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Old 11-22-2010, 06:54 PM
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4.3 v6 rebuild

im rebuilding a 4.3 tbi for a 90 k1500. the block will be bored .060 over and running a "rv" cam. does anyone know the size of the head(cc's) im wondering how much the compression would be with flat tops(5cc valve reliefs)

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Old 11-22-2010, 09:31 PM
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Heads are around 76 cc. Same as production 350. Rebuild flat top pistons are made .020 short. Compression ratio will not be much more than the stock 4.3
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Old 11-23-2010, 12:36 AM
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The heads chamber size is 68cc. I`ve rebuilt many of these so before I give out a huge handful of info which includes telling you upfront will be Expensive. Is this engine converted to carb or does it still have TBI? I can give you the piston number you`ll need to keep the compression in check plus all the mod information you`ll need to make sure it`s done right. To be absolutly honest, it`s cheaper to build and install a small block converted to a carb. Hot Rodding a 4.3 with injection Is Not Cheap. When I did the build on my 4.3 I went a good ways and thus far I`m sure I spent over $4000. I realize your not taking it to the level I did, but still, The bottom end is going to need to be balanced, that usually runs around $250. If it`s not balanced, it`ll be a shaker. If the injection is still in use the injectors will need to be replaced or sonic cleaned. High mileage injectors can`t flow enough fuel past 3500 RPM which causes it to go dead lean, you push the pedal down more but don`t pick up any power, been there done that. Isky and Comp both make replacement RV Roller cams, the price is usually around $270 for the cam alone. As I said, rebuilding a 4.3 is not cheap, especially when you add performance pieces. Had I realized what I was getting into from the get go, I would have just went with a small block, I would have gotten more power plus came out cheaper.
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Old 11-23-2010, 11:21 AM
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im not planning on hotrodding it really. its just basically a stock rebuild using stock tpi. when looking for a kit i found either flat tops valve reliefs or dished no valve reliefs. according to some info i found the motor already has 9.3:1 compression with the dished pistons. do u think the higher compression would cause heating problems since i'm already boring it .060?
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Old 11-23-2010, 01:01 PM
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if your keeping TBI, look for a set of CPI "Vortec Heads" (Not to be confused with CSFI "True Vortec" Heads) these heads will bolt up the the factory TBI block and intake and where used factory on 93/94/95 GMC/Chev Fullsizes and in S10's and vans with CPI (Looks like a TPI setup with a funky intake) Heads are good for 5-10 HP over the "TBI" ones.
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