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Old 02-02-2005, 04:16 PM
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5.565 or 5.7 rods?

Hi, Im preparing to build a small block chevy 400 for street use. This will be my first performance engine build. Id be thrilled to have a 350hp/350lbs torque streetable small block. Ill be using the stock 76cc heads and the stock crank. The motor will not see over 5500 rpms. Rather than buy new stock rod bolts, ARP rod bolts sound like a good idea.

My main questions is related to the connecting rods. Hot Rod and Car Craft magazines have lead me to belive that longer rods are key to making easy power. After reading conversation on this board, it seems maybe these stores are inflated somewhat.

I have a set of 5.7 rods and the 5.565 rods are still in the 400 that I have yet to disassemble. I will have either set of rods reconditioned prior to using them. I have read that a small base circle cam has to be used with 5.7 rods.

Speed Pro hyper pistons for 5.7 inch rods cost $30 more than pistons for the 5.565 rods. Should I save the $30 plus the cost of a small base circle cam and use the 5.565 rods or will using the 5.7 rods be a worthwile investment? Thanks!

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Old 02-02-2005, 04:29 PM
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Go with the 5.7 rod. Less cylinder wall loading. The ARP rod bolts usually have enuff taper on the heads to clear a regular camshaft. If not, only minor grinding, is needed. Every engine is different.
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Old 02-02-2005, 04:36 PM
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5.7 rods

You will not need a small base circle cam with the cam you will be using to get 350 hp. You have to start hitting .500 lift for their to be a problem. The arp bolts leave enough clearance on the 5.7 rod to alleviate cam clipping.

With stock components do not exceed 5500 rpm or you will break parts.
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Old 10-09-2010, 02:00 AM
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I used the shorter rod with one I ran for a couple of years. I beat that engine pretty hard and never had any problems with it. But mine was cammed pretty modest so it stayed under 6k rpm most the time.
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Old 10-09-2010, 07:00 AM
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Quote:
Originally Posted by Onefunponcho
I used the shorter rod with one I ran for a couple of years. I beat that engine pretty hard and never had any problems with it. But mine was cammed pretty modest so it stayed under 6k rpm most the time.

Same here and to make matters "worse" I used cast pistons, this was in 1982 and 383 stuff was pretty hard to come by. The machine shop even had to modify a set of 350 ARP rod bolts to fit the 400 rods. Mine hit 6K more than a few times. I sold it to a friend who put a 125HP Nitrous kit on it and used it frequently for 2 years. It lasted another 1 and 1/2 years after he sold it before the next guy melted the cast pistons.

That said I'm planning another one but with 5.7's, but one built with 5.565 rods wouldn't be a total dog like some people would have you believe. Mine would shred the tires at will in a '72 Chevelle with a TH400 and 3.73 posi.
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Old 10-09-2010, 10:03 AM
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I have a dyno test that show everything the same in a 383 engine the longer 5.7 rods showed 5 hp .The engine builder felt the 5 hp was difference may have been from not degree the cam different for the different piston speed.
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Old 10-09-2010, 11:53 AM
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Quote:
Originally Posted by JohnyR17
...will using the 5.7 rods be a worthwile investment? Thanks!
At the power level you are planning it won't make much difference. The 5.7"
rods are stronger than the 5.565" rods. The shorter rod fails in the big end
above the rod bolt.
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Old 10-09-2010, 02:56 PM
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Before the availability of off the shelf pistons for 383's with the 5.7 rod, I built dozens of them with the 5.565 rod and never had a failure. I always used ARP rod bolts told my customers the rpm limit was 5500.
I built a 406 for my own car with the 5.565 rods and bracket raced the car for 4 years running 30+ weekends a year. No problems at all. After I stopped bracket racing I freshened it up and sold it to a friend who put a small nitrous system(125hp) on it and ran it for another 3 years.
Moral of this post. Use good rod bolts, keep the rpm at a reasonable level and it will live a long life.
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Old 10-09-2010, 06:36 PM
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Less chance of detonation with the short rod because the piston hangs around TDC for a shorter period of time, but either would work fine.
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Old 10-09-2010, 07:17 PM
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Not to start a disagreement airboat, but my understanding has always been the more time the piston hangs out at TDC the less chance of detonation as the combustion has time to occur before the piston moves. Short rods in most cases are considered detonation prone.
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