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Sbc cam experts?? Pump gas & 12:1 ?

Discussion in 'The Hokey Ass Message Board' started by B1gDaddy, Jul 27, 2012.

  1. B1gDaddy
    Joined: Aug 30, 2007
    Posts: 292

    B1gDaddy
    Member
    from aladambama

    Ok, so I don't want to tear this engine down. But a cam swap is easy.

    What I have:
    327
    64 cc angle plug heads
    12:1 forged pistons
    Old fuel unit ( needs a vacuum signal to run)

    Think about an old stock fUelly or dz302 long block

    I have a q/c rear and tko600 5 speed trans. This is going in the 32coupe


    CAN I overcome some compression with a cam so that I can stop anywhere and run pump gas 93 on this engine without problems?? Or do I tear down the short block now!?
     
  2. You should be able to get a cam with enough duration and overlap to get it to bleed off a little pressure but I don't think thay is going to help you pull a hill at speed. remember when you get compression rattle is under load.


    You can run it fat and keep the engine as cool as possible and that will help a little. You can also carry a can of moroso octain boost in the trunk and mix your fuel. That may help more than anything.

    If it makes you feel any better I am in the same boat with an engine that I got and I can't bring myself to lower the compression when I assemble. It is an old engine built by someone that came way before me and I just won't do it out of respect.
     
  3. A bigger cam will help bleed off some pressure, but as stated it is only a crutch. If you can do it, some heads with bigger chambers (76 cc) would help, you could also use thicker head gaskets. All of these are still a crutch.

    You might look into water injection. Snow performance makes a kit that will solve all of your problems. A friend did it on a too high compression SBC and the rattling went completely away. Some of the water injection mix alcohol with it, but straight water can do a lot by itself. Water is free.
     
  4. Phil1934
    Joined: Jun 24, 2001
    Posts: 2,716

    Phil1934
    Member


  5. Get some heads with the biggest chambers you can find.
    I just scrapped a set of 76cc heads for a 307 last month.

    How much vacuum signal do you need ? Bigger cams bleed off cylinder pressure as right along with the vacuum
     
  6. aaggie
    Joined: Nov 21, 2009
    Posts: 2,530

    aaggie
    Member

    Unless there is a reason that you have to use the old Fuel Injection I would dump it and go with a good manifold and single four barrel carb. It will run stronger and be easier to tune.
     
  7. carlos
    Joined: May 2, 2005
    Posts: 1,387

    carlos
    Member
    from ohio

    Read somewhere if you run alum.heads as far as octain it is like 11:1 instead of 12 to 1 as far as octain they run cooler .Somebody correct me if I am wrong:D
     
  8. Pete1
    Joined: Aug 23, 2004
    Posts: 2,254

    Pete1
    Member
    from Wa.

    Water injection will work fine. I ran it on the street with a SBF that was 12-1.
    I used vacuum switch to actuate it so I all I had to do was drive it.
    I had a 2 gallon tank and what with a mild ammount of street racing I filled it with each gas fillup.
     
  9. B1gDaddy
    Joined: Aug 30, 2007
    Posts: 292

    B1gDaddy
    Member
    from aladambama

    What cc are vortech heads? This engine will have the fuel unit even if I need to tear it down and replace the pistons!
     
  10. Mid to low 50s cc
    It would be better to sell it as a race motor or trade it for lower compression motor.
     
  11. Cast Iron w/ 1.280" springs are 64 cc chambers.

    Small-Port Cast Iron BOW-TIE are 66 cc.

    Large Port Cast Iron BOW-TIE are 65 cc.

    Large Port Aluminum Vortecs are 62 cc.

    Both Edelbrock E-Tec 170 and 200 Intake Ports have 64 cc Combustion Chambers.

    Edelbrock E-STREET w/ 185cc Intake runner are offered in 70 and 64 cc Combustion Chambers.
     
  12. B1gDaddy
    Joined: Aug 30, 2007
    Posts: 292

    B1gDaddy
    Member
    from aladambama

    Hey, just FYI, I have had a fuelly factory 12:1 car that had not been torn down. The only way I could make it run worth a flip was with 110.

    A tear down isn't the end of the world. Should I shave the domes or replace the pistons?

    Beaner?
     
  13. Deuces
    Joined: Nov 3, 2009
    Posts: 23,756

    Deuces

    I'd replace those with some flat tops... Sell the 12:1's to someone who could use them... ;)
     
  14. B1gDaddy
    Joined: Aug 30, 2007
    Posts: 292

    B1gDaddy
    Member
    from aladambama

    ^^^

    Kind of thinking the same thing. Was hoping for an easier option like just changing the heads and cam!
     
  15. Rattle Trap
    Joined: May 11, 2012
    Posts: 358

    Rattle Trap
    Member

    I'd tear it down. Much easier to live with in the long run.
     
  16. kyvetteman
    Joined: May 13, 2012
    Posts: 759

    kyvetteman
    Member

    But those angle plug heads are so freakin cool! I'd put flatops in it and keep the heads if I could.
     
  17. Dyce
    Joined: Sep 12, 2006
    Posts: 1,973

    Dyce
    Member

    If the engine runs the way it is I would sell it as a race engine. You just might open a can of worms by tearing into it. The block might be .060 over and worn out. The flattop pistons won't weight the same. If the high compression pistons are hollow dome light weight pistons and weight less then the flattops, you have to add weight to the crank to balance the assembly. It also could have floating pins which I wouldn't recommend in a street engine unless the rods are bushed. Who knows until you tear it apart. On the other hand your 327 could be just what someone is looking for.
     
  18. Avgas
    Joined: Dec 31, 2007
    Posts: 282

    Avgas
    Member

    I run a 302 Chev plus 30 with 12.5 -1 TRW lumpys, Also have a 327 plus 30 12.8 -1 Speed Pro pistons. Both engines run fuelies, slant plug heads on the 302. Both cams run more than .600 lift, and generous duration. The 302 was in my 34 coupe, weighs 1300 Kilograms, 2.2 lbs per kilo, no probs if your engine is efficient and plenty going in and the headers scavenge efficiently. Wayne
     
  19. chubbie
    Joined: Jan 14, 2009
    Posts: 2,336

    chubbie
    Member

    lucky you!!! E-85!!!!!!
     
  20. AG F/C
    Joined: Oct 20, 2009
    Posts: 364

    AG F/C
    Member

    Like PB said a big can will only help you at rpm's off of the engine's peak torque rpm's. When the power band hits is when things go bad.
    You don't have to run the big ignition timing number. Usually with the optimum setup and quench, @ WOT and peak torque rpm range and you'll want 34-36 degrees of total timing. No vac advance in at that point by the way.
    If you want to run less than optimum conditions like fuel quality for your compression take a bit of timing out or limit when the total timing is all in until after peak torque. After peak torque the cylinder pressure's begin to roll off and the engine can accept more timing. Also at higher rpm's detonation is less likely with the high quench induced combustion chamber turbulence.
     
  21. I run a pumpgas motor in my Stude 11.3-1 I have studied high comp.pumpgas combos.I am making 550+ h.p. with my 383sbc on pumpgas! The secret is tight quench,good flame travel,correct valve timing,many factors...alumn. heads and a car with an open engine compartment helps(such as my coupe with no hood sides) besides,it's all about cylider pressure.If I were you,I would tear it down,zero deck it,flattop pistons,good alumn. heads,250 ish @.050 580ish lift 108 lsa solid lifter cam,locked out timing,750 d.p.carb. Screw this combo together and let it eat! jmho...R~R
     

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  22. burgessdg
    Joined: Aug 17, 2012
    Posts: 37

    burgessdg
    Member
    from Morris, Il

    Am I missin' somethin'? 12-1 with 64cc heads? Swap the heads to 76cc. That should get you down to 10-1. Definitely be the easiest thing you can do. Way cheaper and easier than tearing down the shortblock and shaving domes, replacing pistons, and rebalancing a rotating assembly. Before you take the heads off, verify the compression ratio. Volume @ BDC /Volume @ TDC = CR. Then do the the math to ID how many CC's you need to add to chamber volume to get CR you want.

    My 2 cents,
    Dan
     

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