Failure of stock cast 3.9/4.0 pistons at higher RPM? Or Forged options?
Posted: Mon Dec 30, 2019 2:28 pm
AE Hepolite
HRC1828
22059
The "books" suggest that 6K rpm is all these are good for, with maybe an occasion blast up to 6500 rpm.
Has anyone taken these higher on more than an occasional excursion and suffered (or not) a failure?
I'm trying to decide if I should stick with them and pick a cam that starts to peter out at 6200rpm but has a strong mid-range or go forged (second half of this post).
I've got solid adjustable rockers (and would therefor use a solid, not hydraulic cam) so the only limitation will be the factory pistons.
This will be used in an endurance racing engine (literally running for 12 hours over a weekend) so I do need something that's going to work well and be reliable.
Or, do I go for forged pistons?
Maybe the Chevy 305 engine or ford modular 3.700" ?
Will the factory 3.9 liners be reliable with the 3.736" bore of the Chevy 305 pistons?
Is the shorter 1.22" compression height of the ford piston compared to the 1.56" of the 305 better or worse?
What rods could be made to work with either? I've not prioced up a set of Omega's but I have a feeling its entirely possible they are way more than I'm wanting to pay when I can get a set of the above ones for $600...
Lots of questions, looking at options and suggestions.
HRC1828
22059
The "books" suggest that 6K rpm is all these are good for, with maybe an occasion blast up to 6500 rpm.
Has anyone taken these higher on more than an occasional excursion and suffered (or not) a failure?
I'm trying to decide if I should stick with them and pick a cam that starts to peter out at 6200rpm but has a strong mid-range or go forged (second half of this post).
I've got solid adjustable rockers (and would therefor use a solid, not hydraulic cam) so the only limitation will be the factory pistons.
This will be used in an endurance racing engine (literally running for 12 hours over a weekend) so I do need something that's going to work well and be reliable.
Or, do I go for forged pistons?
Maybe the Chevy 305 engine or ford modular 3.700" ?
Will the factory 3.9 liners be reliable with the 3.736" bore of the Chevy 305 pistons?
Is the shorter 1.22" compression height of the ford piston compared to the 1.56" of the 305 better or worse?
What rods could be made to work with either? I've not prioced up a set of Omega's but I have a feeling its entirely possible they are way more than I'm wanting to pay when I can get a set of the above ones for $600...
Lots of questions, looking at options and suggestions.