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Old 03-27-2009, 03:01 PM
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Marine cam in 454

Looking for advice, I am currently building a 454 for street use, Its a 73 truck engine with oval port 206/172 valves, .030 flat tops so the compression should be low. I have a complete Comp cams Xtreme marine 288H cam kit. (cam, lifters, springs, retainers, locks, timing chain) The kit has been sitting on the shelf for a couple of years since I sold my boat. I hate to not to use it for something. According to spec card it's got .570in/575 exh with 244/254@.50 duration with 112 degree lobe seperation. It says this cam is for rpm range of 2500-6500. Intake is a early non-egr quadrajet intake with adapter and holley 750 mechanical secondaries (will fit under stock hood). I really don't see why this won't work in street engine. Am I missing something. From the specs I don't see why the marine cam won't work for street use. Feedback from some of the BBC experts would be nice. Drive train will be a t-400 with rear 3:50 gears. I have not yet purchased a converter, figure about a 2800 stall? This will be street driven 68 Impala with occasional strip use.

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Old 03-27-2009, 03:29 PM
richard stewart 3rd's Avatar
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Hi
A lot of marine cams are very similar to an RV cam
I don't think you'll have any problems with it. I'd be more
concerned about the head flow, what castings do you have?
Good luck,
Rich
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Old 03-27-2009, 04:32 PM
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Casting number on heads are 336781, I believe it to have 118 cc chambers. I think I screwed up and posted this on the basic hotrodding forum when it should be on the engine forum.
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Old 03-27-2009, 04:56 PM
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Hi,
The info you have on the heads is correct, & what you should be using if using stock heads.
Flat tops are around .030 down, have you had it decked? the compression as you said will be low,
do you remember how to figure CR, if not here's a link to a CR calculator.

http://www.csgnetwork.com/compcalc.html

http://www.rbracing-rsr.com/compstaticcalc.html
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Old 03-27-2009, 05:08 PM
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Most 781 heads in fairly stock condition. Will require a lot of work for with that much lift. You will have to use the kits springs/retainers and remove the rotators.. Probably invest in some .050 UP locks. Be sure to get installed height on the springs correct. These stock heads have very SHORT valve springs. Also, that cam needs more compression.
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Old 03-28-2009, 11:02 AM
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Also, I don't believe it was mentioned. Some marine engines rotate in the opposite direction from automotive engines. Make sure your cam is not one of these.
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Old 03-28-2009, 11:32 AM
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Excellent point on engine rotation. I checked and it is for a standard rotation. This will mainly be a street driven vehicle, the 68 Impala is a heavy car, Hopefully it will have good torque to get that weight moving.
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Old 03-29-2009, 10:34 PM
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Yours is a perfect application for Rhoads Lifters.....
http://www.rhoadslifters.com/
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Old 03-30-2009, 01:24 PM
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I've used Rhoads Lifters in a BBC and they worked well to make the cam effectively smaller. Sometimes you just have to work with what you've got.
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Old 03-30-2009, 01:30 PM
How fast is fast enough?
 
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change the cam. The rest of your build calls for a smaller cam so it would make the most sense to change that rather than everything else to match your cam. You can probably use the rest of the kit, just need a differenet 'shaft. An "RV" grind or even something slightly smaller is needed.
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Old 03-30-2009, 01:35 PM
How fast is fast enough?
 
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I just pulled out the ol' clearance catalog from Comp. Products. They have a few cams on clearance for $50 that would do a MUCH better job. I figure $50 is a price anyone can afford. You still need to run tight quench and mill the heads some if you can to gain some sort of compression.

Comp. Products #- 1-920-233-5228 ask them about BBC hyd. cams that are on their "broom sheet". In your case the smaller the better (within reason).
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Old 03-30-2009, 02:06 PM
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cam is way to big and cr is way to low for a cam any bigger than stock.

I would use a compcam 268H or 270H and change the flat tops to a dome piston. Go for 9.25:1 cr.

781 heads are good. you will need to get rid of the exhaust spinners with stronger springs.
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Old 03-30-2009, 03:57 PM
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There is a time and place for everything. If they were so horrible, they wouldn't still be sold 25 years after I first used them. I totally understand what you and others have to say about them and that's OK. You have your opinion and I have mine. No harm, no foul.

It was 1983. I was building a 454 for my friend's 4X4 truck. He wanted more cam than I knew he needed, so I decided to try the variable duration lifters. In that case, they worked perfectly for what he wanted to do, effectively extending the operating range of the camshaft so that it worked effectively at low and high r's.
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Old 03-30-2009, 04:08 PM
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Quote:
Originally Posted by ap72
I just pulled out the ol' clearance catalog from Comp. Products.
I went onto their site and found the clearance section, decided to look around.

I like to fell out when when I found the cam I needed for a non-roller 4.3L V6- FOR $14!!!

At first I was excited, then bummed when I saw when I went to order that it was out of stock. Never taking "no" for an answer (at least when it comes to car parts), I emailed them.

Sure, we have LOTS of those cams. How many ya need? They had a bunch more cams for $14, even rollers- all OEM replacement-type, though.

Oh, joy. Now I get to finish this lump, throw it into the truck and be done w/it! Then the Vortec. At least that'll be more fun.
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Old 03-30-2009, 04:20 PM
How fast is fast enough?
 
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ok, second camshaft that F'bird picked- Man Summit has some deals!

And as noted your compression is still ow, but switching to that cam will help. a LOT!
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