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post #1 of 10 (permalink) Old Nov 7th, 05, 03:11 AM Thread Starter
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cam question

hey all I have a few q's about what would be best for my 383 right now I have a crane cam lift .450/.450 dur .218/.218with stock 1.5 rockers. I, like a lot of people like the sound of a nice lopey cam and this one just is not doing it for me. my first question is if i switch to 1.6 roller tip would I gain anything out of the existing cam. what is the most lift I could run without worrying about valve to piston contact (im running flat top pistons with 2.02 and 1.6 double hump heads). and what is the most dur I could run without losing power brakes. and last but not least a question that has nothing to do with cams im running a 600 edelbrock carb am I robbing the motor of fuel?

o yeah before I forget the guy I bought the car from had a shop build the motor and in some of the receipts I found some notes that it looks like the shop made while building it on a scribbled out part it looks like it says "cam hits rods at tdc retard cam" has any one ever heard of this happening before if so why?
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post #2 of 10 (permalink) Old Nov 7th, 05, 03:59 AM
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Re: cam question

Switching to 1.6:1 rockers will make a tiny difference to cam duration. Maybe a couple of degrees! So, they will not grant your wish of a lopey idle.

The amount of duration for a lopey idle would be around 230 @ 0.050" or more. This will be at the expense of low end torque and I'd suggest getting advice from a cam maker as to what will work for your combination.

Crane will also be able to tell you how much additional piston to valve clearance you will need with the new cam versus the exiting one you have. You really need to physically check the clearance to be sure. It's not hard to do with the motor assembled, a dial indicator with stand, degree wheel and a pair of checking springs.

A 600cfm could be just right for your engine as is, but I would expect something a bit bigger if you go with a larger cam.

The cam hitting rods part... I'm not an expert on small blocks but this can be common with stroker cranks. How much has the cam been retarded for clearance I wonder...?
A small base circle cam might solve your problem.. I said might! Once again, you'll need to enquire.

Me.. I'd pull the engine and check it for myself rather than install a new cam and wham!

Nov 68 Van Nuys. 327 floor-shift-auto, Frost Green and not much else when new.

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post #3 of 10 (permalink) Old Nov 7th, 05, 07:40 PM
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Re: cam question

Agree...a 230 @ .50 (i.e. 280H from Comp Cams) will give you the lope,..but it's nothing until you get to 2500 rpm.

But don't try it unless you have at least 3.73's in back. In your 383 it will pull about 12 inches which is ok for pwr brakes.


Another great cam is the 270H which has 224 @ .50 duration. Again,..you'll need at least 3.42's out back.

1.6 rockers may be worth a try, but don't expect a big metamorphisis.

Good luck!
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post #4 of 10 (permalink) Old Nov 7th, 05, 08:16 PM Thread Starter
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Re: cam question

i do have 3.73 gears out back ill try the 1.6 rocker arms. i think the carb is not tuned eather
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post #5 of 10 (permalink) Old Nov 7th, 05, 11:05 PM
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Re: cam question

If you go for 1.6:1 rockers AND a bigger cam, you must do that piston to valve check!

Nov 68 Van Nuys. 327 floor-shift-auto, Frost Green and not much else when new.

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post #6 of 10 (permalink) Old Nov 8th, 05, 11:05 PM Thread Starter
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Re: cam question

I was looking at cams today on summit's web site and crane cams made a new cam for their energizer model and it has a 230/230 dur and only .465/.465 lift so is has only a 15 degree diference on lift. so if I got this cam would you still recomend checking valve to piston clearence?
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post #7 of 10 (permalink) Old Nov 9th, 05, 12:15 PM
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Re: cam question

Definitely.
Don't intimidated or scared to do it.. it's an easy task with the right tools.

Even if the lift remains the same as your existing cam (and assuming that it has enough clearance too), the additional duration, and change in lobe center angle and/or ramp profile can get your valves too close for comfort to the piston during overlap.
You really need to check the clearance from 15degrees BTDC to 15 degrees ATDC at 5 degree increments as TDC is often not the point where the valves are closest. You must be sure, an over-rev and floated valve could ruin your engine. Consider if the existing valve springs are suitable for any new cam choice also.

I would still be more concerned with the cam to rod clearances that you mentioned, and I would contact Crane (or your choice) and request advice on cam profiles and if a small base circle is available.
Their cam help via fax is responsive. I have always recieved their help.

Nov 68 Van Nuys. 327 floor-shift-auto, Frost Green and not much else when new.

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post #8 of 10 (permalink) Old Nov 9th, 05, 12:28 PM
 
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Re: cam question

you also should consider the possibility of what RPM valve float would occur with a new/different cam. a cam that makes power from say 2500-6500 (i.e. higher duration, more lope) would only be good if you can spin the engine that high w/o floating the valves.
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post #9 of 10 (permalink) Old Nov 9th, 05, 01:38 PM
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Re: cam question

Call an engine builder you trust,..they've likey put an engine together with the same components you have and can speak to the clearance questions.

Good luck!

Last edited by Straight-line-69; Nov 9th, 05 at 03:09 PM.
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post #10 of 10 (permalink) Old Nov 10th, 05, 07:45 AM
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Re: cam question

dont forget retainer to guide clearance if you go with 1.6 rockers or higher lift!and remove the oil drippers on the valve springs if they are still on there!(don't ask me how i know that)
Eric B

86 camaro,383,topline vortecs,scat crank,wiseco forged 9.5:1,6"scat rods,comp xs282s,performer rpm,750 proform vac sec,msd in cap, hooker coated 1 5/8"headers,3"flowmaster,700r4,2800 stall,3.42 10 bolt posi,hotchkiss lca's,aje tube k member & a-arms
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