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  #1  
Old 01-09-2002, 03:19 PM
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cookcs cookcs is offline
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Default Motorhome 413

I purchased a 1972 413 from a 1973 motorhome, it has had very little use, and extremely clean internally. I am curious as to what the compression ratio might be, any ideas would be helpful, it has a pretty good dish in the top of the piston. It is still the stock bore and stock pistons. I have replaced the heads, they had holes in the ends ( steam holes) and an extremely large 4 armed water pump. I have replaced the heads with 906 castings.
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Old 01-09-2002, 07:00 PM
Dr. Righteous Dr. Righteous is offline
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Biggrin GOOD MOTOR!

The old 413 was an excellent truck motor. It will probably have less than 9:1 comp because a motorhome is a severe duty application.
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Old 01-09-2002, 07:16 PM
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I think the engine should have had angled spark plugs with 5/8" heads and a tapered seat? The waterpump housing raised the waterpump? The block has better cooling capacity as did the heads.....?
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Old 01-10-2002, 12:08 AM
jelsr jelsr is offline
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You can not use the original manifold with those 906 heads, it used water in the heat riser passages not exhaust. Before you go too far make sure you have the later style flange on the crank. The old style indexed on the outside of the flange rather than the lip in the center. Could also be a gear driven camshaft which rotates the opposite direction from normal.
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Old 01-10-2002, 10:02 AM
jkailholz@aol.com jkailholz@aol.com is offline
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I think I read something awhile back saying that the truck engines had around 7.5.1 compression. Not exactly a neck snapper. If I was you , I would get some flattop pistons in there to boost the output. I pulled one apart and it had the gear drive that drove the cam the opposite direction. The pushrods were longer than a regular 440, and it had some sort of spacer for the distributor.
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Old 01-10-2002, 11:27 AM
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Default 413

Thanks for the help, yes the pushrods and head bolts are longer, I was lucky, the engine when I purchased it came with the transmission. I have replaced the head bolts and push rods with the correct size for the 906 heads. I have replaced the oil pan, since the motor home pan had a front sump. I am curious if the transmission will work for a Challenger (what I purchased the engine for in the first place) it seems the correct size, I think it is a 727, but not sure. All your help is greatly appreciated.
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Old 01-10-2002, 11:52 PM
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Question

How far can a 413 block be bored out? Will it stand being taken out to 426 bore?
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Old 01-11-2002, 07:09 AM
beardliz beardliz is offline
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i also dragged one of the old 413's home this past weekend. origin unknown? has 4-10-68 cast on the block, stock bearings had 68 stamped on them, which leads me to believe the block is a 68. crank uses the lip to locate flex plate (like slant6/ or small block) motor has chain driven cam, flat top pistons, and closed chamber heads(200 castings). i think it may have the hipo exhaust manifolds, due to their funky curvy shape? no water heat for the heat riser.
factory cast iron 4bbl intake and thermo bog. looking for a set of slugs UNDER $400!?! (cheapest i have found so far) had a 71 car 727 hooked up to it. got the whole chunk for $50 (motor&tranny)
planning to do a close to stock rebuild with max overbore and enough cam to help the closed chamber heads flow a bit. gona drop the thing in a 74 duster and use it for a strip car. cheap (sortoff) and fast, not so much like the slant i have built up! (best time of 16.08 in a 4 dr 78 aspen 3.21 8-1/4 suregrip/904) good daily driver car.
anyone know if the 4.250 pistons from a 383 have the same comp height? (that will make it a 426
thanks all.....chad
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Old 01-11-2002, 07:25 AM
Brian Mills Brian Mills is offline
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Smile 413

413 is 7.5 -1 in truck app.
Chad- if it has a t-quad, it is either not a 413, or not the original carb to the best of my knowledge.
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Old 01-11-2002, 11:43 AM
937CHARGER 937CHARGER is offline
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If the origanal heads were closed chamber and you replaced them with open chamber 906's you will have very low compression.
Also I don't think anybody makes an aftermarket piston for these engines. You might be able to find stock low compression replacement pistons.
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  #11  
Old 01-11-2002, 06:18 PM
beardliz beardliz is offline
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without plugging the #s into the comp calculator, my guess is this is a stock 9-10:1 motor. flat top pistons with a -.015 deck height , steel shim head gaskets, and closed chambers, 7.5:1?
i have found a stock replacement piston for the engine, sealed power hyperuetectics, .030 over, flat top, bout $50 a piece. the pistons in the motor now measure 4.180 (413 bore size) hmmmm
chad
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  #12  
Old 01-12-2002, 02:33 AM
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Biggrin

I hope you can make it run better than that PIG Slant of yours!
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  #13  
Old 01-12-2002, 03:37 AM
beardliz beardliz is offline
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i am sure it will do just fine there, goomba.
at least the track clean up crew wont have to folow me with a torch, scraper, and VHT after "spraying" OIL from the 330' on down!
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  #14  
Old 01-12-2002, 10:16 AM
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Biggrin Yeah, BUT.........

at least I'll be fast BEFORE I "spray" it!
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Old 01-12-2002, 10:58 AM
beardliz beardliz is offline
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what happened to that guy that used to say "it is bracket racing, i will just change my dial in"
charlie says these are good heads to use for street/strip motor with flat tops. tells me the parts i have are the old poor mans 426 combo as soon as i bore it .070 over. found a set of almost new crane adjustable rocker arms and shafts to finished stripping the block last nite, gona do the muriatic acid trick on the h20 jackets for the rest of the weekend, sand blast the heads, etc..
gota get this pig rollin soon. itll be kinda fun watchin a little sprayed out slanter bust its nuts tryin to catch me!
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  #16  
Old 01-12-2002, 10:43 PM
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I won't have to bust nuthin' trying to catch a broken car. Bahahahahahahahaha!!!!!!!!!!!!! The way you tear up stuff with a Slant, you'll never keep a fat block goin'
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Old 01-12-2002, 10:52 PM
beardliz beardliz is offline
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Old 01-13-2002, 02:47 AM
Brian Mills Brian Mills is offline
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Default Beardliz

Sorry if my post sounded confusing. The 7.5-1 comp is for a 413 truck motor. The car engines were set up better. Never worked on anything but the truck one, if I had to guess, I'd say the car engine was 10-1 or real close to that neighborhood.
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