[steve25]

I love when people state there heads flow numbers, but with no lift number tacked on.

The OP told his head/ engine builder guy he wants 260 cfm, well at what the heck lift!?

A RA4 head reworked to flow 260 cfm at around .400” to .450” lift is way the hell different then a RA4 flowing 260 @ .650” lift.

[PAUL K]

Originally Posted by steve25

I love when people state there heads flow numbers, but with no lift number tacked on.

The OP told his head/ engine builder guy he wants 260 cfm, well at what the heck lift!?

A RA4 head reworked to flow 260 cfm at around .400” to .450” lift is way the hell different then a RA4 flowing 260 @ .650” lift.

I'm amazed at the amount of folks that think "porting" is a machine shop operation and every shop can perform the task. The RAIV is probably the most difficult head out there to get to work right. Sadly, because of its flow characteristics it causes even moderately experienced porters to keep removing metal to attempt to get them "right". There are way more screwed up ported IV heads out there than good ones. The saving grace is the majority of them end up on restorations that are rarely driven down the road.

I'm working on a W-31 engine that had the heads ported by the last shop. It looks like a five year old went at them with a Dremel. The good news, it's as hard to do damage with a Dremel as it is to find a measurable gain.