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Thread: Hemi head

  1. #11
    Daniel Coop's Avatar
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    "Daniel, I think I'm going to pass on the Hemi head and flat top piston for now (you weren't suggesting a flat top piston with my non-hemi head were you?)"
    Yes, I was suggesting ditching the stock dished piston for the Hemi flat top piston kit. Same bore size, just a flat top for more compression... It's $15 w/rings. Not swapping out heads.
    I have a non Hemi with RTC 8 head and it's got the 27/25 valves too. Problem I have with them is the 5mm valve stems... You can't get aftermarket stainless valves in that 5mm stem size and they don't make a .0195 or .5mm drill bit so fitting better (aftermarket stainless) valves can be a bitch. I've also seen in the stock valves fail at High RPM. You'll be just fine with a 7k RPM cam though.
    Last edited by Daniel Coop; 01-11-2018 at 11:55 PM.

  2. #12
    Daniel Coop's Avatar
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    "Looks like more work than I'm willing to do/learn at this stage. I'm looking for the cheap, bolt on upgrades - I'm being lazy. It's possible maybe my 2014 Predator has the larger valves? I see in the OMB warehouse, all the various stage kits come with #18 springs. Is this assuming the governor is left in place? Is there a better cam for my limited modification plan?"
    I thought you said you already removed the governor, installed springs, and a flywheel from this previous kit? If that was true, the rod, possible piston and cam would be the next logical steps and shouldn't be too difficult if you tackled those previously mentioned items. There's some decent videos by ARC Racing on YouTube that show you how to change the rod and various other upgrades. These motors are quite simple and as long as you have a decent 3/8 torque wrench with a 12pt 1/4 socket, a small inexpensive ring compressor, some cheap hardware store feeler guages and straight edge, there's no reason you shouldn't be able to do it. If you just want to slap a cam in and call it good, check out Dyno Cams CL1.
    Last edited by Daniel Coop; 01-12-2018 at 12:58 AM.

  3. #13
    JBeasty's Avatar
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    Quote Originally Posted by San Diego View Post
    To determine if your head has the larger valves, see what version it is. It is marked on the underside of the head & should be like RTC-6, RTC-9 or RTB-03, which all have the larger valves.

    If you go with a flat top piston when you change the rod, since you'll have to take them apart anyways, it will bump your compression up to around 10:1, so no need then to do any head milling.

    A rod, or piston are neither bolt-on upgrades. You have to do some dis-assembly & re-assembly of your engine to make either change, along with a cam change.
    Right. I understand that, I should have been more clear. I'm just not anxious to bring parts to a machinist, or do any extensive porting, etc. Good to know milling isn't mandatory. I did a cursory visual of the head (mounted on the engine), and I see a long string of numbers, but nothing with RTC or RTB. Guess I'll find out when I pull the head.
    Last edited by JBeasty; 01-12-2018 at 02:09 AM.

  4. #14
    JBeasty's Avatar
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    Daniel,

    Thanks for the links. Yes, I think I can handle the installations. A flat top piston, #22 valve springs, a Ru*ing Bored & Blueprinted .650 Carburetor, a CS grind cam and a +.20 billet rod are in my future.

  5. #15
    JBeasty's Avatar
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    One last concern I overlooked. Will my torque converter handle the extra power? I had to put it together piecemeal because my frame wouldn't accommodate a Comet type set-up, with the mounting plate included. I ended up mounting the driven pulley on a jack shaft. The parts are "Thrustkit". I'll call gokartsupply to see how much my set-up can handle.
    Last edited by JBeasty; 01-12-2018 at 02:41 AM.

  6. #16
    JBeasty's Avatar
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    Looks like my 3000 series torque converter will only handle up to 8 HP (wonder if they're just CYA). Might be stuck with my current set-up, plus a billet rod. Wish I would have thought this through better before wasting everybody's time. Any thoughts or experience on how I should proceed?
    Last edited by JBeasty; 01-12-2018 at 03:19 PM.

  7. #17
    Daniel Coop's Avatar
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    A lot of the #35 clutches and torque converters are only rated for 8hp, but most of us throw a lot more at them. A few guys have modified 30 series torque converters for racing. There's another member on here @super nate that spins his up past 8k RPM. The 40 series and some of the higher end clutches are rated for more, but I wouldn't worry about it too much. I have a couple 8hp rated Max Torque clutches on motors with 13-15HP and they do just fine. I'm not familiar with torque converters yet, but I know there's some mods and adjustments to maximize performance. You're not getting too crazy with your motor.
    Last edited by Daniel Coop; 01-12-2018 at 05:26 PM.

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  9. #18
    Senior Member Davis's Avatar
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    Maybe without a dyno sheet those motors are only 8hp.

  10. #19
    JBeasty's Avatar
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    Yeah, I guess the worse that could happen is a prematurely worn or snapped belt. It's not like I'm gonna be riding this thing to work every day...

 

 
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