HP at 2500RPM and below, is a stroker worth it?

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NuckingFuts
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HP at 2500RPM and below, is a stroker worth it?

Post by NuckingFuts »

Hi all,
It is time to rebuild my 258 and I am contemplating several options. I have some questions and my intent is not to bash anything. I am just looking at numbers, understanding how I drive my Jeep and being realistic. The options I can do are: 258 stock build, bolt on a 4.0L head to the 258, build a full 4.6L stroker, of swap in a V8.

My goal is not to make massive HP, but would like a little bump for highway power for mountain passes over the Sierra Nevada would be nice if I could. When I drive I tend to keep her at or under 2500 rpm, and drive 60mph max (I am realistic with a CJ7). I have installed the Howell TBI on her and that works wonderfully and would like to keep that. With the NP435 I installed, she just pulls up mountain hills at slow spends wonderfully. But at 60 mph through the Sierra Nevada freeways/highways. well....here I am looking for solutions.

So I can do:
1. A V8 swap. But this options just seems to costly and more work than I really want to do, but it is not off the table yet. It will yield the biggest difference, but at a cost that is not attractive.

2. A 4.6L stroker. I know they make impressive HP, but at rpms I never achieve. This has me thinking that it may be pointless to build for what I am looking for. I rarely see HP/Torque number below 3000rpm. I did see one 4.6L stroker build HP/Torque printout that was at 2500-5000rpm. At 2500 rpm the HP was better than my 258, but it was way less than I thought it should be considering the extra cost to get a new complete engine. This is not a bash, please do not mistake. It just seems more costly for little, if any, gains at 2500rpm and below. Cheaper than a V8 swap, more than a 258 rebuild, unsure if the gains I could use.

3. Add the 4.0L head to my 258. I know the head has is more efficient flowing and has a better combustion chamber design. The 4.0L head design chamber will deter spark knock that the 258 head is know to produce, and to which mine suffers form (but could be from age and deterioration of engine condition too). I don't think this head will produce any real significant increase in HP for my driving, but it will let the engine preform to its maximum (which is a performance increase). This option is less than a 4.6L build, but more than a stock 258 build.

4. Just rebuild the 258 and continue on. If the performance at my relatively low rpm needs from a 4.6L build are marginal at best, keeping the 258 and going to the next step in gearing is best option.

So for the members that went from a 258 (4.2L) to a 4.6L stroker I ask.
What increase or what benefit did you gain from a 4.6L stroker, at this low RPM, compared to a stock 258?
I see none to little increase, but I could be way off.

Thank you.
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by Cheromaniac »

Perhaps this stroker build would be more to your liking:

4.6L Low-buck, low CR "rockcrawler"

Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Custom forged +0.030" bore pistons, compression height 1.380", dish volume 32cc
8.8:1 CR
CompCams 68-115-4 192/200 degree camshaft
DIY ported HO 1.91"/1.50" 57cc cylinder head
Mopar/Victor 0.043" head gasket
0.043" quench height
Ford 24lb/hr injectors for '87-'95 engines
242hp @ 4600rpm, 317lbft @ 3000rpm
1992 XJ 4.6 I6 - 5MT - Stroker build-up, Stroker "recipes" Sold
1995 Mustang GT - 4AT - Modded Sold
2006 Mustang GT - 5MT - Modded Midlife Crisis Car :mrgreen:
Torqsplit
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by Torqsplit »

Not sure what all was involved with adapting a 4.0 head to a 258. I remember something about the coolant ports had to be altered between the head & block? It is a much better chamber design and depending on which Head casting you choose to go with, you get the intake manifold and exhaust headers that are available for it also. If you went with something like the Painless or Mopar Performance EFI conversion kit that used to be available, you'd probly have a great running 258. Roughly 26 cubes less than the 4.0 based strokers and then you wouldn't have to source a new block. Just thinking out loud :)
Torqsplit
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by Torqsplit »

I see you have a Howell TBI setup. Not sure if it would adapt to a 4.0 intake? This is what i was referring to but sadly no longer available.

https://www.summitracing.com/parts/DCC-5249610AE
NuckingFuts
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by NuckingFuts »

Thank you for responding.

I am not worried about spending money, I just don't want to spend extra money where I should not have with no or little results I wanted. I like the 258, great engine. But driving on the Freeways and Highways is a lot different now then it was 35 years ago when she was made.

My 258 brand new makes about 80HP at 2000rpm, where as most stock V8 will be arouond 115HP at the same rpm. That is a difference around 30% more HP over the 258. That is quit a bit increase and would be more than enough for my little Jeep pulling up grades in the mountains.

So what I am wanting to know is where a 4.6L stroker fits into this rpm range?
Again, while I am looking for some more HP, I am not looking for a 400HP engine that will rip my CJ7 apart. My target is around 120HP somewhere in the 2000-2500rpm range. Big mark isn't it! Haha

Can I get that make from the 4.6L at this rpm range? This is what I don't know and I am asking about. If not, then I have to decide whether to do a V8 swap or keep the 258.
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by Cheromaniac »

My poor man's stroker put down 92hp/241lbft to the rear wheels (111hp/290lbft crank) at 2000rpm. Peak numbers were 200rwhp @ 4700rpm & 258rwtq @ 3500rpm (246hp & 311lbft crank).

https://www.angelfire.com/my/fan/Stroker_Dyno_HP.jpg

https://www.angelfire.com/my/fan/Stroker_Dyno_TQ.jpg
NuckingFuts
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by NuckingFuts »

Cheromaniac wrote: January 26th, 2022, 10:56 pm My poor man's stroker put down 92hp/241lbft to the rear wheels (111hp/290lbft crank) at 2000rpm. Peak numbers were 200rwhp @ 4700rpm & 258rwtq @ 3500rpm (246hp & 311lbft crank).

https://www.angelfire.com/my/fan/Stroker_Dyno_HP.jpg

https://www.angelfire.com/my/fan/Stroker_Dyno_TQ.jpg
Thank you so much for the reply and sharing the printout from you dyno-session. This is exactly what I wanted to see and helps tremendously.
Thank you.
greg fricke
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by greg fricke »

you could always do a stroker build an talk to one of the cam companys an have a grind made to suit your needs . then if you need more power turbo it . be sure to put forged parts in it
jeeppoor
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by jeeppoor »

Cheromaniac wrote: January 26th, 2022, 10:56 pm My poor man's stroker put down 92hp/241lbft to the rear wheels (111hp/290lbft crank) at 2000rpm. Peak numbers were 200rwhp @ 4700rpm & 258rwtq @ 3500rpm (246hp & 311lbft crank).

https://www.angelfire.com/my/fan/Stroker_Dyno_HP.jpg

https://www.angelfire.com/my/fan/Stroker_Dyno_TQ.jpg
Interesting that it makes pick HP at 3500 then drop off quit a bit at max RPM
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by Cheromaniac »

The drop off in torque at higher rpm appears exaggerated because of the scale used on the graphs. The engine makes at least 90% of maximum torque from 1500-4500rpm so that covers much of the operating range.
275/350 I-6
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by 275/350 I-6 »

I built a 4.7 using parts from Russ Pottenger a couple years ago. I’ve been driving it about a year now. I probably have 6-8K miles on it. I called him and told him what I wanted, and he put together the parts for the entire build, and I couldn’t be happier.

The new engine makes my 1985 CJ-7 with TF-999 a joy to drive on 87 octane gasoline. I’m on stock suspension with stock 273 gears and 31” A/T tires. My Jeep launches and accelerates great despite the 273 gears on 31” tires. Try that with a stock 258.

The new engine basically doubles the power, and then some. The engine makes power right off of idle, and is smooth as silk. I can drive 70 MPH on the freeway like a modern vehicle. So in a nutshell you are missing something, if you are basing your decision off of the HP/torque graphs. My CJ-7 is a little Hot Rod with this engine!

I have an 8.8 rear out of a Ford Explorer with 373 gears and a lSD that I am narrowing for my CJ-7. When I’m done it will be about 57” WMS or about an inch wider on each side. I think 373’s may be a little too much gear for my TF-999, but we’ll find out soon enough.
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by fibersport »

Could you share some of the details such as what was stock and what was custom? Not looking for any proprietary information, just some general stuff. Your Jeep sounds pretty close to mine although I'm running a T176 with slightly shorter tires. Also what kind of mileage do you get?
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by len1xj »

the only thing that is stock on my 4.0 motor is the block and that is bored out at 3 over, I used Russ for all my parts. I tolled him what I wanted and we talked about parts and what would do what. I made sure all the pistons and rods were balanced. after putting it together I went to a dyno tuner to get the most out of it. I now have a 1998 XJ that has a 4.6 engine that has every thing I wanted in it. 289 HP 345 torque. the torque starts at 800 all the way up to 2500. then it flattens out up to about 4000 RPM. the thing is so smooth I can hardly fell it running until I step on the peddle . lot of work to get here and about $5,000 in the engine. that is parts, and other things I did not count on but decided to do as I was building this. like intake header and so on. so if you got the money, the time and the well. in my humble opinion it is worth it.
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by Cheromaniac »

What parts did you put into your stroker?
Those are great dyno numbers. Can you post the graphs?
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Re: HP at 2500RPM and below, is a stroker worth it?

Post by 275/350 I-6 »

6EC5FB40-B14E-4D79-AA56-6D4BA39BEED2.png
3B888E7A-E1C8-429E-ACAC-2DD38CD481A6.png
6BE95146-B46F-4E98-B66A-6B5EC6D5F883.png
6EB6757B-11B5-4BF3-9238-3428D8EDB8C2.png
B529874F-F3A5-4003-B67C-D87DD5D1F28B.png
Mine got new pistons, rings bearings, rods, cam, lifters, Banks header with 2.5” exhaust including hi flow cat & muffler.

.060” over block, 258 crankshaft, and I ported my 0630 head. it got Manley SS race valves & beehive springs.

Everything came from Russ.
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