Inliners International Forums General Discussion Engines Looking for exhaust recommendation for dual to single

I've got a stock '69 Chevy C-10 with original 250. Upgrades are HEI and soon to be Clifford intake, Clifford headers, and Holley 390. I've got jetting "start here" instructions from the Clifford guys, but didn't really get a sense on where to go with exhaust.

For logistics reasons, I need to run a single exhaust, so I plan to Y the pipes together soon after the header collectors. I anticipate this will also give me a "tri-y" effect and get me more midrange scavenging.

What I'd like to know is what size pipe should I use off the collector and what size should I run out the back. Truck is a "driver" (it doesn't carry or tow anything).

Experts... I await your golden words!

If your going to run a single pipe don't buy headers. Simply use the 292 exhaust manifold which uses the 'larger' 2" pipe.

Run it far back & use a 'straight through' muffler. It will be quiet/use less fuel and won't cost much to build/maintain etc.

Headers only assist in the higher (4,000+) range and not needed for normal driving etc.

Save your money & Good luck.

Thanks, but that's not in the plans. I have the headers and so I plan to use them. I'm looking for recommendations on what size pipes to use with the headers.

As stated in the original post, the truck is NOT for hauling or towing. Also stated, I need to run SINGLE exhaust, not dual. Thanks.

XXL
Use what the collector size is It will keep things simple and much easier to deal with. 2 1/4 collectors If your making your own Y pipe you can size it to 2 1/2 Or even a 3inch. You can then down size it to 2 after the muffler.This will help keep some of sound down Out the tail end.
A added Plus in keeping the pipe size down Is it will maybe?? cost a little less money.Along with the noise.
Hope this helps.

One 3" pipe will flow same as two 2"pipes.

You could use a Flowmaster Y collector, if you do, just use whatever pipe size for the two pipes that the colectors are and then go to whatever size the Y collector exits as. At least that's the easiest way I can think of doing it while using the headers and collecting it into one.

XXL, I have a 292 with Stovebolt cast headers. Those have a 2.5 inch exit. The folks at Flowmasters suggested to taper the 2.5 inches to 2 inches, use a y to join the two pipes into a single 2.5 pipe into the muffler and 2.5 out the back. I suggest you give them a call and see what they say about your setup. S

Rule of thumb iv always gone by...Seems to ring true even more for inline motors.

up to 200hp... 2" duals at the most, maybe a 2 1/2 single

200-350hp... 2.5" duals, 3 inch single is usually good

For your setup i would probably do a Y bolting up to your collectors, with a decent sounding muffler that still provides backpreassure. Seems the inline motors like a bit more backpreassure to run the way they like to.

On my 1975 292 (holley 500, offy intake, offy headers, a little internal work) I run 2" duals, but might be able to get away with 2.5. With my 82 k10 with a 292 I run 2" duals as well, but I think the "big" exhaust on an anemic yet torquey stock emissions 250 could be improved by going to a single or smaller duals, as anything beyond 3000rpm suffers.. My v8 trucks definently require a bit more breathing and their running characteritics benefit the bigger pipes better.

XXL, are the headers short or long length?

The only knowledge recommendation I have seen for tying the two collector pipes (three cylinders each) together for a six cylinger engines has been to empty each pipe directly into a common resonator, muffler, or catalytic converter. The larger volume vessel minimizes the interaction between the two pipes as seen at the exhaust valve ports.

An inline six using a single non-header exhaust manifold experiences some exhaust port flow interference due to an exhaust valve opening every 120 crank degrees, more so than on a straight four cylinder engine with an exhaust porting opening every 180 degrees. So using a shorty header, or one like Tom Landgon's Stove Bolt Cast Iron Headers would be beneficial.

I am considering an exhaust arrangement similar to yours, headers into a single exhaust for a truck application. So far, for a dual in/single out muffler I have located the following:

Flowmaster Model 524703, 70 Series Big Block, 2.25" x 2 in/ 3" Out

Dynamax Model 21308 MegaFlow RV

Both mufflers have large volumes, which does raise the question of its effect on performance.

Didn't the later 292 truck engines used a split cast iron manifold (3 cylinders each)? Does anyone know the exhaust system arrangement for the vehicles using these engines? I doubt they used a dual exhaust.

Dear Mr. Winter;

No; They use the manifold I sugusted.

It's similar to the 250, but a little larger and has a 3 bolt flange that uses a 2" header pipe, which is larger than the stock 250 pasenger car's 1 1/2" one.

There designed for 'commercial' use on large trucks and remove the extra heat, when hauling heavy loads etc.

Headers into a single pipe is just a waste of time, effort and money for stock/street (low RPM) engine/usage. Plus all of the extra/unecessary 'plumbing' involved with it.

Happy trails.

John,

I actually have the large single exhaust manifold for the 292 that you suggest.

Maybe I am thinking about the integrated head used on later 250 engines. Didn't they use a a split exhaust manifold?

The Brazilian Chevrolet 250 did use a split exhaust manifold. Did it use a dual exhaust?

"Headers into a single pipe is just a waste of time, effort and money for stock/street (low RPM) engine/usage. Plus all of the extra/unecessary 'plumbing' involved with it." Don't agree with this statement, especially if the system is configured as I previously mentioned. However, I'm open to proof.

The intergrated US head the exhaust is cast as one unit w/a single big exit.,,, IIRC?

12 port Brazilian head has two exits.

MBHD

W;

I'm not familar with what Brazil has/does.

Headers aid in 'exhaust relief' at speeds at/or above 4,000 RPM and why there used on Hot Rods. Operation(s) below that don't require, any "extra relief" is all.

The question stated, he was going to use a single pipe, wasn't going to haul/tow this "driver" and didn't know where to go.

Under those specific needs; 'headers' are of no value, or any of that "extra plumbing" either..

The 292 manifold fits that set of circumstances (unloaded-low RPM) at a low cost, if some "extra relief" were wanted.

Happy trails.

i,ve got a set of new 3 into 1 headers for a 67-72 chevy truck i,d like to trade for a set of cast iron headers. anybody ?
bob
1 423 384 8938 tn

XXL, follow Larrys (twisted6) advise, use what ever the "Y" pipes outlet size is back to the muffler, the drop down 1/4" in diameter for the tail pipe. With a fairly stock engine and no real hard driving, you are not going to see much gain or loss in pipe size. Keep 2" as your minimum size and don't go over 3", and you should be fine. The intake and exhaust ports are the restictions, not the manifold or pipe size.

Joe

Dear Joe;

What you say is true only for a stock 250 like he has.

However; On the 292 engine (same head) the larger manifold removes the added heat (2" pipe) generated by the larger trucks, when hauling heavy loads.

This holds true also when installed on the 250 for added "exhaust relief" and saves the cost of headers for (mildly modified) 'street' engines etc.

This kid's confused enough, let's don't make it worse.

Happy trails.

You're making lots of ASSumptions there... I'm fairly old and not confused. And... as Joe H alludes to above, the topic of this thread is about my relatively stock 250. I don't have a 292. But if I do, I'll know who to check with on manifold selection and exhaust parameters. :p

I am fairly new to the Chevy 6 cylinder, but have been in dragracing and street cars for a lot of years. Dad has been racing since 1955 and wrote a book about Pontiacs. Check the web for
" How to Build Max Performance Pontiac V8s" by Jim Hand. We have our own flowbench and each of has made 100s trips down the drag strip. One night dad made over 20 passes just checking mufflers, and another night made 25 passes checking intake manifolds. His car can repeat with in a few thousands of a second due to traction a wagon has. Its weighs in at 4030lbs with him in it, runs 92 octane pump gas, 462 cu inch with iron heads, leaves the line at 1800 and shifts at 5400, dot tires, full exhaust with x pipe, and he drives to and from the track. It has run as fast a 11.32 @ 117 mph, and now is running 11.60 @ 116 with a factory intake, Q-jet carb, and a factory camshaft from a 65-70 Ram Air GTO.
http://www.youtube.com/watch?v=Ta6kP3itZ...Goerlichs%20GTO

http://www.youtube.com/watch?v=cu4I6gfF68w&mode=related&search=


My car was a 67 Pontiac, alcohol burning 455, full exhaust running 11.0 @ 122 mph with factory short block, iron heads, and shifting at 5300rpm.

I may not know the inline, but I do know engines what makes them work! Joe

2.5".

All the way back.

Here you go http://cgi.ebay.com/ebaymotors/exhaust-2...6QQcmdZViewItem
Something like that should solve your 2 into one problem. I have an idea that that guy may make them to sell.

OOPS, no edit function. Check his ebay store, then if he doesn't have what you need I would send him message asking if he could make it. Your local custom muffler shop should be able to do the same thing though.

Listen to FrenchtownFlyer. He knows!

First, what are you looking for, Horsepower for racing or sound & power for cruising? It makes a difference.

For a basic all around good system for the street, use the Stovebolt cast headers, 2 1/4"-2 1/2" all the way back. Keep the bends smooth and no sharp turns, and for sound, place a LOW restriction muffler right before the rear axle. Cap it off with a nice 3" or larger exhaust tip and you're set! Most Inliners are going to steer you towards what they have tried or use as we all are proud of our rides.

Rule of thumb: Listen to everything, judge for yourself. If you are over 50 years old, you know what to do! If you're under 50, try a system and if it doesn't work for you, change it.

RapRap
1940 ChoppedChevyCoupe

The later model Chevrolet 250's with the integrated intake & exhaust manifolds did have two exhausts from the head. See current eBay item 270179575751. That definitely added complexity and cost to the manifold casting.

There is a guy who taught auto shop at Lassen College I think. He has a "48 Chevy with a 235 that pulls a travel trailer all over. I think he's a member. He put his car on the Dyno at school and did a lot of testing on pipe sizes. I think his findings are burried here somewhere on this board. I think his best all around results for the street were with 2 1/4 to 2 1/2 duel pipes. What doesn't work on my 270 is Fentons into a 3" single pipe then a 3"Flowmaster and exiting infront of the rear wheel. It sounds great but I lost a LOT of top end. With the driver side window down it feels like vacuum cleaner is hooked to your ear.

XXL, Connecting the two pipes together right after the collectors would not give you a tri-Y and could hurt the scavenging if too close to the collectors. Tri-Y's are used on V8's, because they don't fire evenly with respect to the two header collectors. A cylinder fires on the same side as the previous at least twice, once per bank. Winter eluded to that when he mentioned the four cylinder fired every 180 degrees. A V8 is not as simple as two, four cylinders with two collectors. 5 and 7 fire on the same bank, one after the other. The same with 8 and 4. Six cylinders don't have that problem.
Headers are designed for relatively specific applications. Primary tube diameter is dependent on engine size. Primary tube length is chosen for rpm range. Collector diameter also has an affect on power at certain rpm's. Collector volume (diameter and length) effects the velocity of the gases and that in turn effects the scavenging of the cylinders. If you have a 2 1/2" collector and connect a 2 1/2" pipe to it, all the way back to the mufflers, you have a collector the size of a barn. The gases will exit the primary tubes, loose velocity and come to a stand still. All you have is back pressure. No scavenging and little flow.
If you want to use a single muffler, you should merge them, back away from the collectors in a muffler as winter suggested to you. A "Y" pipe would add restriction unless they go into larger pipe as Sam reported from Flowmasters.

If you're thinking race engines sometimes use a long open collector, without a reducing cone, you are right. They are interest only in how much power they can make at 8000 rpm and they could give a crap about scavenging at lower rpm's.

After consideration I think the best course of action is to get the rig to the point that it is ready for it's final exhaust work and take it to a custom exhaust shop that has a reputation for working on Rods and other rigs with special applications. Instead of saying "This is what I want". Ask what they think and if they think there will be any issues with it.
The guy who put 2-1/4 inch duals on my 51 Merc cussed the whole time he was doing it but he turned out a world class job on a car with a stock frame and 2 inch lowering blocks. It isn't something that Exhaust by Mail can handle but it shouldn't be all that bad.

I've finally got (most of) the exhaust on. I was able to get the 2-into-1 part tucked in neatly under the headers so it's down to a single 2.5" pipe as it runs back. This was a critical element in the exhaust as there is simply NO ROOM for anything else as it's verrrrrry low... truck frame sits on the ground. It's currently an open pipe behind the cab, but it will snake around some of the tube frame back-half until it gets up over the rearend on the driver's side. That's where a Flow-type muffler will go. Then it will snake back down until it gets to the center of the rear of the truck, where it'll have a handmade exhaust tip that fits up into the body. Pics when I finally get to that part.

You might be happier with a hooker muffler than flowmaster - the flowmaster tend to resonate a bit..

It's all bundled up and running again. The guy hung the intermediate pipe (the one in front of the muffler) too low, so now it doesn't drop all the way to the ground (I have air suspension) *grumble grumble* ... so I've got to get that fixed. But it sounds pretty good. It's a little louder than I prefer (40 series Flow), but the noise is at the back of the truck, so it doesn't really bother me while driving. Much better than the previous 'whoosh' muffler that was under the cab for the last 8 years. The 2-1 Y is nice and tight under the headers, which gives me the ground clearance I need for this ultra-low truck, but keeping up with collector bolt torque is going to drive me nuts. I can reach 5 of the 6 relatively easily with combinations of ratchet wrenches and sockets, but the back header's back collector bolt is a nightmare to get to and back up with a wrench at the same time. I wonder if I could justify a hydraulic lift in the garage to my wife .

If you take it back to have the low pipe fixed, have him put a tack weld on the nuts. Then you only need one wrench. You could tack the bolts, but makes it harder to replace the gasket.

XXL, you might want to look on eBay under Tools. I was looking at that last night, and there are outfits who make electric lifts that fit in the average home garage and sell for a relatively moderate amount, and you don't need to dig a hole for the hydraulic ram, either. Relatively affordable translates to about $1100-1500 and most of the illustrations show the things with an SUV on them. I've also seen them in person, a friend of mine has one, and they really work great.