Author Topic: Exhaust Question... (Read 1758 times)

flat4 · « **on:** August 23, 2004, 08:09:59 AM »

I'm running a 1 1/2 merged header. My exhaust ports are roughly the same size. Is there any performance advantages to moving to 1 5/8 or 1 3/4 merged header? Won't the heads only flow as big as the ports?

Bruce · « **Reply #1 on:** August 23, 2004, 12:46:09 PM »

You have to state the engine combo. Engine size also determines the exhaust flow rate.

flat4 · « **Reply #2 on:** August 23, 2004, 11:48:45 PM »

Hey Bruce...Here it goes...

2110
82mm crank
90.5 pistons
CB CNC round port heads
42 mm intake valve
37 mm exhaust valve
314 lift cam, 452 duration with stock rockers
48 idfs on tall port matched manifolds
8.8:1 compression

Bruce · « **Reply #3 on:** August 24, 2004, 04:13:19 PM »

An engine like that needs a minimum of a 1 5/8 exhaust. Some might suggest it needs a 1 3/4, but I wouldn't.

Geoff · « **Reply #4 on:** August 24, 2004, 04:48:29 PM »

Like Brucie said, stay with the 1 5/8 as I think the 1 3/4 may be just a little too big.

Cameron · « **Reply #5 on:** August 24, 2004, 07:25:40 PM »

Quote

314 lift cam, 452 duration with stock rockers

Wow! 452 duration? You going to run this motor in Formula 1, or something high revving like that?

flat4 · « **Reply #6 on:** August 24, 2004, 11:45:41 PM »

I tried to match my cam with the flow specs for my heads. According to the spec sheet, this type of duration will give me a 74% E/I ratio...the heads are supposed to flow best around 75%.

Thanks for the advice everyone. I guess I'll have to shop for the proper header and see if it makes a difference. I'll let you know the results.