Re: Where to set initial timing?? 10 degrees BTC?
[Re: lewtot184]
#1999202
01/26/16 07:39 PM
01/26/16 07:39 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,376
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After replying to your post I reread your build and saw you are using KB 236s. They have the "quench dome" design, it's the 237s which are flat top. With your 452 open chamber heads they are a step in the right direction, because they can create squish. It'd be really good to cc your heads and come up with actual numbers as 85cc can be quite low for a 452 which run all the way to 93. The block's deck height is another variable.
About here someone will jump in and tell you you'll have to mill the combustion chambers for equal clearance on the squish pads. That would be ideal, but more important is to mock up the engine and see what the clearance is with no head gasket. You'd like it to barely touch but it probably won't. You need 0.040 clearance when assembled, but 0.055 or more will still give you some benefits, at least it has on every Magnum 5.2 and 5.9 built over the years. Their pistons come within 0.095 or so of the head surface.
If the engine isn't assembled yet you could enlarge the chamber around the intake valve or other advantageous places.
I am thinking your engine will probably have to have total advance down around 32 degrees to run on pump 93. An FBO advance limiter plate would be a good investment.
R.
Last edited by dogdays; 01/26/16 07:56 PM.
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Re: Where to set initial timing?? 10 degrees BTC?
[Re: lewtot184]
#1999278
01/26/16 08:59 PM
01/26/16 08:59 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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I would set the initial with the vac gauge method after it is broke in then set the total (initial+slots) to ~36 (& the FBO plate makes it easy, $25 to your door). I'd mockup the short block & if you have plateau pistons & can get quench then I would mill the open chambers to equalize and level the quench area then mill as needed to set quench. On my 308's (sb) it is ~.095" deep (& varies alot)/milling needed
live every 24 hour block of time like it's your last day on earth
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Re: Where to set initial timing?? 10 degrees BTC?
[Re: HemiStan]
#1999508
01/27/16 12:47 AM
01/27/16 12:47 AM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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its a fairly new addition and the only FBO part I have used that has not failed me. (2 coils, one leaked out the top and the other died). To Dons' credit (Bless his heart) he did send me the 2nd one for free after I sat on the 1st one for a year. The one that died (2nd one) backfired and blew up the muff & scared the Hell out of the driver next to me & he damned near hit the ditch, I think he thought he was being shot at! I'd have your dist man set the total at 35 when it fires plus what the can offers with the initial set to 18 or so just for startup then do the vac gauge method later on afterwards for a spot on tune up
live every 24 hour block of time like it's your last day on earth
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Re: Where to set initial timing?? 10 degrees BTC?
[Re: HemiStan]
#1999572
01/27/16 02:44 AM
01/27/16 02:44 AM
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Joined: Sep 2015
Posts: 1,096 Australia
ozymaxwedge
super stock
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super stock
Joined: Sep 2015
Posts: 1,096
Australia
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I was always at about 18 and a total of 36 but now have the dissy locked at 36 and have a start retard ignition module
1963 Plymouth Max Wedge 1971 Barracuda
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Re: Where to set initial timing?? 10 degrees BTC?
[Re: HemiStan]
#1999605
01/27/16 04:41 AM
01/27/16 04:41 AM
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Joined: Aug 2003
Posts: 43,315 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,315
Bend,OR USA
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I would, and do, weld up the slots to shorten and then file the welded end flat so I get the initial timing set at 16 to 18 BTDC with 34 to 36 total advance Your rotor plate should have 13 stamp on the bottom so you can measure from the advance pin in the slot to the end of the slot to see how much each degree (22 crankshaft degrrees = 13 distributor degrees)is in thousand and shorten that rascal up to what you want Buying and changing the plate and rerriviting is a unneeded agrevation in my opinion
Last edited by Cab_Burge; 01/27/16 04:42 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Where to set initial timing?? 10 degrees BTC?
[Re: Cab_Burge]
#1999659
01/27/16 11:42 AM
01/27/16 11:42 AM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Actually with the plate all you have to do is lift it up & set it (the weight(s) 1/4" pins) in a different pair of slots, takes 5 seconds, no riveting needed & either way (weld/file or the plate) you do have to take the reluctor off. with a thin/long neck pair of needlenose pliers you are able to spread the clip enough so the reluctor can come up off of the shaft. A good habit to get into is always press down on the shaft as you are prying the reluctor up to keep the plate on the pins (A helper comes in handy as it takes 2 hands to work the screwdrivers opposite each other and sometimes even a tire tool after the reluctor is up aways on the shaft and you need different leverage. In addition I would reduce the lower shaft axial play to .005" and check rotor phasing & dial in the dist timing subsystems & I might add a cup oiler on the side like the 60's points oldies had, ALL for a spot on dist with nothing left on the table. EDIT also check/correct if needed intergear top slot/dist lower tang interface slop and reduce rotor metal blade tip to cap terminal clearance to ~.015"
Last edited by RapidRobert; 01/27/16 12:24 PM.
live every 24 hour block of time like it's your last day on earth
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Re: Where to set initial timing?? 10 degrees BTC?
[Re: HemiStan]
#1999709
01/27/16 01:08 PM
01/27/16 01:08 PM
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Joined: Oct 2003
Posts: 3,698 NE Oklahoma
Von
master
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master
Joined: Oct 2003
Posts: 3,698
NE Oklahoma
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What is the duration at .050 for that cam?
Im gonna say you will be in the 20 degree initial area.
You set initial timing where you get max vacuum at idle....
72 RR, Pump gas 440, 452s, 3800 lbs, Corked, ET Radials,. 11.33@117.72.
Same car, bone stock 346s, 9.5 comp, baby solid. 12.24@110.
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Re: Where to set initial timing?? 10 degrees BTC?
[Re: 68jim]
#2000118
01/27/16 11:35 PM
01/27/16 11:35 PM
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Joined: Jun 2008
Posts: 3,916 usa
lewtot184
master
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master
Joined: Jun 2008
Posts: 3,916
usa
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Stan,
Bring your distributor over and lets see what is does initially and modify from there. I picked up a Sun distributor machine last year so it will be easy to verify exactly how the mods change it. I welded the slots on the Hemi dual point and adjusted the initial timing and it made a nice difference! I used the same chart as posted earlier.
Jim 68 Hemi Road Runner there's a plan!
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Re: Where to set initial timing?? 10 degrees BTC?
[Re: 68jim]
#2000190
01/28/16 12:44 AM
01/28/16 12:44 AM
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Joined: Jan 2004
Posts: 9,066 Eugene, Oregon
minivan
master
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master
Joined: Jan 2004
Posts: 9,066
Eugene, Oregon
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Stan,
Bring your distributor over and lets see what is does initially and modify from there. I picked up a Sun distributor machine last year so it will be easy to verify exactly how the mods change it. I welded the slots on the Hemi dual point and adjusted the initial timing and it made a nice difference! I used the same chart as posted earlier.
Jim 68 Hemi Road Runner That is where its at.... We had a distributor machine in Auto shop ( high school 71-73) Really made working on a distributor nice...
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