a lot of exhaust. Diesel territory.

It also doesn't account for a cat, muffler, resonator, or bends. If 3.5" exhausts were common I'd suggest one of those in this application. But, they aren't. So for the weight/space penalty I am recommending a 4" over a 3" system to avoid any unnecessary restrictions downstream.

Also, no one brags about having a 2.25" pipe.

 

[houston_t]

For the money I like the Pypes system with race pro mufflers. That's my go to on a turbo Buick, that and a RJC down pipe.

 

[69hurstolds]

Also, no one brags about having a 2.25" pipe.

I'm going to brag about even a stock 307 having more than 2.25". In certain spots, anyway.

2.375" to be exact. That is the I.D. of the stock downpipe from exhaust manifold to cat. I'm going to simply forget to mention that it necks down to 2.25" on the outlet side right before going into the 4-bolt flange. GM p/n 22519894. I just whipped one out and measured one.

Go ahead, whip yours out and measure it!

Fool your GF while measuring your pipe! It's also fun at parties!

Or teach her how to use one...(wtf?)

My Dad was right. It actually IS an official measuring unit!!

[img removed bc reasons... remember this is still a "family" site for the most part.... -GP403]

[aaaaaand somehow I managed to not only remove the first image accidentally, but that 3rd one is also no longer attached... wtf, sorry!!]
EDIT: It's ok. I fixed it back.

 

[olds307 and 403]

I'm going to brag about even a stock 307 having more than 2.25". In certain spots, anyway.

2.375" to be exact. That is the I.D. of the stock downpipe from exhaust manifold to cat. I'm going to simply forget to mention that it necks down to 2.25" on the outlet side right before going into the 4-bolt flange. GM p/n 22519894. I just whipped one out and measured one.

Go ahead, whip yours out and measure it!

Fool your GF while measuring your pipe! It's also fun at parties!
View attachment 189251

Or teach her how to use one...(wtf?)

My Dad was right. It actually IS an official measuring unit!!

Don't forget the 2" crossover pipe before it, a pure Horsepower maker. Crazy they shrunk the pipe before the converter, leaving it or enlarging it even more would have helped. GM really screwed around and did anything to avoid a true dual exhaust in these years. Including the insanity MM pointed out on his Camaro, copying the high performance factory head pipes. GM used dual down pipes and cats into a single exhaust, really? I am really curious what the FE3X magic 30 HP gained system was diameter wise from the headers to the cat. Very good info when these parts become obsolete and custom parts will be needed to made for 100% correct Restorations👍. I knew the down pipe where I cut was too large for 2.25" pipe but 2.5" need goop to seal when I cut out the plugged pancake cat on my 81 Delta 88.

 

[86LK]

Well, it does, after a certain point. If the exhaust is too fat, it won't help you scavenge well and you can hurt performance. I'm in the camp with everyone else- 3" duals if the engine is slightly warmed over, or the 4" single that motorheadmike suggested. I wouldn't go over those sizes, personally. It WILL give you more exhaust noise, but too much will just suck donkey balls. So the advice given previously is good to heed.

ahhhh, a SINGLE 4" exhaust. can't remember the last time someone did that. even the ricers with their 4-bangers like to go pipe crazy

GM really screwed around and did anything to avoid a true dual exhaust in these years.

hmmm, don't know about other g-bodies but I wonder if that was why the El Camino had such a funky shaped crossmember? only enough room for one pipe to cross under