Piston selection--300 build up?
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Lead Driver
Joined: Mar 2008
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From: Near Los Angeles
Piston selection--300 build up?
Hello everyone--
I'm a little confused. I'm building a 300 with cam, oversize valves, ported head, intake and 4V carb, and all the other goodies.
What type of pistons should I get. I want to bump up the compression a bit, to 9.0--9.5:1, and stay on regular gas. But most of the pistons I look at are rated at 7.9--8.2:1. Do I need to get a piston with a higher compression rating, or just go ahead and shave a bit off the deck with close to stock pistons?
The size of the combustion chamber and stroke determine the compression, right?
I'm a little confused. I'm building a 300 with cam, oversize valves, ported head, intake and 4V carb, and all the other goodies.
What type of pistons should I get. I want to bump up the compression a bit, to 9.0--9.5:1, and stay on regular gas. But most of the pistons I look at are rated at 7.9--8.2:1. Do I need to get a piston with a higher compression rating, or just go ahead and shave a bit off the deck with close to stock pistons?
The size of the combustion chamber and stroke determine the compression, right?
Senior User
Joined: Jul 2005
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IMHO, F-250 Restorer, it is really difficult to just go buy a lot of cool parts and expect them to work together. How much you shave the heads, change to new pistons, higher lift cam, upgraded rockers, etc etc, depends on the end result you want and whether all the moving (crank, rods, pistons, valves, rockers, lifters, pushrods...) and stationary (head, block) parts will work together in the changed geometry created by the new parts.
At least, that's what the big boys told me
when I started talking about all the neat stuff available from the aftermarket guys like CompCams
But, very best of luck in whatever you do, the "Big-Six's" from Ford-of-yesterday are a righteous piece to work with. ;-)
At least, I think so, IMHO.
At least, that's what the big boys told me
WHOA, cowboy, do you want something that works, or do you just want to spend a lot of money?
But, very best of luck in whatever you do, the "Big-Six's" from Ford-of-yesterday are a righteous piece to work with. ;-)
At least, I think so, IMHO.
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Lead Driver
Joined: Mar 2008
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From: Near Los Angeles
When you raise the compression in an engine, do you need to have pistons rated with that compression?
If my pistons have a factory 8.2:1 rating, and I mill the head a bit/and/or deck the block and create 9.3:1, is that a problem?
If my pistons have a factory 8.2:1 rating, and I mill the head a bit/and/or deck the block and create 9.3:1, is that a problem?
Postmaster
Joined: Dec 2006
Posts: 3,603
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From: Spokane, WA
Not necessarily a problem especially if you specify hypereutectic pistons like these Federal Mogul ZWH519P30 - Speed-Pro Hypereutectic Pistons - summitracing.com and consult with your machine shop on zero decking, milling head and block, and CC'ing the chambers and piston dish to arrive at the compression ratio you want.
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Lead Driver
Joined: Mar 2008
Posts: 7,196
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From: Near Los Angeles
Harte3--
Thanks again. You've been a valuable resource. I'm learning step by step.
I'll soon start posting photos, although I'm sure you've all been there.
I'm thinking about going with an Autolite 4100, rebuilt by pony carburetors, 480 cfm. What do you think about that carb?
Thanks again. You've been a valuable resource. I'm learning step by step.
I'll soon start posting photos, although I'm sure you've all been there.
I'm thinking about going with an Autolite 4100, rebuilt by pony carburetors, 480 cfm. What do you think about that carb?
Posting Guru
Joined: Sep 2004
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Thought you had this figured out. 
This is why folks end up using the 351w pistons, get your machinist to do some measuring and im sure he can figure out which one is ideal for your goals. The v8 do share the earlier rod pin diameter. keith black are popular, I know one will give you what you want but I dont have the part number on hand. Once your machinist CC's the head, measures the block etc, determines a reasonable gasket thickness, Im sure he will know which piston to get you in the ballpark.
If you havent searched, then give it a shot, the info is there.
This is why folks end up using the 351w pistons, get your machinist to do some measuring and im sure he can figure out which one is ideal for your goals. The v8 do share the earlier rod pin diameter. keith black are popular, I know one will give you what you want but I dont have the part number on hand. Once your machinist CC's the head, measures the block etc, determines a reasonable gasket thickness, Im sure he will know which piston to get you in the ballpark.
If you havent searched, then give it a shot, the info is there.
Postmaster
Joined: Dec 2006
Posts: 3,603
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From: Spokane, WA
Classic Inlines did some dyno testing a while back with Pony using several carbs the Pony 4100 being one of them. This was on a moderately modified small block 6 with the CI aluminum head and intake. The results were impressive. The price of one of those carbs is "impressive" too. Your results may differ.
Whilst pondering carbs, check this out: https://www.ford-trucks.com/forums/8...n-a-240-a.html
Whilst pondering carbs, check this out: https://www.ford-trucks.com/forums/8...n-a-240-a.html
