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My only concern would be with the new KB pistons and compression using the 509 cam. According to the KB website, a KB236 piston with unmodified open chamber heads (approx. 88-90CC) and 0.020" head gasket, compression will be approx. 10-10.5.

Thoughts...

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Yup...the lower end is a done deal at this point...balanced and assembled. No cam yet though and I can always change the head gaskets if need be.

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I already have the 906's w/ heavy springs/dampers. The aluminum heads are just a little rich for my blood at the moment.

Also, the engine ran strong with the 700cfm right up to 6500. At the suggestion of a friend, I tried both a 750 & 850, and after tuning them both, I found the larger carbs were not as responsive, and there was really no diff in the et's, so I went back to the 700.

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Yup...the lower end is a done deal at this point...balanced and assembled. No cam yet though and I can always change the head gaskets if need be.

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the KB is a step head piston , what is the distance between the step head and the open part of the chamber ? That piston was designed to mimic a closed chamber head when setup properly , you chose the worst people KB made for that application , but probably because it was the only one they had.

I had my hands in a build with 452's and step head pistons , Diamond made me these to get 9.5 with 89cc head.

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A flat top 0 decked will get you 9.5

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I was considering a thicker composite head gasket as suggested(0.020 to 0.040) to reduce compression, but this will certainly reduce quench, and I fear it may result in either no change, or even increase the likelihood of detonation at heavy loads.

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I'm guessing what your driving at is, I should have cc'd the heads and equalized them, then measured the piston step to calculate exact compression ratio & quench.

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The 906's were never milled and I never cc'd each cylinder to check consistency. Going by production numbers, I'm assuming the heads are somewhere in the 88-90cc range, so based on the KB piston specs of 1.8cc piston step & stock stroke, compression is 10.5:1 @85cc's, 10.0:1 @90'cc. with a 0.04"0 gasket compression, or 10.96:1 @85cc to 10.45:1 @90cc with 0.020" compression.

I'm guessing what your driving at is, I should have cc'd the heads and equalized them, then measured the piston step to calculate exact compression ratio & quench.

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There is no guesswork in proper engine building..........

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I'm guessing what your driving at is, I should have cc'd the heads and equalized them, then measured the piston step to calculate exact compression ratio & quench.

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The 906's were never milled and I never cc'd each cylinder to check consistency. Going by production numbers, I'm assuming the heads are somewhere in the 88-90cc range, so based on the KB piston specs of 1.8cc piston step & stock stroke, compression is 10.5:1 @85cc's, 10.0:1 @90'cc. with a 0.040" gasket compression, or 10.96:1 @85cc to 10.45:1 @90cc with 0.020" compression.

I'm guessing what your driving at is, I should have cc'd the heads and equalized them, then measured the piston step to calculate exact compression ratio & quench.

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Thank you everyone who chimed in. Gave me a lot to think about and made me realize I may have made a few mistakes and false assumptions when bolting the heads on, so I've decided to take a step back and verify some of the critical measurements before going any further with the rebuild.

One mistake was in a suggestion from a friend...who btw is a great mechanic & he meant well, but he's not much on the engineering side. He suggested the Fel Pro 0.037" composite gasket to reduce compression to run on pumped gas. I now realize this is most likely a bad choice at the sacrifice of quench, not knowing for sure if the heads were surfaced, and whether the CC's are equal across all chambers.

The plan is to remove the heads and cc all 8 chambers. A question I have is... once I know this, how close to each other should they be, and what is the best approach to equalizing them?

The second step is to measure the actual quench area across all 8 pistons (both ends and center of piston) to head using the rosin core solder method I've read a lot about. I believe once I know this, I can select the appropriate compressed head gasket thickness.
A few questions;
1) should I make the measurement without gaskets and the heads completely or lightly torqued?
2)Once I have this measurement, where in the 0.035"-0.040" quench area should I strive for...the 0.035" minimum or stay on the safer side of 0.040"? For instance, if I measure 0.018" quench without a head gasket, by using the compressed steel 0.020" gasket, I would be at 0.038" Considering the KB236 pistons, Eagle rods, average rod bearing clearance, and a rev limit of 6000-6500, this would be a good choice.

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I wouldn't worry too much about making the chambers equal unless they are really far apart , the IMPORTANT measurement is the distance from the head deck to the cast area that is the open part of the chamber , they are NEVER the same or even flat in any direction ... at least not that I have ever measured on any of the heads I have machined.

As far as the .037 Felpro composite , no such animal , they are .040ish and you do not have a bunch of different thicknesses to choose from. Steel shim head gaskets run .021 for the most common gasket , Cometic has one that is .027 $$$$

You need to know how far above the block deck the step of the piston is sitting , no gasket.

Was the block SQUARED during any of the rebuild processes ? If not that will add to the fun. Don't be surprised to see the steps not all at the same height , even if the block was squared.


Shoot for . 040 , and hope for between .035 and no more than .045, if the heads were never cut you'll need a step that is roughly .0080 above the deck ... assuming a .021 head gasket and .100 chamber depth.

Measure the head bolt boss under the exh ports , uncut heads will be basically 1.000 , if the heads have not been surfaced they should be so you know they are flat, you can take material off the head decks to get quench , but that is going to raise your compression ratio. don't be surprised to get chamber volumes of 90-92 cc.

also make note that KB , and most aftermarket piston makers for mopar think everyone has blocks that have been decked about .020 when calculating compression ratios and picking a compression height.

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Thanks for the suggestion. I would hate to have to disassemble the bottom end to mill the deck. I'm still not entirely sure if the heads where ever milled. I'm assuming they have at some point.

I need to make all the critical measurements first, then I can make an informed decision on the course of action that get's me close to ideal without breaking the bank.

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ok...so now I have some real numbers to work with. The measurements were taken many times over until I had a fairly confident process with repeatability.

Quench clearance w/no head gasket = 0.045"
- Heads were torqued to approx. 35 lbs
- Used rosin core 60/40 solder over length of step
- Crushed 3 times at TDC
- Both ends & middle of solder measured & averaged
- All cylinder were within 0.005" of each other
- Very little piston rock was noticed across the solder

Piston step head to deck = 0.039"
- Piston brought to TDC with dial indicator
- Measurements made with straight edge & feeler gauge @center of piston

Flat of piston (valve reliefs) to deck = -0.034" below deck
- Piston brought to TDC with dial indicator
- Measurement made with straight edge & feeler gauge @center of piston

Head CC's
- All were 82-83 CC's
- One was at 80 CC
- Double checked all measurements
- Allowed water to sit in chamber for 15 minutes w/ no valve leaks observed.

Head bolt bosses at the exhaust side were also checked as suggested, and were at 0.975" indicating heads were most likely milled.

Looking at the numbers, with a 0.020" head gasket the quench area will end up at 0.065", which is far from ideal.

Also looks like compression is somewhere at 10.5:1.

Any thoughts?

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Yes at .065 you basically have no quench , it is what it is unless you want to cut the heads .020 , I'd cut .025 because of your .005 variance , but then your compression is going to be higher.

Drop your head gasket on the head and see how much overhang of the chamber there is inside the gasket, scribe the gasket onto the head, drop 1\4" dowels in the head to hold the gasket, and scribe the chamber size and grind all the overhang away and polish the chambers and see how much you raised the chamber CC.

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That's what I figured...no quench & I can hear the pinging already.
So if I mill the heads .015-.020, compression goes up too...and there's real no benefit?
I thought I saw this info somewhere and can't put my finger on it, but what is 0.010" equal to in CC's?

btw...I was thinking about one other measurement I made that I did not publish here. I put a straight edge across the head, and measured 0.073" with a feeler gauge to the flat of the chamber. If I take that value, subtract the quench dome of 0.039", that's 0.034" (0.011" less than the solder test). I wonder if the solder didn't crush down all the way. That would place quench at 0.054"...still 0.014" less than ideal, but better.

Is grinding out the head overhang a typical approach to increasing the CC's? I assume leave the quench area alone.

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The solder was obviously causing the piston to rock while crushing, I wouldn't use that to determine a value, doing it with the straight edge and feeler blades, and math is, more accurate.

For BB open chamber head, .005 for every CC , .015 3cc, .020 4cc, .025 5cc

No there is a benefit , but you have iron heads and possibly not high enough octane because of the iron heads not succking out more of the combustion heat, faster, like an alum head does. Quench/squish is not the magic bullet, but it helps.

i'd want .045 MAX , anymore and you may as well leave it at .065.

To increase CC, think about it, the chamber needs to be BIGGER ... yes leave the quench area alone except to maybe smooth it, but try not to make it deeper , the smoother/shiner it is the less chance for hotspots that will help cause detonation.

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Thanks John for the cc info. and all your guidance.

So if I use the feeler gauge numbers it looks achievable...
.073 chamber depth
less .039 dome height
less .010 off the heads
add .020 head gasket
.043 total quench

With .010 off the heads, that will reduce CC's to approx 80-81. The piston is .034 in the hole which equates to approx 6.8 cc. Valve reliefs are at 1.8 cc based on KB236 spec. So with a total CC at approx 88.6, what would the SCR be...around 10.0:1?

I'll take your suggestion and polish the chambers the best I can shy of removing valves to accomplish any major ginding.

Not sure if it's worth anything, but while the heads were off, I selected 8 spark plugs that were indexed correctly.

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Not sure what you mean...
"If it were me I would take the .010 out of the open part of the chamber that way you end up with perfectly matched chamber depths and add CC to the chambers."
Are you referring to grinding back the open part of the chambers to the edge of the head gasket?


I am in Marlborough, MA btw.

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Where do you think SCR is without this extra work...10.5? With the quench at .043 & timing backed off to around 34 degrees, think it's really necessary? Grinding all 8 chambers back to the 4.320 mark is going to be a lot of work.

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It's good practicefor you and your penance for using poor cylinder head choice.

I had 50 hours in the last set of open chambers head setting up for quench I used ... good thing I do it for free ...

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think it's really necessary?

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2. Pushrod length
Having non-adjustable 6-pack rockers, I'll need to verify preload is still within spec. Suspecting .030 was already taken off the heads, now I'm taking .010 more, and keeping within .020-.040 preload, I'm hoping the 3/8 x 9.310 rods I currently have will fall within this preload target.

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The pushrods were 5/16 x 9.31. That was with the original flat top pistons and .040 head gasket. Over the years I picked up 3/8 x 9.31 for the heavier valve springs, but as mentioned I will definately have to revisit this as I'll now be .030 less with .010 off the heads and .020 head gasket.

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What is the length of a STOCK 440 pushrod? The factory used a steel shim gasket , .021 , just like all the steel shim gaskets sold now .

I know this is budget but if you are stuck on using stamped rockers and want specific hyd. preload then I would call Smith Bros and order a set of adjustable pushrods. The last 2 I did have them with stamped rockers because like you I wanted specific preload and it's the only way to get it exact, the valves heights are all a little off from each other unless you had an EXPENSIVE valve job done.

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Must be the difference between a mechanics mentality of time is money, and an engineers attention to detail.

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Dropped the heads at the machine shop today to have .010 take off. Pretty confident I'll get the quench to around .043.

Funny...both my life long friend of 40 yrs, who's restored dozens of mopars, and the machinist...both think I'm being way to meticulous. When I mentioned checking rocker arm geometry & possibly ordering shorter pushrods, they both gave me the look of disbelief, and insist I just put it together already. Must be the difference between a mechanics mentality of time is money, and an engineers attention to detail.

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The engineers that I dealt with just wanted to see the
end results.. they left it up to me how to get there

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Well...got the heads back with .010" off, and ready to hit the shop Fri to start assembly. Now that the heads have a nice clean, machined surface, I'll clean the block really good using acetone until the rags are clean before installing the heads. Hopefully get a good seal.

I'm hearing a couple diff schools of thought on using the VHT Copper Cote on the steel head gaskets. A light coat and install and torque when tacky was my thought. Also head bolts to 70 lbs. They are ARP. Mopar suggests 35lbs, then 70, and ARP suggests 3 equal torques to 70.

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Well...got the heads back with .010" off, and ready to hit the shop Fri to start assembly. Now that the heads have a nice clean, machined surface, I'll clean the block really good using acetone until the rags are clean before installing the heads. Hopefully get a good seal.

I'm hearing a couple diff schools of thought on using the VHT Copper Cote on the steel head gaskets. A light coat and install and torque when tacky was my thought. Also head bolts to 70 lbs. They are ARP. Mopar suggests 35lbs, then 70, and ARP suggests 3 equal torques to 70.

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I've done the 3 step for ever.. it works.. then go
back over them at the total torque just to make sure
it hasnt moved

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I already have the 906's w/ heavy springs/dampers. The aluminum heads are just a little rich for my blood at the moment.

Also, the engine ran strong with the 700cfm right up to 6500. At the suggestion of a friend, I tried both a 750 & 850, and after tuning them both, I found the larger carbs were not as responsive, and there was really no diff in the et's, so I went back to the 700.

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Iron heads with todays fuel and that compression ratio may not be compatable If you have to retard the timing or run the motor fatter than best performance to keep it from detonation your not getting the best performance from the parts, are you I would lower the compression to no more than 9.5 to 1 so I could tune it for best performance As far as your motor not liking the bigger carb. that is a abnormality with all the 440 I've tuned and tested, I would bet money that you had a fuel restriction in the car limiting the fuel supply at WOT on both carbs My reasoning for saying this is I have tested carbs. from 600 CFM to a 1050 Dominator on the same motor, one intake swap for the Dominator carb. and the car would pick up with each larger carb. All the 4150 carbs, 600 DP Holley to a Holley 950 HP DP, where tested on the same intake and jetted for best performance I even tested a BG Holley 750 stage three modded carb. that flowed 920 CFM and it ran better than any of the stock 4150 Holleys jetted Good luck on your build Think twice, act once Edit, I should have read pages 2,3 and 4 before posting this post To late for my Good luck BTW, a colder spark plug will help control detonation. I like to set my BB total timing at 34 to 36, depending on which compression ratio and fuel. I do shorten up the advance so I can get 14 to 18 degrees at idle and then have the timing come all in by 2000 to 2500 RPM.

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Next is 6 qrt pan, windage tray, pickup, and HV pump. Also ordered the Billet rear main seal kit from Mancini which I hear never leak.

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