- Dec 14, 2018
- Reaction score
- So. Burlington, Vt
Is 270 cfm out of a 915 head really considered mild? I was under the impression that it takes quite a bit to flow that much.
I wouldn’t mind doing some clean up at home but I would think you would need flow checked constantly to get equal readings from cylinder to cylinder..how would one do thisThe castings can vary quite a bit from the factory, but for examples where the valve job isn’t total crap, 906/915 heads with no porting typically flow in the high-220’s to mid-230’s.
Untouched 346/902/452 heads are less likely to be in the 230’s(but, IMO are easier to get into the 250+ range....... without having the numbers crash in the upper lifts).
270 from a 915 wouldn’t be an all out job on my bench either, but noticeably better than what I usually see from a home ported effort.
I think a good inside micrometor and common sense and most of all “time” would be a mustMy advice is to read up on porting basics.
Procedures, techniques, fundamentals, etc.
Get a junk head similar to what you’ll be working on, and practice on that first.
Strive for consistent shapes and sizing, and don’t worry about the flow.
I ran mid/low-11’s 33 years ago with mild ported 906’s that were never flowed.
Later on, after I owned a flow bench and had the heads off for some updating.......they finally got tested.
Only flowed about 240....... still made 500hp with a hyd cam.
Then I would just have to find a good dual plane aluminum intake that flows 250 or more, from 3k-5700 rpmI had a set of 906’s here this summer that had been done by a Mopar knowledgeable shop.
Retained the 2.08/1.74 valves.
Had their valve job and bowl blend.
Peaked at .500 on the intake, then dropped off as the valve was opened further.
That’s fairly typical for those heads without really going after the SSR(which was the situation with these).
A little less effort than what went into these 906’s would get you to 250@.500(and more at higher lifts) on a 346/902/452 head.
I realize all heads are different, core shift etc. Do you think there is a number one could go by to get decent results without hitting water? Like say .100 ? I'm talking about how much material someone could take out of the ssr while laying it back.I have seen/tested 906’s that flow good numbers with the SSR still fairly tall and not laid back much........ but I’ve never had any success with that approach myself.
If I’m looking for a pretty big number....... I end up having to lay the SSR back pretty far.
It takes me about 2hrs to do one 906 intake port that will get into the 280cfm range.
About 1/2 hour less for the later heads to that same flow level.
I went thru this thread and skimmed thru my previous posts.
Looks like I’m repeating myself on a few posts.