[ta man]

Originally Posted by slowbird

A properly done set of kre d-ports with stomp iron heads imo. The kre heads Jim tested were out of the box from kre weren't they?

With less effort, my engine is basically what can be done and keep it very streetable with essentially off the shelf parts. 310cfm KRE heads and Dave's OF 2.0 cam which has mild duration and big lift. It is a basically a modern version of Jim's engine..but I would say can run on lower octane fuel versus Jim's engine which I'm sure he was pushing it for pump gas and gets way better fuel mileage.

[PAUL K]

Originally Posted by ta man

With less effort, my engine is basically what can be done and keep it very streetable with essentially off the shelf parts. 310cfm KRE heads and Dave's OF 2.0 cam which has mild duration and big lift. It is a basically a modern version of Jim's engine..but I would say can run on lower octane fuel versus Jim's engine which I'm sure he was pushing it for pump gas and gets way better fuel mileage.

Your car runs great!.. You think 290 cc heads would slow it down? Think 360cc heads would go faster with no other changes?

[ta man]

Originally Posted by PAUL K

Your car runs great!.. You think 290 cc heads would slow it down? Think 360cc heads would go faster with no other changes?

Paul did you mean 290cfm or 360cfm

[PAUL K]

Originally Posted by ta man

Paul do you mean 290cfm or 360cfm heads?

No port volume.... I screwed that up, haven't had my coffee yet.

I'm guessing your heads are about 210cc .... So let's say a theoretical 190cc head and a 260cc head?

[ta man]

Originally Posted by PAUL K

No port volume.... I screwed that up, haven't had my coffee yet.

I'm guessing your heads are about 210cc .... So let's say a theoretical 190cc head and a 260cc head?

I'm a tuner more than a builder..but my guess would be there would not be a lot of difference. That being said there is more power potential with the 260cc head if they do flow much more as they should.

[Steve C.]

"Like all other aspects of engine building, port size is relative to the required airflow of the engine. The smallest port that will deliver the airflow needed by the engine is desirable. That means we will have excellent velocity for port filling, but without any choke that may limit required peak airflow. The needed airflow depends on engine displacement, RPM, and VE at that RPM. And a port big enough to deliver 400 cfm may well be too large for any engine that can only use 300 cfm."

Jim Hand

https://www.youtube.com/watch?v=CmfxHNxk8ew


.

[Jay S]

From what I recall Jim Hand was not of the opinion that Aluminum heads provide an octane advantage for increasing the compression on pump gas. That was why he did not increase the compression much with the KRE heads. I think he was both correct and incorrect on that idea. So long as the heads are identical, every test I have seen changing from Aluminum to Cast Iron has not shown any difference in octane tolerance or power. I think Jim was correct on that idea. But where I think he was incorrect is that a port volume increase does generally allow for more cylinder pressure on the same octane. I suspect increasing port volume moves air flow to where piston speed is faster, likely also leads to a cooler air charge, and also tends to move some engine scavenging around so the power band gets shifted a little higher of spread out. Depending on the car, some of those things will not necessarily improve the engines performance. If you could replicate an iron copy of a KRE or Eddy head, i think the Iron heads would run identical. The Iron to Aluminum contest to me more decide on how thick the castings are to manipulated them. The winner in that area is likely the Aluminum heads.

My 6X heads on my TA are ported to 185 cc. I tried 196cc on another set and lost 16 cfm at peak flow against the 185 cc head. I would expect the 196cc had more flow lift in it someplace, but I could not find it. Here is a couple photos of the 196cc 6X heads. The photo has a 1.77 valve that is sitting down on the valve guide stem.