Inliners International Forums General Discussion Engines Exaust Crossover Pipe

Everything I read about the pipe sizes and mufflers was intersting, however I have Clifford headers and duel exaust on my 250. Someone told me I should put a crossover pipe between the two exaust pipes somewhere between 8 and 18 inches from the header collector. I had never heard of this and I don't even know if it would makes any difference or not. Any ideas from my inliner gurus?

Dear DD;

Headers are specifically designed to get the exhaust gases out of the engine/vehicle as fast as possible.

The 'crosover pipe' has two functions; First it causes a 'ballance' between the pipes reducing the "RAP" sound. Second it makes the twin/dual pipes more stable over the bumps, ruts/vibrations etc.

I personally never use one. In creating the "ballance" & less noise it slows down the gas realease & defeats the job of the headers and nothing is gained.

Patrick's has a dual muffler that works well if you want to reduce noise.

Good luck, John M.....

A crossover pipe tends to improve low end torque and even out the power curve for better response at the expense of peak horsepower. It improves drivabilty as few of us run at maximum RPM for sustained periods. An X type is more efficient than an H type.

I have a H-Pipe on my 235 and a big problem:

(Split header, 2 1/4" pipes, Cherry bombs, H-Pipe 4" bevore the cherry bombs))

On the left pipe that comes from cylinders 1,2 and 3 I have only cold air comming out of the exhaust, on the right side that comes from cylinders 4,5, and 6 the air is hot.

Colortune plug shows bad combustion on 2 and 3

Yes I checked the plugs, wires, ignition and so on. The compression is equal on all cilinders so gaskets and valves are not the problem.

The only thing I can think of is the H-Pipe.

Is it possible that it creates some suction or vacuum in the wrong moment and causes this problems? Flow can be tricky sometimes and cause strabge effects.

I have a mild Howards (3/4) cam so I expected no problems here.

The engine is a fresh rebuild, but idles rugh and got poor milage.

I have always thought that crossover pipes were intalled for equalization. I have a lot of muscle Car friends with Hi-performance motors and only half of them have cross over pipes. The "X" is definately better than the "H" as is scavenges better. I understand from talking to them that these crossover pipes only benefit these big motors at full throttle and really don't increase HP but rather make the exhaust system quieter. The Muscle car guys would love to run 3" or 4" straight pipes but the local police don't like it. The cross overs do reduce the sound by at least 30% so that's the main reason for having them on the street. You don't see true race cars with cross overs so that should tell you something. The less restriction the more power you get.

RapRap
1940 ChoppedChevyCoupe

C-Dan-Dluxe

I have a H-pipe set up on a 235 with a howard M4F cam also in a 52 Chevy pu. With a fresh 235 your compression should be at least 160 across the board with your valves set at .012 & .014. Whats your vacuum guage say? Should be 20+ and steady. I would suspect with "bad combustion" on 2 & 3 ? that the vacuum guage should be moving around. Something is going on, if its running smooth and the guage is steady maybe the exhaust manifold donut is loose. My set up is the following: The front Fenton goes down and across underneath behind the crossmember to the pass side, then the H-pipe. The rear Fenton exits eventually on the drivers side. The pass side because of the extra length of pipe tends to run a little cooler. After thinking abou this I now think your 2 - 3 cyl issue is not related. Check everything again.

52pu

Vacuum is 21 and steady.
Compression is 7(whatever) on all cylinders here on a german gauge - don`t know how to calculate that in US system.

I have a Corvette style (splitted stock)header and both pipes run side by side along the way where the single stock pipe was.

You are right with the donut, it is a bit loose.
I have to tighten it from time to time. But I never thought that it might have that big impact.

Frank

C-Dan,
Maybe its the valve guides for 2 & 3? Was the head reconditioned, new valve guides, seals, inserts? If it don't miss and it runs smooth and the plugs don't fowl I say don't worry.

52pu

The compression gauge is in atmospheres which I believe is ~14-15lbs per.

As far as no real race cars having cross over pipes, I guess Nascar does not run race cars.....

I know from experience,a cross over pipe can sharpen the soft low speed response of an engine with a lumpy cam.

I had the same problem a while back. No hot exhaust out of one pipe, rough idle, poor mileage. The cause was a intake manifold leak at the five/six runner. Suckin air instead of fuel. Engine seemed to run good at higher speeds but would not idle right. Your problem is on two cylinders that don't share a common runner. Pull spark plug wires off one at a time while the engine is running at idle. The ones that drop engine speed when pulled off are making power and the ones that idle speed doesn't change are not. This will confirm you are having problems with two and three and not one and two. Then spray a little WD40 type product (flammable type) on the intake runner where it meets the head and see if engine speed picks up.

Good luck, Gael

Dynamometer tests I have run on a 300 inch motor showed a 5 HP increase (on a 235 HP engine) with a crossover pipe in place. This was on an engine dynamometer under laboratory controlled conditions.

There. Now you have some data to add to the speculation.

Just curious if that 5 hp increase was across the entire rpm range, at peak hp, or at any particular rpm. Does the claim of more low end power hold up?

Can anyone tell me how to tell a Ford 300 six from the 240 six?

Thanks,

Ed Pruss
Longmont, CO

Thanks for the hint Chevyman, I´ll try this and let you know.

Frank

The theory behind the crossover pipe is that it balances the pressure between the two sides of the exhaust banks (extemely sorry that is v-8 speak). Further it helps cancel the resonance of the exhaust sound and gas flow. That means it takes a high frequency wave (short distance between peak and trough) and lengthens it into a low frequency long wave. Thus the sound and gas charge is not continually banging on the inside diameter of the exhaust pipe trying to escape. Theory the gas flow is smoother and faster. How this translates to I6 I haven't figured out yet. The function of any exhaust system is to maintain the velocity of gas flow as high as possible. Remember as exhaust gasses cool they slow down. So really a step system should be best 1 3/4 to 1 7/8 to 2 to 2 1/4. As gasses cool they expand so your fooling the exhaust into a larger area. Yeah right I tried something like that on my 76 Peterbilt w/ Detroit 12. Besides if theory was correct than no manifold/header is needed right. Well I'm a farmer and if I lived in the theory world where everthing works 100% of the time correctly--I wouldn't be farming I would be rich. I6 exhaust still has a head lock on me, good luck and hopefully this doesn't muddy the water.

Dear DD;

PS: An expert is; "someone that gives you 5 times more information than you asked for".

You joined the right club, 'I think.'

John M...

Holly cow have I gotten the responses thanks to everyone. I think I will just leave well enough alone and not use a cross or x over pipe at all I like the sound she makes now and I don't read anyone telling me that if I install one I will do that much better. Thanks guys
DD

Supertraction, as gasses cool down they contract.

Sam, yes absolutely, it should have read to keep the velocity of a cooling gas higher fool it into a larger area.

Thanks

You don't see true race cars with cross overs so that should tell you something. The less restriction the more power you get.

Have you looked under a NASCAR race car lately?
They have been using X style exhaust systems for quite a few years now.
Jim

The crossover actually causes less restriction. How could it possibly cause more restriction?

I am not driving a hotrod, just an old pickup that pulls a travel trailer in the mountains. The deep throaty sound I get is nice so I would'nt want to loose that with any crossover.
If it will give me more bottom end power that is what I am after.
DD

Eric,
The 5 HP increase came at the top end of the power band. The performance increase is proportional to speed and how much backpressure exists in the system at any given speed. In general, the more backpressure you have the more you will benefit from having a crossover pipe. That is why most race cars (e.g. drag cars) with open headers don't need them, but superspeedway cars that have to run a longer system of pipes to get the exhaust past the drivers compartment and out to the outboard side of the track will benefit from them, plus they help in scavenging in that case.

Flyer, thanks for your reply. I figured the increase was at high rpm. Like Desert Dove, I'm looking for more low end grunt.

I have a crossover on my '68 C/10 Chevy pickup. [L6 292 w/ Clifford headers.] The configuration is more like an "N" than an "H" with a 45* angle cross tube between left and right exhaust pipes, after the collectors.
I had it done by Simmons Automotive about 20 years ago. Still works great. They're still there at Country Club and Irvington, in Tucson.

Not brought up here:
Is it really worth the extra plumbing to run duals with or w/o a crossover;
vs running say a 2 1/2" single using a Flowmaster "Y" to join the two collectors?

Hi,

In my opinion the sound is better with duals and the "cool" factor is much higher than a single pipe

Jim