'88 copcar 318 - piston, CR, etc - Magnum heads
#560652
12/23/09 12:26 PM
12/23/09 12:26 PM
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Indiana
Fury Fan
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I’m looking at putting Magnum heads on an ‘88 318 copcar engine. I’d like to be able to do a little CR calculating - anybody know how far down the piston tops are, or what the CH of the piston is?
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Re: '88 copcar 318 - piston, CR, etc - Magnum heads
[Re: Fury Fan]
#560654
12/23/09 01:08 PM
12/23/09 01:08 PM
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Joined: Jan 2003
Posts: 2,111
Bowie, MD
Reggie
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Very rough ballpark estimate on your probable CR: The cop car 318s were 8.5:1 with the open chamber 360 heads. The civilian versions were around 9:1 with the closed chamber 302s which supposedly had a chamber volume ranging from 56 to 65cc. I would guess that you would be close to 9:1 with the closed chamber Magnums which are around 59 cc.
Last edited by Reggie; 12/23/09 01:10 PM.
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Re: '88 copcar 318 - piston, CR, etc - Magnum heads
[Re: Reggie]
#560655
12/23/09 02:22 PM
12/23/09 02:22 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
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my '86 2bbl roller cam motor was .055" in the hole. the cop motors use the same pistons. with the thin Mr. Gasket head gasket, and assuming my magnums were 64cc (I didn't have time to measure them) I should be at 9:1 exactly. I had the motor torn down to the bare block, and in hind sight I wish I would have had it decked .040, that would've given me .043" quench and 9.9:1 compression.
your '88 cop car block, if it's a 4bbl, should be a roller block, but flat tappet motor. I'd try get the entire valvetrain (cam, lifters, lifter "dogbones", spider retainer, pushrods, & rockers) from a magnum donor. & get the roller cam reground
one caveat with the magnum heads, you'll most likely have to rework your alternator bracket, and you may have to space your accessory drive out .2". I had to, to clear the alternator in my 5th ave. the accessory holes are in the same place, but are all on the same plane, vs. the LA accessory holes, which are on 2 planes offset ~.7".
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: '88 copcar 318 - piston, CR, etc - Magnum heads
[Re: patrick]
#560656
12/23/09 03:20 PM
12/23/09 03:20 PM
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Indiana
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Patrick, I was hoping you'd stop by. Your LA knowledge is A-1! I was hoping that a head swap would get close to quench but apparently not. Yeah, I anticipate my engine is a roller block with flatcam. I was under the belief that the Magnum roller parts were different from LA, though.  Isn't the block's lifter bore taller or shorter between Mag and LA? Although this conversion isn't that difficult, sometimes I think makes more sense to swap in the whole Magnum engine.  If I stumble across a good one that's what will happen!
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Re: '88 copcar 318 - piston, CR, etc - Magnum heads
[Re: Fury Fan]
#560657
12/23/09 04:11 PM
12/23/09 04:11 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
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Quote:
Patrick, I was hoping you'd stop by. Your LA knowledge is A-1!
I was hoping that a head swap would get close to quench but apparently not.
Yeah, I anticipate my engine is a roller block with flatcam. I was under the belief that the Magnum roller parts were different from LA, though. Isn't the block's lifter bore taller or shorter between Mag and LA?
Although this conversion isn't that difficult, sometimes I think makes more sense to swap in the whole Magnum engine. If I stumble across a good one that's what will happen!
nope, the roller lifter retention hardware is identical. the LA roller and magnum roller lifter bores are identical. I had them side by side. the roller lifters out of my '86 have a solid cup with no provisions for pushrod oiling. there is a difference in older LA OEM lifters and magnum lifters, but the older lifters are supersceded by the mag oil thrus. I've heard of people with '89ish-newer LA rollers that had lifters with pushrod oiling provisions from the factory. if you look at rockauto, the part number for a '96 ram and an '86 dip roller lifter are the same.
my combo runs great with no quench, short roller cam (bullet HR259/316 lobes on both, on the factory 112LSA for 33 degrees overlap, installed at 108 ICL), and 9:1. cranking compression is ~155-160 PSI.
one other caveat with mag heads. be very careful installing the rockers. torque spec is only 21 ft-lbs, and I didn't bother to roll the engine over to be on the base circle for each valve. I had 4 rockers back off, bending 2 pushrods. so I went and tightened them all to "tight" with my 3/8" drive, long handled matco ratchet...I'd swag I'm closer to 35-40 ft-lbs. no problems since.
and if you do go roller, and need slightly longer pushrods due to dropping the base circle on the cam regrind, etc, comp cams 7828-16 is a steal....spec for magnum PR's are 6.9-6.918" according to my dad's '97 FSM, the comp PR's are 6.936" (and a ford 302 app)
the comps are $26.95 from summit.
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: '88 copcar 318 - piston, CR, etc - Magnum heads
[Re: alpha727]
#560659
12/23/09 05:52 PM
12/23/09 05:52 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
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Quote:
The flat tappet cams had a fuel eccentric and the roller cams didn't if you're running a mechanical fuel pump and you switch to a roller cam you'll need to swap to an electric fuel pump or get a special attachment that installs on the camshaft and allows the use of a mechanical fuel pump.
actually, the roller cams in M bodies have the long snout for a fuel pump eccentric....you could try find an M roller cam at a junkyard to regrind...or if you do a trade in/core (say, buy a hughes regrind), just specify one for a roller cam, or just buck up the $18 for this camshaft snout extender
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: '88 copcar 318 - piston, CR, etc - Magnum heads
[Re: patrick]
#560660
12/23/09 06:54 PM
12/23/09 06:54 PM
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Joined: Jan 2003
Posts: 2,111
Bowie, MD
Reggie
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Joined: Jan 2003
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Bowie, MD
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Quote:
Quote:
The flat tappet cams had a fuel eccentric and the roller cams didn't if you're running a mechanical fuel pump and you switch to a roller cam you'll need to swap to an electric fuel pump or get a special attachment that installs on the camshaft and allows the use of a mechanical fuel pump.
actually, the roller cams in M bodies have the long snout for a fuel pump eccentric....you could try find an M roller cam at a junkyard to regrind...or if you do a trade in/core (say, buy a hughes regrind), just specify one for a roller cam, or just buck up the $18 for this camshaft snout extender
What Patrick said. M-body roller cams will have the long snout for the fuel pump eccentric.
Last edited by Reggie; 12/23/09 06:54 PM.
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Re: '88 copcar 318 - piston, CR, etc - Magnum heads
[Re: Reggie]
#560661
12/24/09 11:26 AM
12/24/09 11:26 AM
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Joined: May 2003
Posts: 15,487
Florida
scratchnfotraction
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I followed Patricks advice on my 88 360 headed 318 cop engine swaped it to the roller cam with all the hardware my cam gear donor was a 1990 tbi 318 had the oil thru roller lifters and hollow PRs and oiled both ways..LA style to the rockers and up the PRs ran the 60710 VooDoo roller cam with the long nose for stock fuel pump and comp 901-16 springs heads have not been off so I dont know how far the piston is down the hole it works very good on the street in a stepside truck regrind the stock roller or any after market retro roller cam and stock roller gear is the way to go IMHO 
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