Replacement for 360LA

[wedgie]

I have a very low budget 360LA in my bracket car. It was just a junkyard motor that I did some headwork on as well as a cam change and 4bbl intake with holley. The thing is pretty tired now but has been running 7.90's in the 1/8th mile. Here's my question....I see junkyard 5.9 engines available at a decent price. I assume that the compression ratio is higher than my factory LA @ 8.5:1 and they must have roller cams. Is it worthwhile to buy one of these to replace my current setup. Keep in mind that it is race car only, but only a few times per year with the grandkids. Will my headers fit? What about intake, water pump, transmission, distributor, etc. Right thought process or should I drop the bucks on rebuilding the LA?
Thanks in advance for any input.

 

[jarvitron]

Intake won't fit, the heads are drilled vertical on magnums, and you can't put your LA heads on the magnum block without doing a preposterous amount of oiling work. Depending on how much meat is on your intake, you could redrill your intake to match. All magnums use the 360 style pan, and putting it in a car requires a swap to a car pan and oil pickup. Your distributor will drop in. Your headers will bolt right up. I've heard some contrary information about the flexplate/converter but it will bolt to your transmission after those two parts are sorted (my best info right now says an LA360 external balance flexplate bolts up and works) Someone smarter than me will chime in about that I'm sure. If you get a cam snout extension and bolt on your LA timing cover you can use the mechanical fuel pump but the magnum cover doesn't have the spot and the cam doesn't have the eccentric for the pump on it. Compression is supposedly 9.1:1, and it's a hydraulic roller out of the gate (with 1.6 ratio arms). Cams with more than stock lift are probably going to require seat work to prevent binding. Search on here and on the internets in general (there is a good though dated allpar article about this swap, and about fifty CarCraft/PHR/MoparMuscle/MoparPerformance articles about magnum heads) is gonna be your friend. If you decide to keep the serpentine accessories, there's a part number out there (dakota/durango forums) for a "short belt" that fits and deletes the A/C compressor. If you're gonna change everything out to v-belts then you just need to bolt on the accessories and mounts from your old motor.

If you can't tell I'm in the middle of a swap myself, so I have been doing my homework. I was able to score a "high mileage" 5.9 for $500 (140k miles) and it came with $200 worth of resellable EFI parts on top and a fatty boom-balatty 90 amp alternator, whereas I kept finding rattlecan rebuilder LA motors (mostly 318s) in the $2-300 range and "fresh when pulled motors" for $800-1000 (or that crazy guy's $2100 sub-8:1 318). Big shop rebuilt 5.9 magnums seem to be in the $1600-1750 range around here (a 10-15% premium over an LA) and they have better designed heads. I'm already in for some extra costs (flexplate/converter/pan/pickup), but coming from a 360 you have a big parts interchange advantage. The fuel pump caveat isn't really that big of a deal for me because I plan on running a relay back to an electric with an fpr/return setup. For your usage, the spring bind/lift issue is gonna bite your wallet a little on a magnum.

 

[rumblefish360]

The balance between the 360's, LA vs. Magnum, are different. IIRC, there is a B&M flexplate to deal with this.

The question is, what is the budget?

IMO, rebuilding the "LA" would be a better idea and do it with new slugs that will be at or near zero deck for a great quench. The block may need to be milled to get to a zero deck height.

Since you have everything, a hone job may be it! Otherwise, a bore and hone, new slugs and rings with a balance job and a gasket set,,,,ehhh, throw in a new oil pump while your at it for a small fee, that is cheap as it gets.