Replaced engine?

[Linas]

Hello,

My 1973 AMC Javelin's documents say that it has 5.7 liter (343 cu inch) engine. However, according to VIN number, the engine should be 304. Based on the photos of the engine, would you be able to tell which size is it? I would appreciate any opinions on this topic. Thanks :)

http://i134.photobucket.com/albums/q91/Linas_Palovis/DSC05318.jpg
http://i134.photobucket.com/albums/q91/Linas_Palovis/DSC05321.jpg
http://i134.photobucket.com/albums/q91/Linas_Palovis/DSC05317.jpg

[FL_Javelin]

343's only available 67-69. Not sure what documents you are talking about. In V8's only 304/360/401 were available in 1973.

Every AMC block is stamped with the cubic inches on the block. I think it is drivers side near the motor mount. Someone correct me if I'm wrong.

Hard to tell from the photos, I mostly see after market stuff anyways.

[Linas]

343's only available 67-69. Not sure what documents you are talking about. In V8's only 304/360/401 were available in 1973.

Every AMC block is stamped with the cubic inches on the block. I think it is drivers side near the motor mount. Someone correct me if I'm wrong.

Hard to tell from the photos, I mostly see after market stuff anyways.

I know, that 343 were available only between 67 and 69. What I mean by documents are the current registration car papers with indicated technical parameters of the engine (size 5,7 liter; 209 kw). I will check for the stamp near driver's side engine mount.

Thing that got me confused was the mismatch between VIN number for 304 engine and documents, saying that it is 343.

[a440plus6®]

A 5.7 is a 360 not a 343...

[Linas]

A 5.7 is a 360 not a 343...

Are you sure? I converted this number with the tool I found in the internet and it showed 343. Maybe I'm wrong...

[a440plus6®]

ooops, I think I'm wrong....5.9 is 360....sorry
Jerry

[Linas]

Every AMC block is stamped with the cubic inches on the block. I think it is drivers side near the motor mount.



I was looking for this number everywhere I can reach on the block (driver side), but still did not find it...

[a440plus6®]

It is actually "cast" into the block. Reach between the motor mount and trace the raised surfaces with you fingers to tell. You will feel raised numbers. You almost have to be a contortionast to do it but that's the easiest way.
Jerry

[donsjave]

As already stated the numbers are underneath the motor mounts on either side. If you do not see any numbers being either in CI or Metric, then you have what is called a Service replacement block. These blocks came from AMC for replacement of defective motors within the warranty time of the engine itself. These motors will not have any identifying numbers to tell you what you actually have.
Also, my bet is if this is the case then you may have a 304 in it. Not the 343 as you may think. But this all depends on previous owners and what they did to the car. On some rare case, someone could have actually put in a 343 but I would find that somewhat confusing because the 360 was probably a better motor and it was available at the time.

[Linas]

As already stated the numbers are underneath the motor mounts on either side. If you do not see any numbers being either in CI or Metric, then you have what is called a Service replacement block. These blocks came from AMC for replacement of defective motors within the warranty time of the engine itself. These motors will not have any identifying numbers to tell you what you actually have.
Also, my bet is if this is the case then you may have a 304 in it. Not the 343 as you may think. But this all depends on previous owners and what they did to the car. On some rare case, someone could have actually put in a 343 but I would find that somewhat confusing because the 360 was probably a better motor and it was available at the time.

Thanks for explanation. So now I can say it for sure - there are no numbers on any side of the block identifying the size of it. Therefore I assume that the engine was replaced, as you wrote. How to identify, what size is this Service replacement block? Were they always replaced with the same size, as the original block, which might have had a defect?

[javelinjeff]

yeah i'll second donsjave on this especially if the vin# calls for a 304,thats probably whats in it,like he said they MAY have installed a 360 if that was in the dealer inventory at the time,but usually warranty requirements would require like motor to replace one in vehicle.any "changes" would be highly unlikely.i would't put too much stock in DMV paperwork as to engine size as they have no way to verify size,and at one time someone could have stated the size upon transfer of vehicle which got entered in system.one way you could find out is to check cylinder volume with motor oil if you could find out how much volume is held in a 304 vs a 360 but in reality just wait intill the time comes to rebuild it then you'll know for sure

[donsjave]

Thanks for explanation. So now I can say it for sure - there are no numbers on any side of the block identifying the size of it. Therefore I assume that the engine was replaced, as you wrote. How to identify, what size is this Service replacement block? Were they always replaced with the same size, as the original block, which might have had a defect?
The replacement blocks I would assume would be mostly all the same size. The stroke (or is it the bore) on a 304 is the same as the stroke on a 360 with only the bore being of a different size. What the dealer did was to order a replacement for the engine that failed warranty. I would suppose that a fairly large dealer could do his own work and the such. Send the engine out for proper machine work etc.
So the short answer to your questions is that under normal situtions the dealer would install like engine with like engine (keeps the cost down that way). The only known way for you to id an engine definitley is measure with a micrometer the bore size and the stroke and this will give you the CI by doing some math. :)

[javelinjeff]

found this on another site but it may or not be 100% correct.apparantly some 1970 360 motors were a thick wall casting and did not have numbers on the sides.i found this on AMC Hornet.com under AMC Myths at the bottom of the page.although it seems possible that some high performance blocks were made this way,you really got to measure the bore to find out.the difference between the standard 304 and 360 is the bore diameter.the stroke is the same

[Linas]

Thanks! I will solve this puzzle, for sure.

[FL_Javelin]

To expand on what others said, I found this:

"Service Replacement" Multi-Displacement Block
There was also a "Service Replacement" block made as a modified GEN-3 design. This is a 401 casting (same casting number) without the displacement cast into the side and with a 360 bore and thicker deck. In theory this single block could be built as any 343-401 GEN-2 or GEN-3 engine. A dealer could stock one or two blocks to use for warranty replacement. It was also sold as a heavy duty racing block, which is speculated to be the real reason it was produced in the first place. It appeared in 1970 in time for the 1971 Trans-Am racing season. Since it was a standard factory part it did not have to be homologated under T/A rules, and was not used in the 2501 "Mark Donohue" Javelins built to homolgate the "duck tail" spoiler.

Found on the website:
http://www.answers.com/topic/amc-v8-engine

Though slim, its another possible explanation.

[Linas]

So going furthe with this issue - yesterday I had compression checked on my Javelin engine and it was about 10.0-10.2. The compression for 1973 304 engine, according to manual, should be around 8.4. So this engine most likely is not 304. Or can it be 304 with increased compression by the previous owner for the sake of higher performance?