5.9L Magnum recipe...

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jtolbert

jtolbert

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So I've got this 166,000-mile 5.9L Magnum I picked up for $300. It's torn down at this point and the machine shop has given it a clean bill of health for a rebuild. Now I get to pick parts.

What do I want out of the engine? A good, solid, fun driver that makes good power on 87-octane gas. I'm not looking for a world-beater here; I just want something that won't get completely embarrassed by stock LS3s and the like.

Machine shop says the crank is fine, but the journals should be polished before it's re-used. They say the block is great and the bores are in good shape, but they recommend an overbore and hone, plus the decks are a bit uneven and should be milled...So I'm going to go with that. But, this stuff depends on what heads I pick, what pistons I pick, and so on. So here I am.

I'm leaning towards the Edelbrock Performer RPM 61775 heads, probably non-ported, with head bolts from ARP. For the rods I am leaning towards the Eagle 6123-CP I-beam rods with press-fit pins.

My real questions are with the cam, intake and pistons. I also need to figure out how to get cam and crank position sensors set up on this engine, and to make matters more fun, I want to run a manual transmission. What pistons and cam would you recommend for this setup? Seems like the flat-top KBs and Speed-Pros can get me right at 9.0:1 compression with an .040" head gasket using the 58cc chambers of the Edelbrock heads, but I don't really know where the limits of 87-octane are with various cam and piston combos. Hypereutectic pistons are probably the order of the day, since I'm staying naturally-aspirated and won't be running the engine very hard for very long. What would you suggest? Thanks!
 
What kind of power does a LS3 make? What do they come in and how faster are those rides.
 
Well if your using aluminum heads i would run 10.5 comp.ratio and still run 87 oct.gas with a little less timing,run 93 when you want to have fun and bump the timing up as needed.A Comp. extreme energy cam around .490-.510 lift.
 
If you're going to spend money to bore an engine that doesn't need it, and then spend money to replace those factory coated skirt, molly ringed pistons, you might as well plan on getting the most you can from those expenditures, and not just because it seems like a good idea.
 
LS3s came in newer Camaros and Corvettes, plus a few other vehicles in various tune/trim. They are rated at 426 HP or 430 HP at the crank, depending on which numbers you look at. Rear-wheel dynos have them putting anywhere between 350 and 370 HP and about the same in ft-lbs. to the ground in newer Camaros. Of course, that's on 89-octane gas; they lose a bit on 87-octane regular.

The machine shop said the bores were two or three thousandths out of round and "a lot of people get away with basic rebuilds using just a clean-up hone, but I sure as hell wouldn't do it for anything over the cheapest stock rebuild." I'm leaning towards just .020" over, since it seems like piston selection is good at that size.

Sorry if I'm not being very clear. all of the other engines I've rebuilt have just been stock-type rebuilds with/for friends. This is really the first time I've had to pick out basically everything.
 
Read this.

http://www.magnumswap.com

He had a really quick dart that ran 11's for like $2500.00

I have a stock bore 360 mag with keith black pistons.
The crank must be balanced with mallory.
Eddy heads put my compression at 11.37 when it was all done.
 
jtolbert said:
The machine shop said the bores were two or three thousandths out of round and "a lot of people get away with basic rebuilds using just a clean-up hone, but I sure as hell wouldn't do it for anything over the cheapest stock rebuild." I'm leaning towards just .020" over, since it seems like piston selection is good at that size.
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F*** that guy. Prying your pocket using fear tactics is lame. The fact is, You don't need to bore it over; it's a Magnum! Those bores are super clean even at 300k taken care of. Small scratches are fine, unless the holes are wallowed out, thanks to fuel injection and metric rings, you just don't need to do it unless something is/was wrong.
 
PoisonDart74 said:
F*** that guy. Prying your pocket using fear tactics is lame. The fact is, You don't need to bore it over; it's a Magnum! Those bores are super clean even at 300k taken care of. Small scratches are fine, unless the holes are wallowed out, thanks to fuel injection and metric rings, you just don't need to do it unless something is/was wrong.
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In agreement here.... What were the original bores measured at,how do the piston skirts look? Mine has almost 200 k,looks new.
 
brewers has flywheel. neutral balance Mcleod with bolt on magnum weight so you can swap between motors just by changing weights
 
Nice tip about Brewers, I'll have to remember that.

I don't run a computer but, the RPM heads should be well preped, use the rpm intake, 1-3/4 headers would be my choice size into a 2-1/2 exhaust, cam size of 230@.050 with as much lift as possible. Use the KB slugs. Use a 750 carb.

This should easily crest 400HP.
 
rumblefish360 said:
Nice tip about Brewers, I'll have to remember that.

I don't run a computer but, the RPM heads should be well preped, use the rpm intake, 1-3/4 headers would be my choice size into a 2-1/2 exhaust, cam size of 230@.050 with as much lift as possible. Use the KB slugs. Use a 750 carb.

This should easily crest 400HP.
Click to expand...

Done the "58 c.c. E.Q . heads,.027" gasket head swap on an retro Howard's 229/233 @ .050 on a 110 lobe centers It idles very nice with 18 initial....(Cl
 
jtolbert said:
I also need to figure out how to get cam and crank position sensors set up on this engine, and to make matters more fun, I want to run a manual transmission.
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The cam position sensor is easy, it's in the magnum distributor so just run that.

The crank position sensor will be tough, depending on what transmission you plan to run. If the trans bolts up to the truck bell housing, run the stock magnum flywheel and you are golden. But most people that want to run a 5.9 in an older car want to run an A833 of some type. If so, you have one or two options. You could try to get the factory 143T flywheel turned down to accept a 130T ring gear and have it redrilled to fit the clutch you want to run. It's been done, but I haven't heard of anyone that has made it work a second time (nobody seems to be able to find a shop that will do the machine work). The other option is to get a custom flywheel built. Look up guys putting viper T56's in their Dakota's, you will need the same flywheel. Pretty sure it was $500-600. Last option is to relocate the crank pick up to the front of the motor and cut holes in the crank pulley to match the slots in the flywheel. Then you can run any flywheel you want.

BTW, you can bolt an R154 5 speed out of a turbo supra up to the magnum bellhousing, or a AR5 out of a Colorado. If you wanted to run a 5 speed that is, and didn't mind the custom work of cutting your floor up. Either of those would allow you to run the stock 5.9 flywheel without being forced to run the truck transmission. Just a thought.
 
Thanks,DionR. That is, a eye opener.....^^^^ Trust the Toyota box,the GM one is interesting.
 
I seem to recall reading that the dakota bellhousing has the same pattern as the toyota R154 box BUT the input shaft is longer on the R154. IF that is the case It will mean fabbing up an adapter plate.

This is just what i have read. I have no first hand experience with this conversion.
 
frosty_the_punk said:
I seem to recall reading that the dakota bellhousing has the same pattern as the toyota R154 box BUT the input shaft is longer on the R154. IF that is the case It will mean fabbing up an adapter plate.

This is just what i have read. I have no first hand experience with this conversion.
Click to expand...

Other way around, the AX15 input shaft is longer so an extension for the throw out bearing needs to be fabbed to mate with the R154 input shaft.

http://www.slantsix.org/forum/viewtopic.php?t=35945
 
Interesting stuff about the transmissions. I thought about using the Magnum distributor for cam position, so it's cool to see that others are doing the same thing.

I'm going to get the block back from the machine shop, see if the machinist actually provides bore measurements...If not, borrow a dial bore indicator from someone and see what I come up with.

What's the rule of thumb on this stuff? How bad does a bore need to be before re-boring is the best option?
 
Not much but I leave to the machinist if the engines apart or if it is running, the amount of oil consumption and oil fouled plugs will be a tail tell sign.
 
Picked the block up from the machine shop. They say the block's bores are worn .0015" - .0020" and just recommend the smallest overbore necessary depending on the pistons I find. The crank is fine at standard size.

I'm nervous about leaving the bores alone and having to tear it apart again. I'd be quite happy to use .010"-over pistons, but apparently they don't start til .020" over.
 
Can you still see the cross hatches in the cylinders?
 
2 to 3 thousandths wear is not worth concering yourself about. You do not need to bore the block. The old service manuals talked about 10 thousandths as being the limit before over boring. Save your money and if you want, get new pistons in standard size that achieve your target compression ratio, taking into consideration the heads you end up using. If it were me, I'd get new pistons and rods, have the block lightly honed for new rings, new cam bearings and freeze plugs - the bottom end balanced and call it a day. Maybe you might need to have the block decked, but my guess is your machine shop is going overboard on that too (probably not needed).
 
a friends 340 was .007" over in one cylinder.honed with new rings and it was good for 40,000 miles.it had the stock cast pistons,did not rattle and would run up to 6500 whenever asked.and it wasn't always nicely either.
keep the stock bore.why change rods?replace the rod bolt nuts and save the money for the cam and intake.
 
ON my engine, I have decided to use some scat i-beams, KB 107 pistons .040, stock heads with the intention to move over to eddy RPMs, RPM airgap magnum manifold, and have the extra cam I scored for 8 dollars on ebay ground at bullet cams. Cars gonna have 3.23 gears and a 904/999 geared five clutch with a custom dynamic convertor. Probably a 750 vac second holley and a DIY recurved distributor. As far as machine work, I plan on having the rotating assembly balanced with the new rods and pistons, and decking the block to zero while using the compressed head gasket to zero in on maximum quench. Hopefully it will make for a fun ride.
 
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