Next step for my 350

Discussion in 'Small Block Tech' started by UNDERDOG350, Jan 24, 2015.

  1. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    No problem Derek, just the feedback I was looking for. Can't believe Gary hasn't offered up anything yet.

    I'm not sure yet how the relocation is going to work. I didn't think of moving toward the center of the chamber but it makes sense from unshrouding side of it. I have concerns about relocating the rockers to match. Also would make the short side radius very tight on the exhaust side. Not sure there's enough iron there to blend it into the port.
     
  2. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Cool, I'm glad I'm on track.

    Before I offer rocker relocation advise I need to ask if you're trying to use all stock(or stock looking) parts for stock class racing? I have a few different ideas on how to move the rockers for stock and aftermarket parts. Are shaft roller rockers allowed in stock class racing?

    We can just move the intake towards the spark plug and leave the ex. where it is and still make the stock rockers line up, I need to know what rules we're playing with though to explain how to do it. The maximum that the ex. valve can be pushed toward the spark plug is only .020" to fit a 1.550" ex. valve where a 1.500" valve was removed, the extra .005" is to make sure you would get a 100% cleanup @ 1.550" diameter. Moving the centerline over .010" would require making the circle .020" bigger to get the old circle to clean up. So in your case the ex. valve can't be moved that much anyway unless you want to get greedy and put in 1.600" ex. valves but then some outward moving will be needed. Only moving them .020" or even the extreme greedy max of .025" for a 1.550" valve should have the extra .040" to .050" material for the ssr to be re-blended.



    Derek
     
  3. alec296

    alec296 i need another buick

    1.550 should fit as gm went to them in later heads.
     
  4. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    We know that Andy, the 1.550" is the stage1 size as well I think? Anyway I was explaining how much the valve can be moved for the 1.550" size for the seat to be machined so it will cleanup 360* of the diameter.



    Derek
     
  5. NickEv

    NickEv Well-Known Member

    Some great info being shared in here
    I wonder though,on a engine like this where you are limited in power by design,if IMO i would worry too much about a larger exhaust valve
    I would try to move the head over on the bore ( dowel/driLLing ,both)and look to get the largest intake valve that will fit ,then get the chamber and bowl above and below said valve to the shape i want(which the larger valves would help with by giving porter more latitude in short side shaping)
    The exhaust on those heads are so low to begin with as Steve stated,adding a larger valve only makes the situaton worse by taking away valuable short side height
    Exhaust demand isnt that great on a N/A engine such as this ,that you couldnt get all the evacuation you need by cam timing adjustments and then some
    Also the INTAKE is where i thing the magic is and would bet if you flowed the heads in any configuration and added that manifold,youll see the extra work you are doing shows a far lower improvemt than you hope for
    I know when i did muy old 350 stuff,i had a lot of time in the manifold and it still was not what i wouldve liked to see
    Not so much chasing just a peak flow number,as that will get you into trouble when porting manifold,but tha cylinder to cylinder variance was terrivle o nthe facotry stuff and not better on the T?A piece
    The plenum on the aftermarket stuff needs a ton of work IMO
    But hey, just my opinion
    Good luck
     
  6. alec296

    alec296 i need another buick

    it would be easyer to relocate the valves in head for bigger valves then relocating the head itself. and there isn't much clearance for bigger valves where valves are located now as they would hit each other
     
  7. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Plus with how streamlined that Buick made the deck there isn't much room to move the locating dowels to move the heads much. Could probably get away with maybe .025" to at the very max .050"? Maybe even less, I would have to do some measuring to know for sure. Besides it would be a pita to slot or drill larger the head bolt holes to do that. So without slotting or enlarging probably .010" to .015" would be the most, not sure it would be worth it.



    Derek
     
  8. NickEv

    NickEv Well-Known Member

    Move a head over 030" on a flow bench to get intake valve away from the chamber wall,and then see how much its worth!!!:TU::TU::TU:
     
  9. alec296

    alec296 i need another buick

    With small valves its not worth it and you would need to open chamber in head around valve also. A lot more from available from porting with bigger valves can be gained without all the work .
     
  10. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    Derek,

    If you are passing by my area could you drop off those head sections? If not home put by big garage door.

    I want to see how much material is under the valve springs for cutting locating shoulder for the new conical springs.
    Thanks
     
  11. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA


    Hey Steve, I'll be passing by your area tomorrow but the head sections are sitting at the head porters. I can see if I can get them tomorrow? If so I might be able to drop them off late tomorrow night? If not it may be a week before I can get them back to you?

    If I get them tomorrow if you want to take a ride up to Dave's shop, its the next exit north on 75 from your exit then about ten miles north from there, probably 10 to 15 minutes from you if you're looking for a machine shop close to you and want to take a ride out to meet Dave? I'll be there to drill the back side of a Buick crank for some Mallory slugs, I got the front done last Saturday.

    PM your phone # if you want to take a ride out tomorrow I'll give you a call to let you know if I can get the sections if you can get away? Can show you Andy's parts for his build that are in the process of being balanced, but the block and girdle are at my garage, may be able to grab the heads so you can see how I moved the valves if you're interested? It would be a lot easier to explain how to modify the rocker shafts in person with a set of heads sitting there for reference too if you're interested in that.


    Derek
     
  12. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    I can't get away tomorrow. There's no rush in getting them. Probably not going to get started for a month or so. I'm around this weekend though.
     
  13. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA


    Saturday is Valentine's day and will be in the teens so I'll probably stay home and try to stay warm? Maybe Sunday? If not within the 1 month time frame shouldn't be a problem we should be able to figure something out.




    Derek
     
  14. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    I don't want to be greedy with the attention. Figured I'd let others share their knowledge too. :bglasses:

    Besides, I've been busy doing other things. Got some big plans...

    I've already gave my 2c on the cam upgrade for the most part. Higher IVC point means less DCR as you go up in camshaft size while retaining the same SCR. If memory serves, yours sits around 7.59:1 DCR with the 66* closing point of the Crower level 3 cam, up from the 58* closing point of the Level 2.
    I'm surprised you didn't ping on premium pump gas with the level 2 cam and that compression.

    The level 4 gives 70* I believe, which drops your DCR even further. With extra overlap though, higher RPM usage might be borderline with detonation depending on how well you're flowing (and scavenging). I think you'll be fine with what you have, though I'd be tempted to bump the compression a tad if it were me, since you plan on using racing fuel anyway on your drag runs and optimal tuning for such.

    Otherwise, tune it for premium pump gas and let'er rip.

    Gary
     
  15. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    With the level 2 I was running stock 1970 spec pistons and deck height. Probably only 9 to 1 max.

    I might cut the new heads a little more to maintain optimal compression.
     
  16. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    Keith Black makes a pretty good set of hypereutectic pistons I hear (or read), made out of 390 alloy I believe? Supposed to add an extra 2% power to your engine simply because of the thermal reflective properties. Add in another 1-2% for the tighter clearances (practically no blow-by and increased cylinder pressure/less bleed-down) and lighter weight vs comparative cast pistons, and you end up with a very nice upgrade.

    These pistons are also supposed to be 30% stronger than factory pistons, more wear resistant (coupled with Buick's high nickel content in the block, would make for a very long lasting rotating assembly) and require less advance for optimal ignition timing, putting the piston closer to TDC for combustion initiation. This would also aid in detonation resistance and/or allow increased compression on any particular grade of fuel octane.

    The top ring has to be fitted with additional clearance to compensate for thermal expansion due to the increased combustion temperatures-this is for the top compression ring only.

    They're good to around 6200 RPM, which matches up nicely with the capscrew conditioned stock rods.

    Summit offers them for the Buick 350 now (instead of having to piecemeal them from v6's and adding a couple of singles) with 1.805 CH and 3.05x.205 dish= ~22cc considering the slope on the dish. They're also offered in the traditional sizes of std, .020, .030., .040, and .060 overbores.

    Let's not forget that the Buick 350, despite its open combustion chamber, has a small combustion chamber due to its relatively narrow bore size (which in this case goes in its favor) which aids in the detonation resistance even with no quench.

    You'll still need to get deck as close to zero as possible and get head cc chambers down to around 50cc in order to bump comp to around 10:1, but it's definitely doable. Most of the machine work cost is in setting up everything and truing things up. Extra material removed is only a little more money.

    Anyway, lest I prattle on further, auf wiedersehen!

    Gary
     
    Last edited: Feb 18, 2015
  17. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    TA offering on 'Stage1' 350 valves is 1.92/1.55 I/E, but I've seen others put them at 1.94/1.50 I/E, which I personally believe is the better option. So in short, I concur with your assessments on valve sizes.

    It also makes installing hardened seats (on later, thicker heads) easier/safer and doesn't have to be ground out quite so far when using the 1.50" exhaust valve. This leaves more room for the 'magic' intake valve. :TU:

    The curtain area on the intake valve is increased exponentially with larger sizes, so the bigger the better on intake valves, and has even been proven to be true for 'low lift' camshafts...

    It also makes a more conducive environment for the typical exhaust emphasis cam designs that the Buick 350 works best with due to exhaust runner design...

    Gary
     
  18. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    When I measured the valve spacing on Andy's heads I came up with 1.770", with that spacing a 1.94" and a 1.550" would fit no problem.

    1.94"/2 = .970"
    1.55"/2 = .775"

    .970" + .775" = 1.745"

    1.770" - 1.745" = .025" gap in between the 2 valves. Or if the 1.50" ex valve is kept the same, a 2.02" intake would fit with .010" to spare in between the valves.

    Anyone planning on going as big as mentioned above should measure the valve spacing first to make sure there is room.




    Derek
     
  19. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    How much clearance should you leave for a 'buffer zone'? Or would you consider that unneeded? I would think maybe leaving some room for expansion, vibration, clearance movement inside the guides, etc. or should the seats become hammered a bit and expand out some, or the guides become worn it might cause some interference. Maybe not at first, but pile some miles on it and you may get a nasty surprise when two valves 'high five' inside one of your cylinder heads.

    Edit: brain fart.

    Gary
     
    Last edited: Feb 18, 2015
  20. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA


    .010" would be a good minimum amount to shoot for because of factory valve spacing variances, Andy's head's valve spacing's were in the range of 1.766" to 1.770". They are now 1.840" apart, sbc valve spacing is 1.875" a .035" difference that will only be .0175" per valve offset to use sbc shaft rocker like these;

    http://www.ebay.com/itm/261518394433?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT

    Or these;

    http://www.ebay.com/itm/171569356414?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT

    Or if we need a higher ratio these;

    http://www.ebay.com/itm/171429048022?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT


    I have a theory why the '74 and newer heads don't flow as good as the 68-72 heads, the valve spacing may have been moved farther apart than the earlier heads to reduce the likelihood of them cracking in that area? Not sure but when the weather gets better I will dig the set of '77 sbb 350 out of a buried in snow car in the backyard and measure the valve spacing on them to confirm. If they were moved farther apart then valve shrouding could be why those year heads won't flow as good as the earlier versions when they're ported and not necessarily for a port change? We will see in a month or 2.



    Derek
     

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