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Old 05-15-2011, 08:48 PM
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4.3 V-6 hop up

I need to know can I use 345NP pistons in this engine. The wife and I are looking to make 250 horses. She wants her truck to handle more than she wants speed. Oh I got the pistons for $30 so I hope they will work. What would be a good ring set too? The engine will live at 2500 RPMS. She has an hour commute on the interstate also which it will make many times. Any help is appreciated thanks Adam

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Old 05-16-2011, 05:10 AM
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The 345 pistons will work. But are .020 short, compression ratio changes very little. Check the clearance between the rod pin end and inner piston pin boss when assembled. The rods don't ride in the center of the piston. Some applications will bind on the inner piston boss. Just narrow the rod eye a bit on that side.

I built a 4.3 for my daughter one time. Used forged flat top pistons, ported heads and a hotter (expensive!) roller cam.

The truck (S-10) ran the same as before. Computer controlls everything.
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Old 05-16-2011, 06:48 AM
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Excellent rings

For a Chevrolet 4.3L/350 you can use Sealed Power R9903 std. gap/std. tension rings. The Sealed Power 345NP pistons are rebuilder cast pistons with 1.540" deck height, which allows a .020" margin for blocks that require resurfacing and are excellent choice for a grocery-getter. The E345NP (hypereutectic) pistons have 1.560" deck height for high performance applications. However, piston failure due to detonation on cool-aid quality pump gas is of no concern if the engine timing advance is computer controlled.
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Old 05-16-2011, 07:22 AM
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I did this on my 92 chevy silverado. First off, it`s not a cheap build. The non balance shaft cranks will need to have the bottem end balanced. As said, I wouldn`t use the 345 rebuilder pistons. There are some things you can do with it to reach your goal, but you won`t do it unless you use a carb and skip the injection unless you want to take the truck to a dyno and have a custom chip made for it on the spot which is $$$.
If you go the carb route I can tell you which pieces to use to reach your goal, but keep in mind, it won`t be a cheap build no matter which way you slice it.
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Old 05-16-2011, 08:15 AM
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Ok ya'all thanks first for such a fast response. I have the stock iron high rise 4bbl intake and a old flat tappet block that I can run a mechanical fuel pump. The wires under the hood died a long time ago and has had a 2bbl carb and intake off of a 229 V-6. What I would like to do is gut all the old wires and keep it simple. I got a set of 229 heads but the head CC is 55 so I'm thinking too much compression and a 229 crank which will take V-8 rods if I shave the big end side a little but that crank is simi odd fire. I know a stock 229 boat motor makes 170HP with a 2bbl so I would think 250 out of a 262 inch engine isn't too far a stretch. Thanks Adam
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Old 05-16-2011, 08:38 AM
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Quote:
Originally Posted by fatdaddyadam12
Ok ya'all thanks first for such a fast response. I have the stock iron high rise 4bbl intake and a old flat tappet block that I can run a mechanical fuel pump. The wires under the hood died a long time ago and has had a 2bbl carb and intake off of a 229 V-6. What I would like to do is gut all the old wires and keep it simple. I got a set of 229 heads but the head CC is 55 so I'm thinking too much compression and a 229 crank which will take V-8 rods if I shave the big end side a little but that crank is simi odd fire. I know a stock 229 boat motor makes 170HP with a 2bbl so I would think 250 out of a 262 inch engine isn't too far a stretch. Thanks Adam
There is no advantage to using the 229 cid crank except to use SBC rods. If you do use a 229 crank, you have to use a 229 cam and distributor- NOT a cam/dist. for the 4.3L V6!

The larger big end of the 4.3 rods makes up for the larger crank pin offset between adjacent rods that makes the 4.3L an ever fire engine, since they do not share a pin like a V8. This should make the crank somewhat stronger than the 229, and if you use ARP bolts and resize the 4.3L rods, that will suffice for your 250 HP build, no problem. But either way you go, don't forget to match the cam, distributor and crank together, 229 or 4.3L.

Using the 229 heads is the same as using 305 heads on a 350. If you want to make a big improvement in the heads, use the V6 '96-up Vortec heads- just like w/the V8. And like the V8 the same considerations about the intake and rocker arms apply- special intake and self aligning rockers. Good for 30 HP at least, all else being the same.
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Old 05-16-2011, 10:16 AM
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I can get my hands on a set of 02 vortec heads and a eldabrock 2114 intake if that would be best. On the 229 crank I was thinking 6inch rods and better pistons. Long rods increase piston dwell at TDC and BDC. Yes? Adam
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Old 05-16-2011, 10:26 AM
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Quote:
Originally Posted by fatdaddyadam12
I can get my hands on a set of 02 vortec heads and a eldabrock 2114 intake if that would be best. On the 229 crank I was thinking 6inch rods and better pistons. Long rods increase piston dwell at TDC and BDC. Yes? Adam
The heads and intake would be the single largest improvement, IMHO. I believe the Vortec heads are worth more than a cam and a stock set of heads- especially if the stock heads are those swirl port pieces of junk. Again, MY opinion, other guys may love the SP's- I'm just not one of them. But combine the Vortec heads w/a decent performer cam (just don't go overboard w/the duration/overlap!) will net you a great running little V6.

There are lift restraints when using unmodified Vortec heads. Usually you can use as much as 0.460" lift w/o clearance problems- but you will need to verify all the clearances of the valve train when you mock up the engine. And there are low or no-cost ways around the lift restriction if needed. The valve springs will need changing if you run a performance cam. CLICK for some more info on Vortec heads and mods to them, etc. The thread is about the V8 Vortecs, but the same things apply to the V6 heads.

RODS-The difference between the two at less than one HP/cid is marginal at best. While the 6" rods may offer some slight advantage, I wouldn't even think of it unless the rods and pistons and balancing cost no more to use than the stock parts. And even then, if the 229 crank was any weaker than the 4.3L crank, that would be a deal killer for me. The basically stock, cast 4.3L crank was used in the Syclone/Typhoon turbo engines. The 229-type crank was never used in any performance applications.

Click HERE for Valve Train Points To Check.

Last edited by cobalt327; 05-16-2011 at 10:55 AM. Reason: Add link.
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Old 05-16-2011, 12:03 PM
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Ok thanks I know also I am limited on lift to the point that the main oil gallery is the left lifter bank and too much lift will make a oil leak from the lifter coming out of the bore too far and killing my oil pressure. Would I be better off to get a cam kit for my specific needs from a cam company? I have decided if the 03 heads will work I will just get them. Do you know the combustion chamber size? I will junk the 229 parts this weekend. Would 1.6 roller rockers be the way to go or 1.5? Thanks!
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Old 05-16-2011, 12:59 PM
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Cam

I have a Comp 09-412-08 computer camshaft in my little 4.3L engine. It has .500" valve lift (0.333" lobe lift) w/1.5 Scorpion self aligning ricker arms. The intake manifold bolt pattern is different on the 1996-up 4.3L heads, meaning 8-bolts instead of 12 bolts so you must use a Edelbrock intake manifold for the 1996-up Vortec SCPI heads. On all the 1993-1995 CPI heads and the 1996-up Vortec SCPI heads, the intake flow and high RPM power stalls above .500" valve lift regardless of which heads you use or how much port and valve work is done. You can install 1.600" exhaust valves to achieve optimim 82% intake to exhaust valve sizing and it will give you new exhaust seats to boot. Larger 2.02" intake valves will buy nothing on a 4.3L engine.

Scorpion roller rockers have the alignment rails on the roller tip rather than on the rocker body for a more precise fit on the valve and they have adequate clearance from the valve locks. I first installed Comp Cams roller lifters but changed to GM 12499225 LS7 roller lifter kit (16 lifters) before the engine was started. Those lifters are the roller versions of the old "high-ball" hydraulic anti-pump up flat tappet lifters first used in the 1965 GTO and Oldsmobile engines until the end of engine production. They give you a additional 500 RPM safety margin before pump-up and valve float. The Chevrolet LS7 hydraulic roller lifters set at 0.0831" preload or half plunger travel. Why change a good thing?

BTW... Yesterday, my 1991 S10 Blazer 4WD with this 4.3L engine passed stringent state vehicle and emissions inspection with room to spare.

Last edited by MouseFink; 05-16-2011 at 01:19 PM. Reason: BTW
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Old 05-16-2011, 05:23 PM
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Quote:
Originally Posted by fatdaddyadam12
Ok thanks I know also I am limited on lift to the point that the main oil gallery is the left lifter bank and too much lift will make a oil leak from the lifter coming out of the bore too far and killing my oil pressure. Would I be better off to get a cam kit for my specific needs from a cam company? I have decided if the 03 heads will work I will just get them. Do you know the combustion chamber size? I will junk the 229 parts this weekend. Would 1.6 roller rockers be the way to go or 1.5? Thanks!
To the best of my knowledge, you won't have a problem using the lift that's needed to reach your goal of 250 HP. And 1.6 rockers aren't needed, either- there are cams that are in the ballpark for what you want that spec out fine w/1.5 rockers.

Being that this is a flat tappet engine, you're more limited than if it was a factory roller. Isky has three grinds, the biggest is p/n 121262. It has 0.435" lift, 262 advertised and 208 @ 0.050" duration and a 108 LSA. Uses p/n 205-D valve springs. Power range is advertised at 2000-5500 RPM. The other two are milder and have less lift, duration and a wider LSA. They can be found HERE, p/n begin w/121. The 131 cams are rollers.

There may be performance cams from other manufacturers for the early 4.3L V6, I've not really researched flat tappet 4.3L V6 cams. A custom grind would be worth looking into, IMHO.
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Old 05-16-2011, 08:41 PM
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Thanks for all the great info. All this info will get me started in the right direction. Adam
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