Need exhaust manifolds

[Chevy Chase]

The 57 wagon exhaust is creating a tapping noise. Inspected the headers and the ox2 sensor wire is charred near the header tube. Also before the collector the header tubes have long flat spots from speed bumps? I'm guessing a header gasket has a burn hole. The 57 has 2" dropped spindles. The engine is a 350, alum heads with straight plugs, somewhat lumpy unknown cam, unknown headers, alum intake, and FI Tech fuel injection.

The plan is to install Sanderson ceramic coated cast iron exhaust manifolds for more ground clearance. Do not want headers. It looks like the Sanderson manifolds will come too close to the spark plug wires tho. See photo. I kinda like the looks of them but will early Corvette-style 2-1/2" ram horn manifolds be less troublesome? Hoping to here from someone who has first hand knowledge with cast exhaust manifolds. Price is not an issue. Thanks, Chevy Chase-Sanderson-Headers-QP1000 (2).jpg

[BamaNomad]

I've never used Sanderson's, but they certainly 'look' better than stock cast iron. I like the 2.5" rams horn manifolds for a mild performance engine; you can buy reproduction versions for a great price at Speedway and perhaps other sellers. They were used in mis-60's Corvettes; the corvettes used heat shields behind the manifolds and routed the spark plug wires behind and up from the rear of the engine to the distributor...

[markm]

I've never used Sanderson's, but they certainly 'look' better than stock cast iron. I like the 2.5" rams horn manifolds for a mild performance engine; you can buy reproduction versions for a great price at Speedway and perhaps other sellers. They were used in mis-60's Corvettes; the corvettes used heat shields behind the manifolds and routed the spark plug wires behind and up from the rear of the engine to the distributor...

Good plan.

[enigma57]

I bought a couple sets of Sanderson QP1000 cast-iron manifolds some years back for a 427 small block stroker. Plans changed and I sold one set. Still have the other set here. I special ordered them (passenger side manifolds for both sides) as I wanted both to drop at the center.

Very good quality castings. And heavy. Should last a lifetime.

Are you running stock '55 - '57 front engine mounts? Or the wider stance Hurst cradle type crossmember with '32 - '48 flathead mounts at the ends?

The Sandersons I have (because they are both passenger side castings) can fit very close to the '58 and later side engine mounts (depends on heads, not all are the same). So if running '58 and later side engine mounts, with the one side, you could run machined spacers similar to the ones used with large tube Stahl headers.

Anyway, I am sure you will like the Sandersons. Very high quality castings.......

https://www.sandersonheaders.com/sanderson-qp1000-cast-series-small-block-chevy-header-set.html

Happy Motoring,

Harry

P.S. >>> The Sanderson manifolds use a 3-bolt pattern with flat flange where the pipe attaches (not machined for donut gasket). So definitely consider copper flange gaskets...... These may fit...... Measure bolt spacing of 2-1/2" copper gasket and flange to make sure......

https://www.sandersonheaders.com/sanderson_copper_collector_gaskets_-pr-.html?category_id=8

[Dave the Wave]

i have "hedman`s" on my small block, they too, have`nt much clearance for the spark plug boot. only ones that actually clear good are "accell`s SUPER STOCK" wires, and come in all colors.

[Chevy Chase]

Thanks for the replies. Printed a list from Wilcoxcorvette.com of all the rams horn exhaust manifolds casting numbers from 1963 to 1972. Went on eBay and CL to get an idea of what they all look like. Conclusion: OEM GM exh manifolds are ugly. The jury is still out on the Sanderson cast exhaust manifolds because it seems they will create heat issues for the GM HEI spark plug wires. Therefore it looks like Summit Racing's Smoothie ceramic coated 2.5" outlet #G-9200S are a good solution. See photo. Can't complain about the price either at $200.99. Summit reducers recommended are # G4755 3 bolt, 2.5" reducer to 2.0", only $22.99. Also, free shipping.

Harry: I like the idea of using copper gaskets for the collector. The copper material probably makes them reusable and of course no burn through.emoji mask (2).pngsum-g9200_sr_xl.jpg

[WagonCrazy]

I second the recommendation on using copper gaskets. I use them and have not had leak issues.

[enigma57]

Which ever way you go with your choice of exhaust manifolds, I am sure you will like the copper gaskets wherever you have a flat gasket surface to seal, Chevy Chase.

If you go with the ramshorn manifolds, they will take a donut gasket, though. If I may ask, why would you go with the 2-1/2" outlet ramshorns and reduce head pipe sizing to 2"?

When I built my 1st '55 Chevy many years ago, I initially ran '55 - '56 manifolds port matched to the 461 heads on my 327 and 2" duals. These manifolds are terribly restrictive. So when I could afford to, I bought a set of 2" ramshorn manifolds and ran them along with new head pipes and the same 2" duals. The engine sounded and ran noticeably better. Eventually, I scored a set of the 2-1/2" ramshorns and had a new 2-1/2" dual exhaust system with turbo mufflers made for it (this would have been around 1971 or early 1972). Again, the increase in power was noticeable over the previous 2" system.

Dug out my exhaust sizing chart just now. Its for full length muffled systems. Not perfect, I'm sure but a good go-by......



2.0" duals will support a max 200 HP
2-1/4" duals will support a max 250 HP
2-1/2" duals will support a max 400 HP

My Note: Personally, I would think 2-1/2" duals would support more like 350 HP.

Of course, you can run a higher horsepower engine through smaller pipes than this, but the exhaust will begin robbing power at higher RPMs as backpressure builds and begins to work against you.

A good compromise for a mild to moderately warmed over 350 engine in a road car running 2-1/2" ramshorn or Sanderson manifolds might be a 2-1/2" dual system back to some good flowing 2-1/2" Walker DynoMax Super Turbo mufflers (largest and longest oval case you can fit in space available) and run 2-1/4" tail pipes. And a good H-type crossover (balance) pipe same size as head pipes, of course.

Happy Motoring,

Harry

[Chevy Chase]

unnamed (1).jpgHarry, Good information. I thought about the exhaust diameter measurement I posted. The measurement was 2" diameter for the tail pipes. Today measured the header pipe diameter in front of the muffler and it is exactly 2.25" diameter, which depending some variables will support 250 hp or a wee more. Attached is another hp chart based on exh dia. When you compare exh dia to hp ratings posted by GM, Gm is far more generous with hp ratings. May be a matter of gross hp compared to net hp.

Looks like I'll be installing 2.5" diameter head pipes and mufflers that are 2.5" in and 2.25" out. I don't believe tail pipe diameter is as critical.

Had a little bit of memory lapse on the doughnut gaskets for the cast iron manifolds. Summit Racing sells SCE copper gaskets with reinforced bolt holes for the exh manifold to cylinder head part #SCE #4311. I plan to go with them. Cheersemoji mask (2).png

[Dave the Wave]

look into "remflex", i swear by them.

[Chevy Chase]

Dave, Thanks for the recommendation. I like the description of them and the reviews. I will give them a try.

[enigma57]

I like your exhaust sizing chart better than the one I have, Chevy Chase! Seems more plausible regarding pipe sizing in the 2.0" - 2-1/4" - 2-1/2" range based on my past experience. The pipe sizing you stated should work well for you. The exhaust gas will have cooled a bit by that point and 2-1/4" tailpipes should do the job.

I was a pipefitter in a former life, so I look at designing a pipe system from a standpoint of flow versus friction losses in turns and offsets. Just make sure the inner core of your mufflers is a full 2-1/2" sizing and you should be fine. Even if you need to run 2-1/2" inlet and outlet and transition to 2-1/4" using a reducer fitting at the discharge end of your mufflers. I like the DynoMax Super Turbo muffler on the street because they flow better than other designs such as Flowmasters and are much quieter than Flowmasters. If you run a full sized H-type crossover (balance) pipe as well...... That will boost torque and quieten / smooth out the exhaust note a bit, as well.

Regarding pipe sizing...... If you are running a modern overdrive transmission with lockup converter and rear gearing that pulls engine speed down to around 2,000 RPMs when cruising at 70 MPH...... Thinking of it from 'the engine is an air pump' perspective...... You probably won't need as large an exhaust system as the same size engine would if it were geared lower and spinning faster (and pumping a greater volume through the exhaust system).

On the other hand, a larger system doesn't hurt anything and I have run a 2-1/2" single exhaust system and turbo muffler behind an otherwse stock 170 cu. in. '62 Dodge slant 6 engine and it ran great once uncorked (original system was only 1-3/4" diameter on those cars). My original exhaust manifold was cracked and I went to the wrecking yard and found one of the 225 manifolds with 2-1/4" outlet that MOPAR used in the early '70s to boost mileage during the 2nd Arab oil embargo. 2-1/2" exhaust tubing slips nicely over 2-1/4" so I kept about 3" of the 400 series stainless steel MOPAR exhaust stub when I pulled the manifold and had a muffler shop bend a 2-1/2" system for the car. Just slipped the new 2-1/2" tubing over the 2-1/4" stub about an inch and welded it on.

Also ran a 2-1/4" single exhaust on a little 1600cc Toyota hemi 4-banger I souped up in the early '80s. Again, ran great. Not overly loud, nice exhaust note when I got down on it and no issues with excess back pressure even if I spun it up past 6,000 RPMs going through the gears (which I did quite often in those days).

I was going to run that size system on my '57 (2-1/2" dual head pipes and 2-1/4" tailpipes) when I drop in the warmed over 292 inline 6 but as I have no tube benders here at home, I decided to scarf up some pre-bent tubing sections off e-bay and cut / fit / weld them to form my exhaust system. Found a really good deal on mandrel bent 2-1/2" tailpipes from Flowmaster, so will go ahead and use them even though 2-1/4" would 'just' do the job. Managed to snag some chambered exhaust intended for 'Vette side pipes so decided to cut the ends off on either side of the straight chambered sections and work them into the exhaust system under my '57 rather than run regular mufflers. If it turns out to be too loud, I'll add some resonators if need be. Or some deadhead J-pipe Helmholtz chambers (closed nodes).

Regarding donut gaskets...... In the '70s I would pick up the 2" Ford versions (I believe they were for early to mid-'60s Ford FE (352 or 390) engines. These really were one of Ford's 'better ideas'. Unlike the standard asbestos (in those days) or graphite (now of days) donut gaskets...... Ford made theirs from a soft metal. And once you torqued them down, they wouldn't leak and they would last longer than the exhaust system. I don't know what soft metal they used, but it was a dark gray colour and reminded me of a soft babbit material. Worked great on 2" Chevy ramshorn manifolds. But Ford never made them in a larger size for 2-1/2" donuts, so had to use what was available when stepping up to 2-1/2" ramshorns or for Chevy big block applications. If I had the stuff here to do it, I'd make some 2-1/2" donut gaskets from either a soft babbit or deadsoft copper for 2-1/2" donuts and they'd last practically forever.

Happy Motoring,

Harry

[enigma57]

look into "remflex", i swear by them.

Remflex is a good brand, Dave. I will be running their #2034 one-piece intake / exhaust gasket on the 292 inline 6 I'm building for my '57 sedan.

Happy Motoring,

Harry

[Dave the Wave]

there`s a happy medium to be found for exhaust gas flow. an old timer, a few years back told me, to small diameter will cause to much back pressure, less flow, as we all know. however, he said to big will cause the gasses to just move to slow, therefor the pipe actually sucks up the heat of the exhaust, actually slowing down the exiting gases. don`t hold me to it, but i read about sizing somewhere a few years back. I THINK it was on flow master`s site.

[BamaNomad]

The smaller the exhaust pipes, the faster the exhaust gas has to flow thru the pipes, and vice versa! If your pipes are too large, the exhaust doesn't do the 'scavenging' action that is desired and you will lose torque! Larger pipes are good for HIGH RPM HORSEPOWER, but pipes on the smaller side are good for low rpm TORQUE. Obviuosly the actual diameters desired are a function of several variables, including CID, expected rpm of operation, etc... Personally if I'm installing headers, I like to keep the primary diameters on the lower side (1-5/8" for small blocks), maybe a bit larger (1-3/4?) for big blocks, although I don't drive big blocks! As the exhaust cools between leaving the engine and exiting out the tail pipes the exhaust gases cool and compress a little requiring smaller tubes for exit.