Got one head off - head & piston questions...?

[defiance]

Ok - got the driver's side head off the 440 today, and wanted to ID the piston before I make the final decision to replace them (I probably will, but want to be sure these aren't up to the task first.

First question - when I pulled out the rear manifold bolt (last time the engine was redone, they used bolts instead of studs), water flowed out from the hole.  Is that normal??  If so, Ok, just wanted to be sure... At first I thought it was definitely wrong, but when it did it on the other side too, I thought maybe it's supposed to be that way...

Next, the pistons in there are flat topped, with no markings or numbers on the top except for the number '40' etched faintly in the top.  I'm assuming that means they're .040 over bore (4.360"), is this a reasonable assumption?

Also, on pistons and compression... if the pistons do not reach the top of the compression chamber at top dead center, the volume of air between the top of the piston and the top of the cylinder - should that be added to the volume of the head compression chamber for the purpose of compression calculations?  I'm assuming so, but wanted to be sure...  These pistons stop a noticeable distance below the top of the cylinder wall.  I'm terrible with distances, but I'd guess .1" to .15" below.  I've attached a pic for clarity.

Also, is this distance a function of the piston (i.e., some pistons made to sit low), or is it a function of rod length? 

Sorry to have so many questions - I'm trying to find the answers elsewhere before I ask, I promise; there's just so much conflicting info out there, it's pretty easy to get lost, and the knowlege level of the people here is simply astounding...


The pic, btw, focuses on piston 1 at exactly TDC.
Thanks!!

[694spdRT]

Next, the pistons in there are flat topped, with no markings or numbers on the top except for the number '40' etched faintly in the top.  I'm assuming that means they're .040 over bore (4.360"), is this a reasonable assumption?

Also, on pistons and compression... if the pistons do not reach the top of the compression chamber at top dead center, the volume of air between the top of the piston and the top of the cylinder - should that be added to the volume of the head compression chamber for the purpose of compression calculations?  I'm assuming so, but wanted to be sure...  These pistons stop a noticeable distance below the top of the cylinder wall.  I'm terrible with distances, but I'd guess .1" to .15" below.  I've attached a pic for clarity.

Also, is this distance a function of the piston (i.e., some pistons made to sit low), or is it a function of rod length?

More than likely they are 40 over pistons. I can't tell from the pictures but, TRW makes a 2266 flat top that sits pretty low in the cylinder. 

Deck height is the term for the distance from the piston top to the top of the cylinder. Most of the calculators have a entry for the distance.

Here is a calculator I use.

http://www.rbracing-rsr.com/compstaticcalc.html

Deck height is a function of the piston design but it will vary with each cylinder block especially if you have a block that has been decked. Of course changing rod lengths, stroker cranks, offset grinding cranks, etc. will change it too.

[Ghoste]

And yes, the rear exhaust manifold bolts tap into a coolant passage.

[defiance]

So - assuming the rod length is stock, and the block hasn't been decked (both I believe to be true, but will confirm before I order parts), would the much-loved Speed Pro 2355's extend exactly the the end of the cylinder wall?

Thanks!  I'm learning TONS this pas week 

[defiance]

Actually, I think I just figured this out - On Speed Pro's site, they mention "Compression Distance" - If I'm reading this right, that's the distance from the rod end center to the piston top - the 2266F40's (which is what I'm thinking are in there) have a compression distance of 1.991", and the 2355F40's (which I'll probably be replacing those with), have a compression distance of 2.061.  That's .070" deeper in the cylinder that the old pistons sit, which is in line with the pictures I'm seeing there.  Somebody please correct me if I'm wrong here, but if I'm right, I just need to get some calipers or something and confirm that the distance on my current setup is .070", and if so, I know that the 2355's will top out in the cylinder perfectly.  If not, then it's probably less and my block has been decked, or it's more, and an odd rod length or crank grind was used (I'm pretty sure the rods are forged stock replacements, and the crank is straight stock, though).

Thanks, and please do correct me if I've got this wrong!

[694spdRT]

Your are right on the compression distance calculation. However, your not likely to be that lucky to end up with zero deck on a 2255 piston. My 2266's were almost 0.090" down in the hole. You will probably need to get the block decked down to achieve zero deck. I don't know your engine combo but a zero deck iron head 440 engine will probably be too high on compression for pump gas.

[defiance]

It won't be Iron head 

I'm trying to hit 10.5/1 compression with 84cc Edelbrock Performer RPM's, which if I'm doing my math right, could be done with 0 deck 2355's and a .023" gasket (If that gasket size is possible) - though even if I'm stuck with .040", 0 deck puts me at 10.1, so not a huge loss; I'll just go however close to .023" I can get and still have a reliable gasket.


As for decking the block...

If I deck it much, it'll make it so that I have to machine the intake manifold, right?  So, I want to get as close as possible to topped out, then deck the the much smaller remaining amount....  Right?

[694spdRT]

Firefighter will have some good info for you if he reads this thread. The important thing is to try and achieve good quench which if I remember correctly is no more than 0.040" distance from piston top to head. With the 2255's, Eddy 84cc heads, and the appropriate head gasket you should be able to achieve it.

[grouseman]

You can stack up feeler gauges to get a measurement below deck. 

Keep us posted.  Like you said, you're learning a lot, and we can all benefit from what you're finding out.  The relationship between camshaft selection and compression ratio is very important.  So is quench, and deck height, compression distances, gasket thicknesses, etc. in determining compression ratios. 

You will feel sooooo good when you fire up your new engine for the first time! 

[firefighter3931]

However, your not likely to be that lucky to end up with zero deck on a 2255 piston.

694spdRT is correct. The uncut blocks are all over the place in terms of deckheights so the proper way to machine it is to have the engine mocked up and re-measure...then cut. Mine had to be milled .020 to achieve a true zero deck. The block was also squared up at the same time because it was higher in the back than in the front, which is not uncommon. With the 84cc chamber/.040 gasket/2355 piston compression is right at 10.5:1 with perfect quench. The larger .040 bore will increase the static comp slightly, but not enough to matter for a pump gas engine.  

The 2355's are very close in weight to a factory piston so balancing the rotating assembly won't be a big chore for the machine shop. The speedpro pistons use a pressed pin so they are designed for a factory rod. The rods should be reconditioned and ARP rodbolts installed while it is apart. This type of build is very reliable as long as you keep the rpm's in check and don't over rev the motor. Basicly, throw a 6000 chip in the MSD and forget it. With the Comp xs282s solid cam, this is an easy 500hp combo that will rip your head off and still idle all day long in traffic.  


Ron

[defiance]

Excellent!

I think I've got this!  Time to get started

[SeattleCharger]

However, your not likely to be that lucky to end up with zero deck on a 2255 piston.

694spdRT is correct. The uncut blocks are all over the place in terms of deckheights so the proper way to machine it is to have the engine mocked up and re-measure...then cut. Mine had to be milled .020 to achieve a true zero deck. The block was also squared up at the same time because it was higher in the back than in the front, which is not uncommon. With the 84cc chamber/.040 gasket/2355 piston compression is right at 10.5:1 with perfect quench. The larger .040 bore will increase the static comp slightly, but not enough to matter for a pump gas engine.  

The 2355's are very close in weight to a factory piston so balancing the rotating assembly won't be a big chore for the machine shop. The speedpro pistons use a pressed pin so they are designed for a factory rod. The rods should be reconditioned and ARP rodbolts installed while it is apart. This type of build is very reliable as long as you keep the rpm's in check and don't over rev the motor. Basicly, throw a 6000 chip in the MSD and forget it. With the Comp xs282s solid cam, this is an easy 500hp combo that will rip your head off and still idle all day long in traffic.  


Ron

    learning a lot here.   I am planning on about a 282 cam in my rebuild, wasn't sure about the hp, 500 you say? That would be awesome if I could get around 500hp.    but what about all this he is doing is giving the 10.5:1 compression?, also I thought under 10:1 was recommended for pump gas. 

[defiance]

Keep in mind that I'm new at engine config, but I'm going to try - that way if my understanding is off, I'll get corrected too

10.5 / 1 is only acceptable with pump gas with aluminum heads.  I'm not sure I understand why yet, but it has something to do with aluminum and quench (I think?) ....  Either way, I've heard from several sources now that aluminum heads are OK for up to 10.5/1 pump, and I'm using the Edelbrock alum heads.

As for what I'm doing to reach that:

1) The chambers in the heads are 84cc, a bit smaller than stock, and they're closed chamber, which helps with quench

2) I'm replacing the stock-style pistons in there with Speed Pro 2355's - these pistons ride .070" higher than stock, which further reduces the chamber size

3) Once I've got the pistons mocked up in the engine, I plan to have the block decked (cylinder height milled down) to exactly equal with the tops of the pistons, once again, further reducing compressed combustion chamber size.

The calculator 694speedrt mentioned above is EXCELLENT - you can play with it to see what you'd need to change from your existing engine.

For reference, my existing setup was flat topped pistons (0cc piston top volume), 906 heads have a combustion chamber of 88cc's, the stock 440 stroke is 3.75", the stock bore is 4.32" (mine's bored .040" over already, so it is 4.36"), most head gaskets are .040", and my personal deck height (the distance from the top of the piston at TDC to the end of the cylinder wall) - which I just got done measuring - was .110"

In the end, I had compression ratio of 8.35/1

With the new setup, it's 4.36" bore, 3.75" stroke, .027" head gaskets (smallest Cometic makes), 0" deck height, 7cc piston top volume (they have valve reliefs that add this much space to the chamber), and an 84cc chamber.  Which, according to the calc, should put me at 10.39/1 - just a tad (not enough to bother me personally) below 10.5



Which brings me to one final question before I make enemies with my wife for a while

Is .040" block decking enough to interfere with intake manifold seating?

[Chryco Psycho]

.040 off the block will mess with the intake fit , generally you do not need to remove that much from the deck though , I would mock up the engine & get an exact measurement Before decking the block to get the piston to deck height , you will also want .040 between the piston & the head minumum for best quench & to prevent the piston ever touching the head so you may want the piston .010 under the deck with a closed chamber head

[resq302]

And yes, the rear exhaust manifold bolts tap into a coolant passage.

Front holes also for the manifold goes into a water jacket.

[defiance]

Yeah, understood - definitely mocking up the engine before milling... Milling's a kinda one-way process

Ok, so I want to leave the piston .010 minimum deck height?  hm...  Makes it much harder to hit 10.5 with the 7cc valve reliefs on the speed pros...
Best I can come up with that way, even with at .030" gasket (keeping with the .040" minimum gap), is 10.1...  Looks like a little bit of deck height goes a long way to reduce compression...

Anything else left that I can do, or is 10.1 really the best I can get unless I get combustion chambers smaller than 84cc?

Either way, the engine should rock   I just figure if it's possible to get those last few compression points...

[Runner]

if you have your eheads in hand you might want to cc the chambers.  mine all came in at 82cc with a couple close to 83.     comp has 2 different 282 cams, one is a 282s cam and it seems like a nice mellow smallish solid lifter cam.  the xe282s cam  has much more agressive lobes,  so it thinks its a smaller cam at idle and has good vacuum but really is a much larger cam.    i love mine!

[Chryco Psycho]

better to lose a little compression than to use the heads to stop the pistons me thinks !!!

[defiance]

Agreed...

I just pulled a little deeper, though... either dad just completely forgot, or the guy he had build this lied......  Whatever the case, these rods are NOT forged.  Curse it. 


So now I'm starting to think...  I've got to replace rods and pistons, minimum $1k for those...  why don't I do a 440source 500 stroker?  The difference is just a few hundred bucks, and the longer stroke allows me to hit higher ratios with MUCH higher clearance (deck height of .04 and .04 gasket with the 4cc reliefs in the pistons that come with that kit hits 10.4 - and I'd *never* have to worry about clearance)

Any reason I shouldn't go that route?  Like I said, now that I've got to buy rods anyway, the price difference is minimal...

[firefighter3931]

The proper way to build it (493 street/strip) is with a zero deck piston and use the headgasket to create your quench zone. You will need a 12cc dish piston to hit your 10.5:1 target with a .040 gasket and 84cc closed chamber. 


Here is very detailed thread on this exact buildup....read it closely and learn ! 
http://www.dodgecharger.com/forum/index.php/topic,782.0.html


Steve's 493 up and running video 
http://www.dodgecharger.com/forum/index.php/topic,13148.0.html



Ron

[SeattleCharger]

  How is a stroker a few hundred more?   a reg. rebuild with bore you need to replace pistons, I prob. need rods too, 

   Were other things in your motor already changed that makes going to a stroker easier?    A rebuild (quote) on my 440 with bore job and forged pistons and nice cam is about 3K.
thanks.

[defiance]

er... not sure what you're asking?

Basically, for the configuration I was considering, I'd need rods, pistons, rings, and bearings - all of which (parts) I could have gotten for around $1000.  The stroker kit (440source) is around $1400, and includes all that (plus a forged crank, which I could certainly use too..).  The labor should be pretty much the same either way (with the exception of the grinding for clearance mentioned with the stroker, which I don't expect to add significantly to cost), and the rest of the parts I would be doing the same both ways.

So, altogether, since labor is the same either way, a few hundred difference.


Thanks for those links, LOTS of great stuff! 

I keep being right on the verge of ordering parts and finding something new that changes my outlook...  I think I'm ready to order parts (again ), but just in case, I'll keep researching for a few more days first.

Thanks for all the help!!

[Steve P.]

better to lose a little compression than to use the heads to stop the pistons me thinks !!!

Neil made a funny....

[Chryco Psycho]

Sorry

[Steve P.]

Neil, don't be sorry. You are absolutely right and it was funny. What better way to remember something??

[SeattleCharger]

Yup defiance, that's what I was asking, thank you.      Hadn't considered a stroker, . . .

[defiance]

What, wouldn't the heads do a pretty good job of stopping them???  





Thanks for the advice - I'll get 14cc valve reliefs (12cc works for 30 over, 40 over -which my engine is - needs 14, though ), a standard cometic .040" gasket, and deck it to 0.000" with the pistons.

Just to make sure I understand the reasoning there, let me explain my interpretation, and you can correct me if I'm wrong

Basically, quench is what makes closed chambers 'better' - it's the turbulence created by having the sides of the combustion chambers come very close to completely closed, forcing the air not only to compress, but to 'relocate' right at the end of the compression stroke.  It works best at very close tolerances, so you want your pistons to come as close to the heads as possible, BUT you don't want to get closer thatn .040" for tolerance purposes.

Thus, 0 decking with a standard .040" gasket is perfect for closed chamber heads, and I should use valve reliefs to snag my target compression.

Did I get that right?

[firefighter3931]

Basically, quench is what makes closed chambers 'better' - it's the turbulence created by having the sides of the combustion chambers come very close to completely closed, forcing the air not only to compress, but to 'relocate' right at the end of the compression stroke.  It works best at very close tolerances, so you want your pistons to come as close to the heads as possible, BUT you don't want to get closer thatn .040" for tolerance purposes.

Thus, 0 decking with a standard .040" gasket is perfect for closed chamber heads, and I should use valve reliefs to snag my target compression.

Did I get that right?

Yep, you've got the general idea. The tight quench forces the air/fuel mix into the chamber to be ignited and burnt. The loose quench engine will have the air/fuel mix ignite on top of the piston instead of in the chamber. This is what costs power and promotes detonation. Obviously, not all the air/fuel will be burnt above the piston in a loose quench engine, but enough of it will be to create issues, especially if the goal is to use pump fuel and make as much power as you possibly can out of the parts available. Most of todays newer engines use small efficient combustion chambers to maximize power with crummy fuel.


Ron