Max RPM for 258

Newbies, and basic Stroker Recipes... Get started with your first stroker here!!
Post Reply
swatson454
Posts: 9
Joined: December 19th, 2010, 9:24 am
Vehicle Year: 1983
Vehicle Make: Jeep
Vehicle Model: CJ7

Max RPM for 258

Post by swatson454 »

Do you guys know about how many rpm's a new set of 258 rods with ARP fasteners can reliably handle in polished and balanced trim? I'll likely be using run-of-the-mill, .030 stock-replacement pistons and a heavy 258 crank. I tried the search function :huh:


Shawn
User avatar
amcinstaller
I love JeepStrokers.com!!
I love JeepStrokers.com!!
Posts: 604
Joined: May 22nd, 2008, 11:57 pm
Stroker Displacement: 4.6L
Vehicle Year: 1980
Vehicle Make: AMC
Vehicle Model: Spirit
Location: Red Deer, AB, Can

Re: Max RPM for 258

Post by amcinstaller »

with both the 258s in my amc cars, they really stopped pulling past 4500, cant see it being much past there
1980 AMC Spirit Restomod in Progress
SilverXJ wrote:Roller rockers won't help that mess you have created. Nor will God for that matter.
swatson454
Posts: 9
Joined: December 19th, 2010, 9:24 am
Vehicle Year: 1983
Vehicle Make: Jeep
Vehicle Model: CJ7

Re: Max RPM for 258

Post by swatson454 »

I just mean the strength of the rod, not whether or not the engine combination can actually get it there or not. My software is showing a 4,750 rpm hp peak with the combo I'm currently considering but I'm not sure that I'm warm and fuzzy taking the rods that far.

Thanks!
User avatar
Cheromaniac
I live here
I live here
Posts: 3180
Joined: March 8th, 2008, 12:58 pm
Stroker Displacement: 4563cc
Vehicle Year: 1992
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Cyprus
Contact:

Re: Max RPM for 258

Post by Cheromaniac »

swatson454 wrote:Do you guys know about how many rpm's a new set of 258 rods with ARP fasteners can reliably handle in polished and balanced trim? I'll likely be using run-of-the-mill, .030 stock-replacement pistons and a heavy 258 crank. I tried the search function :huh:
I have the 12cwt 258 crank, 258 rods (balanced to within 1g), ARP rod bolts, and cast pistons. I've revved my engine to the 5200rpm limiter on several occasions without issue.
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:
User avatar
IH 392
I love JeepStrokers.com!!
I love JeepStrokers.com!!
Posts: 725
Joined: October 4th, 2008, 11:15 am
Location: Eugene ORYGUN
Contact:

Re: Max RPM for 258

Post by IH 392 »

There doesn't seem to be much issue with the rods, the issues is with the crank shafts, it's claimed that they experience "torsional vibration" at 5400-5500rpms and running them at this rpm will snap them, that's probably why they put the 5200rpm rev limiter on the 4.0's?
You can get more power out of ANY engine!!!
ASE Master certified engine machinist, gas and diesel
User avatar
Cheromaniac
I live here
I live here
Posts: 3180
Joined: March 8th, 2008, 12:58 pm
Stroker Displacement: 4563cc
Vehicle Year: 1992
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Cyprus
Contact:

Re: Max RPM for 258

Post by Cheromaniac »

Yup. The crank journals can develop cracks at ~5500rpm and there's a harmonic at ~5600rpm that can break timing chains and throw the distributor out of the block. As IH 392 said, the stock rev limiter is there for a reason.
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:
swatson454
Posts: 9
Joined: December 19th, 2010, 9:24 am
Vehicle Year: 1983
Vehicle Make: Jeep
Vehicle Model: CJ7

Re: Max RPM for 258

Post by swatson454 »

Thanks guys. I've read about the torsional issue on the cranks and, thankfully, that's above my rpm range on this build (budget with a capitol B!). I'm not big on using OEM rods on builds but it seems like they'll be just fine for what I'm doing here. Thanks again for your input. :cheers:


Shawn
User avatar
amcinstaller
I love JeepStrokers.com!!
I love JeepStrokers.com!!
Posts: 604
Joined: May 22nd, 2008, 11:57 pm
Stroker Displacement: 4.6L
Vehicle Year: 1980
Vehicle Make: AMC
Vehicle Model: Spirit
Location: Red Deer, AB, Can

Re: Max RPM for 258

Post by amcinstaller »

i notice that the question is about the max rpm of a 258, and although a stroker build tends to use a 258 crank and rods, id like to ask what youre doing? just as a point of curiousity :cheers: it doesnt sound like youre building a stroker
1980 AMC Spirit Restomod in Progress
SilverXJ wrote:Roller rockers won't help that mess you have created. Nor will God for that matter.
swatson454
Posts: 9
Joined: December 19th, 2010, 9:24 am
Vehicle Year: 1983
Vehicle Make: Jeep
Vehicle Model: CJ7

Re: Max RPM for 258

Post by swatson454 »

amcinstaller wrote:i notice that the question is about the max rpm of a 258, and although a stroker build tends to use a 258 crank and rods, id like to ask what youre doing? just as a point of curiousity :cheers: it doesnt sound like youre building a stroker
Nope, I'm just going to build this old pig. It's mostly to satisfy my curiosity but I'm going to spend some quality time prepping the 258 head and intake plenum, use a well-suited cam and see what happens.

I might just be :deadhorse: but like I said, I sure am curious.


Shawn
Post Reply

Who is online

Users browsing this forum: No registered users and 8 guests