When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
YES.... I was gonna get regular 2.5" ramhorns and do the preservation but there was some amazon deal about applying for a credit card and they gave me 50 bucks off (something like that). I'll find the link
When I put the stock Corvette Central 2.5" (with the parts I mentioned above) I had a Richmond 6-speed in it. I was able to squeeze the stock pipes around that by changing a drain plug on the tranny and wrapping the passenger side section of exhaust next to it (and I HATE wrap).
When I installed the 200-4R -- it was just too damm fat back there ...so I modified my existing crossmember to make it pass under..... and then later I made my own pass-under crossmember. I'll find the post so you can see.
If you are SERIOUSLY considering going to an OD transmission you should consider just going pass-under on the tranny crossmember.... it all around better for removal and installation and the exhaust drops right out.
Let me get some pics/links.
Originally Posted by CanadianRover
Thanks for the feedback carriljc, appreciated.
2.5" Smoothie Ramhorns are aftermarket I assume?
Also, a fatter transmission would be a 5 gear or 6 gear? Something I'm also considering. When I get up to highway speed the engine is loud and revs high like it wants another gear or two.
Cheers,
Mike
It would have been smarter & faster (and cheaper too since I bought a plasma cutter to play with) to buy a Bowtie Overdrives pass under crossmember and just modified the ends to bolt into the "stubs" leftover from cutting my welded-in manual crossmember....
Thanks Eric P, did you notice any difference?
Cheers,
Mike
not really but I didn’t get to make a 1/4 mile pass with the converter on but I have made some passes with the test pipe but short of doing some side by side testing I would have to say no
If you feel that the present system is loud then don't get the Magnaflows. With a 3.70 rear that you have, 70mph is about 3200 rpm, so you would not be happy.
I get a bit hexed when I hear people suggest that removing the catalytic converter will increase horsepower. It is against Federal Law to remove the catalytic from the system. Here in Northern Virginia they look for the cat and if it is supposed to be there they will require you to re-install one or pay a fine. My C3 doesn't need one and my C4 has a High Flow catalytic converter feeding the chambered exhaust spewing clean(er) exhaust. The C4 has all of it's emissions equipment and it is still functional. Between the new catalytic and the Chambered Exhaust the car gained something like 12 hp
You realize, don't you, that you're talking apples and oranges, here???
A C-3, with the OE exhaust, has ONE catalytic converter, therefore the car essentially has a single exhaust system. Your C-4's OE system has two catalytic converters, therefore it's a TRUE DUAL exhaust............Big difference!
The folks I know that removed their catalytic converters have to deal with a DRONE that will not go away.
No drone with my CC system...
Originally Posted by CanadianRover
Thanks.
What does it sound like, is it loud?
Cheers,
Miks
It's louder than stock, but just right IMO.
Remember that '78 was the last year for the big "round" style muffler. GM switched back to the pre '73 oval style in '79.
Magnaflows are the oval style & are also known as a hide-away because they're a lot less noticeable...
You realize, don't you, that you're talking apples and oranges, here???
A C-3, with the OE exhaust, has ONE catalytic converter, therefore the car essentially has a single exhaust system. Your C-4's OE system has two catalytic converters, therefore it's a TRUE DUAL exhaust............Big difference!
This is incorrect depending on the year of the C4. The C4 from 84-91 had a Y-pipe configuration into a single cat. This would have been the X-fire and L98 TPI engines (I do not know about LT5 (ZR-1)). In 92 with the introduction of the LT1 a dual cat configuration was adopted. My 86 and other poster's 88 have a y-pipe config like the original poster's 78.
I happen to also have a 78 like the OP. The real issue with the exhaust is the pancake catalytic converter design, these were notorious for restricting flow, and easily clogging. I have had all three types of exhaust on my 78; OEM when I first bought it in 2004, True duals with no cats using 2.5" RAMS horns (78 L-82 has 2.25" rams horn outlets) and now long-tube headers with x-pipe. I believe the performance is better with the long tubes, but for sound, I think the config where I ran 2.5" rams horns, 65 fuelie front down pipes and 73 big block intermediary pipes without a crossover sounded the best. The X-pipe takes some of the thump out of the sound by smoothing the flow.
This is incorrect depending on the year of the C4. The C4 from 84-91 had a Y-pipe configuration into a single cat. This would have been the X-fire and L98 TPI engines (I do not know about LT5 (ZR-1)). In 92 with the introduction of the LT1 a dual cat configuration was adopted. My 86 and other poster's 88 have a y-pipe config like the original poster's 78.
WOW!! I had no idea. I thought that GM had gotten their s**t together, by C-4 time............
This is incorrect depending on the year of the C4. The C4 from 84-91 had a Y-pipe configuration into a single cat. This would have been the X-fire and L98 TPI engines (I do not know about LT5 (ZR-1)). In 92 with the introduction of the LT1 a dual cat configuration was adopted. My 86 and other poster's 88 have a y-pipe config like the original poster's 78.
I happen to also have a 78 like the OP. The real issue with the exhaust is the pancake catalytic converter design, these were notorious for restricting flow, and easily clogging. I have had all three types of exhaust on my 78; OEM when I first bought it in 2004, True duals with no cats using 2.5" RAMS horns (78 L-82 has 2.25" rams horn outlets) and now long-tube headers with x-pipe. I believe the performance is better with the long tubes, but for sound, I think the config where I ran 2.5" rams horns, 65 fuelie front down pipes and 73 big block intermediary pipes without a crossover sounded the best. The X-pipe takes some of the thump out of the sound by smoothing the flow.
SLVRSHRK, may I ask your opinion as to the performance improvement attributable to your current exhaust system?
SLVRSHRK, may I ask your opinion as to the performance improvement attributable to your current exhaust system?
I would not be fair of me to compare performance just based on the exhaust as my change included the following:
Original:
Comp Cams XE268 Cam (flat tappet)
1969 GM camel hump head equivalent
Edelbrock Performer 2101 Intake Manifold
Holley 6150 Quadrajet Replacement
2.5" RAMS horn cast iron manifolds
65 2.5" fuelie downpipes (non-mandrel bent)
73 Big Block intermediate pipes (non-mandrel bent, and if you have seen these, they have PLENTY of crimps and dents)
Walker Dynomax turbo mufflers (not-straight through)
Newer Setup:
Comp Cams 280 hydraulic roller cam
AFR 195 Eliminator heads
Weiand TeamG single plane intake
Holley Sniper EFI
1 3/4" stainless long-tube headers w/about 15 inches of 3" header collectors
2.5 Inch mandrel bent exhaust system w/x-pipe (I custom fabricated and welded it up. Jet Hot coated inside and out)
Walker Dynomax straight-through mufflers
It's definitely got more go now, but that's a LOT of changes, that's why I only commented definitively on the sound. Doing it over, I don't think I would go through the trouble of the X-pipe. A true dual system definitely has more thump due to the distinct pulses, but the X-pipe does eliminate the drone.
If you aren't going to go full length headers and are staying with the stock L-82, I would not overthink this too much. Like every modification, the benefit depends on the other components E.G. Headers and a big exhaust are gonna make more of a difference the higher performance the engine is, and the stock L-82, while built with really good bottom end components, is pretty mild overall.
Your best best are the tried and true basics, just get to true dual exhausts, and adjust your timing as per Lars papers.
I would not be fair of me to compare performance just based on the exhaust as my change included the following:
Original:
Comp Cams XE268 Cam (flat tappet)
1969 GM camel hump head equivalent
Edelbrock Performer 2101 Intake Manifold
Holley 6150 Quadrajet Replacement
2.5" RAMS horn cast iron manifolds
65 2.5" fuelie downpipes (non-mandrel bent)
73 Big Block intermediate pipes (non-mandrel bent, and if you have seen these, they have PLENTY of crimps and dents)
Walker Dynomax turbo mufflers (not-straight through)
Newer Setup:
Comp Cams 280 hydraulic roller cam
AFR 195 Eliminator heads
Weiand TeamG single plane intake
Holley Sniper EFI
1 3/4" stainless long-tube headers w/about 15 inches of 3" header collectors
2.5 Inch mandrel bent exhaust system w/x-pipe (I custom fabricated and welded it up. Jet Hot coated inside and out)
Walker Dynomax straight-through mufflers
It's definitely got more go now, but that's a LOT of changes, that's why I only commented definitively on the sound. Doing it over, I don't think I would go through the trouble of the X-pipe. A true dual system definitely has more thump due to the distinct pulses, but the X-pipe does eliminate the drone.
If you aren't going to go full length headers and are staying with the stock L-82, I would not overthink this too much. Like every modification, the benefit depends on the other components E.G. Headers and a big exhaust are gonna make more of a difference the higher performance the engine is, and the stock L-82, while built with really good bottom end components, is pretty mild overall.
Your best best are the tried and true basics, just get to true dual exhausts, and adjust your timing as per Lars papers.
Best of luck
Thanks for the feedback, appreciated. You have significant mods, your car is likely much faster now. I'm thinking long tube headers, 3 inch pipe with a cross over and low resistance or flow through mufflers. I will be hoping for about 40 extra HP.
Cheers, enjoy your ride!
A forum member decided to change his original exhaust with the 2-1-2 system to a true dual exhaust system with flow thru mufflers on his 32K, 78, L82. He used a RWHP dyno to plot the change, no guesstimates. Original reading was @175hp to the rear tires, but within the general range for the 78 which might have been about 180rwhp from the factory (depending on what % you want to use for the loss).. Engine compartment was stock. After the change the RWHP was more toward the 200rwhp mark so about a 20hp gain. Add LTH for another 10hp and you will be in around 30 extra horses. If you do not plan to make any changes in the engine compartment than no need for 3 inch exhaust.
His chart:
A forum member decided to change his original exhaust with the 2-1-2 system to a true dual exhaust system with flow thru mufflers on his 32K, 78, L82. He used a RWHP dyno to plot the change, no guesstimates. Original reading was @175hp to the rear tires, but within the general range for the 78 which might have been about 180rwhp from the factory (depending on what % you want to use for the loss).. Engine compartment was stock. After the change the RWHP was more toward the 200rwhp mark so about a 20hp gain. Add LTH for another 10hp and you will be in around 30 extra horses. If you do not plan to make any changes in the engine compartment than no need for 3 inch exhaust.
His chart:
Some interesting numbers for sure. According to published data and I have no idea how accurate they are, the stock '78 L82 was supposed to put out 220 hp at the rear wheels and about 315 hp at the flywheel. The hp increases with exhaust system mods are consistent with what others have reported.
03-12-2024, 10:11 PM
