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Discussion Starter · #1 ·
I’m thinking about upgrading my exhaust manifolds to the 2.5” ones to help my sb 350 exhale a little better.

will the 2.5” manifolds connect to the 350’s heads no problem? Also I’m assuming I would need all new exhaust pipes/mufflers as well correct?
 

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I’m thinking about upgrading my exhaust manifolds to the 2.5” ones to help my sb 350 exhale a little better.

will the 2.5” manifolds connect to the 350’s heads no problem? Also I’m assuming I would need all new exhaust pipes/mufflers as well correct?
what is the current size of your exhaust pipes? and how is it configured? dual exhaust, H- or X-pipe crossover, dual manifold?
 

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There may (emphasis on may) be an issue if the heads are Vortec. That's something I read, but do not know to be fact.

If your car is an x body (62-64), the 2 1/2" ram horn manifolds will fit. Other x body cars should also accommodate them but I am not sure.

Here are some links to some interesting reading on the subject:




The OEM dual exhaust configuration for the 300 hp sbc engines from 62-64 had 2 1/2" ram horn manifolds, 2 1/2" exhaust pipes to muffler, 2" tail pipes from mufflers. Muffler had inlet/outlet to match.

The correct alternator bracket is needed but is a detail that is easily resolved with the correct parts.

When I converted my '63 sbc to the 2 1/2", I bought two left side manifolds and sawed/ground off the bracket on one of them (they are ambidextrous). Put the 'bracketless' manifold on the right side. The 'worked' portion of the manifold goes back by the number 8 cylinder and is basically hidden.

Pete
 

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Discussion Starter · #5 ·
sorry I should of mentioned. It’s a ‘63 impala with a 70s 350 sb. It has rams horns right now with the alternator on the driver side but the current manifolds are 2”.

thanks Pete, the info is very informative.
 

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I bought two of these for my car:


They replaced 2" ram horns that were on the 327 that was in the car when I bought it. When I installed a '383' (based on a 350 block) I upgraded to the 2 1/2" manifolds.

If you upgrade, you will need new exhaust pipes, a new heat riser valve (or a spacer), new mufflers, and possibly new tail pipes (why not? everything else is being replaced).

Here's a pic of the finished 'de-bracketed' product:

Hood Automotive lighting Vehicle Car Steering wheel




I can provide a parts list if you're interested.

Pete
 

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Discussion Starter · #7 ·
Yeah pete if you could provide the parts list I’d appreciate it. Do you know how Chevrolet back in the days would of set up the exhaust with the 2 1/2” rams horns?

Dual exhaust, X or h? To be honest I’m not even sure what the difference is.
 

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Yeah pete if you could provide the parts list I’d appreciate it. Do you know how Chevrolet back in the days would of set up the exhaust with the 2 1/2” rams horns?

Dual exhaust, X or h? To be honest I’m not even sure what the difference is.
they used to say there was no difference but in reality there is.

Bicycle part Material property Auto part Metal Pipe


Yellow Motor vehicle Fixture Automotive exhaust Automotive exterior
 

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Attached is a depiction of the x body dual exhaust; it's not to scale but shows the basic configuration; it's from the '61 ShopManual.

Also attached are screen shots of two pages from the '63 Assembly Manual (they are titled for the 409, but the 300 hp 327 is the same).





Here's a link to the system I installed; it fit like a glove. It does not have the resonators, but they are optional in my opinion.


And here's a link to the spacer (in lieu of the heat riser valve) I used:


If you want the heat riser valve, Show Cars sells them too (as do other vendors).

I could not find the receipt for the hangers.

Oh, I painted the manifolds a basic gray using a simple Rustoleum high heat spray paint (before installing them). I 'spot' touch them up with a brush as necessary.

Hope this is helpful.

Pete
 

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I want to correct something I said in a previous post (I have edited that post).

I said that if the car was newer than '64 the ram horns would not fit. I crossed up my 'full size' with the Chevelle when I said that. They do not fit in the Chevelle. Sorry.

Pete
 

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Upgraded my Rams Horns from 2" to 2.5" as I restored my 64. At the time I upgraded them, I still had the 350 based 383 in the car and the larger manifolds made a big difference in performance. I changed the mufflers at the same time (still stock type), so it could have been the old mufflers being clogged or something.
Bicycle part Tool Wood Auto part Automotive exterior



The difference between 2 inch and 2.5 inch manifolds is HUGE.
Motor vehicle Automotive tire Rim Gas Automotive wheel system
 

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Discussion Starter · #13 · (Edited)
Thanks Dave. Did your manifolds come with an “ear” for the alternator to be positioned on the driver side like they did in ‘64?

I’ve seen a few other sets that have different looking provisions for the alternator like the ones Pete posted above.

I’m going to look at my mine today to see what my drivers side manifold looks like.

Ps what have you guys ran as exhaust X or H pipe?
 

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I got my 2.5 inch manifolds as reproductions from Paragon Corvette. They have the correct casting numbers and the correct alternator mount for my 64 with 327/300. Those Corvette guys really sweat the details, so I did not mind paying the premium for them. I also had them ceramic coated, which has held up really good.
 

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Thanks Dave. Did your manifolds come with an “ear” for the alternator to be positioned on the driver side like they did in ‘64?

I’ve seen a few other sets that have a different looking provisions for the alternator like the ones Pete posted above.

I’m going to look at my mine today to see what my drivers side manifold looks like.

Ps what have you guys ran as exhaust X or H pipe?

The manifold I used was for the '63. It requires the complementary alternator mounting brackets. The '64 manifold are just like dcairns shows and use different alternator brackets. Either manifold will fit on either car but the alternator brackets need to go with them.

dcairns bought the 'clean' passenger side manifold (no difference between 63 and 64). I saved about $100 (as I remember) 'making' my own 'clean' manifold from a driver's side.

Function and fit, either works equally as well. It was surprising easier than I thought it would be. Mine did NOT look as nice as dzauto's but I was VERY happy with the results.

If you are happy with the way your alternator mounts now, you likely can use your existing mounts if you replicate the existing manifold casting (except for the diameter).

As for X or H? I was not at all interested. I did NOT want anything hanging down any lower (reduced ground clearance). Because the entire system requires fitting BELOW the frame, the entire system would have to be custom. That's simply a conclusion. Because I did not use them I can't state claim that as fact.

Here's a pic of the exhaust system as it 'fits' within the x frame. It's not my car, but my car looks like that (except for the glass packs in the pic; I've got the mufflers that came with the system I bought) from that view. The assembly manual drawings show this configuration.

Also attached is a side view of my car. I'm (on purpose) 'up' about 3" in the back; I used the station wagon springs specifically for that purpose. Just a 'visual' for info.

Pete

Photograph Product Organism Font Screenshot




Wheel Tire Car Vehicle Plant
 

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Discussion Starter · #18 ·
Took the alternator out of the car to take a look at what the “ear” on the driver side manifold looked like cause I think I’ve seen two different styles on rams horns. Any how looks like the more commonly seen.
Motor vehicle Hood Automotive lighting Automotive tire Bumper

Ps ignore the dirty engine. I hope to pull the engine & degrease/sand/repaint it & the entire engine bay some time later this year.🤞🏽
 

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That is the '63 version 2" manifold. The 2 1/2" look the same except for the size/diameter. A non-a/c car would have had the 'clean' (no bracket) manifold on the passenger side (I think I crossed that up in a previous comment; just a brain fart). The Dorman 674-504 is a direct 2 1/2" replacement for your manifold. The alternator brackets should simply cross deck. Fab, or buy a passenger side one.

How 'original' looking are you trying to get (if at all)?

I ask because dcairnes 're-did' a small block for his '64 that would be a great model to follow.

Pete
 

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Discussion Starter · #20 ·
As far as originality it’s a later model engine(350)but I have thought about slightly dressing it up as a 327 from ‘63. Mainly just valve covers & oil filler tube in the intake. Not to sure yet.

i am starting to look at mufflers. Not sure what I want to go with yet. I like the rumble the car produces now upon acceleration. It’s not to loud but not quiet either(magnaflows)
 
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