Outline for 4.6... Acceptable?

[Jeep's Jake]

Near as I can tell this is spot for build help, so I'm hoping for some advice from the pros. I've never built a rotating assembly before, so here goes. First off, here is my proposed build - it's a slight rip-off of Dino's Rockcrawler Engine:

What I have:

4.2 Crank (4 counterweights)
4.2 Reconditioned rods w ARP hardware
Silvo-lite UEM 2229 pistons .030" over & dished to 25cc's
Comp 68-232-4 Cam
0630 Head with light port work, resurfaced deck (Assuming 55cc's. Have not cc'd it - Is this a good guess?)
.043 Mopar Performance head gasket

What I intend to do:

Bore .030" over
Mill the deck down to "0" height for a quench of .043".

It's also worth mentioning that this engine will be supercharged. I'm perfectly fine with only running 5lbs of boost through it. My cam selection was based on this fact and a recommendation by Comp. Also, I'm about 1000' above sea level.

Using the calculator I came up with a 9.6:1 SCR and an 8.26:1 DCR. I'm looking for performance, but I'm concerned that this might be a bit high, and I want to correct that now if need be. Because my jeep isn't a daily driver I don't mind running 93 octane. With the winter coming up, I'm hoping to scrounge up enough money to get the machining done and get started building this engine. So I guess right now I'm looking for any advice on whether I need to change my compression or not before I finalize what I want to do for machining. Or if there are any other details that I have missed, make sure to point them out at my expense. Gotta learn somehow.

Thanks in advance.

[doc65]

I believe that is a bit high on the compression for a forced injection installation. On the combustion chamber/head volume, I recently came across the machine shop tag for the head that's on the stroker I'm just now breaking in(machine work & short block were done 7-8 years ago, maybe more). before putting the head on I cc'd it at 57cc's, the tage says the surfaced it .012" to get it flat, so that gives you some Idea.

The one I'm putting together now is:

677's +.020 I plan on having the dished to 24-25
4.2l short rods
heavy crank 12 cwt
possibly that same 68-232-4 cam or a stock HO that I have
decked to .003-.005
.043 head gasket
I figute 9.37 static & right at 8 dynamic on the 232 cam, and like 7.8 dynamic with the stock cam

[Jeep's Jake]

A bit high for forced induction, but what about just N/A? I plan on using the boost as more of a back up to wake it up when I really get into it. The less PSI I run the happier (and cooler) my little blower is going to be. For this particular build, I'd rather see an efficient, gutsy engine with a little boost than a lower CR engine spinning an undersized SC to the moon... At least I think that's the way I want to go.

Doc, do you know the casting number on that head? Not sure if it makes a difference or not but can't hurt to know. Also, what octane do you plan to run?

If I use the numbers you have (57cc chambers, and a deck height of .005"), my numbers do drop down to 9.32 and 8.02 and still keep a .048 quench. So I can drop my compression down a bit by not decking it so much - would it be a smarter way to go? Or am I safe with good tuning and a bit of common sense? How much is .24 (8.26 - 8.02) worth when it comes to DCR? Is the gain of compression worth the increased risk of detonation at this level?

[herbiehind]

A bit high for forced induction, but what about just N/A? I plan on using the boost as more of a back up to wake it up when I really get into it. The less PSI I run the happier (and cooler) my little blower is going to be. For this particular build, I'd rather see an efficient, gutsy engine with a little boost than a lower CR engine spinning an undersized SC to the moon... At least I think that's the way I want to go.

Doc, do you know the casting number on that head? Not sure if it makes a difference or not but can't hurt to know. Also, what octane do you plan to run?

If I use the numbers you have (57cc chambers, and a deck height of .005"), my numbers do drop down to 9.32 and 8.02 and still keep a .048 quench. So I can drop my compression down a bit by not decking it so much - would it be a smarter way to go? Or am I safe with good tuning and a bit of common sense? How much is .24 (8.26 - 8.02) worth when it comes to DCR? Is the gain of compression worth the increased risk of detonation at this level?

what do you get if you polish chambers to 60? and leave deck at zero?

[doc65]

Doc, do you know the casting number on that head? Not sure if it makes a difference or not but can't hurt to know. Also, what octane do you plan to run?

If I use the numbers you have (57cc chambers, and a deck height of .005"), my numbers do drop down to 9.32 and 8.02 and still keep a .048 quench. So I can drop my compression down a bit by not decking it so much - would it be a smarter way to go? Or am I safe with good tuning and a bit of common sense? How much is .24 (8.26 - 8.02) worth when it comes to DCR? Is the gain of compression worth the increased risk of detonation at this level?

Those number I'm duplicating are really close the same as the one I just hit 525 miles on yesterday(biggest difference being short rod on the next one, long rod on the one I'm driveing right now), it runs well on the 87-88 mid grade here, I plan on trying the 85-86 "regular" .24 DSR doesn't sound like too much, but from what I read you are then approaching what you can reliably run on pump gas, depending on Temp, Altitude, etc... as to deck height it seems that the "optimum" quench distance for best quench vs. rod stretch & piston expansion is about .045 so I just figure .005 is an easy number added to the .043 for a total of .048. once I mock up the engine I might go to .000 deck & then be good with .043 as close enough, and still be ok if I had to replace the head gasket and could only get the .052

As to the head that's on this stroker it's a 7120 casting, the next one has a 630 head but I haven't cc'd it yet.

[Jeep's Jake]

With 60 cc polished chambers and a 0" deck height I get a SCR 9.14 and a DCR of 7.87. Is it safe to clean up the chambers this much even after a resurfacing? That's an awesome name too btw.

I'm sensing that 8.0 with a good quench seems to be the limit that can be run on mid grade then... How much should you allow for piston expansion and rod stretch? What is the best way to measure the deck height during the mock up with a cold block and internals? I like the .043 MLS head gasket because It's rated to hold up to 12:1 compression. Not that I'll be on that threshold, but I feel better about running that compared to a composite gasket that is thicker - especially with boost. Than again, I've never really heard of anyone losing a head gasket on these engines. Should I be concerned?

[Jeep's Jake]

Just stumbled across this thread...

http://www.jeepstrokers.com/forum/viewt ... =15&t=2637
What Octane Can I Run?

Good stuff. Ill do some more looking next time. My questions about proper measurement still stand though, unless someone can redirect me to that thread too...

Thanks guys.

[herbiehind]

i answered but it didnt go through i guess . not sure on the resurfaced head but my 2 cents is ,it's okay to do . as far as measuring i'd use a cylinder bridge with dial indicator solidly attached and measure at center of piston along wrist pin axis so if it tips it wont matter . do each cylinder , so assemble with good bearing clearances and oil and rotate and check each one . thanks on the name . i stole it from radio personality from years ago .

[Jeep's Jake]

Very good then, that's what I'll do. Once I get this engine on the road Ill start up a build thread in the projects section. I'm sure more questions will come up. Thanks again for the help.