Back when my nephew and I started getting involved in discussing his project on the net, a lot of people were telling us that Poly engines are very heavy...
In fact, I recall someone telling us they were as heavy as... or heavier than... a 383 big block. Some people referred to sites with lists of different engine weights, but it struck me that these could have been well out for a range of reasons... but principally because they were weighed by different people at different times, some would have been with ancillaries, others without. It would be impossible to tell.
It's bugged me ever since, so I decided I would weigh the bits involved.
The LA (lightweight 'A' engine, lest we forget... ) only differs from the Poly in any significant manner in the heads and block. Crank, rods, timing cover etc are the same or interchangeable, while many other things (rockers, pushrods, cam) would be so close to the same weight as to be the same weight.
So I really only had to weigh a block and a head. Out with the bathroom scales!
Results:
Poly 318 block with main caps,
cam bearings in place,
main shells in place, original bore (3.91") .......... 192 lbs
LA 318 block with main caps,
cam bearings in place,
most main shells in place, original bore (3.91") ... 168 lbs
Poly 318 head with valves and springs only ........ 51 lbs
LA 318 head with valves and springs only .......... 48 lbs
Sum total difference is somewhere in the vicinity of 30 lbs.
Though this is ignoring another area where the LA might be lighter... the manifold. I really should weigh them. I know the Poly manifold comes in at 53 lbs, I can imagine the LA manifold is lighter because of the shorter distance between the heads. I'll have to do that some time, but for the moment I've ignored it because (potentially) anyone wanting to know the difference in weight will be looking at an aftermarket manifold anyway.
Out of interest, if anyone has a 383 or similar block and head they can post the weight of I'd like to know. I cannot believe a big block, particularly with that low skirt on it, is anywhere near the weight of the LA or Poly block. Also, I'd think the heads would be heavier. And the crank. The Poly crank weighed in at 56 lbs.
In the midst of all of this I mounted a Poly block on an engine stand and bolted on the heads. Time to start measuring up and working on patterns for a decent intake manifold.
In fact, I recall someone telling us they were as heavy as... or heavier than... a 383 big block. Some people referred to sites with lists of different engine weights, but it struck me that these could have been well out for a range of reasons... but principally because they were weighed by different people at different times, some would have been with ancillaries, others without. It would be impossible to tell.
It's bugged me ever since, so I decided I would weigh the bits involved.
The LA (lightweight 'A' engine, lest we forget... ) only differs from the Poly in any significant manner in the heads and block. Crank, rods, timing cover etc are the same or interchangeable, while many other things (rockers, pushrods, cam) would be so close to the same weight as to be the same weight.
So I really only had to weigh a block and a head. Out with the bathroom scales!
Results:
Poly 318 block with main caps,
cam bearings in place,
main shells in place, original bore (3.91") .......... 192 lbs
LA 318 block with main caps,
cam bearings in place,
most main shells in place, original bore (3.91") ... 168 lbs
Poly 318 head with valves and springs only ........ 51 lbs
LA 318 head with valves and springs only .......... 48 lbs
Sum total difference is somewhere in the vicinity of 30 lbs.
Though this is ignoring another area where the LA might be lighter... the manifold. I really should weigh them. I know the Poly manifold comes in at 53 lbs, I can imagine the LA manifold is lighter because of the shorter distance between the heads. I'll have to do that some time, but for the moment I've ignored it because (potentially) anyone wanting to know the difference in weight will be looking at an aftermarket manifold anyway.
Out of interest, if anyone has a 383 or similar block and head they can post the weight of I'd like to know. I cannot believe a big block, particularly with that low skirt on it, is anywhere near the weight of the LA or Poly block. Also, I'd think the heads would be heavier. And the crank. The Poly crank weighed in at 56 lbs.
In the midst of all of this I mounted a Poly block on an engine stand and bolted on the heads. Time to start measuring up and working on patterns for a decent intake manifold.
