Q: re: Exhaust Manifolds: - Impala Tech
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post #1 of 17 (permalink) Old 10-19-2010, 03:46 PM Thread Starter
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Q: re: Exhaust Manifolds:

Howdy, all. Time for a new question! (yay).

Was there something special about those double-hump style exhaust manifolds that were so common on the 60's small blocks?

And: Would they bolt-up to a mid-80's 305, if I wanted to make it look more like a real 60's motor - or would it simply be better to just slap some headers on it?

Inquiring minds want to know.

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post #2 of 17 (permalink) Old 10-19-2010, 05:14 PM
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It would be better from a performance point of view with headers.

It would look more original with "Rams Horn" cast iron manifolds prominently used on all small blocks in the fifties and sixties (which actually breath better than the log style used in the eighties or the "W" manifolds of the mid to late seventies which were redesigned not for improved exhaust flow, but to clear emissions equipment).

Beware of the Corvette Rams Horn which is a 2-1/2 inch casting (better for flow) as it dumps straight down right into your cross-member and motor mounts (the Corvette engine is held at all four corners with nothing under the engine to get in the way). A rams horn manifold needs to be angled back at a 45 angle at the exit to hook up a 2-1/8th inch tail pipe.

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post #3 of 17 (permalink) Old 10-19-2010, 06:03 PM
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What car do you have the 305 in? Assuming the 305 sits the same way the other Gen I small blocks do, the straight down rams horns in 2.5 inch flavor will fit. The head pipe is a bit tight, but will fit. These manifolds were a stock item for the 327/300hp engine.





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post #4 of 17 (permalink) Old 10-20-2010, 09:59 AM Thread Starter
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always learning interesting stuff here at Impalas.net! Thanks, guys !

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post #5 of 17 (permalink) Old 10-20-2010, 03:38 PM
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I thought ram's horn manifolds can only used with specific frames.
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post #6 of 17 (permalink) Old 10-20-2010, 04:40 PM
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Medisalle didn't say what car he was thinking of putting them on, I was assuming the 63 Impala in his signature. And I do know the rams horns were used in 61-64 Impala/Belaire/Biscayne and a whole lot more that I don't have specific knowledge of. I seem to recall there is a variant of the rams horns that angles to the rear about 45 degrees (like Big Dave mentioned) that was used in Chevelles and such, but I only recall seeing that some where, not with any certainty.



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post #7 of 17 (permalink) Old 10-20-2010, 08:48 PM
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Quote:
Originally Posted by dcairns View Post
What car do you have the 305 in? Assuming the 305 sits the same way the other Gen I small blocks do, the straight down rams horns in 2.5 inch flavor will fit. The head pipe is a bit tight, but will fit. These manifolds were a stock item for the 327/300hp engine.

These appear to be the same as on my 64 Impala SS convertible 283 obviously installed by a previous owner. Would they most likely be 2.5s or not? Any way of identifying them other than with a tape measure?
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post #8 of 17 (permalink) Old 10-20-2010, 09:58 PM
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These appear to be the same as on my 64 Impala SS convertible 283 obviously installed by a previous owner. Would they most likely be 2.5s or not? Any way of identifying them other than with a tape measure?
Casting number. Every cast part that Chevrolet used has a casting number that identifies WHAT it is. It also has a Date Code that identifies When it was made.

Further if it was a sourced part (not castyt by GM in house) it will have a Vender ID code and further Info to assure quality control.

Only the Corvette got the 2-1/2 inch small block Chevy Rams Horn exhaust manifold. it is the reason the Corvette has a different horse power rating for an engine that in a passenger car was rated at 10 to 25 horsepower less for the identical eengine (same pistons, heads, cam, and carbs). The Corvette is the flagship of the Chevrolet fleet nothing was allowed to have a higher rated horsepower than the Coirvette was to continue to justify it's high cost.

Of course since every part on a Chevy interchanges (may not work in all aplications but you can at least bolt it on), nothing that was an exciusive Corvette part stayed that way long after the waranty expired.

Big Dave

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post #9 of 17 (permalink) Old 10-20-2010, 11:06 PM
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Quote:
Originally Posted by Big Dave View Post
Only the Corvette got the 2-1/2 inch small block Chevy Rams Horn exhaust manifold. it is the reason the Corvette has a different horse power rating for an engine that in a passenger car was rated at 10 to 25 horsepower less for the identical engine (same pistons, heads, cam, and carbs). The Corvette is the flagship of the Chevrolet fleet nothing was allowed to have a higher rated horsepower than the Corvette was to continue to justify it's high cost.

Big Dave
I have heard some argue about this, but Colvin's "Chevrolet by the Numbers" says they 2.5 inch exhaust manifolds were used on 327/300hp engines in full size cars.

Right side 2.5 inch 3797942 62-64 full size 327/300

Left side 2.5 inch 3846563 64 full size 327/300 (different manifold for earlier years with generators).




Quote:
Originally Posted by Red64SS View Post
These appear to be the same as on my 64 Impala SS convertible 283 obviously installed by a previous owner. Would they most likely be 2.5s or not? Any way of identifying them other than with a tape measure?
As Big Dave said, casting numbers. You probably have 3846559 on the left and 3747038 right.
Also you might be able to tell just by looking at them. The 2.5 inch manifolds flare out just before the flange as you can see in this picture.




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Last edited by dcairns; 10-21-2010 at 11:09 AM.
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post #10 of 17 (permalink) Old 10-21-2010, 10:37 AM
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Depending on source books you look at the 2.5" rams was used on "corvette only" (usually Non GM, or multi generation), however In the GM Shop Manual for 1962 and supplements 63 and 64 the 2.5" Rams get put on Full Size cars with the 300/327, along with the Carter AFB vs the RC. The Straight dumps miss the engine support just fine on these years.
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post #11 of 17 (permalink) Old 10-21-2010, 11:37 AM
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Quote:
Originally Posted by dcairns View Post
I have heard some argue about this, but Colvin's "Chevrolet by the Numbers" says they 2.5 inch exhaust manifolds were used on 327/300hp engines in full size cars.

Right side 2.5 inch 3797942 62-64 full size 327/300

Left side 2.5 inch 3846563 64 full size 327/300 (different manifold for earlier years with generators).






As Big Dave said, casting numbers. You probably have 3846559 on the left and 3747038 right.
Also you might be able to tell just by looking at them. The 2.5 inch manifolds flare out just before the flange as you can see in this picture.
Thanks for the good explanation! I have 3846559 on the left and no flare, so that answers my question.
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post #12 of 17 (permalink) Old 10-21-2010, 12:24 PM
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medisalle-

I don't know how much a 305 would benefit from the 2.5 inch manifolds, but I am sure they would help at least a bit.

Also, "double-hump" is commonly used to describe the casting mark of a particular cylinder head also popular back in this era, so you should refer to the manifolds by the more popular "rams horns" to avoid confusion.

I find your idea of dressing up your 305 to look like a 60's engine intriguing. I have done much the same with my 383 stroker (70's 350 with a stroker crank). So that is not really a 327 in my picture



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post #13 of 17 (permalink) Old 10-21-2010, 02:56 PM
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I don't know what books say but the 62-64 full size chevrolet with a 327/300 hp came standard with the 2.5" "Rams Horn" manifolds. I think the corvette only legend came about because they were much more prevalent on the vette and most 327's in the full size were the garden variety 250 HP. But I will assure you that the 2.5" will fit on any of the small block engines from those years and will fit the chassis just fine. I happen to have one out in my garage right now that has the original factory 327/300 HP with 2.5" manifolds (with 2.5" headpipes and mufler inlets). Mine were factory installed by the General and have not been removed since new. If the books say otherwise they are incorrect.

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post #14 of 17 (permalink) Old 10-22-2010, 06:03 AM
 
 
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MY 64 came with a 327/300 and it has the 2.5 inch rams horns. Sadly they are now bolted to a 283.
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post #15 of 17 (permalink) Old 10-22-2010, 09:54 AM Thread Starter
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thanks, all - and for the record: I was talkin' about this 305 being in my '63 Impala .. I've learned a TON so far - thanks!

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post #16 of 17 (permalink) Old 10-22-2010, 10:13 AM
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thanks, all - and for the record: I was talkin' about this 305 being in my '63 Impala .. I've learned a TON so far - thanks!
Ditto that! Thanks here also!
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post #17 of 17 (permalink) Old 10-25-2010, 10:26 AM Thread Starter
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Thanks, ya'll. As i've said before: i'm not really overtly interested in 'horsepower' and all that what-not.. I don't really care. A*N*Y*T*H*I*N*G would be better than the horrible mess it's got under the hood now. I want it to: (a) run quietly and move the car in a forward direction, and (b) be painted orange. LOL. I know it's alot to ask - but honestly, there are NO 327's and 350's here in my state for under $1000's of dollars - apparently someone's buying up all the 350s, so they're hard to come by. I'm not spending too much more on this car.. I'm seriously falling out of love with it, and it's not worth a $1,000.00 engine. A measly little 283 or 305 would be fine. I just like the looks of the rams horn manifolds, and I'll probobly add an HEI distributor - but that's about it.

I'll be happy when I can take it on a 50-mile cruise and not have to listen to it whine, and watch it burp oil all over the place. If a 305 can haul my '89 nicely down the highway, I'm sure it'll do the same thing for this old wretch. I'm half tempted to sell this '63 and keep the '89 Caprice I'm currently getting ready to sell.. at least I love my Caprice!


Thanks also to D.Cairns - I got the PM and the pics.. it looks awesome! I would never have guessed!

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