Post by fugly on Mar 10, 2010 15:16:08 GMT -6
As posted by Ray Bell
Ray Bell
318 Poly engine weight
« on: October 23, 2009, 03:55:26 PM
Back when Ben 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.
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 inconsequential.
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.
In the midst of all of this I mounted a Poly block on an engine stand and bolted on the heads. I expect that in the next few days I'll start making up the patterns to build a decent intake manifold.
« Last Edit: October 23, 2009, 05:23:54 PM by Ray Bell
fugly
Re: 318 Poly engine weight
« Reply #1 on: October 27, 2009, 09:59:08 PM »
Very interesting- I never took the time to check-good info
wayfarer
Re: 318 Poly engine weight
« Reply #2 on: December 19, 2009, 11:36:32 AM »
Very interesting indeed; the poly block is nearly the same as a 392 Hemi block and an empty Hemi cyl head weighs in at 68 lbs. Not alot of difference...
Quality Engineered Components
Early Hemi Parts & Tech help
Trans adapters since 1980
Ray Bell
Re: 318 Poly engine weight
« Reply #3 on: December 20, 2009, 06:08:43 AM »
So you have weighed a 392 Hemi block?
With or without main caps and bolts? Camshaft? Any other extraneous parts?
What was the weight?
I would say the head weight is quite different. 68lbs with no valves and no springs or keepers, is that right? Against 51lbs with valves and springs in place. Or over 20lbs difference per head, 40lbs for the pair. And I'll bet the Hemi head carries more water.
Ray Bell
318 Poly engine weight
« on: October 23, 2009, 03:55:26 PM
Back when Ben 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.
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 inconsequential.
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.
In the midst of all of this I mounted a Poly block on an engine stand and bolted on the heads. I expect that in the next few days I'll start making up the patterns to build a decent intake manifold.
« Last Edit: October 23, 2009, 05:23:54 PM by Ray Bell
fugly
Re: 318 Poly engine weight
« Reply #1 on: October 27, 2009, 09:59:08 PM »
Very interesting- I never took the time to check-good info
wayfarer
Re: 318 Poly engine weight
« Reply #2 on: December 19, 2009, 11:36:32 AM »
Very interesting indeed; the poly block is nearly the same as a 392 Hemi block and an empty Hemi cyl head weighs in at 68 lbs. Not alot of difference...
Quality Engineered Components
Early Hemi Parts & Tech help
Trans adapters since 1980
Ray Bell
Re: 318 Poly engine weight
« Reply #3 on: December 20, 2009, 06:08:43 AM »
So you have weighed a 392 Hemi block?
With or without main caps and bolts? Camshaft? Any other extraneous parts?
What was the weight?
I would say the head weight is quite different. 68lbs with no valves and no springs or keepers, is that right? Against 51lbs with valves and springs in place. Or over 20lbs difference per head, 40lbs for the pair. And I'll bet the Hemi head carries more water.