305 build advice. Any and all advice is appreciated!

[bucket]

Wtf is that engine even for? Lol

I think it's the one that makes our earth turn. Lol.

 

[78C10BigTen]

I think it's the one that makes our earth turn. Lol.

To quote the the taco bell dog.... i tink i need a beeger box!! Or square in this case lol

 

[FireTruck1984]

Wtf is that engine even for? Lol

It’s for Leo DiCaprio’s private yacht, ready for his “Save the environment” world tour

 

[Snoots]

Wtf is that engine even for? Lol

Whole house generator.

 

[Sharkey]

Get yourself a “R” code L31 5.7 .Switch the manifold to a 4bbl. “R” code engines are roller cams with Vortec heads. They are the best flowing heads from factory. Bolt in swap with headers you’ll have a nice engine with more HP and Torque with good fuel economy. I found mine for $200 with 140k. Valve seals replace and amazing how much more power than my 305.

 

[Doublenaughtspy]

I'll completely switch "gears" here and suggest a switch to 3.73 from that 3.08 differential. While it doesn't address the weak motor, it will make your truck feel more peppy while you decide on your engine/build/stroker/crate/SBC/BBC dilemma. Chances are you're going to change it sooner or later anyway and this may be the cheapest improvement you can make.

 

[MikeB]

So, at this rate, may I suggest a compression test? It sounds like the engine MAY be starting to get tired. Find out the condition of what you have. May be throwing good money after bad investing a lot of money in it if it is bad.

That's very good advice! The short block must be in good shape before you start bolting on parts.

As for a cam, only a few will help a 305 with stock compression. You should aim for more lift with just a bit more duration. Chevy made an "H.O." (high output) cam for the 305 when used in the Z28. It's similar to a Summit Racing SUM-1101, but the Summit cam has more lift. If you go too big, your cylinder pressure will drop, and low RPM torque will be less than you have now.

If the budget will allow, get a 3-angle valve job and have the head surfaces milled .030" or so. And then use a .028" composition head gasket.

 

[FireTruck1984]

I'll completely switch "gears" here and suggest a switch to 3.73 from that 3.08 differential. While it doesn't address the weak motor, it will make your truck feel more peppy while you decide on your engine/build/stroker/crate/SBC/BBC dilemma. Chances are you're going to change it sooner or later anyway and this may be the cheapest improvement you can make.

Yes I second that idea, I installed 3.73 gears and I love the difference

 

[Ewhitaker0020]

I'll completely switch "gears" here and suggest a switch to 3.73 from that 3.08 differential. While it doesn't address the weak motor, it will make your truck feel more peppy while you decide on your engine/build/stroker/crate/SBC/BBC dilemma. Chances are you're going to change it sooner or later anyway and this may be the cheapest improvement you can make.

Are the gears hard to change? Do I have to pull the axles or anything to do it?

Sent from my SM-G950U using Tapatalk

 

[SquareRoot]

I pieced together a 305 one part at a time thru Summit Racing. Comp cam, Weiend SR Torquer heads, header's, Pro-flo, etc. It ran damn good in my 85 El Camino.

In hindsight, an El Camino is half a truck and a 305 is half an engine. I'm pretty sure if I spent the same amount of money on a 350 I would have had twice the power.

That said, live and learn. Would I do it again? Hell No!

I'm sure I'll be saying the same thing in the future wishing I had built an LS for the same amount of money I put into this L31. ****!

 

[MikeB]

Are the gears hard to change? Do I have to pull the axles or anything to do it?

Sent from my SM-G950U using Tapatalk

Pulling the axles is the easy part! Changing the ring & pinion is not a trivial task. I've done two 10-bolts and one 12-bolt. Made a couple of mistakes on the first one, but got them corrected right away, and felt more confident doing the last two. You will need a 12-ton press (or better yet 20-ton), dial indicator with magnetic base, a 0-60 in/lb torque wrench, and some way to apply >300 lb/ft torque to the pinion nut to crush the crush sleeve. And of course an exact understanding of how to set up pinion depth. However, I just bought a shim/spacer kit (in lieu of a crush sleeve) for an 8.5" 10-bolt for my upcoming change from 2.73 to 3.23 gears.

The job is a lot easier with the rear end out of the truck, but of course that means removing brake lines and using new u-bolts and nuts to reinstall the rear end.

Worst case, maybe you can find a local garage with an experienced R+P guy. Had a buddy pay around $400 labor a few years ago to have a 77 Nova 10-bolt done. I sort of vetted the guy, and he really knew what he was doing. Worth every penny!

Here's a book that should help:

https://www.amazon.com/gp/product/1...k_look_saved_title_8?smid=ATVPDKIKX0DER&psc=1

You must be registered for see images attach

 

[Bennyt]

Pulling the axles is the easy part! Changing the ring & pinion is not a trivial task. I've done two 10-bolts and one 12-bolt. Made a couple of mistakes on the first one, but got them corrected right away, and felt more confident doing the last two. You will need a 12-ton press (or better yet 20-ton), dial indicator with magnetic base, a 0-60 in/lb torque wrench, and some way to apply >300 lb/ft torque to the pinion nut to crush the crush sleeve. And of course an exact understanding of how to set up pinion depth. However, I just bought a shim/spacer kit (in lieu of a crush sleeve) for an 8.5" 10-bolt for my upcoming change from 2.73 to 3.23 gears.

The job is a lot easier with the rear end out of the truck, but of course that means removing brake lines and using new u-bolts and nuts to reinstall the rear end.

Worst case, maybe you can find a local garage with an experienced R+P guy. Had a buddy pay around $400 labor a few years ago to have a 77 Nova 10-bolt done. I sort of vetted the guy, and he really knew what he was doing. Worth every penny!

Here's a book that should help:

https://www.amazon.com/gp/product/1...k_look_saved_title_8?smid=ATVPDKIKX0DER&psc=1

You must be registered for see images attach

I paid $465 at the local diff shop last month to rebuild my sons rear axle. All new bearings, included a replacement yoke w/ hardware, seals, gaskets, etc. I already had 3.73 gears in it but they said they could swap to whatever used gears/ carriers for a few bucks more.

In the past, I used to know a few guys that did it on the side for around $250 or less including magnuflux of the gears.

 

[85 CA SIERRA 1500]

I paid $465 at the local diff shop last month to rebuild my sons rear axle. All new bearings, included a replacement yoke w/ hardware, seals, gaskets, etc. I already had 3.73 gears in it but they said they could swap to whatever used gears/ carriers for a few bucks more.

In the past, I used to know a few guys that did it on the side for around $250 or less including magnuflux of the gears.

WOW, that is a great price,,,,,I have been quoted $1,000--$1,100.00 in my area for a rebuild with a gear change

 

[Hugeroost]

Friends don't let friends rebuild 305s. You can throw all the parts at you want but nothing replaces... displacement.
They never should have put these engines in trucks.
At least Eric's truck is a 2x, but still not worth it imo.

Sorry I know it's not what you want to hear...

Thank you ! when I saw thread title I thought omg no no no dont throw money at that thing thow the whole motor in the garbage before you spend a can't. I tried that one time years ago w everbody telling me not to, got about 600 bucks in and it cratered lol. Luckily most of that stuff also bolts right on a 350. Best thing the OP can do on the cheap is visit GMperformance.com and buy a direct plug in ready to go, their cheap. That or go used, but GMP comes w factory warranty