308 heads Vs. Magnum heads

Hey all,

What are the years that "308" heads appeared on 360s? I know '90-'92 360, but what about '89 360? Found an '89 truck motor locally and was thinking about harvesting them if they are 308s.

Also, I'm wanting to compare them to a Magnum head. Which would be better for a street build?

I have an '86 360 short block and a '78 Motorhome 360 with a dropped valve (bottom end holds great pressure, checked with mechanical gauge).

I'm pretty sure '89 should have 308 heads. They started being used in '88 or '89. Gotta check for cracks.

Magnums flow a bit more than the 308's on the intake. Both have good exhaust ports. The added expense of adapting Magnum heads to an LA block may not be worth any small gains you may find.

Casting number on the 308's is underneath, so you have to pull the head to make sure. But you could pull the intake manifold and use a small mirror to look under the intake ports.

You have a PM.

Start by popping the valve cover and looking for the gigantic pushrod holes. (.66" versus .50" I think) Trucks seem pretty well picked over, pulled mine out a 15 passenger church van. I guessed no one thinks to look in snub nose vans, after I started wrenching in the junkyard I realized its really no one wants to work in snub nose vans. PITA

The 308 is the best OE iron open chambered SB head & the mag is even better. As you know you need the mag valvetrain related pieces for the conversion & a mag intake or redrill the head intake holes & some have even redrilled the LA intake for vertical holes & used a long bolt with a bushing sliced at an angle on one end. You may need adjustable pushrods and the P5007477 MP pushrods for the conversion may work but I think they are NS1 and they are pretty close in length to the adj MP ones I have. I just posted the measured lengths of all of them the other day for a guy on here but I think I tossed the scrap of paper. Good info on the large pushrod holes so you only have to pop a valve cover to verify. As said reportedly alot of em (OE used mags) have cracks but also reportedly the cracks ain't a dealbreaker & the heads are still useable so the cracks (if present) must not be in a vulnerable area. As you know the mags are closed chambered so the CR will be alot better than using open chambered heads which is another perk. EDIT the better combustion chamber will likely let you lower the total from the SB tried & true 35 down to 31-32 degrees. Check the deck surfaces for flat & good idea on the intake surfaces also. Holler how it works out when you are finished