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Building a good street 350

  
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Building a good street 350

 
niftyrick niftyrick
New User | Posts: 3 | Joined: 03/08
Posted: 03/04/08
11:09 AM

I have a good running 350 engine that is stock other than a holley street dominator single plane intake with the original quad. It ran well and seem to have plenty of torque. I want to bore it 30 over, and I have a set of sportsmanII heads that are 66cc with 550 lift valve springs. What piston do I need to use,to get streetable compression ratio,pump gas ,cam shaft would be best ,and intake. It will be in a street rod, but I would like to get some power out of it, I have a 2000 stall , and 3.25 limited slip rear and the 350 turbo  

GibTG GibTG
Guru | Posts: 1985 | Joined: 10/03
Posted: 03/04/08
08:43 PM

I suggest going to an online static compression ratio calculator and learning the 'ins and 'outs of the values needed to make that calculation.

Try these...
http://www.mindspring.com/~steveflyer/compression.htm
http://kb-silvolite.com/calc.php?action=comp

I suggest staying very mild with the induction and camshaft, as the heads will already be plenty for only 3.25:1 rear gears. Stick with a dual plane intake and a camshaft of around 260° advertised duration.

Switching back to static compression ratio, so much of it depends on the machine work that will be done to the block when its torn down. Decking the block makes a huge difference the final compression ratio of the engine. Performance engines are commonly "zero-decked" to bring the top of the piston crown (not the dome, if there is any) to the top of the deck, so then the only distance between the piston and flat-part ("quench") of the combustion chamber is the head gasket. Then its easily determined what the piston-to-head clearance is. This is also best for flame propagation, combustion-beneficial turbulence, and the getting the highest possible compression ratio. If this procedure is not done then your static compression will probably be three to four tenths lower than possible.

Without spending the dough (usually $150-$200) to deck the block you can regain back some of this lost compression with steel shim head gaskets but these are getting harder and harder to find. Steel gaskets also require more careful consideration when preparing the cylinder top surfaces and it may increase the risk of blowing a head gasket slightly if these problems aren't addressed.  
~Gibs

niftyrick niftyrick
New User | Posts: 3 | Joined: 03/08
Posted: 03/05/08
05:53 PM

So if I deck the block I will probable have to use dished pistons to keep my compression ratio down to keep the engine from detination. Is this correct ,or by tighten the quench it doesnt raise the compression ratio ? I don,t know how this affects the ratio, I don't know much about building performance into a engine. I just know the basics of engines  

thomasp thomasp
New User | Posts: 29 | Joined: 01/08
Posted: 03/05/08
06:09 PM

what is your definition of pump gas, 87 or 93 octane? is there ethanol or ethanol blended fules avaliable in your area?... if you can get ethanol then i would build an engine from the ground up to use it... if you are going to use conventional gas then 87 is only good for 9.2-9.5 compression depending on heads and ingnition system, 93 is good for 10.2-10.7... i built a 355 for use with ethanol which is comming to my area in the near future with alumnium vortec style heads and dome pistons which comes to about 11.2 and am running on 93 but can't run all the advance i would like  

pauvil pauvil
New User | Posts: 7 | Joined: 02/08
Posted: 03/13/08
12:29 PM

9.5:1 is nice street compression, I run 87 octane all day all the time with all advance coming in of idle and no problems. As stated a good ignition is key as well. You can make a nice street motor with plenty of power and stay "safe". Stick a flat top i there after the decking and you'll be close with that cylinder head.