stock crank+boost+rpm=?

Been throwing around the idea of building a blown 355 over the winter and have been lingering around the FI forum alot. I've found most of the answers to my ?'s except for one. I plan on using my stock crank, forged eagle rods, and -21cc dish TRW pistons with the addition of an ati procharger p1-sc...running around 8-10 lbs.

I know the stock crank can handle the power pretty well but just wondering how high I can spin the crank on the boost mentioned and not worry about it breaking?

The car is 95% a street car, but it will probably see the track a little bit next season.

Thanks,
Adam

I ran the stock crank for awhile with the P600B with no problem with a redline about 6K. A friend has been running stock crank, reconditioned stock rods, and TRW pisons for years with no problems with a small blower. You don't need to spin it over 6K with most mild blower cams anyway.

That's exactly what I wanted to hear! Thanks alot.

If you plan on reasonable boost there is no need to replace the OEM rods.

Rich

And for the malory your going to need to ballance the stock crank with the heavy rods and pistons you might as well spend the extra $550 and get the Eagle Forged crank to go along with it.

As in the case with most of us we only start out running a little boost and don't need much. In the future you will want more power and boost so it might be worth it to go ahead and get a good crank and some rods even though the initial cost will hurt. It will cost $200 just to balance a crank. If you replace it later it will be another $200 for balancing on the new one.

I really don't know that I will have the extra $ for another crank or even new rods. If I do, I wll definitely invest in both.


If you plan on reasonable boost there is no need to replace the OEM rods.

Rich

Exactly how much boost is considered "reasonable" on the stock rods and crank? If it's about 10 lbs., then i'm good to go. :cool:

Thanks

The amount of boost some guys get away with my not be the same for you. It depednds on your setup, the crank is stronger than the rods. The powered metal rods are rated @450hp. People also run at 500rwhp, so there is no telling what will happed. You have to figure out how much power do you want and can afford. Then build accordingly, otherwise you may end up building a motor and replacing the crank or rods after one season. I personally would not 10psi or over on stock rods, with heads and cam the 355 your thinking of building will be around 500-550rwhp, depending on if you get afr's and spin it to 7000rpm or port the stock castings and run a small blower grind. Do some more research, see what others guys are running. good luck

I would say the stock crank would be okay, but not the rods. You could get a scat 9000 series cast crank which is stronger for about $200. Scat also has some h-beam rods and I beam rods which are considerably stronger than the stock PM rods.

what smoknz is trying to tell you in advance is the same thing both he and I found out the hard way... the TRW pistons and H-beam rods are going to require the stock crank to have quite a bit of mallory which is not a particularly cheap investment and is adding no value to the rotating assembly, it is just a requirement to get the heavier slug/rod combo to balance.. you will not be far dollar wise from a forged/heavier crank that would not require mallory to balance due to meatier counterweights that would be drilled for balancing rather then added too. if you don't get the forged crank when you go to pick up your shortblock.. you engine builder is going to have a suprise bill for you.. just a little fair warning. paying that much and knowing you could have gone forged is a little depressing.. your buying worthless mallory and gaining nothing in the reliability department.

Chris

what smoknz is trying to tell you in advance is the same thing both he and I found out the hard way... the TRW pistons and H-beam rods are going to require the stock crank to have quite a bit of mallory which is not a particularly cheap investment and is adding no value to the rotating assembly, it is just a requirement to get the heavier slug/rod combo to balance.. you will not be far dollar wise from a forged/heavier crank that would not require mallory to balance due to meatier counterweights that would be drilled for balancing rather then added too. if you don't get the forged crank when you go to pick up your shortblock.. you engine builder is going to have a suprise bill for you.. just a little fair warning. paying that much and knowing you could have gone forged is a little depressing.. your buying worthless mallory and gaining nothing in the reliability department.

Chris

Chris,
Mallory would only have to be added if the pistons/ rods were heavier than the stock parts, correct? Otheriwse, as in my case with the Weiscos and Eagle SIRs, we ended up with the following weights (in grams) which were much lighter:

Piston- 485
Pin- 116
rings- 50
locks- 4
total rods- 549
insert- 49
rotary-890

And with the lighter components, significant weight was removed from the crank to balance the rotating assembly.

I would say the stock crank would be okay, but not the rods. You could get a scat 9000 series cast crank which is stronger for about $200. Scat also has some h-beam rods and I beam rods which are considerably stronger than the stock PM rods.

The rods would definately be the next weakest link after the pistons. I paid $204 ofr a set of Eagle SIR rods which were considerably better than the Scat product. I ahve heard fro mseveral people that the Scat crank needs extensive amounts of mallory to bring it into balance. You would be better off sticking with your stock crank or ponying up the funds for a decent forged one.

I wonder why people think the Eagle SIR rods are better than the stockers?

Rich

Chris,
Mallory would only have to be added if the pistons/ rods were heavier than the stock parts, correct? Otheriwse, as in my case with the Weiscos and Eagle SIRs, we ended up with the following weights (in grams) which were much lighter:

Piston- 485
Pin- 116
rings- 50
locks- 4
total rods- 549
insert- 49
rotary-890

And with the lighter components, significant weight was removed from the crank to balance the rotating assembly.

Seeing as this thread was about Forged TRW slugs and eagle H-beams it's pretty safe to assume we are dealing with a significant weight gain over stock parts :p

Seeing as this thread was about Forged TRW slugs and eagle H-beams it's pretty safe to assume we are dealing with a significant weight gain over stock parts :p

Absolutely, I only wanted to address the fact that if they were to go with lighter than stock parts, then malory would most likely not be an issue. That is unless they got a completely different crank (Scat). I apologize if my statement above seemed to contrast that. I guesss the first think to ask would be how much are you willing to spend.

I wonder why people think the Eagle SIR rods are better than the stockers?

Rich

Rich, you are a guru in this arena and I value your input. I had assumed (stupid, I know) that since the Eagle rods are forged, have the twelve point ARP bolts and are shoot peened, that they would be a better piece than reconditioning the factory rods and installing ARP bolts.

I know there are much better rods on the market, but for $205, I thought it was a smart move for the budget minded builder such as myself. Has anyone broken one on a 500-600 hp application below 6,500?

Cheers,
John

Generally, the rods themselves don't fail first. Usually, the failure is cause by a failing fastener.

-Shannon

I did some additional rsearch (ie SEARCH function) and came up with this thread:

http://web.camaross.com/forums/showthread.php?t=404154&highlight=eagle+sir

It appears that part selection is a matter of personal preferance, budget limitations, and erring on the side of conservacy (which is a good thing). From reading through the endless posts about "Is this a good set-up?" I have come to the conclusion that when on a budget, it's better to back off the almighty hp target numbers and have the car perform within it's abilities. That is based soley on what you are willing to invest and what your goals are.

My advise is:
To set a performance goal
Stick to a realistic budget (you can't make 600 reliable hp on $1,000), Upgrade your weakest/critical areas
Put as much money into the bottom end as possible and upgrade the rest at a later date (it's much easier to replace a set of stamped rocker arms than a crank). It's the motors foundation.
Stop when your wallet/ credit cards/ significant other can't take any more

I would use a good condition set of stock rods with new bolts in preference to the "SIR". But I do agree that reconditioning a set of beat-up stock rods may not be cost effective.

Rich

Regarding the rods, from Lingenfelter's book (1996), on modifying small block chevy engines:

BEAM WIDTH
"Most hot rodders don't know that Chevrolet narrowed the beam width of the small-block Chevy connecting rod beginning approximately with 1989 and later connecting rods. ......I do not use the later narrow rods in any performance application. I have seen occasional rod failures in some of the new LT-1 engines that use this rod. Also notice that although the beam is narrower, the rod is just as heavy, with the weight placed in the big end which actually places more stress on the rod at higher rpm. All of my late-model engines, such as the LT-1 350 and 383 packages, replace these narrow beam rods with either earlier stronger production rods or Oliver 4340 forged steel."

Regarding the balancing, I am using trw pistons with h-beam rods and a stock LT-1 crank. The guy who balanced it removed weight from the crank and flywheel in a few spots, he did not add anything. Been running it for about 6 years like that. There is a slight vibration at 1 very narrow rpm range (perhaps 100-200 rpm) down low but it is smooth after that.

I wonder why people think the Eagle SIR rods are better than the stockers?

Rich

I dunno. Cause they're made in China?

I dunno. Cause they're made in China?

;)

Someday we may have to learn Chinese.

Rich

Bro, I hate to admit it, but they teach it where I work.

I do everything I can to not send work over there. Not only are they still a bunch of damn communists and break every patent & copywright ever filed, they are making near exact copies (knock-offs) of our engines and putting hand-laminated laserjet printed labels on them with our logo, except it's all misspelled. They even have the balls to have some improvements, but then make up for it by shortchanging on horsepower & durability. And if you order some part from over there, you can spec it in green & they will send it in pink cause that's the color of recycled plastic they were handed by their government on that particular day, which they bought from us. If they ever send me over there, some poor soul is going to have to gutstick himself from loss of face when I spit out the live octopus at the business banquet, cause I refuse to send my business their way.