Aluminum heads... polishing and porosity...

Discussion in 'Cams, Heads and Valve Trains' started by NitroInjected, Aug 2, 2018.

  1. NitroInjected

    NitroInjected Active Member

    So I got some heads and I thought man the combustion chambers chould use a s;ight grind and polish.... well I sanded a lot... enough to drop a few cc's and there were still dimples... My camera cant catch em but they make the surface dull. Nothing penetrating the head but some of those pits are DEEP!

    I tried to just ignore the issue and went through from 180 paper to a 240 flapper wheel to 400 dry and a green soft wheel to a red then rogue.... Feels great but look nasty.... I think the surface is not going to help with carbon which is my main enemy.... Is there a filler besides welding or do I just need to say screw it and clean up the outside and get it decked?
    This is my last snag on the head.

    I wish I could get a good shot of the pores. but after several shots I think I would need the good camera and thats a PITA to get the photos from there to here.

    I will say one good thing. they are smooth to the touch and no longer have sharp edges.
     
  2. Loves302Chevy

    Loves302Chevy "One test is worth a thousand expert opinions."

  3. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    about the ONLY area where cast iron heads tend to have some advantage is that in general cast iron casting tend too have on average a denser less porous surface,
    thats more time consuming to smooth and polish, but one thats easier bring to a semi-mirror finish, that the often more porous aluminum head castings..
    you can save a great deal of time and effort and BOOST horse power with the application of thermal combustion chamber coatings,
    the slightly porous as cast or mildly polished combustion chamber surface allows the coating to get a better mechanical grip on the heads combustion chamber.
    the thermal barrier is a bit similar to a thick paint that bakes onto the surface forming a semi shiny wax like appearance, a bit like powder coating finishes, but the higher heat rated thermal coatings tend to be marginally duller in appearance.
    but like porcelain its quite hard and heat reflective.
    on the plus side it greatly reduces the heat transfer rates from the combustion chamber too the cylinder heads and that heat tends to boost power,
    ESPECIALLY, with nitrous or TURBO use.
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]





    In addition to piston dome coating, the same high-temperature heat-barrier coating may be applied to the combustion chamber, all valve faces, exhaust valve throats, and exhaust valve ports. This completely encapsulates the combustion stream path. (This head was coated by Dart.)
    [​IMG]






    All of the coating shops offer thermal barrier dome coating and anti-friction skirt coatings. Here’s an example of a piston treated with a thermal barrier coating on the dome and moly-coating on the skirts.


    http://garage.grumpysperformance.com/index.php?threads/thermal-coatings.2610/#post-12861

    https://www.hotrod.com/articles/ctrp-1102-parts-coatings/

    https://www.hotrod.com/articles/hrdp-0612-engine-coatings/

    https://www.musclecardiy.com/performance/automotive-engine-performance-coatings-and-treatments/

    https://www.chevyhardcore.com/tech-...re-they-a-priority-when-rebuilding-your-mill/

    http://swaintech.com/what-to-expect-from-coating-my-engine/

    http://www.enginebuildermag.com/2017/05/goes-goes-anatomy-engine-parts-coatings/

    http://dsportmag.com/the-tech/education/quick-tech-thermal-barrier-coatings-for-more-power/
     
    Last edited: Aug 2, 2018
    NitroInjected likes this.
  4. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    I would run it.
    Its going to get carbon all over the surface right away running on pump gas.

    Racing Gasoline burns much nicer and cleaner.
    Same with Methanol and E85.
     
  5. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    If you found aluminum casting porporosity its throughout the cylinder head.
    I would limit Turbo boost to 21 psi.
    Anymore and you risk blowing out the combustion chamber in the cylinder head right into the water jacket.

    Its a common issue with aluminum.
    Billet aluminum heads solves that issue.
    Its Super expensive.
    Can no longer street drive because water jackets are gone.

    Is what it is.

    Pontiac V8 no aluminium head available can hold up to Nitromethane.
    They fail right away.
    Just like early years only Factory Cast Iron Heads hold up and not fail to Nitro Fuel.
     
  6. NitroInjected

    NitroInjected Active Member

    Thanks for the replies and I did read the articles. I would rather blow the head off than run under 28 PSI... we wont be seeing over 450 H.P. until I get a new trans lined up. Cars got to go on the road before fall.
     
  7. NitroInjected

    NitroInjected Active Member

  8. NitroInjected

    NitroInjected Active Member

  9. NitroInjected

    NitroInjected Active Member

  10. NitroInjected

    NitroInjected Active Member

    They look better with a fresh polish this looks nasty because of the fluid I used for CCing... wont make that mistake again. BTW any dedfects left in the head are quite on purpose such as the ridge line... I know its there and I know the inlet is uneven but that's how bad this casting was. I may post up another photo after final polishing but I dont think its noteworthy... Just know I think this is the bare minimum anyone should do to a port. You could go farther but that needs welding.

    EDIT: They started as the worst ports I have ever seen topping fords 302.... Which are real nasty...
     
  11. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    thanks for posting the clear pictures as it makes understanding what your doing far easier
     
  12. NitroInjected

    NitroInjected Active Member

    Yeah I figured out that linking through Facebook is easiest. I dunno if I said but the pins are ordered. The only thing that needs to be done before balancing is they need to be cut down until either they hit target weight or minimum thickness. Turns out in stock form these pins are good for 2000 H.P. which is a joke for this engine and transmission. The crank would split and the gears would bounce down the road like BB's. The flywheel is next but thats all machine shop. standard stuff. Going to profile my crank webs. I am cutting a minimum of 257 grams off per rod already. I am trying for 300 so hopefully with the pins final outcome and a touch up on a rib on the rods I will hit the goal. thats 1200 grams off per side or 2.4kg/ 5.2lbs that the crank don't have to throw around plus whatever can come off the flywheel.
     
  13. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    reducing reciprocating mass , like rods and pistons is generally a good idea,
    reducing the rotating mass like damper crankshaft and flywheel, at the expense of structural strength is rarely beneficial.
     
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  14. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Hi Boost it is. Lol
     
  15. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    A long time ago Pete McCarthy put put a VHS Porting video for the Pontiac Guys.
    He showed port entry mattered very little.
    Just 3-4 cfm gain.
    Less than 10 hp.
     
  16. NitroInjected

    NitroInjected Active Member

    Yeah the real nasty mc nasty was the port shape and the bowl area was just messed up but those heads actually flow Id bet as I got no bench 30 cfm higher or better than stock as this head is notoriously bad in the flow dept. Ill try to find a photo but imagine a stock 2 stroke pipe.... Thats what it was... now at least its more like a water park slide... still not what I want but at least the air can move. The exhaust was fine except for a ridge in the short side radius. BTW I got my bike inspected today. Had to take the race pipes off she didnt like it one bit being carburreted but she passed without issue.
    From 15 when I was sat down by my ... Idol and teacher for vehicles I thought about engines like he said it: The engine makes a lot of power its all of the stuff that the guys in the factory put in the way that rob the horsepower. Your freeing up the power not making it unless your messing with compression or boost but theres no sense raising the boost if the air is running through a shitty port with a valve that cant flow enough. So to raise the boost or compressionj you have to make sure nothing else is holding back the power. If thats all clear and you are making too much you can dial back the power with a smaller carb or injector with a lower final boost setting.... It changed the way I seed the engine.
     
  17. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Yes.
    There is NO Venturi shape in the intake Port Like a Pontiac V8.
    Similar used in SBC & BBC.

    When You Run Hi Boost Pressure the Exhaust Valve Glows Red Hot 1400F & often higher.
    Hot Tensile strength becomes important.
    Ferrea Super Alloy Valves are good if on a tight budget.
    Have Manley XH428, High Temp Orange Titanium.
    Del West Racing Valves.
    They custom make what you need.
    Ferrea be most budget friendly.

    You need to verify Valve Seat runout 1st hand with this engine.
    .0000" runout desired.
    No more than .001".
    Can not see or check hand lapping valves in like typical done here on Grumps.
    I bought a Valve seat runout gauge for myself. Need special Pilots too that I bought.

    When at the machine shop make sure you check 1st hand with your machinist.
    He will or should have the gear stuff.

    Cast Iron Heads also have the advantage of No Valve seats dropping out like aluminum heads.
    #1 issue with all LS engines drag racing.
    Valve seat drops out and engine destroyed all in seconds.
    KAABOOOOOM !
     
  18. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Hi Boost is Torturous.
    Mitsubishi EVO on 44 psi Boost last Fall .
    I built the Longblock engine.
     
  19. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    I follow Chad Spier on Facebook.
    Has his own Page.
    He has gone back to Grinding Valveseats with Sioux Valvegrinding stones like I do on my own.

    Its the only way to maintain accuracy down to .001" or less valveseat runout over and over consistency.
    Lots of Finess required to do it.
    He has state of the art Head machines costing $20 K.

    He showed...
    I smiled & laughed.
     
  20. NitroInjected

    NitroInjected Active Member

    I am only going to undercut the intake valves by a mil each making the inlet area 48mm giving me the ability to run bigger throttle bodies. No work will be dont on the valves as these are already great valves. I dunno the specifics but the exhaust are for sure sodium filled. The intake are some kind of alloy... I have the details but they are with the owners manual as the P/O bought them. Spent like 2 grand or so... They didn't do the guides so I need to check that... Machine shop... Actually all has to be done at the machine shop now except for the assembly. I am dropping from 170 grams on the pins to H13 156.7 before the bore and taper. After bore and taper they will be under 140 which is great. My eyeball is now on the pistons. but with fingers crossed on the pins I am dropping 320.5 grams off per assembly 1282 grams by 4 and 2568 in total. Which is over 5lbs. If I can shave another 500 grams off somehow between the pistons, ribs and crank webs that would be real cool. Engine stress will be so much lower and maybe a billet bearing carrier is in the future but not yet. I will be taking tracings of the outside dimensions but in truth I hate this motor so much. I could be in a V8 pushing all that torque!
     

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