Anyone every swap TRW HO Pistons/rods into a lopo or explorer motor?

[Alice87]

Hey everyone,

Like the title says: Anyone ever swap a set of factory Ford 302 HO '87-'93 TRW Forged pistons/rods into a '87+ lopo or '96+ explorer 5.0?

I'm pretty sure the 302's in question are all 50oz balance. I think the rods and crank are the same between a HO and Lopo...

So I think there will be no balancing issues with the rotating assembly... but has anyone tried this or have any info to throw in?

Any comments appreciated, Kyle.

[gadget73]

Rods and rotating assembly are the same after '82, its just the pistons themselves. No reason you can't swap them but most of the time there isn't much reason for it. The lopo pistons are not special at all but the Explorer ones will suffer most of the same abuse the forged ones will. For an N/A motor it doesn't matter a whole lot unless you happen to need the reliefs for valve clearance or something.

[Alice87]

I hear ya, the hypereutectic's in the explorers are good enough for N/A builds (don't know what lopo's got).

I’m more worried about PTV clearance.

I'm planning on running aftermarket heads with bigger valves + higher lift cam & supporting fuel system.
I can get a nice set of used TRW HO pistons/rods for a reasonable price. So I’m thinking I’ll swap them in just to be safe.

Good to know ‘82 and up are all pretty similar.

[Arquemann]

What comes to stock HO pistons, piston to valve clearance becomes an issue quite easily with more duration and lift. Unless you're getting something like Twisted Wedge heads, be mindful of PtV clearance.

LoPos all got bog standard cast aluminium pistons, with varying valve reliefs and compression. If in good condition, even the stock cast pistons will get you pretty far if you stay away from high compression, high rpm and forced induction. Hyper pistons are cast too, just a bit better. Hotrod Mag made 500hp with a stock Explorer bottom end.

[gadget73]

The lopo pistons don't have valve reliefs, so there is a bit more clearance with the forged ones. I don't think the height or any of that is particularly different though. Where you really have to mind the clearance is with long duration cams. Thats about the only time the exhaust valve will be open when the piston gets close to the top. Total lift really doesn't bother it since the valve is fully open when the piston is well down in the bore.

other thing to consider is the bore of the engine. If yours is out of round and needs to be bored out to get back in spec those stock diameter pistons aren't going to do you any good. Fair guess thats why these are available in the first place, whoever had them now has an engine thats been bored oversize. Thats why the engine in my Towncar has hyper pistons instead of the forged ones that block originally had.

[Arquemann]

The lopo pistons don't have valve reliefs

Mine have

[Alice87]

thing to consider is the bore of the engine. If yours is out of round and needs to be bored out to get back in spec those stock diameter pistons aren't going to do you any good. Fair guess thats why these are available in the first place, whoever had them now has an engine thats been bored oversize. Thats why the engine in my Towncar has hyper pistons instead of the forged ones that block originally had.

Good point. The seller says he turned his 302 into a 347 stroker, but I only have his word for that. For all I know it had massive blow-by with a ridge developed at the top of the bores.

I'm gonna run a mild cam for low end torque; most of the cams im looking at have mild advertised duration (258 Int./264 ext.). I may just risk it with the lopo short block with a bearing/gasket/ring refresh. It has good compression and doesn't burn oil.

Mine have

Wait now im confused lol. I was under the impression all lopo's had dished with no reliefs from the factory.

[gadget73]

All of the 86+ engines do at least, I don't know what 85 engines had.

[Arquemann]

Good point. The seller says he turned his 302 into a 347 stroker, but I only have his word for that. For all I know it had massive blow-by with a ridge developed at the top of the bores.

I'm gonna run a mild cam for low end torque; most of the cams im looking at have mild advertised duration (258 Int./264 ext.). I may just risk it with the lopo short block with a bearing/gasket/ring refresh. It has good compression and doesn't burn oil.



Wait now im confused lol. I was under the impression all lopo's had dished with no reliefs from the factory.

You could just slap in new bearings in the bottom end and send it. You need good heads to get anything substantial out of a better cam. I put an Explorer cam in mine, mainly just sounds different.

My '85 flat tappet engine has flattops with reliefs, D9OE-6110-AA. Highly doubt anyone's been in there before me, had '84 dated Ford bearings and such.

[Alice87]

Oh interesting. I see the '85 block has the provisions for a roller cam. It must be a mid year transition thing with the flat tops. Hey, it gives you a little boost in compression which is nice.

As far as my lopo goes, I'm still deciding on what heads to go with. Heck I'm still up in the air on the fuel system as well (no SD for sure).

[Arquemann]

Oh interesting. I see the '85 block has the provisions for a roller cam. It must be a mid year transition thing with the flat tops. Hey, it gives you a little boost in compression which is nice.

I was quite chuffed to see those threaded bosses when I popped the intake off the first time. I don't think every '85 got them.
And the flattops don't help any because '85 has E5AE heads with 68-70cc chambers so the CR is still 8.4:1.