Timing requirement for a SBC

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by MKR-588, Oct 29, 2017.

  1. MKR-588

    MKR-588 Member

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    Just curious on what total timing a SBC with 23° heads would want on the safe side.
    Engine is 4.125 bore with 3.50" stroke and has a Littlefield 871 competition alcohol blower with 10% OD.
    Engine made 22lbs boost measured in the intake @ 5500 rpm but both MLS head gaskets leaked with one torching then head slightly on the dyno.
    Thanks for any help.
     
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  2. Ray Hadford

    Ray Hadford New Member

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    We run 32 degrees max.. Our motor is 4.125 bore with 3.75 stroke. (400 cu in)

    11:1 compression ... 8-71 boost at 15% overdrive is 20 psi peak. Not sure where that happens.

    Our heads are AFR 220 23 degree type.

    We turn the motor 8000 max. Fuel is Methanol.
    Head gaskets are .060 copper with wire O rings. We have over 45 runs without tear down. Still going strong. .. low 6.70s and 200 with a converter and Glide trans.

    You may be a bit on the lean side.....

    Ray H.
     
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  3. MKR-588

    MKR-588 Member

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    Thanks Ray, can you tell me if your block has separate 'O" rings on each bore or are they joined in the middle like a figure 8. ? They recommend around .100" between each O ring and on a big bore SBC it doesn't leave any room on the edge of the bore. Just wondering if you know how yours was done.
     
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  4. Ray Hadford

    Ray Hadford New Member

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    We have the figure 8 configuration. O rings are in the block with receiver grooves in the heads. I have a spare head from the previous motor owner. The head was badly torched on one outboard cylinder. There is not a lot of room for placement of the receiver grooves.. Holes for studs and water passages are very close. Looks like the problem started at a hole in the head that was too close to the O ring. Plugged port nozzle may have also happened.

    SCE gasket Co. gives dimensions for wire grooves and receiver grooves based on gasket thickness. Look at Good Vibrations web page.

    I did not build my current supercharged motor, I bought it and have not had the heads off. Leak down was good cold, so I did not take it apart. Leak down gets considerably better warm as the copper gasket expands. We also run circulating water in the block and heads with a Dedenbear 15 gpm electric pump . I have a swirl pot (vertical dry sump) tank for coolant and run it non pressurized. A small block with the two exhaust valves close together builds way too much heat without the water coolant.

    If I were starting from scratch I would use gas filled rings or "Hoops" as Alan Johnson calls them.... I ran those in my naturally aspirated 17:1 comp. A/ND motor for many years, starting in 2004. That motor required iron heads and block. per the rules.

    We circulated coolant in the heads only, pumped in between the exhaust valves and out at the 4 ends of the intake.

    There is a machined counter bore at the top of the cylinder wall that the rings fit in. We used a thin shim gasket of Stainless to seal coolant. The depth of the counterbore depends on your gasket thickness. AJPE can give you guidance on this subject. Not really sure what they do for shim or gasket. They do not run coolant. Will Hanna may also have some ideas.

    Ray H.
     
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  5. MKR-588

    MKR-588 Member

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    Thanks for your help Ray, much appreciated. In regards to your swirl pot, does it just have one line in and one out at the bottom to feed the pump with a percentage of the pot empty to allow for any expansion of the coolant or do you have another tank to capture the overflow?
     
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    Last edited: Nov 5, 2017
  6. Ray Hadford

    Ray Hadford New Member

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    The dry sump tank cost about $120 from Speedway motors. Mounting parts and clamps are also available from Speedway.

    The Dedenbear remote mount water pump is mounted low on the frame. It is connected to the # 12 outlet at the bottom of the tank . We feed the water from the pump into the two rear lower block freeze plug holes. One on each side. I bought some special O ring freeze plugs with # 8 fittings from Neal and Parks. The number 8 coolant returns come out of the top, front of the intake manifold. One on each side, and return to the top of the tank. One tank inlet for each hose.

    The tank is mounted so the coolant ( water and Red line water wetter mix) level is about 2.5 in below the top of the tank. The coolant level is the top of the intake manifold, where the return lines are located. The tank is not pressure sealed. The cap seals the lid, but an open # 6 line leads to our two gallon puke tank. We get very little over flow into the puke tank.

    Send me a phone number and I will send you a text with pictures.

    rayhadford@frontier.com

    425-238-3235

    Ray H.
     
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