Sgruenauer96

I've been seeing alot of people talk about the early 70s 350s, I found one near me I'm gonna go look at tommorow. Anyone have some info on them? Hp, what heads came on what years, any specific things that would make one better than another? Going from a 307 to a 350, I plan on trying to make some power on it but nothing crazy

Sgruenauer96

Also can I just use a MT engine to swap in it? I have the 307 for a donor flywheel

joe_padavano

The 1970 350s used #6 heads and came with either 9.0:1 or 10.25:1 CR, depending on the piston dish size
1971 and 72 350s used #7 (71) or #7A (72) heads with 8.5:1 CR on all motors. Again that is from the piston dish, not the combustion chambers.
1973-76 350s used #8 heads with much larger chambers that dropped CR even further.

All of these options have solid main webs and are a good starting point. If possible, avoid the 73-76 motors with the #8 heads. If you are asking about using an MT motor in a car that has an AT, that is not a problem. If you want to go the other way, the AT cranks typically are not drilled for the pilot bearing needed for a manual trans.

Sgruenauer96

Thank you, this is exactly what i needed to know, short sweet easy to use info.

v8al

Be sure to lookup the block/head casting numbers (or bring a cheat sheet with you) so you know what you are looking at. In general your best bet if you can find them are #5, #6, #7 and #7a heads.

olds 307 and 403

The #8 heads aren't bad once a bowl cutter is used under the exhaust valves especially. They are about 10cc larger than the early heads mentioned. Either use the Speedpro flat top or DSS 3cc dish forged pistons would be needed to get into the 9 to 1 range.

Sgruenauer96

cheat sheet? As in just the head numbers to look at or is there more info I should look for?

Sgruenauer96

Bowl cutter?

v8al

When looking at a block, how do you know if it's a 260, 307, 330, 350, 400E, 400G, 403, 425 or 455 block?
Check the block casting # versus your cheat sheet:

joe_padavano

Don't believe everything on that chart. I have in my possession a 455 block with a 1974 VIN derivative and a sans-serif "F". It has the threaded clutch pivot ball hole and an MT crank. I also have photos of an FA block that also has the clutch pivot ball hole.

JohnnyBs68S

"Possible" SMW 403???

v8al

If that's the worst mistake in the chart I think I can live with it.

Is there a definitive factory document available that identifies all engine casting numbers?

Sgruenauer96

Found myself a 1972 350 rocket, not gonna do power mods just yet but it'll happen at some point. This 84 98 is gonna want a tad bit more to get moving like I want

olds 307 and 403

Good choice. The Mahle 10.2 or 12cc DSS pistons will give low to mid 9 to 1 compression when you want more power. Either way gain 20ish HP/TQ over the 307. Add dual exhaust and a good tune up to gain more.

brownbomber77

While it's out of the car, pop the oil pan off and clean it. Might not hurt to replace the pump and pickup. Not to go down a rabbit hole, but timing chain, if original, probably still has nylon on it so, replace that.

Depending on how far you want to go beyond that, on used engines, I like to fill the oil pan with my favorite solvent and prime the whole system getting 50 years of varnish and gunk out cleaning the oil passages. Do that a few times, drain, change the filter, refill with a couple quarts of cheap 5w20, prime again, drain to be sure all the solvent is out, then fill with some VR-1 and run it from there.

Maybe consider replacing the heavy *** iron intake while everything is accessible.

Sgruenauer96

Yea shell get some love, but I'll end up jove cleaning it up nice and running it for a bit while I buy some parts, then rip it out, rebuild and go from there. I added your recommendation to my build notes

rallyeman@sbcglobal.net

I have a 1970 350 rocket short block that came out of a W31 and I have the water pump also 404847. If your interested email me and then I'll give you my number.