I was looking through my Chilton book at the specs on the 305 and 350 and noticed that for the most part, they're the same damned specs! What I was wondering is are there any differences that aren't readilly visible from those specs besides the bore? If not, would it be possible to bore a 305 block out to 4 inches? I know it's crazy, and I'm expecting to be put over the hibachi for this one. LOL

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1986 Firebird, LG4 305, bored .040 over, Crane cam, Edelbrock headers, Hooker Aerochamber muffler, loud and fast.

"Gimme fuel, gimme fire, gimme that which I desire!" - Metallica, "Fuel"

 

This isn't the first tiem, and probably won't be the last time this question is aked so don't feel bad. You can't overbore that far because of the placement of the water jackets for one thing. To get effective cooling, the water passages are roughly the same distance away from the bores in all blocks, which means if you overbore the smaller ones too much, you'll punch into them. There are probably more reasons, but that's one that I know of.

 

So... Say I wanted to swap out to a 350 block... The cam and the crank really can't be reused because of wear patterns, can they? But the heads (which would end up being upgraded), intake/exhaust manifolds, carb, and some other stuff can be reused, right?

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1986 Firebird, LG4 305, bored .040 over, Crane cam, Edelbrock headers, Hooker Aerochamber muffler, loud and fast.

"Gimme fuel, gimme fire, gimme that which I desire!" - Metallica, "Fuel"

 

Well, I may get grilled over this, but, yes. A lot of people will tell you not to use the heads though. While they will bolt up, and probably work fine, they are definately not good for performance! I have used LG4 heads on 350's before (non performance application) with no problems.

The intake, and exhaust manifolds, and everything else on the outside will bolt up fine.

The crankshaft is different. Not only the bore on a 305 is different, but also the stroke. It would bolt in and work, but why bother?!?! I know there are some people that use this combo though, I would just prefer the more cubic inches of a 350 myself.

Hope this helps you out!



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Working on:
'84 Z28 LG4 305
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350
using primarily GMPP parts.
Block is in shop!

Awaiting results from all 8 ASE tests.

Starting to look like the Kicker poster child!

 

As far as the heads go, you sure can reuse them, as long as they are massaged. Keep in mind that the 305's are 58cc cumbustion chambers and you will raise compression when using them. I just ordered a set of AFR heads that I had milled to 58cc's to raise the compression for my 350. You will need to run a piston with large vlave reliefs or "dished" pistons. Also, the vlaves and intake/exhaust runners are way restrictive and need to be opened. I hope you know a good machinist!!

 

Actually, according to the specs in the Chilton manual, the 5.0 crank and the 5.7 crank are the same. Plus, like I said, the heads will be upgraded. Most likely the intake, too.

But, on the note of a whole new motor... I just found out the GM Goodwrench crate motor is only $1300, fully assembled (without intake).

On a side note, my bro and I found a Found On Road Dead 302 block and heads for $50. We're gonna check it out and see if it's worth rebuilding for some deniros.

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1986 Firebird, LG4 305, bored .040 over, Crane cam, Edelbrock headers, Hooker Aerochamber muffler, loud and fast.

"Gimme fuel, gimme fire, gimme that which I desire!" - Metallica, "Fuel"

 

The crank has the same stroke, but I believe the journals are different.

The cam is the same, so are the exhaust manifolds, the intake manifold, along with the lifters, pushrods, rockers, springs, etc.

If you want a 350 engine, you need to start with a block that is 4" bore. A 305 has a 3.73" bore (am I close?). There's no way to bore it another 1/4" to make it 4".

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

Lemme see if I can let Mr. Lingenfelter shed any light on this subject...

"One of the subtle differences that lie in wait for the small-block Chevy engine builder is the great 305 vs. 350 crank caper. Both engines use crankshafts with the same main and rod journals , stroke and even the same casting number (3932442). Unfortunately, even though they can be used interchangeably, the crankshafts are not identical. The difference lies in the way the cranks are balanced for the different reciprocating masses of the two engines...The best way to spot a 305 without having to spin it up on a balancing machine is to lay the crank down horizontally and position a straight-edge along the machined surfaces of the crank. A 305 crank will allow the straight-edge to lay flat across all five points." -John Lingenfelter, On Modifying Small-Block Chevy Engines.

-Mark W.
'88 SC Camaro w/ 305 TBI

 

lingenfelter is my god.. :P

 

Wow! Lingenfelter is god! Thanks for clarifying that! i knew there was a reason they were different!

What's the deal with the "F" word 302? Not a good thing to talk about on here! LOL Just kidding!

So are you just looking for something to rebuild for the experience, or something?

------------------
Working on:
'84 Z28 LG4 305
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350
using primarily GMPP parts.
Block is in shop!

Awaiting results from all 8 ASE tests.

Starting to look like the Kicker poster child!

 

LOL Actually, the deal fell through on that. LOL $50 for the engine and heads... $300 for the shipping!!! LOL HAHAHAHA

Anyhow, I was hoping for the experience... I'm kind of a pud when it comes to mechanics... My dad and (younger) brother are the mechanics and I feel like an idiot, so I wanted to put together an engine so I understand everything going on in there.

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1986 Firebird, LG4 305, bored .040 over, Crane cam, Edelbrock headers, Hooker Aerochamber muffler, loud and fast.

"Gimme fuel, gimme fire, gimme that which I desire!" - Metallica, "Fuel"