Rebuilding 98 4.0 ohv, sohc pistons possible?

[cp2295]

Hi I'm in the process of rebuilding my 98 4.0 ohv and I'm going to put in a 410 comp cam and want to bump the compression ratio up a point or so. I was reading you can use sohc pistons but I don't know what year to use, and if I'll have valve clearance issues with the higher lift cam. Also as far as pushrods go for the 410 it seems the general consensus is 5.550" length with 3/16" ball end with no oil passage and 5/16" tubes. Is this correct info?

If the sohc pistons aren't gonna work does anyone know where to get high compression pistons for similar price to a set of oem replacements?


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[downer]

there's a ton of info out there on this, but flat top pistons are gonna put you quite high. if I remember right, 90-94 pistons with 98 heads will put you around 10:1. flat tops will be well above that.

 

[cp2295]

90-94 pistons have any interference issues with the valves or do not you know?


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[RonD]

95TM heads with '90-'94 pistons will still have valve clearance even with larger cam.
But you won't be able to run 87 octane fuel.

 

[cp2295]

Ya that ain't an issue for me, but it's doable then? I read somewhere interchanging parts from different years "will burn the motor up in a few thousand miles", sounds kinda weird, as long as it doesn't ping with 91 octane I don't see what the big deal is?


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[RonD]

People don't tend to spend money on a higher performance engine to "baby it", and not much point in spending the money for extra power and then not use it

So yes, engines do burn up or out if pushed, even factory high performance engines do.
I am sure some parts would be questionable to use on some builds but not earlier model factory piston.

Most of the parts are rated for 9.0:1 compression and 160HP in the 4.0l OHV engine, you will be exceeding those numbers so..............it will either be fine or you will find the weak link in the drive train, hopefully it is just a U-joint, lol.

 

[cp2295]

Okay but I should be fine with piston to valve clearance and as long as I run higher octane fuel it should be okay? I'm gonna get clevite bearings and all the good stuff for the rebuild so they shouldn't be a weak link


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[cp2295]

Obviously yeah I run the risk of doing something to the tranny or whatever but as long as the engine will be fine I'm good with t

I just figured the pistons will be the same price no matter what so might as well get some 90-94 if they'll work and bump the compression.


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[cp2295]

Also curious is there anyway to tell if the cam synchronizer is on its way out? Are there any bearings I should feel for roughness/play? Don't wanna have to replace it if I don't need to but don't want the oil pump to quit working on me!


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[cp2295]

Also curious is it okay to reuse rod nuts/studs and main cap bolts? Or are those TTY like the head bolts?


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[cp2295]

Using the 410 cam, 94 Pistons, 98 heads, and 5.550" pushrods with the delta cam rocker shaft proved good. Spinnin the motor by hand I can see through the plug hole that the valves aren't colliding with the piston. And when I shine my light thru the plug hole and look through the ports when the valves are closed there is no light visible (it's a really bright light). So I think everything checks out good, can't wait to drop it in


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[cp2295]

Just wanted to let everyone know for future reference everything works, there's minor valve tick (I'm leaning more towards an exhaust leak, or a lifter that quite hasn't pumped up all the way), and the engine runs nice and smooth. I didn't have the machinist balance the rotating assembly, and the motor is actually quite smooth. Figured that might be an issue with a reman crank and different model Pistons but so far so good!


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[cp2295]

https://vimeo.com/148836282 here's a vid of it idling


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[RonD]

Sweet, up and running