906 or 915 ?

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44o gts dart said:
Impressive stats,,, stupid question here…. Sorry… what exactly is bowl blended???
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Go to the small block engine section and look at the sticky thread at the top about porting 318 heads.

There’s lots of pics and descriptions in it.
 
450 HP is easy, build a quench motor. Runs on pump premium. My build: 915 heads mild port & polish flowing 270cfm, SRP pistons, total quench .040. Mopar .528-284 mechanical cam. 522HP with headers. Im guessing about 485 the way it sits.

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1968rt said:
450 HP is easy, build a quench motor. Runs on pump premium. My build: 915 heads mild port & polish flowing 270cfm, SRP pistons, total quench .040. Mopar .528-284 mechanical cam. 522HP with headers. Im guessing about 485 the way it sits.

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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 built my first 440 for my road runner back in the day. Home ported 452 heads with stock valves, had no idea what I was doing. Car ran low 13 seconds with a comp .501 cam.

I bought a set of 915 heads with 2.14/1.81 valves that had been hogged out by a local racer… they looked great.

I had them checked at the local machine shop and swapped them out, changing absolutely nothing else.

The car idled rougher and felt more snappy around town, due to higher compression I guess, but the quarter mile times were identical.
 
on my bench, 270 from any stock iron bbm head is more porting than a basic bowl blend.
Especially the 906/915 heads when you’re looking for the curve to hang on beyond .500 lift.
 
I guess I shouldn't have said mild, but to me they aren't all out. When I find the pictures or flow sheets you will understand why they flow 270. It was a lot more than a bowl blend. Short turn pushed back, valve guide shaped, chamber unshrouded etc.
 
The 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.
 
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PRH said:
The 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.
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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 this
 
My 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.
 
PRH said:
My 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.
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I think a good inside micrometor and common sense and most of all “time” would be a must
 
I 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.
Flowed 240/171@.500

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.
 
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PRH said:
I 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.
Flowed 240/171@.500

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.
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Then I would just have to find a good dual plane aluminum intake that flows 250 or more, from 3k-5700 rpm
 
I've read any and everything i can find about the 906/915 style port. What I'm doing is quite time consuming so far but thats fine by me. So far I've blended the bowls to 85% of the valve size (2.14/1.88) and im currently cutting/shaping the guide boss. All I've done to the ssr currently is go 90° straight down from the 70° cut. I've been researching laying down the hump, raising the roof and sides to slow the air for the turn. Ill save that for last when I've got all the information I can soak up.
 
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.

Edit:
I went thru this thread and skimmed thru my previous posts.
Looks like I’m repeating myself on a few posts.
 
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PRH said:
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.

Edit:
I went thru this thread and skimmed thru my previous posts.
Looks like I’m repeating myself on a few posts.
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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’ve never actually measured how much height I’ve taken off.
I start with what I feel is a somewhat conservative attempt, but something I feel is possibly “enough”.
The first attempt rarely gets me the result I’m looking for, so I start tweaking the shape.
Sometimes I don’t quite get everything I’m after, and end up stopping......... not wanting to find water looking for a few more cfm.
For me, i do the SSR by feel.
 
I remembered I had a cracked 906 head here I had done some testing on......

On that head, the inside height at the SSR is 1.600 for a stock port.
On a test port that’s in the 280 range, that dimension is 1.710.
That’s an added .110” in height, but material has been removed on both the roof and the floor.
 
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