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#1
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Help with my 383
Last year we rebuilt a 383 engine with a Summit bottom end kit and a Mopar .509 lift cam. The combo was a disaster, as we lost compression, (Probably only 8:1) and the cam was too big. What do I need to do to the engine to make this cam work? We are thinking of shaving a set of heads that have be gasket matched, adding headers, and changing the intake to an Edelbrock Performer RPM. Anyone have any suggestions?
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#2
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Use the correct pistons to bring up the static compression ratio or use the right cam for your current compression ratio.
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#3
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I don't think it's the cam grind, it could be installed wrong though. For what you have, it needs to be installed at 102 - 104 degrees, that would boost your bottom end back up.
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#4
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That cam needs compression, seen it all over this board. 8:1 is not going to do it justice. Use your compression to buy a different cam and youll be miles ahead.
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#5
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make it work
if your trying touse your bottom end as is try a comp cams extreme energy something under 500 lift ive built 2 383s with them having good results.if your using composition head gaskets you can gain 1/2 point of compression using origonal steel shim gaskets ,you can avoid costly milling.
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#6
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For starters I like Lunati Cams. I used a computer dyno and checks several different cams and none could stand up to Lunati. Also what kind us springs are you useing? I had the entire upper end redone on mine. New cam, lifters, springs, also went mechanical adjustable. Made a world of difference. My little 383 is rocking the house. More cam then it is suposed to be able to handle they say. 600 lift with 326 duration. talk about thump. Then the throttle control with a big carb and high rise intake, predator, of course. Nothing can match the responce. Zero to top end before you can blink an eye. Seriously, check your dial in. I had a hard time getting mine right. Dialed in around 106. Then set the gear back 4 degrees for major lower end torque. clearances are at the extreme, especially afer leveling the heads, but everything runs great. Mine came out of a 68 roadrunner with factory 10.5 to 1. After milling and all my compression is up there. yours sounds like it is ready for NOS. may check into it.
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#7
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Quote:
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#8
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I'd give........
Racer Brown a call and see what he says you need for a cam with the piston set-up you have.
If that dosesn't fit what you want, you will have to go with new pistons to get the compression up. Too much bleed off by the cam and low static compression is a killer. I'm sure he can pick a cam that will resore the wanted performance. Not to mention a great guy to talk to. Just thinking out loud. |
#9
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The starting point would be finding out what CR you really have. Knowing that you propably only have about 8:1, will as propably give a wrong cam for your combo. Don't assume anything when building engines. MP 292 is a good cam grind, but it's a pretty big one. With low CR it will be very soft at the low rpm, and will not even respond very well at high rpm. With the 292 you should have at least about 9.5:1 cr, the rpm intake should work, and you should have pretty short rear gear and a manual or high stall converter to get everything out of it. Remove the heads, check the piston position at TDC, calculate the CR and see where you are at and what you can do to it, then start thinking about the cam choice.
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#10
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If you just rebuilt the engine, you can most probably just swap out the pistons for a higher comp. set. It should not be a problem unless there forged. Once you have better pistons in there, it'll wake up.
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#11
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I just ran across a site that sells B/RB steel shim head gaskets for 15 bucks a set if anyone is interested in gaining a point or so cheap. http://www.speedwaymotors.com/xq/asp...qx/Product.htm
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#12
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It seems a shame to back off on the cam to live with the CR. I bought a Summit kit for a 360 and fortunately before I buttoned the thing up I read a post about the CR being low. When I checked it the pistons were way down the hole and I was realistically looking at not much more than 8:1, which wasn't much more than the 7.8:1 dished pistons I'd just taken out. I'd already had the heads shaved but it still took another .050" off the block to get me up to 9.2:1, with questionable quench even at that. Seriously think about more machining (on the block if that's what it takes to get it closer to the deck height you want) or a piston change. Personally I wish I'd just changed the pistons in the first place instead of pulling the motor apart again and dragging the block to a machine shop - $160 later I got the CR I want but I still only have hypereutectics.
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#13
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I agree, correct pistons for the desired CR should be used and "band aids" to make major changes in CR should be avoided. I think about .060" is the most even partially sensible amount, after that and maybe even at that point you start spending more money correcting certain things (manifold fit, lifter preload), than what new pistons would have cost.
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#14
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Mopar has not designed or produced a new cam since 1987Some of the tooling used on the cam shaft blanks cause soft spots and causes lobe failure during break-in. 30 year old blocks have tappet bore alignment problems that prevents the tappet from rotating properly which also causes exxcessive cam wear. Hughes pionered the Mopar cams for todays useage and should be considered as a source for the proper cam for your vehicle.
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#15
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Hughes doesn't even make their own cam. They contracted out to a third party.
Racer Brown custom grinds every cam to your needs and setup. |
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