FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: gregaba on December 27, 2023, 02:13:28 PM
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I need someone smarter then me to figure my CR.
I just spent all morning ccing my heads and was a little surprised at the results.
The heads cced out at 68-69 cc across both of them.
Edelbrock 427 Aluminum heads with 220-173 valves.Heads have been worked but not milled.
Here is what I have 428- Bore is 4.164.
Pistons are flat top race tech sticking out of the block 0.005.
Stock stroke.
Block was square decked and blueprinted.
Crank assemble balanced to 1 gram.
I have forgotten how much of a pain it is to cc heads and it took me a lot longer then I remember having to do in the past.
Thanks
Greg
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I need someone smarter then me to figure my CR.
I just spent all morning ccing my heads and was a little surprised at the results.
The heads cced out at 68-69 cc across both of them.
Edelbrock 427 Aluminum heads with 220-173 valves.Heads have been worked but not milled.
Here is what I have 428- Bore is 4.164.
Pistons are flat top race tech sticking out of the block 0.005.
Stock stroke.
Block was square decked and blueprinted.
Crank assemble balanced to 1 gram.
I have forgotten how much of a pain it is to cc heads and it took me a lot longer then I remember having to do in the past.
Thanks
Greg
What is the piston volume? What head gasket?
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A person needs more information to figure CR. From what you describe I'd say you'll need rocket fuel for it to run. The Static CR won't tell you much as the Cam will decide the DCR you run. The cam will decide when your valves close to enable compression in the cylinder. DCR stays with the engine through any rpm and is the most valuable tool to decide useable cubic inch of motor and what octane gas you'll have to run to keep it from pinging.
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Brent, the only pistons I see on their website are the Autotec version with -11.0 cc dome volume. Looks like it will be around 11.0:1 static CR depending on gasket thickness.
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Brent, the only pistons I see on their website are the Autotec version with -11.0 cc dome volume. Looks like it will be around 11.0:1 static CR depending on gasket thickness.
I wouldn't assume that he's got shelf pistons. A lot of guys run custom slugs. Also, an 11cc dish isn't considered a flat top. A flat top is usually around 3-6cc.
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Sorry for not including all info.
The pistons are Auto Tec part number 1021059 custom ordered from Brent.
They have a 5 cc dome volume.
Gaskets are Cometic 0.40 thick.
As of now I will be running compressed natural gas for fuel.
Cam will be the Ford D cam for a while and then a custom solid roller that I will let Brent decide what I need.
Greg
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Sorry for not including all info.
The pistons are Auto Tec part number 1021059 custom ordered from Brent.
They have a 5 cc dome volume.
Gaskets are Cometic 0.40 thick.
As of now I will be running compressed natural gas for fuel.
Cam will be the Ford D cam for a while and then a custom solid roller that I will let Brent decide what I need.
Greg
A 4.164" bore, 3.980" stroke, 68cc chamber, .040" x 4.400" head gasket, with a 5cc dome piston sticking .005" up out of the hole would yield an approximate compression ratio of 13.36:1.
You said flat top in the post before, so if it's a 5cc flat top instead of a dome, compression ratio would be approximately 11.85:1.
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Its a flat top, no dome.
11.85 I can live with, I was afraid it would be a little higher but the amount of driving time on the car will not be much.
13.36 would worry me a little but is doable with the CNG for fuel with an octane of 140.
It will just be a fun car and not a everyday driver.
I just don't want to be disappointed when I get on it.
Thanks for taking the time to figure this out for me.
Greg
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I get, 11.7, I don't think Brent added the crevice volume.
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I said “approximate” because you can’t add crevice volume when it’s not been measured. It varies from piston to piston.
I also based the calculation on 68cc and he said the chambers varied a little bit. That’s also why I said “approximate”.
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don't think it has been mentioned here yet but have you looked at what your dynamic compression ratio will be?
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Yes ^^ have someone that knows, calculate your DCR. I wasted a long time on a similar combination only to have Brent line me out in no time by calculating my DCR. In Brent's words it was a "no go" and I have moved on to changing the pistons.
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There is always going to be crevice volume, no matter what. On his 4.164 bore, it basically will not be less than .81 (.200) nor more than 1.22 (.300), or no more variance than .41cc.
When I do DCR, if I don't want to calculate the exact crevice volume, I just add 1cc to the chamber volume, for FE bores of 4.08 or more.
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Of course there is crevice volume, Frank, I’m not sure why we are having menial conversations considering I have caveats up above. Crevice volumes can be all over the place and I didn’t add it for that reason, even if racetec averages about a cc. A .1 change in compression ratio has absolutely no bearing on Greg’s questions. If this were a super stock motor, I’d have a difference answer.
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I always add it in, it is there in all applications.
You could have also said that the CR was approx 11.7 and been a little closer to reality. As I said, it doesn't very much on a FE bore, from 4.08 - 4.26
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I always add it in, it is there in all applications.
You could have also said that the CR was approx 11.7 and been a little closer to reality. As I said, it doesn't very much on a FE bore, from 4.08 - 4.26
Frank, you add another estimated variable and even estimate it for DCR?. SCR to the second decimal point using an estimation is a little sloppy to base an argument on IMHO
Here's a crazy fact, as you build many engines, the number doesn't matter...consistency in calculation and knowledge to apply what you see does, think on that
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I always add it in, it is there in all applications.
You could have also said that the CR was approx 11.7 and been a little closer to reality. As I said, it doesn't very much on a FE bore, from 4.08 - 4.26
I said approximately 11.8. 11.7 is approximate to 11.8.
Quit nit picking on something that’s inconsequential.
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I haven't used this link in a little while but it has some calculators for getting your numbers. Takes a little bit to get used to it.
Hope it helps.
https://www.gofastmath.com/Horsepower-Calculators/Horsepower-Calculator
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So, you guys are trying to tell me accuracy isn't important, right?
I guess so, because you both have told me this multiple times! I'm not a engine assembler, I'm a machinist of 50 years and a mechanic before that. In MOST cases, there is a world of difference between the two, when it comes to accuracy. So, you can complain all you want about me being to accurate but, I will continue down this accuracy path. Who cares if there is very little or no difference between 7.8 and 7.82 DCR, the answer is I do. It's the way I was trained, to be as accurate as possible.
BTW Brent, you actually said 11.85 not, 11.8 and by your standards the 11.85, is closer to 11.9. Nit picking? I don't know but, I try to be as accurate as possible. If my calculation would have been 11.69, I would have said that.
BTW Ross, how much difference is there between the DCR for 87 oct and 92 oct at standard elev, intake temp and barometer pressure?
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So, you guys are trying to tell me accuracy isn't important, right?
I guess so, because you both have told me this multiple times! I'm not a engine assembler, I'm a machinist of 50 years and a mechanic before that. In MOST cases, there is a world of difference between the two, when it comes to accuracy. So, you can complain all you want about me being to accurate but, I will continue down this accuracy path. Who cares if there is very little or no difference between 7.8 and 7.82 DCR, the answer is I do. It's the way I was trained, to be as accurate as possible.
BTW Brent, you actually said 11.85 not, 11.8 and by your standards the 11.85, is closer to 11.9. Nit picking? I don't know but, I try to be as accurate as possible. If my calculation would have been 11.69, I would have said that.
BTW Ross, how much difference is there between the DCR for 87 oct and 92 oct at standard elev, intake temp and barometer pressure?
Use my words, not yours, I have never told you accuracy is unimportant. I am saying you imply exactness when convenient to call out other people but are not really exact. It can be very misleading and frustrating
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So, you guys are trying to tell me accuracy isn't important, right?
I guess so, because you both have told me this multiple times! I'm not a engine assembler, I'm a machinist of 50 years and a mechanic before that. In MOST cases, there is a world of difference between the two, when it comes to accuracy. So, you can complain all you want about me being to accurate but, I will continue down this accuracy path. Who cares if there is very little or no difference between 7.8 and 7.82 DCR, the answer is I do. It's the way I was trained, to be as accurate as possible.
BTW Brent, you actually said 11.85 not, 11.8 and by your standards the 11.85, is closer to 11.9. Nit picking? I don't know but, I try to be as accurate as possible. If my calculation would have been 11.69, I would have said that.
BTW Ross, how much difference is there between the DCR for 87 oct and 92 oct at standard elev, intake temp and barometer pressure?
1. I’m saying that you’re nit picking because I said approximately, knowing that there were other variables. You’d have to treat every single cylinder individually, Frank, to calculate the amount of accuracy that you’re discussing, that doesn’t have any bearing on anything.
2. You don’t know the answer to the question you asked Ross, because you haven’t put an engine together in 20 years.
Lay off the nonsense. Happy New Year.
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Ross, all I said was that my calculation was 11.7 and that Brent had most likely left out the crevice volume in his 11.85. Both you and Brent, do that a lot but, it means something to me and it is the OP's favor, for his situation. We (Bent and I) used the same specs, because I re-calculated it with 0 crevice volume and I got his 11.85, doing that.
What is wrong with what I did?
Again:
How much difference is there between the DCR for 87 oct and 92 oct at standard elev, intake temp and barometer pressure?
Happy New Year, Brent :)
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Frank, I am out the door shortly so can't keep up all this fun, to be honest I should keep my mouth shut.
However
1 - The difference in what you said with an estimated crevice volume was 1.4% from Brent'... on a cranking compression of 200 lbs that under 3 lbs difference,. Overlap effects will have more of a difference than that.
2 - Your DCR question is another attempt at the illusion of precision to pull away from the fact that yours was an apporximation too. I can play a little but will not share the details of my "engine assembly" I adjust a build based on range of variables I expect the engine to operate in, from experience, DCR itself is only one tool in the box, when combined with all other factors that influence octane tolerance, it's a fool's errand to try to assign a DCR delta for the illusion of precision.
So despite your stern request, I can't answer in a way you would be happy with and your question is certainly designed to try to pit me against some other answer you found on the internet
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What is wrong with what I did?
You know what you did. You took a shot across the bow just to be a dingleberry about things.
I put "approximately" for a reason. The reason is that there are things, such as crevice volume, how far each individual piston is down the hole, what each individual combustion chamber volume is, etc. that play into the compression ratio. He gave a chamber volume of 68-69cc. That's .1 of a point of compression right there. If #1 piston is at zero and #4 piston is .002" down, that's another factor.
You can't be anal about compression ratio when none of us have every single piece of data needed to perform the calculation. So calling me out on being a tenth of a point off was completely asinine.
To be straight up about it, every compression ratio calculation should be an approximation because so much plays into it. Don't get me started on aluminum blocks again.
And don't act like you have any idea on what octane numbers work with what DCR values. You don't have any data for your own except for the data that we put up on dyno results or camshaft calculations that you see accidentally given out on a forum post. You basically just read what the engine builders put up and then mooch the data.
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1 - The difference in what you said with an estimated crevice volume was 1.4% from Brent'... on a cranking compression of 200 lbs that under 3 lbs difference,. Overlap effects will have more of a difference than that.
The question was, "What was wrong with what I did?"
Ross, regarding DCR, if you'll remember, you and I had a conversation (PM's) about 87 Octane and DCR, a couple of years ago, or so. Have you had any more insight, since then?
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You know what you did. You took a shot across the bow just to be a dingleberry about things.
Brent, I can't help it if you don't use all the info to calculate compression ratio's but, it's just like head gaskets, not all engines go together with a 1020 gasket. Head gaskets can vary from 4.65 to 14.20. As a matter of fact, the Cometic .040 (I just looked it up), comes in 2 flavors, 9.30 & 9.97 and it's on me, that I didn't ask.
Each time you leave out info, decimal points or round things, it changes the answer, in some way.
For everyone's info, Ford, at least through the '60's and earlier, didn't use crevice volume either, to calculate the CR's of any engines and in the early FE's it was substantial. The top ring land was .400 thick on the high compression engines of at least '58 & '59 on the E361 & 352's.
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You know what you did. You took a shot across the bow just to be a dingleberry about things.
Each time you leave out info, decimal points or round things, it changes the answer, in some way.
Exactly. That's why I put "approximately" in my response to him. I didn't have all the data and you don't either. You can't call me out on not including crevice volume when none of us have all the data and his compression ratio can vary by more than .1 from cylinder to cylinder.
Quit being a poser, Frank. You try to come across like you're an engine building expert but you haven't put anything together in decades.
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You know, Frank, it would be nice if a thread went on its logical course without falling into purse swinging, which adds zero value to the thread. Nobody wins in these.
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Gerry, I'm sorry but, I don't own a purse.
Brent is just trying to justify his non inclusion of something that is always included in real CR calculations.
I didn't start this, I only offered a CR calculation WITH the crevice volume. Brent didn't have to say anything or he could have said "yes, I didn't include that" but, instead, he took it to this level (with Ross's help, as always). I have only been defending myself.
I'd be interested in everyone's opinion on whether or not, people on this forum think that crevice volume should or should not be included in CR calculations, as a regular component of it.
I'm sorry that Brent can't take constructive criticism or correction where it's warranted.
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If I were you (not knowing a lot about engines) I'd hang onto every word people like Ross Bullock has to say. He gave me advice on building an engine years ago. I built a 410 engine that produced 385hp @ 4600rpm, uses 87 octane gas for my 57 Fairlane. It's the big Fairlane (@4300 lbs w/me) and I consistantly ran the quarter mile in 14.3 seconds on 215 X 15 street tires. I've put about 35,000 miles on it so far and it's never been apart. When I got thru drag racing I put the engine in my 63 Galaxie.
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If folks want an opinion - - just stop fixating on DCR.
It's sometimes useful to keep you out of trouble if your combination is "way off in the weeds" somewhere.
But it's damn near useless for determining real world fuel tolerance. It does nothing - nothing - to account for the variables in combustion chamber configuration, piston dome contours, intake port and manifold configuration and charge/flow efficiency, exhaust port and system efficiency, fuel chemistry, fuel charge cooling effects, or a host of other things. Your 13:1 engine is gonna be a 13:1 engine at peak torque even with a cam oversized enough to murder power below torque peak. And it'll rattle on junk fuel at an RPM where you won't hear it until the parts bounce off the pan.
90% of the folks reading this should dedicate time to good process, solid parts selection, and comparatively conservative compression choices - and not fixate on optimizing an arbitrary formula trying to find an unquantifiable 1% improvement. I have seen and measured a +/-4% difference in peak power going from 9.8:1 and 10.8:1 - that's roughly 20 or 25 horsepower in a 445. Does anybody honestly think that pushing it to 11.1 or some other arbitrary value to gain DCR would be worth the sacrifice or risk in a street cruiser where 98% of it's life will be at part throttle?
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I have seen and measured a +/-4% difference in peak power going from 9.8:1 and 10.8:1 - that's roughly 20 or 25 horsepower in a 445.
Sorry, Barry, you're not allowed to make estimations/approximations here. The resident armchair engine builder will flay you.
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I have seen and measured a +/-4% difference in peak power going from 9.8:1 and 10.8:1 - that's roughly 20 or 25 horsepower in a 445.
Sorry, Barry, you're not allowed to make estimations/approximations here. The resident armchair engine builder will flay you.
And I am supposed to care?
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Frank...Stop trying to pick the fly shit out of the pepper. ::)
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Since were are being all technical and such, flys don't shit, they puke. They have no assholes.
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Sorry but, I don't eat shit ;D
For those that think I don't know Ford Engines, I was a mechanic from '62 - '70, in the hay day of the FE and worked on them regularly. My first FE was a 300 hp, 352, in 1963, that I put into a '60 Ford (had a 223 in it). I had 2 K code cars ('64 Fairlane & '65 2+2 Must) and a third 271 HP 289 engine. I built my LR 427 in '69, with a Chet Herbert roller cam, before that I put another 427 LR together for a friend that bought it unassembled. I was popular in my mechanic days. In '73 - '79, I built 3 Coswoth DOHC 4 cyl engines, as seen in my pictured Formula Atlantic, as well as my 1500cc push rod, Ford Cortina engine. Since then, I've built multiple 289/302's, Z20 & 2, Ka24E Nissan's. And my dad, before me, was a mechanic at a major Ford rebuilder (Meyer & Welch). I got his Snap On tool box to start (still have it) and lots of help from him in getting started.
I also a sold V-belt and timing belt drives and a water pump, of my design, in my machine shop business, in the '80's as seen by my ad in Circle track.
So, don't tell me I don't know SBF & FE engines. If you want to see some of my handy work, look in the Project threads for my Austin Healey. I'm 79 yrs old and have other interests (vintage tractors) and don't get things done as fast as I once did but, don't tell me I don't know Ford engines or what I'm doing.
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Frank, give it a rest. Wouldn't want Jay to kick you off the Forum for being a drudge. Can it and move on, okay?
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Bob, do I have a right to post accurate info on this forum or are you uncomfortable with it?
Jay is a little more open mind than some on this forum.
Send me a PM, if you like, we can continue to discuss what you see wrong.