I really wanted headers for my 3800 build, but I also knew that, in their stock form, the cheap 3800 ebay headers require cutting out the trunk. I couldn't pass up $130 for stainless headers, even if only the front would work. I figured there's a way to cut them up to make them work, and sure enough, I got them to fit. I think the photos speak for themselves. I had to beat the trunk in to clear the muffler which I also did some beating on to flatten it out. It's hard to see, but everything clears. The front required no modification besides bending the firewall heat shield back a bit. I modded the header and crossover using just what I cut out.
[This message has been edited by Stricken (edited 10-24-2020).]
Love those headers. Incredible job of exhaust plumbing. It took quite a bit of measurement as all the bends are now in the right places. While I mig weld myself I could not have done as well. I would have probably gone the easier route and used mandrel bends on the rear side.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
While seems good because can weld thin tube w/o a leak etc. because Most people can't do the same... Sadly, might not last long.
Engine and exhaust will move quite a lot and load any weak section(s) causing cracks at minimum. Highlights: Even tho muffler has springs/hangers to mount, muffler and pipes are heavy enough to hammer the header and the short "down pipe." Engine itself and exhaust "grows" and "shrinks" as it runs then shuts off. Exhaust insulation tape can add to this problem as keep heat trapped to "overheat" the pipe.
Heal cycling and motion is why header kit came w/ flex part(s). Is why many OE Doughnut joints have "spring bolts" to allow movement and rotation as engine moves on 3 planes.
"Dog bones" and engine/trans mounts try to limit engine moving but doesn't prevent exhaust hammering as you go, stop, hit pot holes, backup and hit the exhaust, and so on. (Is likely why GM spend money to add an extra joint and "hanger" in the down pipe for 88 Fiero L4 to stop breaking exhaust manifold. Upper section is bolted to the tran's. Extra joint is in 180° turn for the cat.)
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Originally posted by theogre: Even tho muffler has springs/hangers to mount, muffler and pipes are heavy enough to hammer the header and the short "down pipe."
The ideal scenario where a flex pipe is not feasible would be to have the exhaust hanger supports be fixed to the powertrain, and not the spaceframe/cradle. This way, as the powertrain rocks, the exhaust hangers move in unison, without imparting stress on the exhaust. You just have to check for adequate exhaust tip to bumper clearance on launch.
I remember seeing fieroguru doing exactly this in one of his project threads. He had engine/trans-mounted struts going out to the back to help support the exhaust pipes. Guru, care to share?
In my Fiero project I did it the way theogre mentions, with the flex pipe, and the exhaust supported by the cradle:
Both ways are valid, but flex pipes do eventually die.
[This message has been edited by pmbrunelle (edited 10-25-2020).]
Originally posted by pmbrunelle: Both ways are valid, but flex pipes do eventually die.
Maybe but when that happens you hope to only need to fix the flex. Most OE installed flex last for many years, even several decades, vs. DIY installed flex is anyone's guess how long it will last.
Originally posted by pmbrunelle: The ideal scenario where a flex pipe is not feasible would be to have the exhaust hanger supports be fixed to the powertrain, and not the spaceframe/cradle. This way, as the powertrain rocks, the exhaust hangers move in unison, without imparting stress on the exhaust. You just have to check for adequate exhaust tip to bumper clearance on launch.
I remember seeing fieroguru doing exactly this in one of his project threads. He had engine/trans-mounted struts going out to the back to help support the exhaust pipes. Guru, care to share?
Worked great! I will be doing something similar with the new exhaust post turbo.
My 3800SC muffler is suspended on springs. The exhaust pipes are supported using rubber/metal hangars. No flex joint, no cracks, seven years and no problems. I did upgrade to the Spintech muffler two years ago but that didn't affect anything . It just lowered the sound. I am thoroughly impressed with Strickers build. He must be a professional welder.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
My 3800SC muffler is suspended on springs. The exhaust pipes are supported using rubber/metal hangars. No flex joint, no cracks, seven years and no problems. I did upgrade to the Spintech muffler two years ago but that didn't affect anything . It just lowered the sound. I am thoroughly impressed with Strickers build. He must be a professional welder.
Many thanks for your kind words. I'm definitely no pro welder, and the welds only look good if you don't get too close to them
Nice work on the custom headers! Keep on takin the bull by the horns and doing it!
If it has an issue, I am sure you will come up with a solution and make it better. Fun to take a chance, engineer, modify, fabricate and let her buck to see if it works as you want it to!
Thanks for sharing!
------------------ 84/87 NB, 3800SC, E-85, VS Cam, 2.8 Pulley, 4T65E-HD, HP Tuners, AEM Wideband, Regal GS Gauges, S-10 Brake Booster. 1/4 mile -11.85 at 114mph
[This message has been edited by DimeMachine (edited 10-26-2020).]
The op reported that he had to beat the muffler and trunk wall to gain needed clearance. To avoid this the Spintech muffler would have not required that. I was able to fit that 13" muffler and still have the trunk heat shield that I believe is critical. I've seen luggage melt in a friends swap install that didn't use the shield.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
The op reported that he had to beat the muffler and trunk wall to gain needed clearance. To avoid this the Spintech muffler would have not required that. I was able to fit that 13" muffler and still have the trunk heat shield that I believe is critical. I've seen luggage melt in a friends swap install that didn't use the shield.
Wish I would have known that! The Magnaflow is a bit fat to be sure.
