Hi Guys
Can anyone tell me if the pistons in a '65 HiPo motor are the same as a stock 289?
I am concerned particularly about compression height and valve cutouts.
If these are specific to a HiPo and anyone knows what they are please tell.
I see pistons offered with different heights and cutout cc's
Thanks
Tony Gregory in his book "The 289 High Performance Mustang" talks about two styles of pistons for the 289. One was a dished piston used on the 2bbl 289 that yielded 8 1/2 : 1 compression. The standard 225 hp 4bbl engine had a flat top piston with four small valve relief eyebrows that yielded 10 1/2 : 1 compression on early HP engines and 10 : 1 on later versions (the difference was due to the size of the combustion chamber on early vs late... Gregory goes on to state that this was the same piston used in the K. Gregory suggests that if you can't reuse your old pistons that TRW, Federal Mogul, or Power forged Series L2482F would be a reasonable substitute. Just as a sidebar.. I would assume that you would do a piston to valve clearance test as part of the engine reassembly just to be sure that any set up you used would not create a "fatal" condition.
Thanks Robert
I see the power forged pistons have a smaller piston head volume than others I have looked at, 2.70cc as opposed to 6cc on some others.
Will CR be adversly affected much by going for larger cutouts?
The correct compression ratio for the 1965 289 HiPo was 9.8:1. HiPos always had valve reliefs. Early 1965 225HP 289 4Vs used flattop pistons without valve reliefs and were true 10:1 compression engines, but mid-year the pistons were changed to include valve reliefs, so comression dropped to 9.8:1 -- same as the 289 HiPo. The pistons were not the same. The HiPo piston reportedly used a higher strength aluminum material. Today, materials are much improved, so the same piston can be used in both applications.
P.S. The 10.5:1 compression ratio was associated with the small-chamber 1963-early 64 heads.
Is there an alternative to the power forged L2482 piston in a + .020"
that keeps the same CR ?
Back in 2004 I wrote an article on 289 pistons and compression ratios. This might help in your decisions.
Thank you Bob, thats very interesting I can appreciate that a lot of work went into that.
I was concened that the valve cutouts being between 6 - 8cc would lower the CR too much, but seems that may not be the case.
I must try to have a proper work out to see what I will get as per your article.
Edited by - cobraboy on 03/21/2010 05:04:19
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