DAPSUPRSLO

iTrader: (14)

First off let me say I have to apologize for all of the questions but I am trying to make up my mind on a lot of things rite now with the car and have a lot of questions. Thanks for tolerating them.

What do you guys think of a iron 370 with forged rods and pistons with a stock crank with a F1-R. I can get a hell of a deal on the procharger stuff as I tune for a shop that is a dealer.

I know the stock crank will be ok with a turbo to around 800rwhp (according to everyone here) but what about a charger. Obviously a charger will put a lot more stress on the crank i.e. the front snout and first few bearings. Do you think it would be wise to move into the eagel/scat crank or are they only marginally better then the stock piece. I don't really want a 4" stroke because I don't think it is necessary with forced induction. Correct me if I'm wrong but I just think a longer stroke will do more harm then good with forced induction because of the longer throughs increasing piston speed and putting more load on the rod.

Any input is appreciated.

BTW, 700rwhp or so with 93 octane and 8 to 1 compression would be nice. I will run low low compression because this car will see alot of 93 octane and I'd rather let the charger do the work. I don't like alky injection either. I will run the appropriate fuel system (already have mototron 60s and huge fuel rails). I will pulley up with race gas if I'm not happy with what I get. Also, what's the skinny on a belt system that will work with no slip. This car does not have ps, a/c, and I don't mind cutting to fit a 12 rib system. Thanks.

mongse

iTrader: (2)

Even if you keep the stock crank, at least get it double keyed. I did it on my LT1 and never had a problem. I'm not an LS1 expert, so I'll let someone else tackle the crank strength question.

DAPSUPRSLO

iTrader: (14)

Cool, thanks for the input.

69firebird

iTrader: (14)

The stock crank should work just fine, just get it treated, and youll be fine. I did mine that was, and I am pretty sure I remember Harlan was using a stock treated crank.

Pro Stock John

iTrader: (34)

I have a custom strut brace on my Vortech YSi setup, like the Renegade Mustangs run.

69firebird

iTrader: (14)

Thats great john, how does that help answer the question????
ed

DAPSUPRSLO

iTrader: (14)

When you mean treated I'm assuming just a good polishing like all the SB builders do as well as keyed for the added stress. Hey John, is there a stock crank in your 348? Thanks.

Sandmann120

iTrader: (1)

I would look into a cog drive pulley system for your application. That would effectively eliminate the belt slip issue, although it will be fairly noisy. Also, in the event of a backfire, it could either break the belt, or place undue stress on the front of your crank. One nice thing about cod-drive or gilmer setups is that they do not have to be incredibly tight to prevent belt slip, which takes some of the stress from the bottom end.

DAPSUPRSLO

iTrader: (14)

Thanks for the advice. Does ATI offer the cog setup or is this something I would purchase from another company?

Sandmann120

iTrader: (1)

That I'm not sure of. I know they are available, but I'm not sure who manufactures a 'kit'. If I were doing it, I would likely just build my own, but I have quite a few cog pulleys laying around already.

69firebird

iTrader: (14)

No,
Treating, is either nitrating, or cryo treating, it is a process very similiar to forging, however it is done after something is made, rather than while it is being made.

Pretty common, I had my crank cryo treated, I know others have had theirs nitrated, it just adds a bit more strength, Harlan is pushing well over 1000rwhp with a stocker, if my memory isnt failing me
ed

DaveSchott

iTrader: (5)

By similarity you mean their objective is create a stronger crank, no way are they similar. Forged cranks can be nitrited as well, as it is a surface hardening technology.

69firebird

iTrader: (14)

Yes your right, I was more trying to make a laymans comparrison since he had not herd of either process.

I fully understand that the processes are not the same.
ed

DAPSUPRSLO

iTrader: (14)

I've heard of the processes, just don't really know the details involved with them. I.e. would it be better to run a "treated" stock crank or a eagle? Maybe a "treated" eagle crank. Callies equals $$$$$$$$$$

DaveSchott

iTrader: (5)

I don't know anything about the cyro treat, but I know from years ago that people nitrided their cranks to harden the bearing surfaces to make them hold up better. Personally, I'd only look at a replacement crank if I ws going to stroke the motor or build an all-out stock stroke engine, meaning well above 800rw and thrashed upon regularly.

FastKat

iTrader: (10)

Just want to point one thing out about what you're saying about the longer stroke and piston speed...

A longer stroke increases the "torque arm" or sort of the leverage arm in your engine. (You increase the torque arm of your rachet by putting a breaker bar on it.) More leverage gives you a potential for more torque. Obviously if you increase your displacement you're going to feed it with more fuel/air mixture.... and you're going to increase your torque! and we all know that's the fun stuff!!

And now about piston speed... your piston hits it's maximum acceleration (or negative acceleration) when it actually stops and is changing directions at TDC and BDC. Remember, acceleration is rate of change of speed. Maximum piston speed is actual reached right in the middle of the stroke where the torque arm (crank and rod) is exerting the most leverage (on the crank and thus to your rear wheels.) This is also where you see a tremendous gain in the power stroke from a stroked engine AND a forced induction setup!! It's a win/win situation!!!

Don't decide against the 4" stroke setup because you're worried about piston speed. Piston speed and bearing loads at TDC and BDC are only functions of engine speed and the weight (mass) of pistons and rods. It seems like half the people on the FI board have stroked motors and if their setup can handle the addition to the loads at TDC and BDC, yours can too.

Bottom line: unless you're trying to run crazy-high RPM's, you have very little to lose if you're using all forged bottom end products and a HUGE amount of torque to gain.

For more explanation check out my post on this thread
https://ls1tech.com/forums/forced-induction/326799-how-many-have-broken-rods-fi.html

DAPSUPRSLO

iTrader: (14)

Thanks FastKat, now that's the kind of information I'm looking for. Reading the post now.

DAPSUPRSLO

iTrader: (14)

Sounds like the biggest isue would be that of TDC after the exhaust stroke. I don't think this is an issue with n/a with an efficient exhaust system as the exhaust will actually create a vacuum and suck the exhaust mixture out causing the piston to have to do no or minimal work to force the exhaust out. I guess in a forced induction setup the piston has to push the exhaust out though obviously putting a compressive load on it until TDC when all the load is realeased and the piston is unloaded and yanked back down toward BDC.

Her's another thought. I notice alot of the fast guys are not using big strokes. Is this because of the greater exposure to harmonics which probably could be a real issue with such high stress loads on the crank (especially with a blower) or is this because they blow the tires off with all of the torque.

A 4" stroke would be cool especiall with such low compression and even more so with a turbo because it would spool so much quicker.

FastKat

iTrader: (10)

Hmm, dome good points...

At TDC of the exhaust stroke you're got the compresive load of the piston and rod compressing the exhaust gasses into the manfold. Is this the part of the stroke where the cam has overlap and also where the exhast valve stays open? If so, that would keep some of the compressive load offseting the tensile (pulling) inertial load that the piston experiences at TDC. I guess if that's not the case, the worst scenario is that the piston feels the full brunt of the inertial load at TDC, which is normal with a N/A setup anyway.

I don't know much about the harmonics, however I am guessing that in a serious high RPM setup you are not going to want to use a fluid type harmonic balancer/damper? I would think that the harmonics would come more into play at higher RPM's but I am not sure. Educate me on this one! I am curious myself. I doubt its' an issue of blowing the tires off though... there aint no replacement for displacement. Look at the guys running C5R blocks with long strokes AND bigger bores. I think the only time stroke isn't going to help is if you are in a racing class and limited to a certain displacement and you have to chose between more bore and more stroke... or in other words strike a strict balance that is right for your applicatoin.

I personally am sticking with my stock crank because of my budget. It seems like falling into a stroked crank alone will set you back an easy $1000 for the bottom of the barrel stroked forged crank. The LS1 cranks are strong for stock cranks as it is. The longer stroke will increase driveability and spool your turbo faster... I think it comes down to your budget!!

DAPSUPRSLO

iTrader: (14)

I'm not 100% sure on harmonics myself. I would just think they would be a bigger issue with a forced induction setup because of the higher cylinder pressures. I don't plant to spin anything over 7000rpm, probably more 6500 or so as I will be using a hydraulic valve train.