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    Results 41 to 58 of 58
    1. #41
      Join Date
      Nov 2006
      Location
      Flo-rida
      Posts
      1,204
      So i can get away with 11:1 compression with aluminum 64cc heads if i built a motor?


      1993 Camaro Z28
      2001 Camaro Z28
      1969 Camaro



    2. #42
      Join Date
      Mar 2005
      Location
      Jackson Ms
      Posts
      1,220
      I built a 12.5:1 438w for my old mustang. tonight ithe new owner ran a 9.63 on motor on 93 octane pump gas. so it can be done. now if the tank would have been full of 110 he would have bumped the timing and ran some 9.30's
      Chris V
      SOLD


    3. #43
      Join Date
      Apr 2006
      Posts
      23

      High Tech equals High Cost

      Hey Lowend,
      All that Audi high tech stuff is fine until the repairs come up. We have a 6 year old A4 4 cyl all wheel drive in our shop at the moment that has a transmission fault when it's hot. It has a C.V.T.with the computer in the oil pan and here in Australia there are no parts available. Audi's answer is a replacement unit at $19k plus fitting and it has expensive oil too. Cant see why the engine would be any different.(Ouch)

      Long live build yourself engine combos. It is affordable fun and even if the Audi wins they dont have the style of the old muscle cars.

      Merry Christmas car dudes and I hope to have the old 68 camaro going in '08
      Grandpa Ronsy
      It's hard to be sincere with a poor memory

    4. #44
      Join Date
      Apr 2006
      Posts
      23

      High Tech equals High Cost part 2

      Lowend,
      I forgot to add
      The mileage indicated was 137.000k's which is about 80.000miles near enough. The average guy in our country probably afford to replace/recondition the engine if it lost coolant!!

      Anyway loves you all
      It's hard to be sincere with a poor memory

    5. #45
      Join Date
      Jul 2005
      Posts
      202
      Country Flag: United States
      Another important consideration besides the cam timing is the combustion chamber design, both the head and in the piston. Some of the more sophisticated head designs have a much lower inital timing requirement and these would be a good place to start since they need less timing lead to begin with. I have some CHI heads for my Ford motor that require less advance (29 is absolute max) and help me to run more CR.

      It's hard to find the perfect combination that does everything great and 12.5 CR with the target rpm range and gearing you are willing to run might be a challenge.



      Good luck

    6. #46
      Join Date
      Nov 2007
      Location
      canaveral groves florida
      Posts
      20
      Country Flag: United States
      back in the day, i ran a destroked 327 (302, just gotta love that engine) with 12.5 to one compression, a small cam (.480 lift), 192 casting heads, and an old edelbrock tunnel ram that looked like a shoebox on amoco 93 day in, day out with never a bit of trouble. it was in a 75 monza so it bay have helped being in a reletively light car, but i always attributed it to a smaller displacement engine. always seemed to me that any of the big blocks i ran were more finicky about compression and cubic inches.
      just my 2 cents
      good luck and happy building
      mike d

    7. #47
      Join Date
      Mar 2005
      Location
      Jackson Ms
      Posts
      1,220
      here is a little vid of the 438 red coupe making a mid 9 second pass on 93 octane and 12.5:1 compression.

      Chris V
      SOLD


    8. #48
      Join Date
      Sep 2006
      Location
      Southern Indiana
      Posts
      4,699
      Country Flag: United States
      With aluminum heads you can get away with 1 to 1.5 points higher compression.
      I have found that using Evan NPG+/NPG-R coolant can let it run even better with lower octane.
      BUT the big ticket for which octane to run is the dynamic compression (take a good compression tester, remove the check valve that makes it hold pressure, then screw it in and start the engine and watch the needle the high pressure is the one you have to tun for. My rules have been for the last 15 yrs is 190psi and lower 91/92/93/ anything over 200psi you better have 93 and octane boost, 94 Octane Sunoco Ultra or 100 octane "race" unleaded.
      My engine I was bragging about had a cam that my buddy had ,it was an old hyd split lift/split duration designed by Lingenfelter for the Accel Super Ram, i used an older Edelbrock Scorpion intake, Carter 600 AFB, and old 991 truck heads, I rebuilt them with 1.94 intakes and 150 ex and throated the ports to the inside of the valve face(s) both intake and exhaust and I have always raised guides (spotted them) up 5/32(fun thing I do on a head machine used for installing guides and seats, I would zero on the stock guide then use the cutter stop and a 5/32 drill bit nad spotted the guide in the port.
      Trust me I have done hundreds of heads this way to clean up the flow of stock heads. and so far have never had any issues with excessive guide wear.
      honestly the rought stone I used I contoured on the seat grinding stone truer and just contoured them to a smooth radius.
      The fact that the engine just plain made torque like no other throw together engine (it was from my 71 Monte that had broke a cam and damaged 2 rods/pistons. 2 new pistons (cast) new molly rings and some new rod bearings, Oil pump out of corner with new drive and pickup, and new timing chain as at one time I would get tripple key way timing sets from autozone cheap.
      With Monza headers ,2 1/2 " duals and Flowtech Afterburner mufflers it all just worked.
      sold it with out the intake,carb,headers. New owner used a eppoxid Performer RPM air gap and a 750 holley I set up and it went into his Gbody and was teamed with same trans/converter I had TCI/Sat SPCL and 373a posi and it still rips from what I heard.
      The real trick is cooling, no dome to interupt mixture motion, and some quench area to induce mixture motion if ports dont do enough.
      Lots of factors are critical and if you dont have dyno with knock microphones/sensors and some smart tuners you can trash an engine on one of those high compression low octane setup very quickly and never rune Hypertech pistons in something like this, Forged, ,heck nitrous spec pistons are the strongest.

    9. #49
      Join Date
      Sep 2004
      Posts
      135
      I think some of the guys are realizing that hypers can turn ta aluminum gravel under detonation!

      pdq67

    10. #50
      Join Date
      Dec 2006
      Location
      Livermore
      Posts
      53
      This whole compression thinng brings up motorcycles for me. My old triumph daytona 650 had 12.65 to 1 compression and the honda cbr600rr = 13 to 1 , etc


      I dont even want to go into explaining compression and theory. I do advise that if your really wanting to know pick up a race engie building book at borders. I didn't go that route, I just read a hell of a lot off the net and built my own engine with some of the top guys in northern california. I urge all of you that are interested to just ask questions.
      1965 GTO convertible
      GM design Award winner 2009
      Still having fun with it too.

      COYBILT INC
      M-F 8-5
      925-454-1965
      10605 Altamont Pass Rd
      Livermore,CA 94551

    11. #51
      Join Date
      Dec 2007
      Posts
      59
      This is a great piece...2 things.
      1. I recall an article by hot rod or car craft on rod ratios on compression, basically they were getting 12:1 compression with a mild cam on 87 pump gas.
      2. I went to school for mech eng and had a professor named Dean Hill that was a famous hot rodder in the 60s, anyway, he had a basically stock engine that was running 16:1 compression on 87 gas. Of course the manifold was about 5 feet tall and had to do something with the atomization of fuel. That was about 8-10 years ago, you would think some people have advanced on this.

    12. #52
      Join Date
      Apr 2005
      Location
      Cartersville, GA
      Posts
      1,300
      Country Flag: United States
      I'm running 12.3:1 in my 97 Camaro SS (run 93 octane), and it works fine...of course, it has an LT1 (reverse cooled),ported factory heads, and a really good cooling system. I'm running 236/242 duration. Nothing unusual for an LT1, and honestly one of their few redeeming factors now that LSx parts have become so plentiful, and come down so much.
      Joe Hinds

    13. #53
      Join Date
      Sep 2006
      Location
      Southern Indiana
      Posts
      4,699
      Country Flag: United States
      Two of the tricks to get high compression and low octane to live together is mixture motion(ie a more homogenous (re even) mixture and also peak cylinder pressures
      If you get to high cylinder pressure it will knock, kill the cyl pressure down to the 180-190,, maybe 200psi if you use good (ie hi octane) the engine willive, aluminum heads loose heat much faster and help so you may even get to push it.
      I just havent seen that much in an increase in engine out put by the compression increase so drastic. If you build it right and keep it properly cooled, maybe even add on a water injection (just run winshield washer solvent as the plain blue stuff is water and methanol) for when you cant get good fuel and drive.
      Honestly I see so many people who want to run garbage a$$ crap 87 octane and just F--K up every thing trying to "dial" it in.
      Got a fella who has a 72 Continental with a factory 460/4bbl made to run on 91 LEADED which comes out to about a 93 or 94 octane unleaded.
      Idiot keeps letting other people work on his cars and they took pefectly fine factory carb off engine, (trying to diag a dead plug I think) and put on a 600 Edelbrock electric choke. The Edelbrock works fine, but the factory carb was rated BY FORD at 600 CFM, but not by the same specs as aftermarket carbs and it had a (by aftermarket specs) a 735cfm carb.
      But they had the tranny kick down bent, the throttle cable wont fit straight(had to mod the cable bracket more) lots of stupid stuff.
      Oh did get to change all the freeze plugs IN CAR too.
      I try to make people understand 1 point will make in the range of 4% to 6% but isnt worth the hassle and expense.
      If you have a reasonable cranking compression dont raise it, if its low (like below 180psi to 190 psi) try a thinner head gasket or advance the cam.
      Peak torque is made best at the highest cam advance without going the other way or getting it too far off from the grind numbers.
      Any cam can be advanced for best cranking compression number and will produce the best peak torque.
      Aluminum heads can add 1 to 1.5 points in the compression dept. with no bad effects.
      Use the Evans Cooling NPG+ or NPGR and you can gain a little more leeway.
      Iron heads hold heat more and wont take the numbers.
      The smaller the combustion chamber and no dome makes a better more detonation resistant end product, add in some good mixture motion and you will have a great running hard to beat detonation resistant combo.
      Oh and you may never hear any of the knocks and still break things.

    14. #54
      Join Date
      Sep 2004
      Posts
      135
      Anybody have any real world experience using Singh's grooved head theory?

      http://somender-singh.com/content/view/7/31/

      I know there's somebody that is doing something about like it, only to the piston top. I think they dimple it and it's top is also swirl ramped, but I can't find where they are made??

      I even handled one out at SEMA, the year I went.

      pdq67

    15. #55
      Join Date
      Oct 2004
      Location
      Papillion, NE
      Posts
      203
      DCR is one thing, I use it, and I run a 489 inch FE with .048 quench, 8.33 DCR, and 10.7:1 static compression ratio

      Its happy as a clam on premium and will even run mid grade if I am just cruising.

      However, remember that as RPM increases, the more overlap you have, the more efficient the overlap period gets at pulling in more a/f mixture.

      That means that despite a low DCR, at RPM cyl pressure still skyrockets

      Bottom line, quench distance and a turbulent chamber are great for detonation resistance, go for it, but you cant just go with a monster cam and run 12+:1 compression, eventually it turns into a pig down low, with unmanageable cylinder pressure and a timing curve forced to be very slow. (Doesnt sound too impressive huh)

      In other words, tighten up that quench and use a turbulent, small chamber with some sort of reverse chamber piston, thats a good thing, but if the cam choice doesnt seem to match, its probably wrong. Dont pick a cam that kills compression, pick one that matches the RPM range and then pick a compression ratio to match
      70 Mustang - 489 cid FE, KC ported Edelbrock heads, Modified Victor Intake, Mass-flo EFI, Erson valvetrain, Supercomps, TKO-600, 4.10 9 inch.
      71 F-100 4x4 SB 4x4, 461 cid FE stroker, Edelbrock Pro-flo 4 EFI
      13 Ram Laramie 2500 4x4 6.7 diesel - trailer puller

    16. #56
      Join Date
      Jul 2008
      Posts
      2
      I have an 11:1 383 sbc in my S15 Jimmy. It has aluminum heads(65cc), 242/[email protected] cam, 8.19 DCR, .042 quench (.039 gasket+.003 deck). I use 93 octane and I've had no problems at all even in the heat of the Florida Summer.

    17. #57
      Join Date
      Aug 2004
      Location
      Walla Walla, WA
      Posts
      1,505
      Country Flag: United States
      Quote Originally Posted by nastee383
      I have an 11:1 383 sbc in my S15 Jimmy. It has aluminum heads(65cc), 242/[email protected] cam, 8.19 DCR, .042 quench (.039 gasket+.003 deck). I use 93 octane and I've had no problems at all even in the heat of the Florida Summer.
      Pretty much the same engine in my '68 Camaro: 11:1 383, 232/242 @ 0.050", 0.040 quench, Dart Pro Ones, 6" rods, about 8.2 DCR running just fine on California's 91 octane.

      That said, there seemed to be a lot of mis-information in this thread.
      Mike Kelcy - '68 Camaro with some stuff done to it.

    18. #58
      Join Date
      Sep 2006
      Location
      New York, NY
      Posts
      458
      Country Flag: United States
      me 3
      383 SBC
      11:1 pistons
      AFR 75cc 195's
      236° / 242° @ 0.05 hydraulic roller

      hoping to run on 89 octane, will use water/methanol injection if necessary. engine has never been fired though.

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