ok guys- have a question- lets say i want to replace my stock exhaust (ive got an all original l-48) and i want to go true dual, no cats- can a 2.5" system hook up to my stock headers without mods? specifically, im referring to the manifold to exhaust hookup. its getting time to replace the rear muffler/y pipe, and i figure just dump the cat and go dual. as it is now, ive got a hole in my muffler the size of my fist.

seems like the catalogs mention 2.5" and 2.25" depending on engine type

im assuming that a big block engine has a 2.5" manifold, and a small block is a 2" diameter.

i dunno im totally confused on what i should order

i know you guys out there have a good answer for this- havent failed yet!!
stevep31638901.4472337963

Well, when I first went to true duals, my buddy that owns a muffler shop,cut the y pipe just past the manifolds enough for him to start there with the pipes on each side. He went back from there with a short piece of 2 in. and then into a 2.5 into flowmasters. He knew I would eventually put on headers and would go with all 2.5. I eventually went with a set of DynoMax ceramic coated headers. Save yourself the trouble and just put the headers on now

Dave

i see your point- makes sense to me, but what about those dual exhaust conversion kits that mid america and corvette central sells such as these:

http://www.corvettecentralexhaust.com/c3perfdual.htm 

would any of these bolt up to my factory exhaust manifold?

That's the system I put on my '78 L82...it hooks up with no problems to the factory manifolds. It's made for them. Of course...this true dual system is for "off-road use only"!

one of the first two should work.

there were no big blocks in 79... only the l-82...  a slightly peppier small block.

I would recommend replacing the manifolds with headers though.

Make sure to use small tube if you do.  like 1 5/8 primaries converging to a 2.5 and then 2.5 all the way back.

[QUOTE=cthulhu] one of the first two should work.

there were no big blocks in 79... only the l-82...  a slightly peppier small block.

I would recommend replacing the manifolds with headers though.

Make sure to use small tube if you do.  like 1 5/8 primaries converging to a 2.5 and then 2.5 all the way back.[/QUOTE]

That's exactly what I did.... (click here to see)

(changed large image to a clickable link - Norsky)

Paul

Norsky38901.892337963

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[QUOTE=LukesVette][QUOTE=cthulhu] one of the first two should work.

there were no big blocks in 79... only the l-82...  a slightly peppier small block.

[/QUOTE]

so i am assuming that the L-82 2.5 system should bolt up to my stock manifolds on an L-48? (i want to switch over to headers at some point, but lack of $$ prohibits that for now besides, i keep reading that the stock rams-horn manifolds work better than people think)

i want the l-82 system so i can order the magna flows with them from corvette central

[QUOTE=stevep316] [QUOTE=LukesVette][QUOTE=cthulhu] one of the first two should work.

there were no big blocks in 79... only the l-82...  a slightly peppier small block.

[/QUOTE]

so i am assuming that the L-82 2.5 system should bolt up to my stock manifolds on an L-48? (i want to switch over to headers at some point, but lack of $$ prohibits that for now besides, i keep reading that the stock rams-horn manifolds work better than people think)

i want the l-82 system so i can order the magna flows with them from corvette central
[/QUOTE]

it should...  doing headers later is fine..  the ram-horns are good as manifolds go..  but arent as good as headers perfomance wise.

thanks for the info guys- think i gots me the info i needs

I bought the 2-1/2" 1974 L-82 pipes from Ecklers. They have a 2" flange that bolts up to your Ramshorn manifolds for about a foot then expands to 2-1/2".

If you decide to go with full length headers, have your pipes installed at a custom muffler shop that is willing to install bare pipes with no cats. The Hooker full length headers aim straight through your crossmember. It is a matter of a straight pipe from the headers back to the rear axle, then 2 90 degree 2-1/2" elbows (available at AutoZone or Advance) to get over your axle. Pretty simple DIY job if you can't find a shop to install the pipes without cats. It is illegal in Nashville and I'll bet it is even more so in regulated NJ.

Dave

[QUOTE=Autom8r]I bought the 2-1/2" 1974 L-82 pipes from Ecklers. They have a 2" flange that bolts up to your Ramshorn manifolds for about a foot then expands to 2-1/2".

If you decide to go with full length headers, have your pipes installed at a custom muffler shop that is willing to install bare pipes with no cats. The Hooker full length headers aim straight through your crossmember. It is a matter of a straight pipe from the headers back to the rear axle, then 2 90 degree 2-1/2" elbows (available at AutoZone or Advance) to get over your axle. Pretty simple DIY job if you can't find a shop to install the pipes without cats. It is illegal in Nashville and I'll bet it is even more so in regulated NJ.

Dave[/QUOTE]

it shouldnt be illegal in NJ if i have historic registration- the car will never really be inspected. but try to get the muffler shops to do it is another thing. for the time being, i think ill stay with the stock manifolds and if i do some engine work later, then ill modify what i have to fit to them.

The cat removal will really wake that L-48 up with about 10+ extra horses. It sure did on my '76 years ago. It was noticeable....

The 1974 (last year B4 cats) 2-1/2" L-82 exhaust pipe kit is Ecklers P/NA3688A for automatic trans., runs $220.00 plus a couple of mufflers, 2-1/2" Walker DynoMax from Advance Auto will easily adapt.

Dave

You can get a complete system from Allen Stainless.  They have regular as well as stainless.  They custom bend the pipes to fit specfic cars.  Then made my 2 1.2 in true dual to fit my 75 automtic.  They have the spec to make a custom "Factory fit" for cars that never had that type of system.  Mine fit very well.

In NJ, you can also get away with a collector car registration. No testing involved outside of making sure the odometer turns (they limit you to 2500 miles/ year)

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stevep316 i have a good set of headers i pulled off my 78 just before PF and replaced them with new flowmasterceramic coated headers.

the old headers are in good shape and have plenty of run time left on them the are nothing fancy but good corvette headers. if you want them i can ship them to you for the ups charge    but i think you would be better off doing a new set to begin with

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Annicorvette
Lifetime member # 35

Rams horns are fine for normal use, however the more gas you can extract from combustion chambers with good flow from the exhaust manifold, the more you can push in through the inlet manifold, hence more power.  We call "headers" "extractors" in Oz for a perfectly good reason.  They help extract the gasses from the combustion chamber.  Just from the way rams horns are cast, makes them have different length tubes for each cylinder.  Headers "should" have identical length pipes for each cylinder to be tuned correctly.  This should ensure you get the same amount of gas moving for each cylinder.  The gas moving through the exhaust then becomes a mutual thing rather than fighting itself as it would with untuned pipes.  Small pipes to larger pipes to the outlet also helps as the gasses expand.

Maybe the master can give us a better explaination?  But that's how I understand it.

Hey anni.....

What do those ceramic coated headers do to your underhood temps????

I was real concerned about that and wrapped mine and they are butt-ugly, but the temp is down.... You may have noticed my hood wasn't open at PF.....

Dave

[QUOTE=annicorvette]

stevep316 i have a good set of headers i pulled off my 78 just before PF and replaced them with new flowmasterceramic coated headers.

the old headers are in good shape and have plenty of run time left on them the are nothing fancy but good corvette headers. if you want them i can ship them to you for the ups charge    but i think you would be better off doing a new set to begin with

[/QUOTE]
that would be awesome! could you send me a digital pic to see what the y look like? i might find them useful.

atom8r

 i didn't notice a change in temp- but before PF i changed the intake, the carb, complete new flowmaster exhaust, keisler 5 speed tranny with clutch-pressure plate-throwout -even new dust covers as well as installed 160 degree thermostate (was more worried about the temp being too low) my car has duel snorkles the snorkle that fastens over the top of the radiator makes it run a lot cooler)guess it keeps the air flowing low around the engine to disapate heat

part 2

stevep316

tomarrow i have to take the wife to the hospita for some test

i have a jeep in the shop with a warped head job to repair and a chevy blazer needing a radiator replacement and am trying to get the vette ready for the homecoming at bowling green in a few weeks the headers are hanging on the wall if i remember the camera friday i will take pictures and post here.

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Annicorvette
Lifetime member # 35

Steve,

Where did you find the snorkles? Are they the factory L-82 tubes??? Mine were missing when I bought the car.

Dave

[QUOTE=Autom8r]Steve,

Where did you find the snorkles? Are they the factory L-82 tubes??? Mine were missing when I bought the car.

Dave[/QUOTE]

actually, my engine is in fact an l-48, and what you see is totally stock and original. its got every single piece it came with from the factory

The only thing on mine that came from the factory is the body......

Dave

looks like circumstance has upped my decision making- last saturday, i was taking the vette out for a ride, i went into a deli for a coffee, and left half the exhaust in the parking lot! turns out there was a deep pot hole that i did not see till too late, and the car bottomed out and seperated the y pipe (which was shot anyway) from the cat! I could not believe the noise it made! almost needed earplugs just to get home! gotta admit id did sound pretty cool with open exhaust!

ordinarily, id be pissed off, but i look at it as a chance to upgrade- after looking around, i think im going with corvette centrals l-82 kit with magnaflows. they seem to have the best price of all the places, including allens stainless and the other big vette catalogs.

anyone have magnaflows? are they good?

anyway, this is what im thinking of ordering:
http://www.parts123.com/parts123/yb.dll?parta~dyndetail~Z5Z5 Z50000050q~Z5Z5Z5ABMTP~P321.55~~~~S1V40RMDO670211510906a~Z5Z 5Z5~Z5Z5Z50000050Q

That looks like the perfect way to go. Price is right too. I like those hideaway mufflers. Mine ruin the looks of the rear end of the car....

Dave

BTW.... When you get ready to unbolt the remainder of the pipes from the ramshorns, it would be a good idea to saturate the studs and nuts with "PT Blaster" and let it sit for a day or two. You can't apply the stuff too much or too often. I did this to a '76 a few years ago and ended busting an ear off the ramshorn, and they are REALLY hard to find now.. I had to give 90 bucks for one back then. I found a couple of spares later on at a junkyard and bought them for $85.00 for the pair. Since everything I have now has headers, I'll part with them If you bust one.Autom8r38931.491412037

[QUOTE=Autom8r]That looks like the perfect way to go. Price is right too. I like those hideaway mufflers. Mine ruin the looks of the rear end of the car....

Dave

BTW.... When you get ready to unbolt the remainder of the pipes from the ramshorns, it would be a good idea to saturate the studs and nuts with "PT Blaster" and let it sit for a day or two. You can't apply the stuff too much or too often. I did this to a '76 a few years ago and ended busting an ear off the ramshorn, and they are REALLY hard to find now.. I had to give 90 bucks for one back then. I found a couple of spares later on at a junkyard and bought them for $85.00 for the pair. Since everything I have now has headers, I'll part with them If you bust one.[/QUOTE] i sure hope that doesnt happen! the nuts/studs are kinda rusty, so ill go very carefully- if i feel its gonna be a bitch, ill have a shop do it.

There is another post where I went into detail on header operation.  It may be quite some time back.  If it isn't found I can redo a very good description of how and why headers work, and the difference in performance in different types of headers.   If anyone is interested let me know.  Be happy to do it.

well, finally took the plunge and ordered a true dual exhaust from corvette centrals exhaust website! i got the true dual kit with the magnaflow mufflers. got all the parts last friday and started to dismantle the old system.

a few observations:
1) a muffler cut off tool and a tap and die set would have been REAL handy to have
2) old cats weigh MUCH more than they appear
3) nothing is more stubborn than that last bolt or nut to remove!
4) there is nothing worse than  that rust particle crap that gets in your hair when youre spending a few hours being up close and personal under the greasy side of your vette!

in the end i took everything off that i could and left the front y-pipe and manifold studs for a competent mechanic to deal with! you could imagine the noise it made as i drove it down to the shop!
all goes well, by tomorrow ill have a sweet new exhaust and a couple of pics to post!


and for the record- the center exhaust hangers will require drilling the cross member to attach them. i thought it would have been a bolt in job, but alas no.

Re: #4...

That crud that falls off under there is always a pain in the eyeballs....

Dave