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Old 12-21-2011, 07:32 PM
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5.7 or 6.0 rods and what pistons?

I have a set of 370 chevy heads. What i would like to know is what is the best rod 5.7 or 6.0 and which is better a 2 valve relief or a 4 valve relief piston? The motor i am building is for a dirt track car. The cam i have to use is about a 435 lift hydraulic cam. ANY HELP WOULD BE GREAT THANKS

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Old 12-21-2011, 07:44 PM
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I edited your thread title, you need to be more descriptive, more than simply "need help".

BTW, do you mean 307 heads?
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Old 12-21-2011, 07:47 PM
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well if you buying rods anyway, you might as well buy 6" rods. the pistons are lighter. 2 valve relief flat top, dish, or dome depending on what your doing.
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Old 12-21-2011, 07:54 PM
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What motor are you building? If it's a 383, I don't like 6" rods because then intrude into the pin bore, and typically require ring support rails. For a short term comp motor this may not matter to you, but for a street motor, that's my only my opinion. Although it's always debated, it appears there is very little performance gain with the longer rod.
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Old 12-21-2011, 07:57 PM
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They are 350 chevy heads and the casting # is 370. I also have a set of 993's and a set of 487x heads but was told that the 370 would make more power. The class that i run say i have to use a flat top piston.
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Old 12-21-2011, 07:59 PM
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I race a dirt track car on a half mile track
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Old 12-21-2011, 08:06 PM
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it's not a 383 just a 350 bored 30 over. i'm new at this any help would be great. Just want to put my money on the right thing the first time.
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Old 12-21-2011, 08:06 PM
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Quote:
Originally Posted by ace 97
I have a set of 370 chevy heads. What i would like to know is what is the best rod 5.7 or 6.0 and which is better a 2 valve relief or a 4 valve relief piston? The motor i am building is for a dirt track car. The cam i have to use is about a 435 lift hydraulic cam. ANY HELP WOULD BE GREAT THANKS
Did you mean 307 heads or are these a set of those crazy Canadian 300 horse/350 heads, casting 3973370?

So what is the engine?

Dirt track, long or short track?

Cam timing? Not a lot of lift but what else?

The data you give is thin indeed. Depending on these answers and perhaps more will be recommendations. About he only thing I can say at this point is 2 valve relief pistons are probably a little better to use than 4 simply because the reliefs under the squish/quench deck reduce the effectiveness of both functions. A 6 inch rod might prove to be more useful than a 5.7 but that depends on how invasive the pin position is to the ring package of the piston what stroke length your running and the RPMs this is expected to turn. For a competition engine, you also need to start thinking about floating wrist pins rather than press fit pins and the use of H beam rather than I beam rods. But the track rules may help limit what can be done, so you might want to check them out first.

Bogie
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Old 12-21-2011, 08:14 PM
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stock crank 7200-7800 rmp's and yes i will use h-beam rod's. not to sure what the heads came off of.
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Old 12-21-2011, 09:55 PM
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i wouldn't use h beams, there's a reason everyone uses i beams. for a restricted head and can combo use the longest rod you can. 2vr pistons. there are no draw backs to even consider in this case, its pretty cut and dry.
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Old 12-22-2011, 01:13 AM
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If you dedicate yourself to this, you'll have your time in the sun as it were, but not until the basics are addressed. At this stage of the game, HP is the least of your concerns. Your main focus needs to be on tuning the chassis and practice practice practice. The engine making 15 HP either way is not going to matter one bit. Build it to survive and leave the trick of the week stuff to those guys who are either that good or that naive.
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Old 12-22-2011, 02:53 PM
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I got the set up and the chassis right been working on my driving and car for the last 5 years. I've won about 4 or 5 heat race's finished in the top 5 alot. I just need a little more motor that will last.
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Old 12-22-2011, 04:07 PM
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i'm pretty sure a 370 casting as an oddball double hump head like the 186 & 492. i still say 6" rods for the 350.
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Old 12-22-2011, 05:56 PM
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Quote:
Originally Posted by the nitro man
i'm pretty sure a 370 casting as an oddball double hump head like the 186 & 492. i still say 6" rods for the 350.
Yep, it was available over the counter in the US as a performance head with either straight or angle plugs, a 64 cc chamber and 2.02x1.55 or 1.6 valves. It was a production performance head in Canada, those lucky dogs. Typical of the HP heads of the late 60s early 70s, pretty good for its day.

Winding into the 7 grand mark on a factory shaft however, makes mine pucker.

Bogie
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Old 12-22-2011, 07:35 PM
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Thank's nitro man
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