How do I stop the downpipe from hitting the front suspension?

[BRAD_PADGETT]

I just had installed a 2 1/2 downpipe on my 85 and it works great. The problem is that it is too big and it knocks on the front suspension bracket. This causes false knock and I cannot tune my car because I can't rely on the knock gauge. I test drive and the knock gauge goes up and I back off a little and bury it with no knock. I only have 1/4 inch between the pipe and the suspension bracket. I know it is the downpipe because I get knock on the driveway as the engine torques to the passenger side on lower rpm and boost.
The downpipe had to be dented in order to get past the Poston passenger header uppipe flange. Should I remove the downpipe and dent it to get past the suspension flange or is their any other alternatives? Thanks- Brad

 

[tenright]

Hey Brad- the downpipe should not be anywhere near the "A" frames or any suspension parts whatsoever. Yes it does butt up against the up pipe flange on the poston headers but that should not have been an issue. Denting it was definately not the way to handle that. You could have left it against the header flange it would not have caused any issues. It's more likely the pipe is hitting down around the starter. This could be catastrophic should it contact the power wires to the starter. Jack the car up and look around it should be pretty obvious where it is hitting....



T

 

[cool 84]

If it's hitting the a-arm new motor mounts could help but you should be nowhere near the arm. If it's hitting on the firewall, you can bend the body seam out of the way or install new body bushings. My 3" Lee Thompson pipe fits fine with no rubbing so the 2.5" pipe shouldn't be a problem.

 

[Jerryl]

.......... My 3" Lee Thompson pipe fits fine with no rubbing so the 2.5" pipe shouldn't be a problem.

As a general statement; I have only seen a pic of the LT DP and not sure who's DP Brad has .......... I would think that Lee did a MUCH better job designing the DP to prevent contact. Don't think OD is the issue here.

 

[Dwayne]

2 things I see here, can you re-clock the exhaust side of you turbo so you can "lift" the DP and also a solid motor restraint might do away with your knock. Get it up on jacks and lets us know what you find out.

 

[BRAD_PADGETT]

I will get the car up on jacks this afternoon and remove the passenger tire and rim. This will give me a clear view and I can post a pic. Thanks- Brad

 

[cool 84]

As a general statement; I have only seen a pic of the LT DP and not sure who's DP Brad has .......... I would think that Lee did a MUCH better job designing the DP to prevent contact. Don't think OD is the issue here.

That's sort of what I was getting at. The clearance is there assuming the pipe is bent right and everything else on the car is right.

 

[BRAD_PADGETT]

I probally blew out the passenger side motor mount. The motor twists so much now that the down pipe hits the front suspension. I can get knock on the driveway by revving the motor. There is no way my mechanic(I only do electric type installations) would allow this. I posted on GNTTYPE.org and a blown passenger side engine mount will cause the downpipe to drop.

This situation was prediced by Tom Tenright. I have already ordered an engine strap. I did have alot of fun in breaking the engine mount. I was testing an Sat. for my final tunes when at a red light with no traffic in front of me a Suburu Wex4(What ever-the fast one) pulled up behind me. I looked in my rear view mirror and the were all giggling and it was obvious to me that they were going to do pass from behind and blow by me. I punched it and gave them my lane and they tried and could not catch me. They gave up. Once I get a final tune I can get a Subaru. Brad

 

[JOELO'S T-TYPE]

Subarus are ok, but nothing compares to brute Buick force.

 

[JOELO'S T-TYPE]

My 3" Lee Thompson pipe fits fine with no rubbing

I've never seen one of this, are they still avaliable?

 

[Dwayne]

I've never seen one of this, are they still avaliable?

Nope

 

[tenright]

Sorry to hear about the motor mount, strap won't help you now if it's broken. I have the poly mounts which are a great permanent solution. But they do cause a slight vibration.....You will need to have it rewelded to the frame....then decide if you want to go the poly route or the strap.

ounce of prevention is worth a pound of cure.....

T

 

[BRAD_PADGETT]

I took the car to my mechanic and I have real answers. The motor mounts are in perfect shape-not broken and they are only three years old. The 2 1/2 downpipe was rubbing on the A-frame bracket. My mechanic heated up the downpipe and bented it up slightly so it does not hit the A-frame bracket. In looking at the hot-air setup I do not think any bigger downpipe is possible without major changes. I no longer have knock revving up in the driveway and several test runs showed no knock. I am running at 15 psi boost and the tires break loose in first. I will increase boost tomorrow and test. Thanks for all your help. Brad

 

[cool 84]

I took the car to my mechanic and I have real answers. The motor mounts are in perfect shape-not broken and they are only three years old. The 2 1/2 downpipe was rubbing on the A-frame bracket. My mechanic heated up the downpipe and bented it up slightly so it does not hit the A-frame bracket. In looking at the hot-air setup I do not think any bigger downpipe is possible without major changes. I no longer have knock revving up in the driveway and several test runs showed no knock. I am running at 15 psi boost and the tires break loose in first. I will increase boost tomorrow and test. Thanks for all your help. Brad

What do you mean you can't fit more than a 2.5"??? I'm running a 3" along with a few others with no problems. If it's hitting on the a-arm especially it's a cheap pipe. Don't give bad info.

The tires breaking free is not a good indication of power. Mine break free on the freeway at 65mph. I'm embarassed not proud.

 

[tenright]

Thats good news about the motor mount

BTW 3 and 4 inch DP's are possible since these pipes basically route through the same areas the intercooled cars do, but because of other restrictions on our cars I doubt they would be a big proformance boost over the 2 1/2 inch pipe. The whole argument is pointless anyway since no one makes them for us anyway....

T

 

[BRAD_PADGETT]

Guys-I am checking out and see you on the otherside. I leave this site to the braggards. Bye Brad

 

[cool 84]

Guys-I am checking out and see you on the otherside. I leave this site to the braggards. Bye Brad

Don't give false info. There's no bragging here. You can't keep saying things as fact that aren't true. You said in the first post your DP was too big. This is not true, it's poorly made or you need new motor mounts. Telling people you can't fit a bigger DP on a hotair when there are people currently doing it is wrong.