Is there anyway to tell a 305 from a 350 with out pulling the engine out of the car?

 

Pull the heads off and measure the bore.

 

I thought that too but I don't want to get any dirt or dust in there. My garage isn't the cleanest in the world.

 

Check the casting numbers on the block.

 

On the back of the block right below the head on the drivers side it will say either 5.0 or 5.7. Your going to need to move some wires and maybe even use a mirror to see it. Its going to be in the area between the firewall and the engine.

 

throw it in the water see how long it takes to sink then get a LS they have fancy stamps on the back that say exact size

 

Not on an older block, but it will have a casting number in the same spot.

 

I didn't see any numbers back there so I was trying to see if I could feel some and its smooth.

 

They're back there. Top surface of the block behind the head.

 

I don't see them anywhere here I stuck my camera back there and took some pictures

 

mouse turds

 

have you run the vin number or checked the RPO codes in the glove box in the trunk

what model year and TPI carb ect

 

I checked the vin and it should be a 305 but it had some aftermarket parts in it which leads me to believe it may not be a 305.

 

350 and 305 parts are the same so it is most likley a 305 some guys like to mod 305s because you can get higher RPMS out of them and spin them all day long

what aftermarket parts are on it

If its a 305 it will be tbi with auto or standard but it can be a z28 with TPI then if it is auto its a 350 if its a standard its a 305

 

Try cleaning up the area with some solvent and a wire brush to see if you can find numbers under the caked-on crud.

 

Its got a carb and a manual transmission. I am not sure of all the aftermarket parts include as far as I know, elderbrock valve covers, cowl induction hood, GT grant steering wheel, Hurst shifter, than a sound system.

 

I am on it.

 

all signs point towards 305 unless its not the original motor and judging by the grime it looks like it is

 

But the orange paint on the oil pan makes me nervous

 

Cleaned it off some and took another pic and GOT THE BLOCK NUMBER!!!!!!!

 

Congratulations, it's a 4" bore.

 

It has a dang 350. First my 307 turned out to be a 350, now my 305 what the same heck?

 

Thanks for the help guys.

 

010 block. Thats a 70s era block and a 2 piece rms. I have one in my 88 too (i put it there lol). Its most 'likely' a truck motor that someone put in there thinking it was going to be faster. If it has stock truck heads on it though its probably slower than the 305 that it replaced. It is however a very good starting point for a performance build.

 

Yeah I have two of them now. haha

 

Hey does anyone know a way to tell a 2 bolt main from a 4 bolt main with out taking off the oil pan? I ran the casting number on the block 3970010 and it says for the 350 it could be either one. The head castings are 3998993. So I know its a 350 truck motor from 68-72. So does anyone know if it would be a 4 bolt or a 2 bolt main?

 

Without taking the pan off there's absolutely no way to know. Fortunately there's little reason to care.

 

Assuming those anchors errr heads are the originals then I think it is a 2 bolt. Most of the 4 bolts got 1.94 valve heads like 333882s.


Not really a big deal. Toss the heads out and put something better on there and wake it up a bit.

 

Yes, floor it, you'll know soon enough...

 

Sure there is. If its are 4 bolt I can take it to a lot higher RPMs.

 

Haha Actually after finding things out about my 350 I believe a stock 305 would be faster.

 

I agreed these heads are pretty much worthless, but luckily switching heads isn't that big of a deal.

 

No. In the list of things that affect high-rpm operation, the number of bolts that happen to be holding the stationary main caps on is dead last.

 

No a 2 bolt main is at risk if you push over 6000RPMs, but a 4 bolt you can push 7500RPM and be great.

 

Who told you that nonsense?

Factory 4 bolt mains are most common in highly-loaded, low-rpm truck engines. What does that suggest about their design intention?

 

I just read about a guy with a 327 2 bolt main that tore apart at 6500RPM. Think about 2 versus 4, the 4 bolt has double the strength.

 

What about the 4 bolt 305 that tore apart at 4500 RPM? Or the 2 bolt 383 that lives at 7000 RPM?

A 4 bolt main has double the number of bolts, not double the strength.

 

4 bolt 305? I have never heard of a 4 bolt 305 before.

 

Some low-performance 305 truck engines built in Canada were 4 bolt main. The "high-performance" 305s in cars didn't.

 

I still highly doubt that a 4 bolt 305 ripped apart at 4500RPM. Unless it was pushing 1000HP and over 750 pounds of torque

 

Like Apeiron said, 4-bolt mains have double the amount of bolts, not double the amount of strength, the strength is in the casting. Exactly how much power do you think the factory main caps and bolts can withstand...?

 

I would personally have a 2 bolt main go to 5500RPMs and a 4 bolt main go to 7000RPMs.

 

But the orange paint on the oil pan makes me nervous

 

What's stronger, something with 2 holes drilled in it, or something with 4 holes drilled in it? Doesn't matter though, RPM isn't what splits blocks.

At the end of the day there's no appreciable difference in strength between factory 2 bolt and 4 bolt mains on the same casting, especially in pretty much any build that could be considered streetable.

If you had an application where you really had reason to be concerned for the strength of the mains, and you were convinced you had to stay in a stock block, you definitely would not use a 4 bolt main block. You'd use a 2 bolt block, because you can drill it for splayed steel caps, which are stronger.

 

Too early for '882 heads, and the 4-bolt blocks were either 'vette or pickups heavier than half-ton. As such, the 4-bolt blocks got either the 2.02" valves for 'vettes, as not all 'vettes got the 4-bolt. LT1 / L82 did, L48 / LM1 were 2-bolt with 1.94". Trucks heavier than 1/2-ton typically got 1.72" intake valves. and not all '993 heads came with 1.72s. Very few 4-bolt blocks got 1.94" intake valves, if any. GM practice rarely stands to hot-rod reason.

 

So you're saying that there is a good chance my block is a 4 bolt main?

 

I am not talking about the block splitting cause they are the exact same thing besides the caps. I am talking about the caps coming off. And I agree that if I were to be pushing ridiculous RPMs that you would go with a 2 bolt main and drill it for splayed steel cars.

 

Anybody that plans to build big horsepower wants a 2 bolt block instead of 4 so that he can add splayed aftermarket caps. That configuration is much stronger than a factory 4 bolt setup.

But even that has nothing to do with high rpm capability. 2 bolt, 4 bolt or splayed, it's got nothing at all to do with rpm capability. Your valvetrain, rods & rod bolts and crank all have infinitely more to do with safe high rpm capability.

 

600 hp (with the 75 shot) and 7100 rpm with the 2-bolt stock bottom in my Impala, no problems after 2 seasons of racing it.
My buddy's 2-bolt main 383 spinning to 7100 rpm DID exhibit some main cap "walk" when he rebuilt it after racing it for 3 seasons. He's 4-bolt splayed now.

 

The longer stroke multiplies the forces exerted on the crank & caps. Horsepower + longer stroke = cap walk.