300hp out of a six???

Is this possible??? I saw a motor on ebay that a guy is claiming to get 3 hundy out of a 258. I can't believe this is possible, but someone tell me I'm wrong. What do the 258 strokers have for power?
Thanks
blegenam

 

Probably not possible. Some major balancing & blueprinting, porting, FI, HEI, etc would be needed to get anywhere near that.

The 258 is a torque producer, and doesn't like high RPMs.

JMHO

 

That is kinda what I thought. Go to ebay, this guy got pissed when someone questioned him about the 300 horse claim. Parts probably wouldn't last long even if it were true
Thanks
High5

 

Hell I plan on getting 400 + (blown) from a 4.6L stroker (4.0 cherokee engine) for my hornet.. the bottom end is solid on these and so is the oiling system so building power is just a matter of good old fashioned engine building.. I have seen some really hot 258's make right around 350 HP @ 6500, that took some time on the heads but it is not inconceivable, they used to run the dixie 4 x 4 mudruns in samsula FL back in the day.. they sounded awesome too!!

BUBBA

 

I had a buddy that had right around 300 hp out of an older 232 straight 6 in a 72-75 cj5, while it didn't idel real great it would snap the crap out of your neck with the t18 that had the 4.? 1st gear in it. It is entirely possible to get 300 hp out of a straight 6 and make it reliable as all get out doin it. I have known several guys that probably made close to 400hp out of the old 225 Chrysler slant 6's.

 

I do believe there are some stroked 4.0s out there getting 300 or more hp. There was a website showing some different stroker combos and what there hypothetical hp should be. Of course I don't know how accurate those numbers are.

I built a budget stroker with the early 86-90 fuel injection and head. Using a stock heavy 258 crank and rods with aftermarket pistons and a performance cam to help bleed off some compression it supposedly would produce 230hp. No idea what it does make and that number might be for an HO head. I think its more likely to be 200 or so. Its definately way better than the stock 258 that was only running on 5 1/2 cyls.

Kevo

 

Hey boyink.. that old rambler would sound reeeeeeeal good with an EFI 4.0 in it... I gotta finish the jeep first but I can't wait to get into that hornet project.. kinda funny when I mention I have an AMC around the import crowd they ask me what country that came from...

BUBBA

 

Yup, entirely possible, done all the time. While not a straight six, I had a 225 bent six that was engine dyno'd over 500 hp. No bottom end torque at all but would twist quick and rev all day. Takes a lot of work and some good know how, but very do-able. Nickmil.

 

More Power!!!! {Tim Allen Grunt!!!!!}

 

For a typical OHV engine, I think the rule of thumb is about 1.25 to 1.5 HP/cid and still be streetable. 258 * 1.25 = 322 ... quite do-able. I wouldn't run a 258 over 5000 RPM though - the stroke is too long for high revs (makes the piston velocities too high, and the crank journal overlap too small). In terms of maximal HP, this is a fairly severe disadvantage. Recall that HP goes like torque times RPM. The rest of the engine has a lot of potential though.

 

Thanks for all the input. So tell me, what kind of money and time do you guys have into these motors that put out that kind of power???? I mean fuel injection is one to two thousand, plus all the head work and stroking the motor. I know that this is crazy talk, but wouldn't a fuel injected and cammed 360 be just as powerful with a lot less work and money??? And, what good would a Jeep motor be that doesn't make any low end grunt??
I'm not saying I don't like the 258, I've got one. But that has to cost a lot to do, for a non-engine builder.
Thanks guys
High5

 

Tim the stroke on the 258 is actually shorter than a large chunk of big blocks that run well over 5000rpm.

Sure but its gonna cost more as there are fewer of them out there and you already have the 258, you could change the cam, put an aftermarket carb and header or better exhaust on and make alot more power, port and polish the heads and do a 3 angle valve job and all of this together will probably double the stock hp.

 

Mike, I don't have a lot of statistics at hand. I'd be interested re which engines you are referring to. In my table, the only engine with a longer stroke and less journal overlap is the Chevy 292, at 4.125" and 0.137" respectively. The 258 is 3.906" and 0.248". I looked at the Sallie page for the 454HO, 4" stroke and forged crank and rods. They recommend a maximum RPM of 5500.

In **** Datson's book, he makes the following observation wrt the 258. Using the Navarro 199cid AMC Indy engine as a benchmark (640HP @ 6800RPM), the piston velocity was about 3400 ft/sec. This was with a steel 199 crank and custom steel rods. Translating the same piston velocity to the 258, that's 5200 RPM. I'd expect the Navarro team was running as high a revs as they felt were safe for 500 miles of reliability. Regardless of what others may be doing with various V8s, this seems to me like good data...

<edit> Heh. More banned words!

 

Yeah,
I already have a ported head, four barrel clifford intake, split header, and dual exhaust through glass packs. It sounds great, but I don't have the right carb or an HEI distributor.....yet. It just runs really rough and I haven't had the opportunity(cash) to fix the problems. The jeep is currently garaged at my dad's house, which is 3.5 hours away. "The plan" is to sell my truck, get the jeep here, and dump some money into it.
I've heard that Crane makes a good cam for the 258, anyone know of a better one than Crane makes???
Thanks
High5

 

A motor in a Jeep with no low end? To go fast of course. It was originally built to race, and that's what it did. I had it in my Race Jeep until it broke a wrist pin. I had $450 into it. The guy who originally built it in the early '70's had $5000 in it at THAT time. I got it cheap from a guy who had it in a Willys pu and got tired of destroying TH-350's, 18 transfer cases, 25 front ends, and Dana 53 rear ends. After the 4th Dana 53 blew he decided to sell it to me. He now has a turbo 231 out of Grand National in it and quit blowing up parts. Nickmil.