Mild 383 build
- Thread starter Shorty Thompson
- Start date
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It's an early 70s "BH" casting. Supposedly they are supposed to be a heavier, thicker casting. This one certainly is.
That's the whole reason boring adds power. Period.
Turk,
I will answer your question first. Post #98. Both engines will make the SAME POWER.
That is because both pistons have the same total force applied [ 100 lbs ] ; what will be different is the lbs per square inch. The respective areas of a 4 & 5 inch piston are 12.6 & 19.6 sq in.
The pressure on the 5" piston is 5.1 lbs/ sq in; on the 4" piston it is 7.9 lb/ sq in....which adds up to total of 100 lbs. Any other scenario would mean energy is being created.....
I will answer your question first. Post #98. Both engines will make the SAME POWER.
That is because both pistons have the same total force applied [ 100 lbs ] ; what will be different is the lbs per square inch. The respective areas of a 4 & 5 inch piston are 12.6 & 19.6 sq in.
The pressure on the 5" piston is 5.1 lbs/ sq in; on the 4" piston it is 7.9 lb/ sq in....which adds up to total of 100 lbs. Any other scenario would mean energy is being created.....
It's 100 lbs per square inch not a 100 lbs divided by the area in square inches.
273,
Now you are introducing red herrings. Your original story, which was wrong, was that a bigger piston exerted more force because of it's greater area.
I do not know how many examples are needed until the message sinks in. So I will try some humour....
There is a lump of dog s**t on your patio. You get the garden hose to get rid of it. You adjust the hose nozzle for a concentrated stream...& blast away the mess. Had you used a fan pattern with the hose, it would not have removed the s**t. The pressure was the same in each case, but spread over a wider area with the fan pattern, & therefore less force per unit of area.
Now you are introducing red herrings. Your original story, which was wrong, was that a bigger piston exerted more force because of it's greater area.
I do not know how many examples are needed until the message sinks in. So I will try some humour....
There is a lump of dog s**t on your patio. You get the garden hose to get rid of it. You adjust the hose nozzle for a concentrated stream...& blast away the mess. Had you used a fan pattern with the hose, it would not have removed the s**t. The pressure was the same in each case, but spread over a wider area with the fan pattern, & therefore less force per unit of area.
273,
Post 106. Nope wrong again. Confusing weight with pressure.
As I said earlier, if big piston areas were able to perform your magical idea, it would be reallllllllllllly easy to make reallllllllly big HP........& we would see lots of engines with huge pistons. But we are not...
Post 106. Nope wrong again. Confusing weight with pressure.
As I said earlier, if big piston areas were able to perform your magical idea, it would be reallllllllllllly easy to make reallllllllly big HP........& we would see lots of engines with huge pistons. But we are not...
You can make as many dumb analogies as you want, your just wrong.
Newbomb Turk
Well-Known Member
You’re kidding right? Anyone who is making power is using the biggest bored they can fit.
Oh **** it. You aren’t worth the effort. If you can’t grasp pounds per square inch and how pressure works on it you just are too stupid to bother with.
Or you are just and argumentative prick.
Newbomb Turk
Well-Known Member
Maybe this will do it. Force per unit area. The coin sinks into the plasticine further when pushed end-on because it has more pressure with less the area.
Get it now Turk or are you too dumb???? Get it now 273???
Get it now Turk or are you too dumb???? Get it now 273???
That's not even the same comparison to a piston in a piston driven engine. I can't believe you're this obtuse.
Say the combustion is 1000 psi, you got a 1000 psi pressing against all the surfaces inside the chamber which includes the total top of the piston aka piston area, so each square inch of the piston is getting a 1000 psi.
This Video just came up on my feed for some reason, swear google/YouTube monitors what you saying.
The second half of the video @ 5:15 is the 383 Chev vs 383 Mopar might be an interest to the OP.
The video starts with the RV 440.
The second half of the video @ 5:15 is the 383 Chev vs 383 Mopar might be an interest to the OP.
The video starts with the RV 440.
The largest advantage of a large bore and short stroke engine is that the piston ring to cylinder wall interface is responsible for the most friction loss in the engine. The less they travel along the cylinder, the presumed less friction loss. But unless you’re planning to maximize that effect with careful ring selection (I.E. thin and reduced tension), you won’t see a difference. Reher Morrison Racing did quite a bit of research into that field. Probably the biggest advantage of a larger bore engine is giving the valves a little extra breathing room. But I mostly view bore to stroke ratio with about the same regard as rod to stroke ratio. Unless you’re building for the last three or four horsepower like for nascar or other pro racing teams, there are a lot better areas to focus on for a street engine. More cubic inches is always good providing there’s adequate cylinder head to take advantage of it.
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Okay update time. I have 2 sets of 906 heads, and 1 set of 516 heads. Suggestions?
PRH
Well-Known Member
Use whichever ones need the least amount of $$$ put into them to reach the goal.
junkyardhero
Well-Known Member
sell all three sets to offset the cost of new aluminum heads.
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Alu- min-ium heads are so,,,, costly. Tell me true. Are they worth the money, seriously?
Newbomb Turk
Well-Known Member
YES THEY ARE WORTH IT.
There is no reason to use iron heads. Unless it’s a W2 or something like that.
Sell that pig iron crap and get an aluminum head. Wasting money on those heads is just that. Wasting money.
junkyardhero
Well-Known Member
the short answer: it depends
the longer answer is: what is your ultimate intended goal? the alum heads probably have more room to grow, or will support a lot more power in out of the box form vs stock 906/915 heads. an aftermarket head is generally machined for larger valve springs, larger valves, hardened exhaust seats, updated valve guides and seals.
so basically, all of the stuff you'd need (and should) be doing to update a factory head for not only performance but also general use and longevity. then, add in standardized chambers and flow numbers that rival steel heads that have already been ported.
i'd bet dollars to donuts if you sat down and did the math, new alum heads would be darn near the same price as a set of full worked over 906's by the time the dust settled.
PRH
Well-Known Member
Machine shop prices can vary greatly depending on where you are.
At my shop, for parts and labor……it’s pretty easy to spend as much reworking 50+ year old factory iron as what the more budget friendly aluminum heads cost.
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Then suggest a head. Let's see what happens.
- Joined
- Oct 17, 2009
- Messages
- 136
- Reaction score
- 69
Gentlemen, then suggest a head and let's see if I can go that way or not.
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