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Author Topic: detonation prevention open chamber head???  (Read 30997 times)
wyoming4x4
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« on: January 28, 2011, 11:20:28 pm »

 working some D3ZE 4v heads on a 400 ford. gonna be in the 9.6 comp ratio hyd roller. My question is on the combustion chamber and polishing the chamber. Polishing the chamber will help with hot spots and carbon build up. these are the heads I'm gonna run in this application and trying to get everything I can get out of it. meaning detonation prevention. Running 88 octane or better pump gas or 91 octane. If their is something I'm missing drop a message. 
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Brian S
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« Reply #1 on: January 31, 2011, 03:44:51 am »

Unless you're running a somewhat small cam you should be fine. Some say a multi-spark ignition helps detonation with open chambers but I've never seen any real testing to back it up. Make sure you use the correct thermostat.
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68mustang405
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« Reply #2 on: January 31, 2011, 12:11:30 pm »

How do you figure a small cam will help? I would think that would build up cylinder pressure if the intake closes early. If you use a came with a later intake closing it would help bleed off some of the compression. Usually that's bigger duration cams. Also remember polishing the chamber will slightly increase it's size.

What's the whole combo? What are you going to do with it?
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« Reply #3 on: January 31, 2011, 01:06:43 pm »

So you are going to use a 351C head on a 400? Also what did you do to get the compression up that high? I know it's stupid to say that 9.6 to 1 is high but all of the 351M/400s came with 8.0 to 8.4 to 1 compression ratios (except for the 1971 400, which had a 9.1:1 CR). I'm just curious.
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Brian S
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« Reply #4 on: January 31, 2011, 01:41:26 pm »

How do you figure a small cam will help?

I didn't say a small cam would help. I said he should be fine unless he's running a somewhat small cam (like a cam with less than 220 @ .050). Hot Rod did an article years ago with a 400, 9.5:1 compression, polished open chamber 2V heads and it ran really well with a 268XE cam. It probably used 91, possibly 93 octane fuel. All they had to do to bump the compression was to use flat tops and deck the block enough. 400s have a lot of deck clearance.
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par442k
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« Reply #5 on: January 31, 2011, 02:22:57 pm »

Some say a multi-spark ignition helps detonation with open chambers but I've never seen any real testing to back it up.

Brian, I have heard this as well, but I was told by a MSD tech that the muti spark pretty much is done by 3k.
Make sure any sharp edges are smoothed over, I would also debur the sharp edges on the pistons while your at it.

Rick
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68mustang405
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« Reply #6 on: January 31, 2011, 02:45:03 pm »

How do you figure a small cam will help?

I didn't say a small cam would help. I said he should be fine unless he's running a somewhat small cam (like a cam with less than 220 @ .050). Hot Rod did an article years ago with a 400, 9.5:1 compression, polished open chamber 2V heads and it ran really well with a 268XE cam. It probably used 91, possibly 93 octane fuel. All they had to do to bump the compression was to use flat tops and deck the block enough. 400s have a lot of deck clearance.

Oh wow my mistake, yea definitely read that wrong. He could use a small duration cam and retard it a little if it was pinging, but using a larger duration cam would be the best bet.
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Brian S
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« Reply #7 on: January 31, 2011, 03:58:18 pm »

IMO there were a lot of reasons why these engines detonated. Vehicles were heavy and poorly geared, carburetors were very lean, coolant temps were high, ignition advance rates were all about lowest emissions, EGR was temperamental and some would disconnect it thinking it would make more power...but all it did was make the engine ping more. Like I said, 9.6:1 should be fine because I doubt you're running a stock type or RV cam.
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wyoming4x4
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« Reply #8 on: February 01, 2011, 10:41:02 pm »

thanks guys for checkin in. yes the compression is around 10 and with cam comes in at 9.6 comp. My intake valve shuts at 33 degrees. It has some duration but don't have my cam card with me. custom cut by www.mpgheads.com for my application. Scott is a high elevation guy and knows my air we have. Its a .520 lift for towing mainly. Waiting on block and haven't settled on compression ratio yet but this is where I'd like to be. But my biggest concern is building some prevention into this setup. Polishing and smoothing combustion chamber is common sense. I'm running a cleveland piston flat top with a valve relief for intake. Gonna get the piston up around .020 below deck and heads are cc'd at 73cc and a cometic head gskt around .051. Msd 6a and a msd distrib. air gap 351 cleveland intake with spacer plate, price motorsports. I live at 4000' and play higher often. catch you later and waiting on block at line hone.
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wyoming4x4
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« Reply #9 on: February 01, 2011, 11:00:59 pm »

 forgot to mention the d3ze heads are epoxy ported smaller to help with port velocity. wanting a strong 2000 to 4500 rpm. Ran the 2v heads before and ran well and this is a experiment I've been wanting to do for awhile and now the money is being spent for my science project. d3ze heads are the 4v heads/cj with big valves 2.190/1.71. 5 speed tranny manual with 4.10 gears on 32" tire. 4wd truck around 5500 to 6000lbs. but if haulin trailor/weight goes up. hoping the 5 speed will help in splitting up the load on engine. catch you later.
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Brian S
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« Reply #10 on: February 02, 2011, 12:30:58 am »

If you can supply all the specs I'll run the numbers through a compression calculator to get a better estimate where the Dynamic (Net) Compression will end up.
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wyoming4x4
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« Reply #11 on: February 02, 2011, 12:39:27 pm »

 block .020 deck at this time. waiting on line hone. block has been torque plated. heads d3ze 73 cc. 4v heads. 2.190 int 1.71exh. cleveland piston flat top 3cc valve releif. have .041 head gskt but lookin at .051 cometic or thicker. thinking the .051 is right at 10 to 1. cam is 33 degrees int close and a .520 lift. 400 ford 6.58 rod length. 4000' elvation is at my house and often run higher. Did the keith black compression calc. and said little over 10 to 1 and cam makes it around 9.6 comp. this close to where i think I should be maybe a little lower. thanks guys and catch you later
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Brian S
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« Reply #12 on: February 03, 2011, 07:43:11 am »

Is .020 the piston deck clearance or how much (if any) was removed from the block?

If it's the deck clearance I got 10.17:1 static compression using a 4.1 dia x 051 thick gasket. To calculate the net compression I need the valve closing point after bottom center using advertised duration. I'm pretty sure your 33deg is the number based on duration @.050. If you don't have the number I can figure it out if you tell me the advertised durations, Lobe Separation Angle, and the Intake Centerline Angle.

My calculator does take altitude into consideration to estimate cold cranking (PSI) compression. It has no affect on compression ratios.

...Did the keith black compression calc. and said little over 10 to 1 and cam makes it around 9.6 comp.

What do you mean by the cam makes it around 9.6 comp? The number is way too high to be correct for the "dynamic" or "net" compression. Should be in the 7.5-8.5:1 range.
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wyoming4x4
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« Reply #13 on: February 04, 2011, 01:06:13 am »

I'll pick up cam card tommorrow and give you some better info. thanks for checkin in. gonna be at a archery tournament all weekend and not gonna be getting back till sunday eve. Catch you later.
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wyoming4x4
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« Reply #14 on: February 04, 2011, 01:08:58 am »

On compression I was using the keith black compression calculator. thanks and talk soon.
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