L31 Extreme Budget Build

[L31MaxExpress]

That should sound nice!

I am half way done with it. Before I cut all the pipes to fit the muffler into place, I am going to grab a pair of 2.5" OD to 2" ID adapters, set the stock replacement 2" tailpipes I have into place and hook the pipes directly from the cats to the tail pipes and see how it sounds with only the cats and true duals. Sometimes they sound surprisingly good. I know my Express sounds great under throttle true dualed through only the high flow cats. Did have a deceleration pop that was exaggerated at the time because it was a bit rich on heavy throttle tip-in.

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[L31MaxExpress]

Even with straight pipes off the Hooker manifolds this 87 was not crackly on decel like my 97 can be. Something different between the GM and Edelbrock control I am sure.

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[L31MaxExpress]

It is a shame to have to go with 2" tailpipes but 2.5" looks dang near impossible to squeeze between the leaf spring and fuel tank. 2.25" on my 83 was tight enough it was nearly touching the fuel tank. I briefly considered dumping it near the rear end, then remembered the exhaust has to clear the passenger compartment in my state and probably not the greatest idea with the condition of the current weatherstripping.

This was my evening progress so far. Removed parts of the old exhaust, the old hangers, the manifolds, the downpipes and turn downs I had on the manifolds. Then put the driverside header on and started hanging new exhaust pieces. The muffler is hanging slightly in front of where it might end up residing but needed it for a reference to know how long the pipes would need to be trimmed to and the front hanger is temporarily holding it.

When I said before this old van is pretty much rust free, I was also dead serious. Very solid old van.

I picked up the rear KYBs today that had to be ordered last week. Will throw them on tomorrow too. I have a touch more harness clean up and looming to do as well as a final shake down inspection for missing/loose hardware on anything I touched and it is ready for some drives around town.

A tip for DIY guys. When you crank down those lap band clamps, the tubing might as well be welded. Avoid clamping pipe joints with the horshoe clamps I am using as temporary hangers as they always leak and they crush the pipes in a way you can never take them apart again atleast easily. I have some actual tubing hangers that do not need the horseshoe clamps, but the horseshoe clamps and L hangers make heavy exhaust parts much easier to hang by yourself laying on your back under your vehicle. Leave the clamp a little loose and you can snag into the L of the hanger. I use those for mockup then switch to the cheaper tubing hanger setups as everything falls into place and multiple hangers are holding things up. Always support the front of your exhaust from hangers, never the manifolds or headers.

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[BVRPLZR]

I've got an 88 G20 in need (want) of a new exhaust and these last few pages have been deeply inspiring (damaging to my wallet)

Been really enjoying following along

 

[L31MaxExpress]

I've got an 88 G20 in need (want) of a new exhaust and these last few pages have been deeply inspiring (damaging to my wallet)

Been really enjoying following along

Summit has a fairly nice kit for the G-vans that comes with Hedman headers, mufflers and a 2.25" dual exhaust tubing kit that dumps ahead of the rear tires on each side. Not sure what your emissions smog checks are like, but could add a pair of cats to help keep it clean.

I have installed this kit a couple of times on a van and van based class C motorhome. My old 1994 G10 had a 305 TBI and the 1995 G30 dually RV had a 406 TBI. Friend of mine payed me to put the engine in after a machine shop built it to my specification, build the exhaust and tune it years ago. I added cats to both and a universal H-pipe kit to the motorhome. It opened both of them up noticeably.

Summit Racing 05-0160 Summit Racing™ Dual Exhaust Systems | Summit Racing

Free Shipping - Summit Racing™ Dual Exhaust Systems with qualifying orders of $109. Shop Headers and Exhaust Systems at Summit Racing.

www.summitracing.com

Oh one thing on those headers, I am not a fan of the ball and socket system Hedmans have, they always end up leaking down the road. On the 700r4/4L60E vans one of the collectors is too long, IIRC passenger side and exits literally facing the transmission crossmember. I cut the collectors down and use a Flowmaster cone reducer and and those stepped lap band clamps, much less of a chance for leaks or constantly loosening collector bolts. With the reduced pipe size, can snake the smaller tubing between the transmission and crossmember. Much easier to do than modifying the crossmember which is also an option. The crossmember could be modified by cutting it on the passenger side and adding more of a L shape to it with some plate steel. More fabrication than I wanted to do to keep the collector design I already do not like.

Modifying transmission crossmembers is nothing new to me either. The one I modified to put a 4L85E in place of the 4L60E variants in my 97 Express van. The massive OE dual 3" pipes to the muffler bent to clear the OE crossmember did present a bit of a clearence issue with the modified crossmember on the 97. The RH pipe cleared like stock, but the LH did not due to the setback and added plate steel. I ended up heating the LH side pipe a bit until it was glowing with a MAP gas torch and hammering it flatter with my 2 lbs mini sledge to provide adequate clearence, probably flattened it out 1/2 to 3/4" or so for about 3-4" in length to keep the tubing from rubbing the revised crossmember. With the huge for a a small block 350 at the time 3" pipes it was not a restriction and still not a restriction even on the ~500 hp 383.

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[L31MaxExpress]

My tip of the day for anyone considering Hedman headers. Anytime I install a Hedman header of any kind with a 3" collector, I cut the dumb ball and socket end off and use these, much less of a PITA over time. Flowmaster also makes these in 3.5" to 3" for larger header setups on bigger engines.

Flowmaster R3025 Flowmaster Reducer Cone

Forms smooth transitions from one pipe diameter size to another. Available in various sizes.

www.holley.com

 

[Scooterwrench]

My tip of the day for anyone considering Hedman headers. Anytime I install a Hedman header of any kind with a 3" collector, I cut the dumb ball and socket end off and use these, much less of a PITA over time. Flowmaster also makes these in 3.5" to 3" for larger header setups on bigger engines.

Flowmaster R3025 Flowmaster Reducer Cone

Forms smooth transitions from one pipe diameter size to another. Available in various sizes.

www.holley.com

What problems are you having with the ball and socket? I kinda thought they were the best thing since sliced bread.

 

[Scooterwrench]

What problems are you having with the ball and socket? I kinda thought they were the best thing since sliced bread.

Nevermind, all I had to do was go up one post to get your answer.
I had that problem the first time I installed a set with the ball and socket and after that I started tapping the adapter up over the ball with a dead blow hammer to make it conform to the ball before I assembled it all under the vehicle.

 

[BVRPLZR]

Summit has a fairly nice kit for the G-vans that comes with Hedman headers, mufflers and a 2.25" dual exhaust tubing kit that dumps ahead of the rear tires on each side. Not sure what your emissions smog checks are like, but could add a pair of cats to help keep it clean.

I have installed this kit a couple of times on a van and van based class C motorhome. My old 1994 G10 had a 305 TBI and the 1995 G30 dually RV had a 406 TBI. Friend of mine payed me to put the engine in after a machine shop built it to my specification, build the exhaust and tune it years ago. I added cats to both and a universal H-pipe kit to the motorhome. It opened both of them up noticeably.

Summit Racing 05-0160 Summit Racing™ Dual Exhaust Systems | Summit Racing

Free Shipping - Summit Racing™ Dual Exhaust Systems with qualifying orders of $109. Shop Headers and Exhaust Systems at Summit Racing.

www.summitracing.com

I actually already have that link saved from somewhere else you had posted it lol

You mentioned that you had some tubing hangers that don't use the horseshoe clamps, what style are you using?

 

[Supercharged111]

My tip of the day for anyone considering Hedman headers. Anytime I install a Hedman header of any kind with a 3" collector, I cut the dumb ball and socket end off and use these, much less of a PITA over time. Flowmaster also makes these in 3.5" to 3" for larger header setups on bigger engines.

Flowmaster R3025 Flowmaster Reducer Cone

Forms smooth transitions from one pipe diameter size to another. Available in various sizes.

www.holley.com

I like the looks of that, much smoother transition. But how well does a regular band clamp work when that cone shape is gonna be bigger than 2.5" OD where the band makes contact?