So about a year ago I bought a 1984 Pontiac T/A ws6 from a guy that was selling it for a friend. He told me the engine was a 383, edelbrock performer rpm intake, hooker super comp. shorties, and all this happy crap. Well I finally checked the engine casting numbers and it turns out that the numbers are 3951509, a 400 block casting number. So now I am wondering, the engine doesnt have flat top pistons, theyre domed so I'm guessing the engine was bored over at one point. So could I have a 406? or could it be a destroked 383 or 377?

 

What you can tell from the information you've shared is you have a 400 block.

Domed pistons don't say squat about whether it's been bored. Could be stock bore domed pistons.

You need to find out what crank you've got. Are the damper and flexplate/flywheel weighted? If yes, it's probably a 400 crank as well. If not, it may be a 3.48" stroke crank, or an internally-balanced 400 crank.

What heads are on it?

 

I know it might not be bored but those pistons deffinately arent stock. I dont think the flexplate has any weight on it but I haven't been under to look for sure. The balancer looks like this one... http://static.summitracing.com/globa...o-872004_w.jpg

I'm guessing it is a 406 but I dont know. How can i tell what crank is in it? Would the crank have numbers on it?

 

How far down are the pistons at the bottom of the stroke?

 

Given that it has that crank damper, with the "missing" chunk so as to make a counterweight, it's pretty certain that you have a 400. Maybe it's been bored, maybe it hasn't; but it should be considered a 400, not a "406". Even if it does happen to have about 406 cubic inches. More than likely, your 400 probably does have 406 CID though, since it's unusual for somebody to put dome pistons into a block without boring it.

 

Ok well even if its not bored over its still a 400 block, and the balancer looks like its one from a 400 and not a destroked 383 or 377. I just bought another 400 engine that I was going to build up too. It has stock 333882 heads on it. I'm not sure how far down the pistons go. The engine is still together and I prefer not to take it apart right now unless it's just dropping the oil pan or something. Could this be why my car doesnt want to start either, because I have a staggered bolt pattern for a 350?

 

If you had a bolt pattern issue, the starter wouldn't even be bolted to the block.

 

No it bolts up right but doesnt a 400 have a 168 flywheel and a 350 have 153?

 

Any size engine has whatever size flywheel is bolted to it. An engine of any size and a flywheel of any size are not incompatible in any way.

When I had a 400 in my 3rd gen, it had a 153-tooth flywheel. Bolted right up.

Of course, like most any other pre-1978 or so motor, I had to drill the later-model 153-tooth bolt hole into my earlier-model (73) block. Yours however, might either be a 78-up one and came with the hole from GM, or someone might have added it much like I did.

 

Pity the guy that buys my car after I'm gone:
Domed pistons in an un-bored block... Check.
168 tooth flywheel on a 350... Check.
Camel hump heads in an '88...Check.
Automatic electric fans and TCC with no ECM...What the???

 

If the walls are in good condition, wouldn't a hone be all it needed?

 

Yep. Hence the reason to find a good block.
I didn't even use a hone, (here come the flames) just 400 paper around a fist and WD-40. Enough to take the shine off the walls to let the rings seat.
Of course you also have to have the guts to be able to not call your "new" engine a 355.
With new pistons the same weight as the factory ones you can preserve most of the original engine balance. To rebalance it only requires very small changes. You can't do that with oversize pistons.

 

I'm just wondering why the guy told me it's a 383 stroker when its a 400 engine. The thing about the starter...I told the guys my engine was a sbc 350 engine when I was buying a new one because the old one was all siezed up. So could he have given me a starter for a 153 tooth flywheel when I have a 168 tooth which is what was on a lot of 400's? Could that be why my car doesnt start for squat? I'm still dumbfound about this whole situation. How can i check the stroke?

 

:shrug: Well, unless he happens to frequent this BBS and is willing to post up his motivation, you likely won't be able to find that out here. That lives inside his own head.

The 153-tooth flywheel is 12.8" diameter. The 168-tooth variety is 14" diameter. That means that the one starter will COMPLETELY MISS the other flywheel by 5/8"; or if they're mismatched the other way, the starter won't even go on, because the nose of it will hit the flywheel about an inch from its outer edge. If it works AT ALL, then that's not "the" problem.

You can check the stroke, or at least whether it's 3.75" or not, by identifying the crank damper. I believe we've already done that, and if your pic is an accurate representation of what you've got, then you have the type of damper with the counterbalance weight; which is used ONLY on 400 cranks. So if you REALLY have that damper, that question is settled: you have a stock-balance 400 crank. Case closed.

Likewise, a 383 is made from a 350 block (4" bore). the 509 block is a 400 block (4.125" bore). Therefore, we may reasonably conclude that you have a 400 crank in a 400 blockl which makes {drum roll please} a 400; and move on to other matters now that the motor is identified. Assuming of course, that your description of the damper is accurate. A pic of YOUR ACTUAL ONE showing the "missing" chunk of the inertia ring would settle the matter.

What starter do you actually have? (no, "350" or "400" is not adequate) Look at your receipt and give us the part #. Or take a pic. Pics are your friend.

I'm dumbfounded that you're dumbfounded. There's nothing mysterious here at all. The parts are what they are, beyond dispute, period. They respond poorly at best to what a PO "thinks" or "says" they are. The PO didn't know what he had, AS IF that has NEVER happened before!!!!, and you got lucky. What's to dumbfound?

 

The starter I have is #3510.

Here are the pics of the balancer on the engine in my car.
http://i164.photobucket.com/albums/u...er/josh007.jpg
http://i164.photobucket.com/albums/u...er/josh006.jpg
http://i164.photobucket.com/albums/u...er/josh001.jpg
http://i164.photobucket.com/albums/u...er/josh003.jpg

Here is the balancer on my "new" 400 engine.
http://i164.photobucket.com/albums/u...er/josh008.jpg
http://i164.photobucket.com/albums/u...er/josh005.jpg
http://i164.photobucket.com/albums/u...er/josh004.jpg

As you can see they are both the same balancers, so would it be safe to say the engine in my car is a 400?

 

I also want to know whats the cam diffrence for the 400. I know when you put a cam in a 383 stroker its more tame and seems smaller than if it was in a regular 350, so whats the diffrence in cams. If i go with a bigger sbc cam will it seem smaller in the 400?

 

Yes, more cubes need more cam and more heads to stay fed.

 

most all blocks had all three starter mounting holes BTW


one bolt hole shared the same location/position regardless of the starter nose


i have yet to see a block before about 1968 that didnt have three starter mounting holes in it except under a very rare circumstance possibly

1978 was waaaay after they started putting all three holes in them

i just had an all original codes and number matching '77 chevy K-10 pickup with the 509 casting 400 engine in it and it was the large 168 tooth flexplate

pics:






509 wasa great casting, nice block, not rare or anything but very good, i sold mine but should have kept it it ran strong and awesome

good luck

 

I would definately disagree with you on this one. It is not uncommon at all in the sbc world to find a block that does not have all three holes in it. My 3970010 casting did not, it is listed as a 69-79 casting.

 

My block only has two holes for the starter and they are for a staggered bolt patten. I have yet to check the other 400 I have thats not in the car. But I know for a fact the engine in my car has only two bolt holes. Want a pic. to prove it?

 

3510 is the starter for a 14" flex plate; so if you have that one, and it engages the flex plate AT ALL - that is to say, if it TOUCHES it - then your flex plate is 14".

Most 400 blocks are like you describe yours being about the starter bolt holes; they ONLY have the pattern for the 3510 and its brothers. The 3rd hole for the late-model starter for 12.8" flywheel didn't appear until about 77 or 78. The 400 I ran in my T-5 car (no choice on flywheel size... HAS TO BE a 12.8" in that setup) was a 73 block, and I had to drill the extra hole. Been there done that.

The 3rd hole on the early blocks is NOT the correct pattern to fit the 6316 late-model starter. It fits the 3rd hole in a 3560 (cast-iron nose) starter that, like the 3510, works with 14" stuff. The hole in question is about 5/8" diffferent in its location: the early model block's 3rd hole is that much FARTHER from the crank than the late-model hole. The reason they ADDED the hole in the new location closer to the crank when they invented the 12.8" setup was because a bolt in the farther-out early-model hole would have to go RIGHT DIRECTLY THROUGH the middle of the 6316 starter drive, since the 6316's shaft is ALSO 5/8" closer to the crank (14" - 12.8" = 1.2" ; half of that = .6", and that's how much closer to the crank the starter guts have to be, in order to meet the 12.8").

Meanwhile, Randy's pix are excellent examples of 400 stuff, they clearly show the counterweight on the flex plate and the "missing" section on the damper's inertia ring. If a motor has those features, it can ONLY be because the crank is a stock (or stock-balance, anyway) 3.75" stroke with the short 5.565" (stock-length) 400 rods.

 

Well I know for a fact I have the same balancer and you can see that from my pics. I'll go under the car today and look at the flywheel to see if it has the added weights on it. So if I have that balancer and the weights on the flywheel, then my engine is diffinatley a 400, no doubt about it? I just wanna know for sure, after that guy saying it's a 383 stroker I just wanna know what I do have. I'm still trying to figue out why he said it was a 383? So how good of a block is the 509?

 

Yes, if it's a 400 block and has a 400 crank, then it's pretty definitely a 400. Kind of hard for it to be anything else.

None of us here are going to be able to help you with figuring out why the PO told you what he told you. Not to be a twit or anything, but there's no point in flogging that dead horse any further. If you really want to know, ask him. Could be anything from, he didn't know, to he thought you'd pay more for a 383 than a 400, or you'd be scared off by its "overheating" if he told you the truth. I have no clue and can't read his mind from this far away.

A 509 block is just that: a block. That particular casting is a 400, so IMO it's better than a 350 (4" bore) one, and even better still than a 305 (3.736") one. Whether it's a "good" one OF ITS OWN KIND or not is determined by its condition, like, how many times it's been bored, and stuff like that.

 

I can't even ask the guy I bought the car from because he wasn't the one that built the engine. His friend did and then came into financial troubles plus a drinking problem and owed the guy I got the car from money so he gave him the car. Then I found the car and bought it. Atleast now I know what I have and $500 for a rustfree/ bondo free car is great!

 

The stock L98 (350) from my '88 has a weight on the flex plate (flywheel) so...
Let's simplify the engine ID for future searchers:
1. Three freeze plugs on the side of the block (one under motor mount)= 4.125" (400) block.
2. Counterweighted harmonic balancer=3.75" stroke (400/383) crank.
Now ain't that simple?

 

Both of my 400's have only 2 freeze plugs on the sides of the block, so what you're saying can't be correct.

 

Are you including the one hidden under the motor mount?
350 will have only one visible when installed.
The 400 will only have 2 visible when installed.

 

Not all 400 blocks have the 3 freeze plugs. Only the first couple of years, the ones that were typically fitted with 4-bolt caps.

Here's a 400 block I have laying around. 509 casting. You can even see the counterbalance on the damper.

 

We'll I know for a fact that my engines both have only 2 freeze plugs on each side. One is casting #330817 the other is #3951509 and both have the same balancer and flexplate, with only 2 freeze plug holes on each side. They look just like the engine in the picture.

 

Well, who said you couldn't teach an old dog something new.
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