BB Mopar "906" Head Rebuild, Costs vrs Flow/Perf Potential

[PRH]

I tightened up the columns as it was all jumbled up on my small screen on the phone.

A- OOTB Stealth    
B- Stealth W/10 Hrs Porting      
C- OOTB Sidewinder        
D- Our test "906" Iron (assuming 10 Hrs Porting)

--------------A----------------B---------------C----------------D
            Int     Exh       Int    Exh        Int      Exh      Int     Exh
.100"      64.1 /56.4      72.8 /63.2      69.7/ 57.7      67.0/ 54.8
.200"     131.9/107.3   144.1/122.5   146.0/107.0   138.9/102.4
.300"     196.0/145.4   205.9/159.3   209.8/143.7   201.8/144.8
.400"     235.7/170.2   258.1/186.5   244.8/166.9   254.0/169.6
.500"     253.7/183.2   285.1/204.7   260.6/177.3   275.3/186.9
.600"     265.4/192.0   295.5/216.7   270.0/183.0   272.1/197.5**
 
**(.600" Flowed after on 906 Iron for comparison)

-----------------------------------------------------------------

IMO, the 906 high lift flow you have there is quite good for that amount of time invested.
If I did a 10hr porting job on 906/915 heads, I doubt I'd be at 275cfm.

[Challenger340]

Excellent Bob.  Thank you very much!.

Will the low lift numbers get better when you put the finished valve/seat grind in? What do you use for finished seat widths?

We'll see when done I guess ? I will Flow at the end when done with Pics of Final Seats & widths
That said,
I am not applying any targeted fatter low-mid Lift seat preps here(custom Radius cutters, etc), those are proprietary.... I am using just the std 30/45/60/75 valve seat angles that would be commonly found and easily repeatable in the marketplace at any Shop.

What I think is getting interesting ?
Is if a fella starts "estimating" where he will end up for pricing by the time these things are Done ?

I mean let's face it here ? IMO, People should be starting to see by now, that these old Irons in Parts & Labor are going to cost as much, or more ?? for LESS performance potential....
versus,
than what can be purchased in an Aluminum Head and then spending wisely to have prepped properly ?






   

[cdr]

looking forward to see the low lift flow after back cut.

[Challenger340]

I tightened up the columns as it was all jumbled up on my small screen on the phone.

A- OOTB Stealth    
B- Stealth W/10 Hrs Porting      
C- OOTB Sidewinder        
D- Our test "906" Iron (assuming 10 Hrs Porting)

--------------A----------------B---------------C----------------D
            Int     Exh       Int    Exh        Int      Exh      Int     Exh
.100"      64.1 /56.4      72.8 /63.2      69.7/ 57.7      67.0/ 54.8
.200"     131.9/107.3   144.1/122.5   146.0/107.0   138.9/102.4
.300"     196.0/145.4   205.9/159.3   209.8/143.7   201.8/144.8
.400"     235.7/170.2   258.1/186.5   244.8/166.9   254.0/169.6
.500"     253.7/183.2   285.1/204.7   260.6/177.3   275.3/186.9
.600"     265.4/192.0   295.5/216.7   270.0/183.0   272.1/197.5**
 
**(.600" Flowed after on 906 Iron for comparison)

-----------------------------------------------------------------

IMO, the 906 high lift flow you have there is quite good for that amount of time invested.
If I did a 10hr porting job on 906/915 heads, I doubt I'd be at 275cfm.

Yeah, I was a little perplexed at that "275" as well ? So I went back and re-did it.... same same ?
I kind of expected mid 260's @ .500" and maybe touching "270" by .550" which IMO would be pretty darn good 906's for me and what's in them ?

Dunno what's up with that, we'll have to see if it stays or is still close in other ports tested when done. Before going any further I'll do a re-cal / FlowCom leakage again etc., just didn't want to stop as in a hurry yesterday and time is limited anyways on this project ?  Long story short I may have a "Blooper" there.  
Stay tuned and we'll revisit a few Lifts to Final against that "275".

[Challenger340]

looking forward to see the low lift flow after back cut.

Lots of work left touching/adjusting the V/Seats with Stones... lapp contacts, before I get to a Final and can Back-cut the Valves.

Gotta stop and go back, do a re-Cal/FlowCom/leakage etc. again, and re-Flow before proceeding, I was suspicious of that "275" number @ .500" for what's there ? but had limited time.
Maybe get a velocity probe and see what's going on between .500" and .550" if it stays after retest.

[PRH]

I'd probably leave it for the time being if it were me, and see if that number (or something really close to it) shows up on another cylinder, before I questioned the test equipment.

I was testing an Indy CNC 345 the other day, and the .200-.300 numbers looked a little better than normal.
I stopped right there and tested for a leak...... But didn't find one.

This particular set of heads had a slightly smaller bowl ID as rec'd from Indy, and that gave me a little more room to get the valve seats and approach angles the way I like them..... And that's why the heads were better than "usual".

Frankly, when I test a head that flows particularly good....  Or bad....... it's very rarely(as in almost never) the equipment.

[cdr]

Nice Flow bench set up you have now Bob, I am out of the porting businesses, but I still have my toy bench that I have had since 1990, I mess with my own stuff some.

[PRH]

I also had a SF-110 I bought new in 1992. Used it a ton, and finally got something bigger (Saenz S-600) in 2007.

I learned a lot using that little bench.

[cdr]

I am really enjoying what Bob is doing here.

[chargerbr549]

Very interesting, lots of good information!

[Challenger340]

Nice Flow bench set up you have now Bob, I am out of the porting businesses, but I still have my toy bench that I have had since 1990, I mess with my own stuff some.

IMO, the SF110's are great machines Charlie, lots of Shops still using them, they work extremely well and provides lots of useful information 
We only went new and larger as tired of fixing, and for the sensitivity to small changes on larger heads, just easier to see.

[Challenger340]

I'd probably leave it for the time being if it were me, and see if that number (or something really close to it) shows up on another cylinder, before I questioned the test equipment.

I was testing an Indy CNC 345 the other day, and the .200-.300 numbers looked a little better than normal.
I stopped right there and tested for a leak...... But didn't find one.

This particular set of heads had a slightly smaller bowl ID as rec'd from Indy, and that gave me a little more room to get the valve seats and approach angles the way I like them..... And that's why the heads were better than "usual".

Frankly, when I test a head that flows particularly good....  Or bad....... it's very rarely(as in almost never) the equipment.

As time permits,(Cast Iron feels like an after school detention project), I'm just going to do all 8 ports and test a few more to see the consistency.

After giving it some some thought ?

I think it's more a "volume" problem above the Valve with the FAT guide intact, and it hits a "sweet spot"(275) before going unhappy.
Needs some added roof Volume/"Time" for it the air to turn.  I might have to narrow the guide a bit.
Back in the day we always did guide shaping as a std prep... just never thought it would have that much impact on these Heads ?

[tan top]

 interesting info guys , thanks for sharing 

[PRH]

Bob,
The only 906's I've ever tested that flowed good at high lifts, and still retained most of the short turn height were ones CNC ported by Jeff at Modern.
He did have the guide boss mostly gone, and the bowl was pretty big as well.
I was never able to get that to work for me, even after seeing how his were shaped.

Even with the bowl at the same diameter, and the guide boss removed, I've always had to really knock down and lay back the short turn to not have the numbers back up(too bad) above around .550 lift.

The best 906 I've had on my bench were some of the "312cfm" CNC ported ones that MM was selling a few years ago.
I'm pretty sure they were done by Modern, and they looked the same as the ones I knew had come from there.
The MM ones had 2.19" 11/32 stem intake valves in them, and after polishing the CNC lines out of them flowed 297cfm.

[Challenger340]

Thanks for the info Duane, much appreciated 

From what I remember about the old high floor 915/906's, just as you describe, they hit a wall without rolling the short back, and then it becomes a "timing" thing to the floor where all of a sudden Flow dramatically increases at the higher lifts ?
But it's alot of work getting in there to get those short turns right, and difficult, so I was hoping just to "keep it simple stupid" narrowing the guide boss a bit and see what happens ?
I can't remember what more volume in the bowl does without also rolling the short back more than the minimal I've done ? could be the "275" blooper I saw just before it goes sonic ?

These 906 Heads being (hopefully) still a decent pair for a resto deal, I didn't want to get too carried away, no point having gunga Flow @ .500"+ for a short Cam ?
But what the heck....
it's a 10 Hr Porting project, so I'll see where I'm at time-wise, and see where it goes on the short-turns. I can always shelve these for posterity and do the guy another set, LOL !

I won't have any time until next weekend, gotta keep the lights on because these 906's sure won't !

[PRH]

My "path"  to get 906's into the 260-ish range is to blend the machined areas of the bowls into the cast areas, slightly bullet nose the guide boss, and roll the sort turn back, along with opening the pinch about like what you did.
For this amount of flow I don't do any trimming to try and reduce the bulk of the guide boss itself.
Without a ton of work in the bowl or pinch area, I've found the best bang for your porting buck(time) is spent properly contouring the short turn.
I don't start reducing the mass of the guide boss until I start looking for flows in the 270+ range.
For me at least, it's a pretty big jump in the amount of time invested to get a 906 port to go from say 260-265, up to 275+.

The 346/902/452 have almost no guide boss to begin with, so very little time needs to be spent there even for pretty high effort heads, and they also have basically no short turn, so again..... It just takes less time to rework those areas of the port.

[500Jon]

Just love the '906' porting work Guys!

I ran a 440 '906' motor some twenty years ago that made approx. 600hp.
The heavily ported 'Rob Loring ICE-UK' heads were the best I've ever seen.
1/2'' raised ports with channelled port floors to make the intakes the normal '906' size again.
5/8'' ali spacers screwed onto the intake faces to allow normal intake fitment.

Sorry no pics as I sold the motor about 15 years back, she was a beaut, REAL OLD SKOOL...

I'm going to get someone to Flow-test my UK-Weslake Ovalport/D-port 1969 iron-heads soon for a '906' comparison.
Open chamber design with Motorhome extra water passages, 2.250 intake and 1.800 exhausts.
Also has 'taper-seat' plugs as per MH too, thought those mods weren't introduced till the mid 70's?
Extra-thick deck around the exterior bolt holes for better strength.

[500Jon]

Found a blurred pictures of the ICE port!

[PRH]

Wow!!
Those oval port bb heads are pretty cool!!

On the 906's, with that material added to the floor and the roof raised, you get a much better approach to the short turn.
I bet those worked pretty well.

[500Jon]

They made approx 600hp and ran a 440 dart into the nines without NOS! (ex Sixpack 69 1/2 engine)
The ports were raised so high they broke out at the top, just visible in the lower picture.

Its good to see Folks still spending time and effort on 50 year old iron heads!

The 440 engine and its derivatives have fueled UK drag racing for most of our lives!
Only a handful of 426 iron hemi's have ever been run in the street classes due to costs.
Without the humble iron-headed 440, European drag racing for Mopars probably wouldn't exist!

Aluminum plate added to intake flange, with a Team 'G' highly ported Domi manifold.
Runners were welded and rasied to improve flow too, this is how it was in the 80's-90's.
MAKE DO AND MEND!

[500Jon]

I just remembered, this wonderful 440 engine was removed from a 69 1/2 Sixpack Superbee in the 80's!

Fortunately someone realised and the engine was re-united with her again about ten years back.
When the engine was rebuilt with another block, IT BROKE into many pieces!!!

SP Superbee is now in France...with her original NINE second Rob Loring 'ICE' engine lol...

God moves in mysterious ways...

[PRH]

I'm in the final stages of getting a set of OE heads done for a customer.
For what he's doing with the car, aftermarket heads aren't an option....... So reworked OE it is.

I'm not going to get into specifics on what each thing costs, but for these heads.......complete and ready to bolt on....... Steel retainers and budget friendly roller springs, Ferrea 1.81/2.14 valves, ported to flow 278/211 @ .600, 281/215 @ .700, milled to 78cc and the intake side corrected accordingly ......... They cost just about the same as two sets of ootb RPM heads(at the current Summit price).
In the porting, flow testing, and general deburring and clearancing for pushrods(1.6 rockers), there's about 20hrs of labor in just that part of it(which is just about the cost of one set of RPM heads).

Just figured I'd give this post a little bump.

[BSB67]

What would you think the crack potential is?

[c00nhunterjoe]

What was the flow at .450 and .500???

[Challenger340]

Yeah I gotta get back on those 906's as soon as time permits, awefully sorry 'bout that fellas, just so damn busy right now.  The guy who's getting the 906's ain't in a hurry, so other priorities for Spring right now.