He got it wrong. He may have been assuming the 383HP piston.
Mild 383 build
- Thread starter Shorty Thompson
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Can't tell you what I don't know. This is my " first time " I can say this " Tech said .050 Gasket thickness and said that would give a head chamber of .078 cc. Piston CC I am clueless. The others I am clueless. That's why I came in here . For guidance.
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Well. I got .025 with the 383 piston when I checked it. The tech also recommended a .050 composite head gasket to keep CR around 10.5-1. Now if he's wrong, and your right! Then yeah me. Because that's a win/win for me.
He made a sale.
junkyardhero
Well-Known Member
all of this is an assumption if you don't know the true deck height and the real cc of the chambers.
you can get right close with published numbers, but with production tolerances it's just a guess, albeit an educated one.
junkyardhero
Well-Known Member
speak for yourself, Dr The Mrs tells me all the time.
So he said the heads are 78cc even though they're listed at "about 80" and people here have clearly said they're "a little more"? Yeah. I think I'd take his advice with a grain of salt. But then, that goes for anyone's advice until you actually measure yourself.
Newbomb Turk
Well-Known Member
You’re saying you are .025 in the hole AND a .050 gasket??
Ain’t no way on Gods green earth would I ever do that. You are asking for a tuning pain in the *** among other things.
I’d call Cometic and get the thinnest gasket they make even if it’s .030 and it could be thinner yet.
.030 plus .025 is still .055 deck clearance. If you can get it to .040 you’d be far better off than what you are saying.
The compression would be what it is. I don’t think very many people have a grasp on compression ratio and octane requirements. Or even how they test to get octane numbers.
I’d rather be 11.25:1 with .040 quench than 10.5:1 and .075 quench. That’s a ******* disaster and you can tell the dude at Jegs I said he isn’t qualified to give out advice at a Burger King, let alone advice on things like this.
Affirmative...but the compooter say it's aaaall gude............
Shorty, I apologise for interrupting your thread but you & the readers are being fed absolute bullshit by '273'' & Newbomb Turk with their claim that increasing area of the piston creates more push on the con rod. They know it is wrong but haven't got the guts to admit it. They are getting force & pressure confused, two different entities, high school physics stuff.
First, just look at the common sense [ or lack of it...] Going from a 4" to a 5" piston gives more than a 50% increase in piston area....& according to these two that translates to 50+% more instant HP. If it was that easy to get that sort of HP increase, with no penalty anywhere in the rpm range, wouldn't people be building engines with HUGE pistons?????? Of course, but that is not how it works....
Turk, you got Bettes's book..... pity you didn't read it..... Turn to page 145... & learn something.
Below is p.145.
Power & piston area. Notice in the formula piston area bottom line is divided into the top line. That means the resultant power piston gets smaller as the piston area gets bigger
First, just look at the common sense [ or lack of it...] Going from a 4" to a 5" piston gives more than a 50% increase in piston area....& according to these two that translates to 50+% more instant HP. If it was that easy to get that sort of HP increase, with no penalty anywhere in the rpm range, wouldn't people be building engines with HUGE pistons?????? Of course, but that is not how it works....
Turk, you got Bettes's book..... pity you didn't read it..... Turn to page 145... & learn something.
Below is p.145.
Power & piston area. Notice in the formula piston area bottom line is divided into the top line. That means the resultant power piston gets smaller as the piston area gets bigger
He asked us to stop, start another thread if you can't accept that your wrong
Drop it man. Just drop it.
Shorty said in post #1 he was looking for suggestions. I am giving him suggestions on how to avoid making mistakes, by avoiding the advice of certain people......who are giving him WRONG INFORMATION.
Your argument has no bearing on what he is doing. It is entirely too technical and amounts to nothing for what he is doing. Cut it out. Don't make me come down there. Then we'll have to go Australian beer samplin. lol
Well, RRR, the beer is always flowing for ya.....bring ya summer weather with ya....
I just do not like bullshit. I have made lots of errors, some on this forum, & have owned them when they are pointed out.
I get the impression from Shorty's posts that he is trying to learn.....& listen to new ideas. Fundamental to learning new tricks....is to understand the fundamentals, the foundation.
I just do not like bullshit. I have made lots of errors, some on this forum, & have owned them when they are pointed out.
I get the impression from Shorty's posts that he is trying to learn.....& listen to new ideas. Fundamental to learning new tricks....is to understand the fundamentals, the foundation.
The OP is the one who said stop it, so obviously he doesn't care about why your wrong lol
Here I started a thread for you.
Here you go Bewy, Piston area and force.
Shorty said drop it Dude, & that formula is simply a reference metric, it has nothing to do with cause & effect. Now drop it please & have a beer.
Dartswinger70
Well-Known Member
383 build? wasn't there just a "383s make no power" thread on here...? lemme guess after a year and a half plus of bickering about 318s its moved on to 383s am I close? 
They probably just meant that the 400 has a bigger bore as the stroke and rods are the same. Kim
Gomer Pyle
Member
It's best to calculate compression on a regular calculator as opposed to an online comp calculator which just gives you a general idea and the guy at Jegs is way off IMO. In this case lets assume there is a zero deck height and you're using a Fel Pro 8519 PT-1 which we'll round off to 10 CCs from 10.187 CCs for this demo. Lets call the aluminum head 80 CCs. Here is the math, 4.32 divided by 2 = 2.16 then 2.16 x 2.16 =4.6656, 4.6656 x 3.14 = 14.649984, 14.649984 x 3.375 = 49.443696 which is the cylinder cubic inch, 49.443696 x 16.3872 = 810.24373 which is the cylinder volume in CCs or what is now commonly called swept volume. You have no deck CCs as there is zero deck height so you add gasket plus head which is 90 CCs and add it to the cylinder volume which is 810.24373 CCs, this gives you 900.24373 CCs when the piston is at the bottom, remove that swept volume and you have 90 CCs left. 900.24373 divided by 90 and you have 10.002708, that is your compression ratio with these specs and probably not far from what Shorty will have.
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And Shorty can live with that. Not to be a Debbie Downer, but! 11.0-1. is " not ! " what I want, at all. Got a couple things I'm looking at getting done to [ hopefully !!!!!! ] give you guys more input.
I don't think there's any way in hades you have 11:1, BUT as I've mentioned now at least twice, you really need to take direct measurements. It's the only way to know for sure.
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And that's exactly what I'm talking about.
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