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  #16 (permalink)  
Old 12-12-2012, 08:08 AM
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I'm from old school, I like dome
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Last edited by lg1969; 12-12-2012 at 08:13 AM.
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  #17 (permalink)  
Old 12-12-2012, 09:09 AM
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dome pistons vs. flat top

Quote:
Originally Posted by BigDawgsEatFirst View Post
I would put money on the flat top, with a quench of .040 the flat top would provide a better squeeze into quench area providing
combustion efficiency.
In the first place if you have a 350 block with a stock crank, 5.7 rods and have a set of 5cc flat top pistons with 64cc head your compression ratio will be 10.381. Now if you have a 350 block with a stock crank, 5.7 rods and have a set of -11cc dome pistons with 64cc heads you will have a 12.9 compression ratio. So the motor with 12.9 compression will make more power. There is no way possible to have a 10.1 cmpression ratio with the same 64cc heads with any size dome piston. The question doesn't make sense.
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  #18 (permalink)  
Old 12-12-2012, 10:08 AM
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I have nothing scientific to offer, just an opinion. I have never cared for domed pistons where another head could be used with flat-tops to get the same SCR. In my mind, I see the flat-top shooting the mixture straight across the chamber toward the spark plug, while the domed piston presents a slight restriction to the movement of gases over the dome. I also see the dome getting in the way of flame propogation after the plug fires. I see nothing wrong with using a dished piston to reach a target SCR, so long as the piston still has a generous squish pad opposite the chamber side, like the D-cup Keith Black design.
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Old 12-12-2012, 01:53 PM
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Quote:
Originally Posted by philr View Post
I was just wondering if you had a 350 with a small dome piston with 10-1 comp. and a flat top piston with 10-1 comp. Same heads same cam and everything which one would run the strongest with a quench of .035.This is something I was just wondering and ther e may not be an engine like this. I waas just wondering how much the dome hurts the power. Thanks philr
If same heads you can't have 10.1 on both.If the flats are 10.1 , the domed will increase it to higher than 10.1, depending on the dome size.I doubt you have 10.1 with flat tops.
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Old 12-12-2012, 03:07 PM
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Chevy had 68, 69, 70 350 rated at 300HP they had 10.25: 1 comp using flattops. They used small chambered heads. It depend which heads you are using
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Old 12-12-2012, 03:53 PM
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The best way to clean pistons is in your ex-wifes dishwasher. I'm a really big d-cup fan when it comes to pistons (and other things).
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Old 12-13-2012, 06:24 AM
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GM only used domed pistons in the small block V8 engine in the 1965 327 CI, 375 HP Ram Jet FI engines. Those pistons increased the compression ratio one point, from 10.25:1 with flat top pistons to 11.25:1 with domed forged pistons. The 1965 375 HP, 327 CI engines were the only FI engines that had forged domed pistons and a forged crankshaft.

In the fall of 1965, I purchased a GM 327 CI, 375 HP (L84) short block and installed it in my 1959 Chevrolet Impala and raced in AHRA F1-E/HR at the Odessa (Texas) Raceway Park Fall Nationals. The short block came less camshaft, lifters and oil pump. I installed a GM 30-30 camshaft, GM edge orifice lifters and a 409 Chevy oil pump since a HV oil pump was not available for a SBC.

Interesting note:
The Chevrolet dealership where I purchased the 327 FI short block was one of the few dealerships that received 1 of 69 COPO ZL1 Camaros in 1969. It was #6 COPO Camaro originally ordered by Fred Gibb Chevrolet in LaHarpe, IL. I was a friend of the dealership owner and he let me drive #6 COPO Camaro around town for an hour and to a coffee shop with a salesman. The #6 COPO Camaro was Cortez Silver and had an all aluminum ZL1 427 CI engine with a TH400 transmission. After a week of negotiations, the #6 COPO ZL1 Camaro was purchased off the showroom floor by Jim Hall from Odessa Texas and was prepared for the 1970 Trans-Am Series. After driving #6 COPO Camaro in the 1970 Trans Am Series, Hall scrapped the car. The 1970 Trans Am Series were Jim Hall's last racing events. I must be the only person that knows what happened to that car.
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Old 12-13-2012, 08:58 AM
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Quote:
Originally Posted by lg1969 View Post
Chevy had 68, 69, 70 350 rated at 300HP they had 10.25: 1 comp using flattops. They used small chambered heads. It depend which heads you are using
I understand it depends on heads,and i know you can have 10.1 with FT's.at My point was he stated that he was using the same heads, with either piston!
Jim
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Old 12-13-2012, 11:36 AM
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I agree, that would be confusing. You change the heads or the pistons or increasing the cubic inch or decreasing the cubic inch will change the compression, too.
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Old 12-15-2012, 01:50 AM
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I've been looking into this. I want to use the brodix ik 200's 64 chambers with probe -3.5cc domed pistons. I figured the -3.5 cc pistons would have a small enough dome to allow decent flame travel while still maximizing on power expression of the piston and CR. with a .04 quench you get about 11.3 cr vs flat tops at a 10.4. Cr's are off the top of my head from memory atm don't feel like finding the calc.
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