.40 over 170 rebuild

Slant 6 Engines

  1. 68val_100

    68val_100 Member

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    Heyguys and gals. I have a 68 valiant with a 170 and a column 3spd. Original motor. I am enrolled at my local college and in my engine machining class my shop teacher gave me a short block 170 someone left there over 5 yrs now. I opened it up and everything is new or no miles since rebuilt. Crank, cam, 40 over pistons, bearings, and timing chain. I am going to tear it all back down and clean out the grime from sitting all these years and reassemble.

    Now I am asking what else should I do for performance wise? I plan on a 4 barrel setup and dutra manifolds. Mill the head and block? Get the cam reground and what specs for a more agressive sound and performance? And this car is my daily driver.

    And this is what its going in. [​IMG]
     
  2. adiffrentcity

    adiffrentcity Bent Rodder

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    What rear gears are in the car? I ask because performance upgrades will inevitably decrease torque and driveability. Make the motor too peaky and you'll need some tall gears just to be able to drive around.

    First thing is to verify the block is square, don't trust what you don't know, check all tolerances etc.

    IMHO milling the head is probably a waste of time and effort. You might just have to deal with what comp ratio you get.

    That being said it was free so maybe offset milling the rod journals would be good practice for you and put your pistons further up in the hole.

    Talk to the good people at Oregon cam grinders about what grind would motivate the car best. You'll need to have the motor back together and know your compression. Also by that time you'll need to decide how street able you want it and decide on a rearend ratio to suit that driving style.

    Also since you'll wind up down the spiral anyway, plan and collect parts for a 4-speed O.D. Swap.:burnout: And put it in the floor where it belongs!

    Intake and exhaust sounds fine so far. Just don't get too big of a carb. I had a 500 cfm Holley two barrel on a 225 that was built to the gills, you should prob go for a 600 or smaller four barrel.. Yes I know that is a very short list of available carbs once you start looking.

    Good luck and have fun! Remember all the changes you make will affect the rest of the car so be sure to invest in brake upgrades as well. :cheers:
     
  3. 68val_100

    68val_100 Member

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    I believe the gears to be 3.23's or 3.55's. Its horrible on the freeway.

    I plan on checking on the tolerances when i have it torn down. Now why would increasing the CR be a waste of time?

    And someday I would love to change it to a 4spd on the floor.
     
  4. adiffrentcity

    adiffrentcity Bent Rodder

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    I didn't say increasing the c.r. Would be a waste, I was trying to make the point that milling the head prob won't get you enough of a reduction in chamber size to matter. And you could weaken the deck, there is water(coolant passages) all over the place in the head.

    If you want to bump the compression without changing parts MAYBE milling the block would get you partway there but there are limits to how much you'd want to do, as too much will put you into the water jackets and it's likely been milled already.

    Those things are what led me to the the idea of offset grinding the crank, putting the piston up higher is the preferred way to get your target c.r.

    You need to figure out where it's at before you decide where to go, you could have nice compression in your free motor already. Then it's just a matter of cam selection etc.
     
  5. Charrlie_S

    Charrlie_S Well-Known Member

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    To adiffrentcity. I'm sorry, but I disagree with most of what you said.
    First of the most "bang for the buck" on a slant six is to increase the compression ratio. Within limits there is no down side. It will increase torque, horse power, and economy.

    68val_100
    Most slants sixes from the factory have less then 8-1 CR. For a street driver I would try for between 9.0 and 9.5 to 1 CR. A 170 engine is different then a 225. The 170 is a zero deck motor (piston comes up to the top of the block). In the real world the piston is usually about .015 down from the deck (a 225 the piston is about .170 to .180 down), so you can't mill much from the deck. If the deck is flat just leave it alone. Mill the head to get the combustion chamber to the size required for the CR you want. Measure to find what you need. A slant six head can be milled as much as .100-.125. This can give over 10-1 (too high for a daily driver).
    Offset grinding to crank is too much money for the minimal gains, and you need to be carefull you don't raise the piston out the top of the block.

    I would shoot for about 9-1 CR, a mild cam. free flowing exhaust (dutra duals are good, but I would stay with a single pipe). Offie intake, with a 500 Edlebrock (that carb is a little large but it should work OK). Electronic distributor (recurved) and a HEI icnition system.

    I have a 64 Valiant street car with a 9.5 CR 170, the mild MP cam, It is .060 over (bored and honed with a block plate (not necessary in your case), Balanced (again not necessary in your case). Stock intake/exhaust manifold, stock 1 bbl carb (I plan on trying a 4 bbl manifold and a Q-jet carb, in the future), free flowing single exhaust. Ign as described above. Car gets around 26-27 mpg, and is very peppy. 3 sp on the columm, and 3.23 rear.
     
  6. Darter6

    Darter6 Well-Known Member

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    I'm with Charrlie on this one. He knows 170's.
     
  7. VDART

    VDART Well-Known Member

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    Charlie is the man-- ask his advice on the slant & the 170 he won't steer you wrong,
    Lawrence
     
  8. 68val_100

    68val_100 Member

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    Thx for the replies guys, Especially Charrlie_s. I will Check all the parameters this monday in class. Now when you say mild cam, what do you consider mild? I have the cam profile card from oregon cams but this is where I tend to get lost.
     
  9. Darter6

    Darter6 Well-Known Member

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    A photo or the specs from the card will be helpful.
     
  10. Charrlie_S

    Charrlie_S Well-Known Member

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    Yes, the compression ratio and cam should work together. You can run more compression with a bigger cam. With a real mild cam, you don't want too much compression, or you will need premium fuel. It will also be harder to get a good usable timing curve. If you don't have much experiance, I would suggest staying about 9 to 1.
     
  11. 68val_100

    68val_100 Member

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    This is the print out of cam profiles they can grind.

    [​IMG]
     
  12. vntned

    vntned Well-Known Member

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    Hey Charlie, I've got the old tired 170 out of my '64 that I've been wanting to dig into. I'd like to do a fun street motor that could be driven on a regular basis, but still be a hotrod power plant.

    I've collected a new Clifford HyperPak intake manifold, a pair of Clifford shorty headers and a new Holley 390 carb, and really need some direction on what to do about the rest.

    What would be a good recipe, top to bottom, utilizing the parts I already have?
     
  13. adiffrentcity

    adiffrentcity Bent Rodder

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    Sorry to all, I thought I was making common sense suggestions that might have saved him some heartache
     
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