Header size - 3.0 ??

[ecm911]

Geting confused .

Car: 3.0 euro SC - track Only.
Heat exchangers gone and off the car. Now looking to put on headers.
Car is stock w/ CIS , smog pump removed located in North east USA.

BA recommends 42mm ( 1 5/8 ") ID
Bursch are 1 5/8 OD
Euro racing headers are 1 5/8 OD

spoke with several mech- ranges from 1.5 OD to 1 5/8 ID.

To say I am confused is putting it mildly.


What do peolpe use?

Thanks again
Earl

[jluetjen]

From talking to Richard Parr at PMO, I've learned that headers are refered to by the OD of their tubing. So a 1 5/8 inch header is actually have more like 1 3/8 inches which is about 35 mm's.

I'm just reporting what I've been told.

[Vipergrün]

Going from memory, I believe the stock heat exchangers are 1.5" OD. I also believe the SSI's for a 3.0l are 1.5"Either should work, however, the torque range would probably be moved around with one vs. the other.

[jpachard]

Headers typically have a .0625" wall, or 1/16" for you fractional types. So with that in mind a 1 5/8" (1.625") Outside diameter equates to a 1.5" inside diameter. I don't understand why folks have insisted on using the OD dimension as the number since that's not the important one. 1.5 ID/1 5/8 OD is what you want though. I hope this clarifies things.

Cheers, James

[Bill Verburg]

The size and length you want depends on the size of the engine, cams, gearing, and where you want the powerband. For a stock 3 l SSI sized headers @ 1 1/2" OD(1 3/8" ID) are pretty decent, w/ bigger cams and a higher powerband 1 5/8"(1 1/2") might help. You can also juggle w/ the length of the primaries, longer moves the powerband lower in the rev range, shorter higher. A nother variable will be the collector size and design.

W/ stock cams the lack of overlap severly limits the scavangeing effects of true headers. So you are mostly just looking for good flow. In general you want the smallest pipes that will still flow well at max revs.

[ninesixfour]

Originally Posted by Bill Verburg

W/ stock cams the lack of overlap severly limits the scavangeing effects of true headers. So you are mostly just looking for good flow. In general you want the smallest pipes that will still flow well at max revs.

So do you think the power gain isn't enough to be worth the money and time spent on a set of racing headers? What are we talking here, 5hp or less depending on muffler choice?

[Bill Verburg]

Originally Posted by ninesixfour

So do you think the power gain isn't enough to be worth the money and time spent on a set of racing headers? What are we talking here, 5hp or less depending on muffler choice?

I used SSI's on my 3 liter, Everything else was stock Carrera 3.0 CIS. The ssi's gave a little more of a cammy kind of effect above 4k, nothing wild but nice.

SSI have 1 3/8" ID primaries(35mm) which is 1.5" OD(38mm), exhaust is usually designated by OD.

It is a lot of expense(you also need oil lines and muffler) for not a huge reward on a stock 3.0. Is it worth it? I was happy. For others I dunno

as the engines get bigger, the SSI option is increasingly a poor one. I tried them on a stock 964 engine for awhile and they totaly strangled it.

cams have a similar effect as displacement increases wrt exhaust needs. For a cammed 3.0 SSI will be good but larger ~1 5/8" OD(41mm) will be better especially for a race car that is always operated above 4.5K, for a street car that is usually operated below 4k they are going to be a good and durable option.

lastly materials are a big deal wrt exhaust. In the early days of 911 a CO monitor was a desireble option because the mild steel pipes would rot allowing exhaust gas into the cabin, so for a heater box car ss inner pipes are an absolute necessity for safety. For non heated cars the safety issue is moot but mild steel has a very limited life in the highly corrosive exhaust pipe arena.

[ninesixfour]

Originally Posted by Bill Verburg

I used SSI's on my 3 liter, Everything else was stock Carrera 3.0 CIS. The ssi's gave a little more of a cammy kind of effect above 4k, nothing wild but nice.

SSI have 1 3/8" ID primaries(35mm) which is 1.5" OD(38mm), exhaust is usually designated by OD.

It is a lot of expense(you also need oil lines and muffler) for not a huge reward on a stock 3.0. Is it worth it? I was happy. For others I dunno

as the engines get bigger, the SSI option is increasingly a poor one. I tried them on a stock 964 engine for awhile and they totaly strangled it.

cams have a similar effect as displacement increases wrt exhaust needs. For a cammed 3.0 SSI will be good but larger ~1 5/8" OD(41mm) will be better especially for a race car that is always operated above 4.5K, for a street car that is usually operated below 4k they are going to be a good and durable option.

lastly materials are a big deal wrt exhaust. In the early days of 911 a CO monitor was a desireble option because the mild steel pipes would rot allowing exhaust gas into the cabin, so for a heater box car ss inner pipes are an absolute necessity for safety. For non heated cars the safety issue is moot but mild steel has a very limited life in the highly corrosive exhaust pipe arena.

This would be for an E class Euro 3.0 engine so stock everything including cams. Right now I'm running a USA cat and no muffler which is probably less power than the correct Euro pre-muffler and stock muffler. What would you recommend?

[Bill Verburg]

Originally Posted by ninesixfour

This would be for an E class Euro 3.0 engine so stock everything including cams. Right now I'm running a USA cat and no muffler which is probably less power than the correct Euro pre-muffler and stock muffler. What would you recommend?

Either ssi(heat/ss) or George Narbels European headers (no heat/mild steel)
assuming you need mufflers either dual Coasts or dual Phase 9

ssi can also be purchased w/o the heater box to save a few bucks and ounces

[ninesixfour]

Thanks Bill.