2½" Downpipe

[b4black]

I think I have come to the conclusion that the next mod to my car needs to be a 2½" downpipe. The most boost I can get is about 13 psi with the cone air filter and the exhaust disconnected before the converter.

I know a few other people here are looking into new DP's. I need to figure out what involved with removing the old one and installing a new one. I'm not sure if anything (starter, exhuats manifold, AC compresser) needs to be removed to make room.

I also wonder if a new DP could be bent using the stock one as a pattern without actually having the car. If that's the case, I have an extra DP I could send to someone as a pattern. Then it would just mean finding someone with experience and a mandrel pipe bender.

Anybody have any input? Anybody else ready to buy a DP?

 

[fc227]

Hey Rich,

I had Eric Rankin do my. I left the car with him. So I don't know how he did it for sure. But Think I remember him saying that he did use the original pipe has a template. But there was some tweaking he had to do.

I my self-found it much easier to remove the passenger fender when do header repairs, etc on the passenger side of the car. Every thing is exposed.

Don't forget to enlarge your wastegate hole to a little smaller than the puck size to stop boost creep when you do this mod.

 

[Ttype83]

I had the guy that did the exhuast on my look into making a DP. He need the old one for a template, but he would still need the car to tweak it in. He said that he would be able to make a 2 3/4" DP($500 for one), but that would be the largest that would fit without moding the car. If we can get the same person to make them, then they would only need one car. Then the rest could be made from that.
I think that he said that he would have to lift the engine to get it in unless it was made into a 2 peice....but not sure if this would fit.

Rich...13 psi bummer your spring is to strong.

I will ask about pricing on a couple, I need to go back any how....blown HG Oh I let my wife drive my car when I went to charleston last week. When I got back she said that my car was makeing a funny whisling sound when you get into gas. ROTFLMAO

Jim

 

[buick83-T]

Anyone considered using mandrel bent 45 and 90 degree pipes to make their own downpipe? Seems like it would be much cheaper from what I have seen on the prices of a custom downpipe.

 

[Neil Smedley]

Summit Racing has a 2 9/16 mandrel bent J tube in their catalog for $40......I heated and bellmouthed one end and installed it on my 81 trans am turbo 301.......with no other mods, it went from 101 mph to 104.5 mph on the quarter....It was the cheapest horsepower ive ever bought.....I ran that pipe into a 3 inch pipe and the whole unit is about 3 feet long......This is a strip only car. The car got quieter with this larger pipe also......I dont think it would be a good idea to increase the size of the inlet pipes though.....We need all the velocity that we can get.....Another interesting thing.....Even though I can get 20 lbs of boost, the car runs just as fast at 15.......

 

[buick83-T]

Hey Neil have any pics of your downpipe? I was going to try for a 3 inch downpipe planning on removing the elbow and go to a external wastegate also.

 

[fc227]

I'll try and get some photos this week of mine. It is a Two piece and stainless.

 

[Scott Adcock]

Rich,

I would consider a two piece downpipe as it makes engine removal a lot easier. My 2 1/2" pipe is a two piece unit that was constructed using the old pipe as a template, however, the shop still wanted the car for clearance measurements, etc.

 

[buick83-T]

Downpipe pics

Anyone got the pics of there downpipe? FC227? Niel Smedley?

 

[fc227]

DOH !!!! I forgot, later this weekend.

 

[turbofish38]

Hey couldn't you use a DP from a hot-air car. I see Lee Thompson (dont know if he posts here) has a 3-inch and possibly a 2.5. Since the turbos sit at about the same spot as on the carb cars maybe one of them can be adapted or used as a pattern. Just a thought.

 

[b4black]

Lee posts in the Hot Air section. He's making some 3" 84/85 DP's over the winter.

The 84/85 DP exits at 90° to the turbo, while the 78/83 is more like 45°. I don't know if changing the elbows would help.

I think if someone had one made well, it could be used to make a jig and then we could "mass produce" them (mass production in this case being 6-12 units).


Eric, where did your 82 GN go.

 

[buick83-T]

downpipe elbow

Anyone know if the elbows bolt pattern are the same for the 84-85 cars as ours? If we swaped the elbows maybe we would be able to bolt up a atr 2.5 downpipe posssibly?

 

[turbofish38]

Hello Rich, My 82 GN is pretty much history. I saved it from the crusher with hopes of restoring it but about the only thing that could be salvaged was the VIN and the turbo6 emblem on the speedo. It might still be in the Omaha NE area. The car was pretty much wasted by the last owner as rust consumed the floorpans and the original turbo motor was missing. I'd have to write this GN off as history.

 

[turbofish38]

Hey buick38-t, I have some carb-turbo turbos and some hot air turbos laying around. If I get some time I will compare and see. I did this like 6 years ago with some hope of finding some secret HP gains on a carb car but stupid me I didn't write any info down and i'll be damned if I can remember. Might take me a couple of days.

 

[buick83-T]

Made a post in the "hotair" section and got a reply saying that the 84-85 turbine housings bolt pattern are the same as ours. .

 

[buick83-T]

downpipe pics

Anyone got pics of their downpipe yet ???

 

[fc227]

Well, I broke my foot (back on the day before thanksgiving) and can't drive. I've been meaning to get the Digital camera home to take the pictures, but it just has not happened yet.

 

[b4black]

Originally posted by buick83-T
Made a post in the "hotair" section and got a reply saying that the 84-85 turbine housings bolt pattern are the same as ours. .

Maybe I'm wrong, but I don't think the turbine housings are the same. (It's more possible that the Riviera housings are the same than RWD housings.) Even if they have the same bolt pattern, they would need to be in the same physical location for the DP to fit.

But, I would love to be wrong on this. So to help figure this out, I took a picture of the turbine's elbow. And not forgetting the 301T, I took it's picture as well.

The Buick V6 is on the left and the 301T on the right.

As you can see, these to elbows are very different. The Buick V6 uses four bolts, while the 301T has five. The first question I would ask is "How many does a Hot Air have?"

Now we just need a Hot Air to take a look for us. I wonder were we could find one?
http://www.turbobuick.com/forums/showthread.php?s=&postid=439562#post439562

 

[6 to go]

Well, I have a couple of the hot airs and a loose turbo that I took off my 84. The elbow is bolted to the turbine housing with 4 bolts.
HTH.