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How much RPM can a stock bottom end 5.0 take?


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Posted

Just curious... have one in my Panoz w/ a built top end making 314 rwhp at 6500 rpms. W/ my new 3.89 gears I spend alot of time at or over 6k at VIR. I'm worried that I'm on borrowed time based on what some have told me.

Posted

Considering the factory fuel cutoff on a 5.0L is set at about 6250, you should be good up to that point for a long while, assuming everything is in good condition and not being overly abused.

Posted

I have a junkyard motor that spends most of it's life above 5k rpms thanks to my 4.30 gear. (oops.) It hasn't exploded yet, but I make closer to 240 hp.

Posted

Last season we started with a stock block 5.0 with after market rotating mass.

 

We dyno'd the morning of the Gateway race. 316hp/325tq at the wheels. Had a 6100 rpm chip in the MSD box.

 

See the links below for the results in Saturdays race.

 

http://picasaweb.google.com/nascarj20/ItSDeadJimCrankFailure#

 

I've heard the stock 5.0 is good to about 300-320 tq at the crank.

RPM depends on the balance and quality of the spinning parts.

Posted

Dang... crank failure? That's not what I've been hearing as one of the normal problems. From everything I've seen the newer blocks can split in 1/2 over 400 crank horsepower.

 

I didn't realize the stock fuel cutoff was 6250 in a stock 5.0... good to know.

 

Our short-block is 100% stock... the top end is built w/ AFR 165s, cam, edelbrock, pro-systems carb, etc. Running through FMS shorties and custom sidepipes.

Posted

Your question is rpm.

My question is hyd or solid lifters?

If hyd, that's what makes the diff., I wouldn't go over 6200, after many years of blowing motors. I wouldn't worry about the block at our power, but I would rpm's.

Refresh your springs and lifters when needed and listen to your motor, it will talk to you!

I just wouldn't listen and every time they talked to me too!

Posted

We put new lifters in w/ the H/C/I setup... hydraulic lifters can do 7000+ rpms in my Corvette motor w/o issue so I'm not too worried about that.

 

Most people are saying the rods are shit and the rod bolts are even shittier and that's what I have to worry about. The blocks can split when over 400 horse, but we're at 360 and since the car is prepped around ST2, not concerned with having more power.

 

I just need the RPM at VIR w/ my new gearing and want the car to stay together.

Posted
Dang... crank failure? That's not what I've been hearing as one of the normal problems. From everything I've seen the newer blocks can split in 1/2 over 400 crank horsepower.

We clearly broke the crank in half, but the block was also shattered from the 2nd main forward.

 

It was kind of the chicken and egg issue. Which one happened first?

Posted

I had a stock crank break too, 5900 shifts with 290hp/300TQ.

 

My photo's look exactly like the ones posted above.

Posted

I'd be more concerned about the valves in the AFR heads breaking. We have had more than our share of stock AFR valve failures in race motors of any power output in this region over the years. They are cheap junk really and should be replaced with a quality race replacement.

 

As for the bottom end....I've seen plenty let loose at 350 crank hp or less when not zero balanced or have a quality balancer on them.

 

If you are building a 5.0 based motor for AI with AFR heads, zero balance the rotating assembly, add good rod bolts, don't run it lean and change the valves to race parts. It "should" last a few seasons that way.

 

That whole offset balance thing is pretty goofy anyway....especially in a race motor.

 

Good luck!

Posted

I've got a 347 in my ex-AI car, pushing 400rwhp through 3:73 gears. It's got 17 hours on it, running HPDE3. Block is stock, rotating assembly is not obviously. I got such a good deal on the longblock that I bought it even with the stock block. It's a carbed setup, I'm telling myself it'll have a short lifespan while hoping for a long one! My shift lights come on a 5500, the chip in the box is at 6K. I run a good balancer (ATI SuperDamper) and it's balanced to 28oz. Interestingly I read that the 0 balanced engines break before the 28oz ones, and the 50oz stock balance is the worst - no idea why that would be the case, unless they have to remove too much material from the crank to balance it to 0. I hope to make it last by limiting the rpms to under 6K...

Posted
I'd be more concerned about the valves in the AFR heads breaking. We have had more than our share of stock AFR valve failures in race motors of any power output in this region over the years. They are cheap junk really and should be replaced with a quality race replacement.

 

As for the bottom end....I've seen plenty let loose at 350 crank hp or less when not zero balanced or have a quality balancer on them.

 

If you are building a 5.0 based motor for AI with AFR heads, zero balance the rotating assembly, add good rod bolts, don't run it lean and change the valves to race parts. It "should" last a few seasons that way.

 

That whole offset balance thing is pretty goofy anyway....especially in a race motor.

 

Good luck!

Well that's bad news... I bought AFR heads because I thought they were the best for the application. This is the first I've heard about them having crappy valves. I put whatever balancer Ed Curtis at FTI spec'd for our package/intended use. I can't remember the brand.

 

I think I'll start planning a built 306 w/ the 4-bolt mains, then when it comes time to swap parts over I'll do that.

 

Can you elaborate on offset balance? All of my motor work experience is on LSX stuff. I paid a shop to do this 5.0 stuff becuase I was too busy at work.

Posted

 

Can you elaborate on offset balance? All of my motor work experience is on LSX stuff. I paid a shop to do this 5.0 stuff becuase I was too busy at work.

 

To keep people from putting non emmission motors into later cars, they started using externally balanced rotating assemblies. In other words, the balancer and fly wheel are not zero balanced, and neither is the crank/rods/pistons. They are "offset" to then balance out. You can buy zero balanced flywheels and balancers though and build the bottom end just like you would an SBC...they also last longer that way! Mod motors are zero balanced like the SBC too and makes your engine builder not cringe when he sees you coming!

 

I can't remember the exact numbers but there are also TWO different offsets...I want to say 16oz and 28oz....my 5.0 memory gets smaller everyday.

 

As for the AFR valve issue....they are GREAT heads. I have many buddies running them on street and drag cars with Zero problems. It only seemed to be the road raced cars where sustained heat/rpm seemed to break a lot of valves. Those guys then put good valves in them and had no problems after that. Also, good piece of mind to just do the valves anyway especially with a used part...

Posted

I can't remember the exact numbers but there are also TWO different offsets...I want to say 16oz and 28oz....my 5.0 memory gets smaller everyday.

 

As for the AFR valve issue....they are GREAT heads.

 

SBF's come in both 28oz and 50oz imbalance. The 5.0's are factory at 50oz, 351's are at 28oz. Most strokers are at 28oz. They can all be made to 0 balance, but it's more $$ to do so.

AFR heads are great heads, but the valve and springs are crap. I ruined my 306 at summit because of a broken valve. My 347 has canfields on it now. The AFR's have been rebuilt, sitting on a shelf for my next engine, probably will be a 4 bolt 331....

Posted

Turns out we have the competition heads w/ upgraded valvesprings. Also, FTI says AFR has upgraded to a new "8mm" valve.... whatever that means. Not sure if the stem is stronger than before or not.

Posted
Turns out we have the competition heads w/ upgraded valvesprings. Also, FTI says AFR has upgraded to a new "8mm" valve.... whatever that means. Not sure if the stem is stronger than before or not.

 

 

I think that's why AFR went to the new valves... stock size is 5/16" I think, 8mm would be a tad larger. If Ed (FTI) spec'ed the AFR heads you should be good, I run his valve spring upgrade on the 185's in my FFR. BTW, were you pulling into VIR last Friday evening with the Panoz on a flat trailer? I was leaving the trackdaze event at the same time. Nice looking car, I was looking for one before I bought my AI mustang... sometimes I wish I would have kept looking for one, would like to check it out sometime. Did the weather hold for the mazda event? I've never run with them...

Posted

Yeah... that would have been me and my father. Was towing with is white/tan F-150. The weather held and it was great all weekend. We had about a 5 minute sprinkle on Sunday AM during one of the sessions.

 

We decided to build the car around ST2 specs and used Ed @ FTI to spec out a reliable 310-320 rwhp setup.

 

I'm signed up to run TTS for Oktoberfest @ VIR and my father will be in HPDE 2 or 3 depending on which gives us space between TT and the HPDE group.

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