I'm going to the junkyard in about a month to find a 350 block. I'm building a 350TPI. Anything that I should definately stay away from? Also, what is the difference between a truck 350 an a car 350? I'll be replacing all the internals, so would there be a difference? I'm using heads and TPI from an 87Formula 305TPI. Also, one more quick question, is there an EZ way to tell a 305 from a 350 by looking at it?

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yes, the bore is bigger on the 350. Just take a measuring stick or caliper with you.

the other ways aren't so easy because you'd have to remember several casting numbers.

some 305's used smaller dampers and flexplates, but don't count on that. Many can be visually identical on the outside. Measuring is the only sure way.

ODB

 

Any more on the rest of the questions?

 

There are a few things you should look for. First of all, in 86 chevy changed to a one piece rear main seal, which helped prevent leakage. In 87 the cars went to a roller cam, while the trucks didn't change until 88. Roller cams are better, but they're more expensive. If you have an older block, you can convert it from hydraulic cam to roller with aftermarket lifters and a cam button. Why are you using heads off a 305? Yes, they will raise the compression ratio, but they won't flow as well. You'd do better to go with the heads that come with the 350 block. Or get some aftermarket heads if you have the money. If you do decide to use heads off the 350 block, remember that the angle between the heads and the intake changed after 87. That's all I could think of.

 

One more thing: I'm pretty sure 3/4 ton trucks came with a 4 bolt main.

 

Look for 4 bolt blocks from trucks.

Other than that they are all pretty Much the Same, Well, post 86 anyhow ( 1 peice rear main )


As far as Not accidentlaly getting a 305, check the casting numbers.

Also, Check the harmonic Dampner, If its hollow, its a 305, Solid its a 350, In stock trim anyhow.

Other than that, The blocks are externally the same

Also, Dont use those heads, They will choke off your Motor,and put your compressions Sky High.




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chances are that most 350 heads you will find in a junkyard today will not flow better than your 305 heads will. You can get lucky and find better heads, but it's unlikely in a junkyard. Better to hang around some engine building performance shops for leftovers laying around or heads no one ever paid for or picked up.

I personally like the old style two-piece rear main seal better than the newer one-piece design.
Also, I would stay away from anything that looks to be externally balanced (rare for a 350). You can tell by the weights on the flexplate or an odd shaped damper. That would cause you headaches and cost more money in the longrun.

ODB

 

On the differences between angles of the head and intake. I'm needing something that WILL bold up to the 305TPI an Intake that I'll be using, so how can i be sure of this? Aftermarket heads are out of the question ($$$) but if i get some good 350 heads, I'll use them. Also, someone told me that truck engines have more torque than car engines, this true?
As far as the internals, I'm looking at a 350 master rebuild kit, or a 383 stroker kit. Can anyone tell me the advantages of forged pistons over cast?

 

The heads off a 350 will only match up to your intake if they are from an 87 or newer. If you get an older engine you can have the heads or intake redrilled at a machine shop so the angles will match. As for truck engines having more torque, that is probably due to the camshaft differences.

 

don't worry about the TPI bolting up. At most you may have to elongate the center bolt-holes on the intake with a drill.

no difference in truck & car engines.

factory 4 bolt blocks will cost more money from the yard and are not worth the trouble. Two bolt mains splayed for four bolts are much stronger, but not necessary on the average street performance engine.
Put your money into the stroker kit & heads.

Forged cost much more and are much heavier requiring more balance work. The forged have a more sloppy fit in the bore that sometimes makes noise or leads to broken piston skirts. The forged pistons are stronger, but the cheaper forged pistons like TRW have very little strength advantage over cast pistons. The good forged pistons usually cost at least $800 per set.

you can make well over 400 horsepower with the cast pistons if you are concerned with budget restrictions.

seriously for power I would put the money into the stroker. I paid $40 for my stock 400 crankshaft, and I reused my stock X-rods. I had to get a 400 balancer/damper and a 400-style flexplate. Besides shorter pistons and some machine work, the rest of the engine rebuild is the same as a 350.
I have 3 or 4 extra 400 flexplates sitting in my garage right now. You could probably get the damper and flexplate for free if you look around.
You can use your 305 heads on a 383, but you will need to port them well and used dished pistons to keep it running on pump gas. Some people enlarge the combustion chambers on the 305 heads to unshroud the valves and to lower the compression.

 

Here we go again ...

The balancers and flexplates/flywheels on 305s and 350s are the same. The difference of hallow and non-hollow are due to design changes over the years. Since both are internally (or neutral) balanced, like all SBCIs, they use the same stuff. One-piece rear main seals are slightly different in that they are "externally" balanced, kinda. But the balancer and flexplate/flywheel issue still holds true. This myth (I believe) has come about from people who are unsure of parts interchangeability between SBCs and are repeating what they've been told is truth. It is a total farse that cannot be proven because GM used interchangeable parts, just look up part numbers and you'll see. The only other SBC to be externally balanced is the 400. Balancers and flexplates/flywheels from 400 should not be used in any SBC engine (except for the hybrid 383 if externally balanced).

I know some of you will take this as a flame, DON'T! Only those who do want to learn will either believe me (by researching the info for themselves), or post factual info which contradicts me (doubt it).

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I am one of those "inexperienced" guys that believe the balancers are different between 305s and 350s. I've only been building and modifying small and big blocks (among others) for 30 years.

It is true that a 305 balancer will physically interchange with a 350 balancer (depending on timing tab location), but they are different in size and shape, in most cases.

Most later model 305s I have seen and worked on have had hollow balancers. I have seen solid balancers on some early 305s (mid 1970s) which were physically similar to low output 350s of the same time period.

As some evidence I encourage those readers that have a copy of the "Chevrolet Small Block V-8 Interchange Manual" by David Lewis (mine is the 1989 edition) to look at pages 33, 34, 35 and 36.

There are pictures of various small block balancers, including general descriptions. There is also a box which contains balancer dimensions, engine sizes, part numbers, use description and hub size.

6-3/4" x 1-3/16 is listed for the 305, 327, and 350. Part number 6272221, described as base performance with a 4-3/8" hub size. This balancer is pictured and is the same height (but not as wide) as the hollow balancer. This balancer is solid.

6-3/4" x 1-11/16" is listed for the 267 and 305. Part number 458653, described as base performance with a 4-3/8 hub diameter. This balancer is pictured and is the hollow balancer (and noticeably wider than the solid balancer). One of the pictures describes this balancer as appearing in the late 1970s and not recommended for interchange due to the outer ring walking (I've seen this several times).

The next size (in the chart) is 8" x 1-1/2", listed for the 350, part number 6272222, intermediate performance, with a 6-1/4" hub. Solid balancer.

The same size is listed for the 400 (only), part number 6272225, unbalanced intermediate performance 6-1/4 hub (this balancer is machined partially around the outside).

Next, in the chart, is the 8" x 1-3/4", listed for the 302, 327 and 350, part number 3947708 is described as Special High Performance with a 6-1/2" hub. Solid balancer.

Last, same size as above, with same engine sizes, is part number 364709 described as Nodular iron ring, off road racing with a 6-1/4" hub. Solid balancer.

I would ask that those readers, with a known original 305 (from the 1980s) in their vehicle, reach down and feel the backside of the balancer. It would be my guess that most late model 305s will have the hollow balancer.

I would then ask other readers, with a known original 350, to also reach down and feel the back side of their balancer. I would guess these would be solid.

These balancers, other than the 400 version, are interchangeable, and would run on a mild engine, but I wouldn't want to run the hollow 305 balancer on a performance 350 unless I was trying to pass a larger engine off as a 305.

Short and sweet---it is my belief that a hollow balancer means 305 in the majority of cases.
jms

 

I'm with you JMS,

my 86 305 uses the same damper as an older style 350, but the 305 has a small flexplate with a weight on it for balancing.

I also have an older 70ish 305 that has the smaller damper and a normal 350 flexplate with no weight.

man it's confusing...

and if you're looking through a junkyard the casting numbers are usually covered in rust or grease.. then after you clean them, you still can't make out all the numbers.
That's why I say just measure the bore. It's very unlikely you will find a 327 in a junkyard, so any 4" bore is going to be a 350.

 

I thought even 1/2 ton trucks got the 4 bolt. I mean they only had 1 350 for the trucks in the L05 years right?

Is it right that in '88 the trucks got roller cams? I think once I got curious and went to carparts.com to look up a cam for my dad's '88. It was only $50, I think it was non roller.

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[This message has been edited by Keith5 (edited February 22, 2001).]

 

Don't the older truck motors spin the distributer counter-clockwise. It's not a block difference, but a cam/dis gear difference. Changing the cam corrects this.

 

So basically what your saying is... if it's a newer block (80's) and it has a solid balancer (feel behind it, you can feel the outer ring, and then in maybe a 1/4 inch is something solid behind it) it's going to be a 350? The motor I was looking at had a solid balancer! woo! And it definatly stock... everything was stock except the holley and carb spacer...

Can anyone come up with an argument for this general rule of thumb?

 

I have a couple of bare 350 blocks. I can get you casting #s if you want. They are 2 bolt mains. I also have a couple of rebuilt 350 shortblocks (block, crank, pistons) all assembled. They are all the pre 86 blocks. Let me know if you are interested.

Chris

 

where in the blue hell did you hear that at?

and what was the guy smoking? cuz i want some

someone please correct me if i am wrong, but i have an accell blueprint distributor that is compatible with all chevy small and big blocks, of all sizes

 

The trucks did not get rollers untill 96 BUT, the block may be able to be drilled and tapped to accept the factory roller set-up.
On my 88 block at the rear of the block just behind the head it says 5.7LG.