Hey guys,

Are centerbolt valve covers used on 350 and 305 motors in 1987? I am trying to determine if I have a 305 or a 350. Can't easily get to block casting number. Someone told me I could tell by the harmonic balancer on the crank. What do I look for?

 

The casting number really is the only guaranteed way of knowing what it is, as far as the engine block is concerned. You could remove a cylinder head and measure the bore, obviously...

If the motor is original, you could crossreference the VIN. Also, if the motor is original and the heads and block are matching numbers, you could tell by the cylinder heads casting numbers.

As far as the balancer, probably what was being alluded to is the fact that 305's (older ones especially) had the timing tab placed at 12 o'clock (viewable from behind the water pump). 350's got the timing tab placed at roughly 1:30, viewable from the angle.

 

I'm not sure when GM started to put the casting in the block but on the sides of the block, you should find a 5.0L or a 5.7L cast in the block.

 

I thought I would post this in case it would help. The guy who told me about the harmonic balancers seemed very sure it was a 350. There are a few signs that point otherwise however.

The vin says it is a 305. (As does the RPO codes I found) It has a 5000 red line (which I hear means its a 305 as the 350s have a 5500 red line) and it has centerbolt valve covers which I hear means its got 305 heads.

Now the guy I bought it from who is a mechanic and has kept it in such imaculate condition swears up and down that its a 350. That guy mentioned above said the harmonic balancers point that its a 350 sure as sh*t. No question. It had 5.7 stickers all over (i know thats not exactly proof lol) It does feel like it is a 350. I have had this car for a little over a year and am about to make some big performance upgrades but if it's really a 305 then I will be deeply pissed/ sad/ not want to do stuff to a 305.

Now here are some possibilitys too: Maybe the guy who originally bought the car put a new engine in it? Maybe it was changed at the dealership for some special order or something? I am the 3rd owner of the car so surely not much could of happened to it. Everything on the thing is just peachy. Even the interior looks brand new. The engine pulls great and I just can't figure this one out.

I had just gone out to try and peek past those damned heads but there are just too many wires and such. Question for you guys, what is that in the picture? (the part I have the arrow pointing to) I may be able to see it if I can take that off.
What is it and how hard would it be?

Sorry if i rambled a little bit there. Any help would be great.
Thanks!

 

Wiper motor. 305s and 350s use the same balancers, there's absolutely no way to tell from looking at them. Get the casting numbers, or pull the heads.

 

Thanks for the help guys. Guess I will rip everything out until I can get to that blasted casting number. Sheesh.

 

a good way to find that casting number is it should be on the driver's side rear of the engine i believe where the transmision bolts to the engine (on that lip)

 

They made a 305 IROC in 87? I always thought that was when they switched to the 350 for them.


My 305 and 350 had different sized balancers. The 305's was fatter. But it may just because of the year difference, the 305 was cast in 86 and the 350 in the 70's.


When i wanted to get to my casting number i used a camera, in close-up mode, and a flash light. Just aim down between the wiper motor and distributor, its on a lip down there near the bellhousing. You may have to move a wire harness, theres one directly over it in my old 305.

 

Yes and as mentioned above, it's almost impossible to tell which one is which by just looking at it. All the data so far points to a 305 but that doesn't mean someone didn't change it to a 350.

There's a pad on the block in front of the passenger side head. There will be a bunch of numbers stamped on it. These numbers might be easier to see than the casting numbers at the back of the block. These numbers can tell you if the engine is original or not.

 

I swapped the engine in my car. Doesn't matter if I was the first or the fiftieth owner, it only takes one owner to change an engine. If the VIN says 5.0 and the tach is a 5grand red line it would make sense since they go together, doesn't mean the engine hasn't been replaced. My 350 has center bolt valve covers, so that doesn't mean anything. Just check the casting number on your engine, all this speculation won't get ya anywhere. Good luck though, I hope its a 350 for ya!

 

I get a good laugh reading these there was one where a couple people were pretty positive that the oil fill on the valve cover was at the front on all 305s and if it was in back it was a 350 99% on this one is just as funny the 350 and 305 used the same balancer same intake valve covers ect. same layout to the last nut and bolt. if the vin says 305 I would be pretty sure it is a 305 no mater what this"mechanic" said. if he swaped one in I am sure he would have said that. even if he did not I would have expected him to say that


like what was originally said. the ONLY way to tell is the casting number on the block located at the drivers side upper corner. or measure bore (4.000)

 

Best way to tell, and easy at that, it what Angelis83LT mentioned.

Get a flashlight and look down behind the engine on the drivers side. On the flat of the block where it meets the bellhousing is cast in B I G letters: 5.0L or 5.7L

If the valve cover is a leaker then use some degreaser on it (Gum-out or BreaKleen). Once that designator is found no one can argue with what block it is.

Another good check to make is to get a head casting number. Sometimes these can be seen through the oil fill cap. Most of the time a valve cover needs to be pulled. Funny how many times swirl port heads are found on a TPI motor. . .

RBob.

 

There are also 3 numbers on the sides of the block. If you crawl underneath you can usually spot them just above the motor mount on the pass. side.

Those are the last three of the casting number, in case you didn't know.

 

One more way to tell, crawl under and look right in the middle of the block on each side. The numbers will be upside down but they are big 627=305.....638=350 or if it is a late model swap 880=350

 

Yeah.

What he said, that I said, that he said to.

 

its a good idea to check before you start upgrading, very good idea, haha..
this summer while i was installing dual exhaust system on my friends '80 malibu; the malibu he got for like $300 from some guy who claimed it had all these great parts, and a 350, and yadda yadda yadda, but he never got around to checking.. he bought new intake, new carb, headers, dual exhaust etc etc etc..

after we were done i got bored and decided to run all the casting numbers I could find, stock 305, stock heads, stock everything, it was cool
he was pissed

moral to story dont listen to what people tell you just run the numbers

 

Buy the car, not the engine.