Eagle SIR rods:

Advertised Horsepower Rating (hp) 500 hp


How serious do you think that should be taken? I've run GM "X" rods to around 560hp and never broke one.


Was thinking of pushing this current combo to the mid 600s.


-- Joe

 

if you wanna go i beam i would go with the scat pro comps over the eagle. There rated to 750hp. Or if you are stuck on eagle then upgrade to the h beams. just my 2 cents.

 

I have the short block assembled and balanced.. I was just wondering what other folks thoughts are. I can go 500hp naturally aspirated, or toss a blower on it and run in the mid 600s. But I don't want a rod to go through my nice new 400 block.

I agree, I'd do H-beams had my original target been 600+ hp.. It wasn't until I realized how much the car weighed that I came to the conclusion that I need more power to make the same trap speeds as a thirdgen fbody..

-- Joe

 

revs kill rods you'll be fine.

 

Really unless someone has a lot of experience with breaking those rods, its guesswork. Usually parts have some sort of factor of safety but less so with stuff like connecting rods. I'd imagine 50-100HP over the rated power wont kill it but likely beyond that you're venturing into risk territory especially if they're not totally perfect.

Have you tried contacting Eagle? Just ask them what their factor of safety is, if any.

 

What kind of rpm's are you expecting to be turning?

 

I spoke to them once. I spoke to a guy who is more paranoid than my machinest. Asked about their cast cranks for a build, told me not to even think about using it in a manual car unless the car weighed 2000lbs and I was slipping the clutch.

I asked about the rods, he said I had the "old SIR rods" (with the bolts not cap screws). He didn't really give me any indication of guarantee one way or the other, and like you guys said, he said it's a factor of RPM more than anything. But again mentioned that with a manual trans things shock.


Now, I have a TH350, so I'm sure it will be mooshy but I went with the forged crank because I may put a TKO in the car eventually.

Ken:

Cam is XR288HR. In a 400 I think it's safe to assume it will flatline around 6,000.. Figure 6200 max.

The combo should be pretty stout. Figure, 525 or so hp naturally aspirated if I go with 10.9:1 compression. If I went like 9:1 and ran 10+psi of boost it could potentially be in the mid 600s.. Though durability starts to be questioned.. (1976 400 block, bored .060 over, I beam rods, 2 bolt mains)..

My machinest told me to keep it in the low 500s. If I do this again, I'll buy a dart block I think.. The '70s 400 might have been a poor choice on my part.

-- Joe

 

NO WAY would I put boost of ANY kind on that block.Run this one N/A,and enjoy the HP.At .060 over,what started as a ticking time bomb (the stock 400 block) turned into an A-bomb.I'd bet you any amount of money you want that if you boost it,it will split a cylinder within 20 full passes.
The SIR rods,however,are safe way beyond their rated HP level.Never had a single failure due to one in any engine,Ford,Chevy,Mopar,SB or BB.