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I have headers on my 1979 with a built-up engine. However, the car is daily driven and I'm considering switching back to exhaust manifolds. I have Corvette Central's 2.5 inch dual exhaust from the crossmember back. In order to keep 2.5 inch pipes from the engine to the back of the car, I was thinking of using the 2.5 inch outlet Rams Horn manifolds that came on 1963 Corvettes.
The question is: given the similarities between the C2 and C3 chassis, would I be able to use reproduction 2.5 inch downpipes from a 1963 Corvette to connect the manifolds to the rest of the exhaust? That would save me from having to get an exhaust shop to make some pipe and would allow me to do the job myself.
I have done this....and have not run into any issues that I could not easily resolve.
DUB
Out of curiosity, what issues did you run into? I just want to be prepared beforehand so that I don't get stuck halfway through.
Worst case (if the downpipes don't fit) is I can cut out a section of downpipe and clamp on some flexible metal exhaust pipe from AutoZone to get it working lol.
I bought some from Speedway Motors.
I bought them of the "garage sale" area so they were a little less expensive. I also bought some 2-1/2" Header collector to connect the pipes to the manifolds. Silver Manifolds
Last edited by redwingvette; 10-09-2016 at 07:39 PM.
I bought some from Speedway Motors.
I bought them of the "garage sale" area so they were a little less expensive. I also bought some 2-1/2" Header collector to connect the pipes to the manifolds. Silver Manifolds
I didn't realize those manifolds existed, so thank you! I'm now thinking of getting the raw ones and getting some high temperature Rustoleum and saving some $$.
I guess now the only remaining question is about the fitment of the downpipes.
Why would you remove perfectly good headers to put on cast iron manifolds?
They eat spark plug wires on angle plug heads. Last time I had my spark plug wires replaced, 3 of them were damaged. A year and a half later, another one was damaged.
They get really hot (that heat has killed every CS-130 alternator I've put in there, possibly contribute to the engine running hot in the summer, and heat up the footwells... thankfully the A/C works really well).
The guy that built the engine and installed the headers (And put the same headers on his own 1977 Corvette with a 406SBC) doesn't like headers on street cars. His own Vette isn't used as often and is built as a streetable, stock looking 10 second car. Mine is essentially daily driven.
All legitimate issues, but ones with other solutions. And I'm not sure those problems are entirely due to the headers. I would hate to see you switch back to manifolds, lose the performance gains of the headers, and still have the problems with heat.
The heat issues with cast manifolds is nothing like headers. There are shields that GM uses to reflect the heat from plug wires.
The customers I have that have cast manifolds on there engine and drive them daily never complain that they do not have enough power with the 2 1/2" cast manifolds. No burnt wires...no fried starter solenoid.
The customer I have with headers....there are many things they added to try to stop the heat at the spark plug area and or wires being burnt up...and starter shields/blankets.
It is basically a 'plug in and play' scenario. The only issue is may run into is any front engine items that the manifold may need to be attached to. Often time I take my Porta-band and cut off the mount for the alternator made into the manifold and grind it to look nice. Other than that...I guess it will depend on how your alternator mounts and IF you need the provision cast into the manifold to do this.
I used to run headers and looked at running the rams horn manifolds however I found Sanderson and they make high flow cast iron manifolds/headers. Got mine ceramic coated and have been on the car for about 10 years and they're a great alternative.
I run a set of 2.5" C2 manifolds on my wife's 70 LT-1....the C2 headpipes work great in this application. If you have a manual trans I think everything will bolt in but, a TH400 might get in the way of the C2 OEM headpipes. My 72 LT-1 went 12.60's at the drags with these same manifolds....went 12.28@117MPH when I swapped on some headers but, I spent hours porting them and broke $90 worth of carbide burrs porting them for better flow.
I used to run headers and looked at running the rams horn manifolds however I found Sanderson and they make high flow cast iron manifolds/headers. Got mine ceramic coated and have been on the car for about 10 years and they're a great alternative.
I have been thinking about switching to Sandersons to quiet things down a bit. Do they reduce the noise level?
I have been thinking about switching to Sandersons to quiet things down a bit. Do they reduce the noise level?
They are quieter plus a lot less heat and not a single gasket failure. I now run them into a set of side pipes with inserts for track use so more noise from that now.
If you end up with the stock C2 manifolds, you don't want to use Rustoleum on them.
Get them blasted or clean them with wire brushing. Then wipe them down with lacquer thinner and immediately give them a [spray] coating of Seymour "Cast Blast" cast iron colored paint for exhaust manifolds (2000*F). They make a similar product for 400*F, but you want the Hi-Temp stuff.
Spray two good coats of Seymour on the manifolds and let them dry. They will not be cured, so install them carefully so as not to damage the paint. Once the engine is running, the paint will start to cure. It needs to be at exhaust temps for about 4-6 hours of use to fully cure. The cured paint turns into a ceramic coating that does not look to be "painted".
The curing paint smokes and stinks so make sure you have fresh air coming in the car. Once cured, no smell; and your manifolds will look like newly-cast iron....FOREVER. Great stuff. Used it for my '71 and been on those manifolds for over 6 years.
If you end up with the stock C2 manifolds, you don't want to use Rustoleum on them.
Get them blasted or clean them with wire brushing. Then wipe them down with lacquer thinner and immediately give them a [spray] coating of Seymour "Cast Blast" cast iron colored paint for exhaust manifolds (2000*F). They make a similar product for 400*F, but you want the Hi-Temp stuff.
Spray two good coats of Seymour on the manifolds and let them dry. They will not be cured, so install them carefully so as not to damage the paint. Once the engine is running, the paint will start to cure. It needs to be at exhaust temps for about 4-6 hours of use to fully cure. The cured paint turns into a ceramic coating that does not look to be "painted".
The curing paint smokes and stinks so make sure you have fresh air coming in the car. Once cured, no smell; and your manifolds will look like newly-cast iron....FOREVER. Great stuff. Used it for my '71 and been on those manifolds for over 6 years.
1000%
I have done it... and use it and YES...it lasts and looks good.
Get them blasted or clean them with wire brushing. Then wipe them down with lacquer thinner and immediately give them a [spray] coating of Seymour "Cast Blast" cast iron colored paint for exhaust manifolds (2000*F). They make a similar product for 400*F, but you want the Hi-Temp stuff.
I think the high temp stuff is called Hot Spot High-Temperature Cast Iron Coating 16-2668.
Redwing... what did you do for the rest of your exhaust system?
2.5 all the way back from a kit? Custom fabricated? Catylic converters? Keep the Y-pipe?
I bought the same manifold set not knowing that I did not have 2.5 system on my '76 - but I would like to use them.
i have a Magnaflow system with 2-1/4" pipes so I cut the ends of the pipes and welded the 2-1/2" collectors to the pipes and bolted them on. If you have 2-1/2" pipes with flanges you could use the round gasket seals that you can get from any parts store
Last edited by redwingvette; 10-15-2016 at 03:50 PM.
I have the even worse 2.0 RHs. I run 2.25 ex w/H-pipe, cheapo mufflers.
My SB puts out 280 rwhp &315 rwtq. My TQ peaks at 4K so it is not as restricted as my hp. My 218-224 w/1.6 RRs put out 275 rwhp @ 5K
It only gained 4 rwhp to 279 rwhp @5.4K.
I would think my cam should peak @5500.
You can see how it is strangled over 4K.
I have the 2.5 RHs and want to see the diff on the dyno.
I believe there is 20 hp and 10 tq in there.
The idea of 300 rwhp sounds cool to me, 325 rwtq isn't bad either.
Can someone tell me the compression of a 64cc chamber, .060 SB
2 valve reliefs, zero deck, .040 gasket.
For some reason I was under the impression that was 10-1.
Now I am starting to wonder?
The 63 and 64/65 downpipes were made to bolt onto the stock 2.5outlet ramshorn, but the downpipes themselves were a bit different because the 63 has a storage compartment (I think that's the reason).
The only part I was a bit nervous about was the connection between the downpipes and the manifold, but it ended up working out just fine. The downpipes came with a metal sleeve that fit up into the manifold about an inch, and then pressed into the downpipe with a "donut" gasket that sealed against the flared end of the downpipe and manifold. Everything fit as if it was designed to go together.
Notes on installation, in case anyone else goes through this:
The passenger side downpipe is almost touching my starter. I may put in a mini-starter in the future if I notice any heat soak issues (though it was surrounded by 4 header pipes for 45,000 miles without issue).
The intermiediate pipe connections had become warped by the clamps and were no longer round or big enough for the new downpipes to fit into. So, I bought one of these: http://www.harborfreight.com/large-t...der-69549.html It worked perfectly fine for expanding that bit of pipe enough for the new downpipes to fit into. Best of all, it was locally available so I didn't have to wait for shipping.
I was able to get my passenger side header out intact. Disconnect the battery. I didn't and the header ended up arcing on the starter post. After reading that removing (installing) the driver's side header required removing the Z bar for the clutch, I decided to use a sawzall and cut it up in order to remove it.
The AC compressor bracket will need to be removed, since it's held in place by one of the manifold bolts. The stud that was there seemed like it would fit and give the proper clearance with the manifold installed, but the bolt hole to the head was off by a quarter of an inch when it was installed. I'm not sure if it was the original stud, though (it had a hex nut about halfway down the stud so it could be tightened to the manifold and then the mount slid over the end and was held in place by a nut). What I ended up doing was getting a 3/8 bolt 3.5 inches long. I attached the mount to all of the other mounting points, and saw there was a small gap (smaller than the nut on the stud, which was the problem), so I used a small spacer and ran the bolt through the mount, manifold, and into the head. Once everything lined up, it worked well.
The car is already much quieter. The raspiness of the headers is gone (though, I kind of liked that sound). It sounds like the engine is behind me since all of the sound is coming from the mufflers. I haven't noticed much of a decrease in power. The ports on the heads were significantly smaller than the ports on the headers, so I think the headers were oversized for what I have. The manifold ports are just slightly smaller than the ports on the heads, so I doubt there will be much of a difference under 5,000rpms. I'm happy to trade a little top end power for a quieter, cooler car that doesn't eat spark plug wires.
Anyways, I hope this helps someone who is considering doing this sometime in the future.
10-09-2016, 06:07 PM
C2 2.5 manifolds and downpipes on a C3 (79)
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