whoo hooo! Stroker time!

[rj454]

Did you buy a built 4.0? if so what all did you have to add to it to complete it? how did it run for you?

And what did it cost? Motor=$$?? and with everything $$?? Thx-RJ

 

[Dr. Dyno]

F*CK,
This is getting out of hand. You will not get an extra 50 HP out of a 4.7 vs. a 4.6. The long rod version stroker with a .030 bore is nearly dead on 4.6L. The 4.7L .060 bore is more like 4.66L or so.

Absolutely right. A stock bore stroker is 4516cc (4.5L), my own +0.020" stroker will be 4563cc (4.6L), +0.030 makes it 4587cc (4.6L), and +0.060 makes it 4657cc (4.7L).

When I built my stroker, I talked with Mike at Accurate a lot. Mike talked me into going 4.6 over 4.7. He said at BEST I might see "a few" HP difference and that it was not worth it to go the extra bore unless it took that much to clean up the cylinders. He said going .030 still left one more rebuild in the block (at .060) if needed in the future. According to the 4.0 builders I have dealt with, a .030 bore isn't much on the 4.0 and the .060 is easily doable. I have heard of 4.0 blocks going .090 to .100 over, but only after sonic checking AND a realization that it is not going to be a long lived motor.

Right again. The difference between a 0.030" and a 0.060" overbore with all else being equal is 0hp/4lbft, so it's really not worth doing a 0.060" overbore if the cylinders will clean up with +0.030".

We aren't building race motors. I can't see why anyone puts so much f'n emphasis on the HP stats. Are you ever going to use all the HP the 4.0 can put out in the rock- let alone the HP of a stroker? H*ll build for low end torque and enjoy the feeling of being able to pull long hills in overdrive and having a more controllable power range when wheeling.

So I can smoke a S10 Extreme with my 33's and 6.5" lifted XJ, it's not what I built it for. I built it to pull low in the RPM range. That is where the long rod stroker shines, and there isn't going to be a noticeable difference in the extra .06L. I have enough power to twist main shafts at part throttle now, what the h*ll is any more power going to do for me?

Bones :skull1:

Agree. Build the stroker for low/medium rpm torque. Most of us drive for 99% of the time with the engine operating under 3000rpm so what's the point in building an engine that produces most of its torque above that?
Maximum torque arriving at about 2500-3000rpm would be just about ideal for a street stroker. The stock rev-limiter comes in at 5250rpm so ideally you want maximum HP to be at about 10% below that i.e. 4700-4800rpm. If you set a target of 325-330lbft maximum torque, maximum HP will be in the 260-265 range.
If you design your stroker within those parameters you can't go wrong. That's what I'm aiming at and you can find out how I'm doing here.
I'm building a short rod (AMC 258) version with Sealed Power 677P cast aluminium pistons. Nothing exotic or expensive here. I prefer the longer skirt pistons (as opposed to Accurate's short skirt forged items) to avoid the piston slap issue (so my engine doesn't sound like a diesel) that's characteristic of the AP stroker.

 

[Bender]

Dino,

I have a very similar setup to yourself and I'm picking it up from the engine shop tomorrow afternoon for a weekend install.
I only have experience replacing simple stuff like bearings so I figured I'd leave the assembly to a good local shop.

My base engine was a 1989 4.0L bored out .030"
1987 4.2 crank..short snout version with matching rods.
Sealed power 677CP pistons
Comp Cams 68-231-4 with matching lifters
Mopar Performance valve springs, retainers, and keepers.
The head was machined .010" with a mild port and polish to help increase volume.
HO fuel injectors at 22lb/hr with fuel pressure bumped to 43 psi
MAP adjuster probably set up around 6 volts

I'll be sticking with the non-HO computer and injection system so hopefully the EGR and knock sensors will allow me to run 87 octane gas.

With the head and intake being somewhat more restrictive on the older NON-HO engines my calcs only show about 22.5 lb/hr fuel injectors being required so hopefully the HO injectors will flow enough to prevent a lean condition at WOT.

I'll keep you posted on the test drive next week

 

[Dr. Dyno]

It looks like you've got a nice combination there Bender. Your CR will be slightly higher than mine at 9.7:1 but you also have a slightly longer duration camshaft to compensate for the higher cylinder pressure.
I think you'll do fine on mid-grade gas and even if you get some ping on 87, the knock sensor should take care of that.
Your injectors will be flowing 22.1lb/hr at 43psi. That's a bit low and you may run lean but that shouldn't be a problem if you have the ability to adjust the fuel pressure higher or increase the MAP voltage. I don't think you'll need a MAP as much as 6v. Start at 5v and work your way up in 0.2v steps until you're right on the money.
I have my MAP adjuster set at 4.2v on my modified 4.0 (with Ford 24lb injectors) and it's just on the lean edge of stoichiometric for best gas mileage.

 

[HossHoffer]

Just a word of encouragement to you guys wondering if it is hard to build a stroker. It is the same as any other engine rebuild. You're just substituting some parts out of the old engine. I had my son put ours together this last year for his class (note to fathers: it's a great experience watching your sons first rebuild but be prepared to hold yourself back from helping! :laugh: )and his engine was one of only two that was finished by the end of the class. It's in and running great and I'm very proud of him for the good work.