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1st engine build need help
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Pruneman99
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PostPosted: Thu Feb 22, 2018 5:18 pm    Post subject: Re: 1st engine build need help Reply with quote

Small chambers and high compression would be useful to someone building a race engine N/A on race gas or building an E-85 engine. I wouldn't try using those on a street engine. If you must, dishing the pistons would be better than running big deck heights.

You need to mock up your engine and set your deck height .04-.06. enter that into a compression calculator. Play with combustion chamber CC's until you get the compression ratio your chosen cam calls for. Order heads with the correct CC's.

Or

Slap it together and hope it's not a dog, pings badly, or melts itself.
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FeelthySanchez
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PostPosted: Thu Feb 22, 2018 5:27 pm    Post subject: Re: 1st engine build need help Reply with quote

I'd suggest sending all the parts to a shop (like Roy's) that can properly handle the needed mods.
Piston crowns are solid, about 8-10mm thick, so it's very doubtful that a light cut will harm them.
Bob Brugge wrote:
I am interested in getting the pistons dished, but doesn't that weaken them a bunch?

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modok wrote:
I would like if you had enough clue to communicate what you are doing.
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Enough clue..Whats that mean?
OldIronSpine wrote:
I'm not sure how compression works.
Turbos don't produce torque, they produce HP. Instead of torque.
The real problem with NA engines is you don't hear the nice whine of the turbo as it spools up.
Before I commit, I'm going to do more research because I don't really know what piston rings are.
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Bob Brugge
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PostPosted: Sat Feb 24, 2018 10:47 am    Post subject: Re: 1st engine build need help Reply with quote

My favorite vw mechanic says the jugs are designed to fit to stock spec, etc. I want to measure stuff so I know how to do it, so I borrowed a caliper. Having spent half of my adult career as a carpenter I understand how to measure things or so I thought.
Every time I measure something (measure twice cut once!) I come up with a different number. Not radically different, but different none the less.
For instance, the same head in the same spot measures 93.16mm 94.59mm and 94.05mm. Same thing with deck height using the depth gauge, making sure as I can that it is plumb or level off of the cylinder I get .042, .062, .056, .048 on the same cylinder at the same spot.
I try taking the measurement while rotating the crank shaft a few degrees each way past TDC as well as feeling when the crank has the piston @ TDC and I can't get the same measurement twice.
I am using em 1502 digi caliper and I have no instructions.
Any tips from the Pros? I try to keep the tool square, plumb, or level with the work. Not sure what else to think of.
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Pruneman99
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PostPosted: Sat Feb 24, 2018 11:05 am    Post subject: Re: 1st engine build need help Reply with quote

Your deck height is right where it's supposed to be. Get heads with some chamber, and your golden.

Measurements take practice and a light touch. I still have to measure 3-4 times to get an acceptable measurement. Notice I said acceptable, not accurate lol
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Bob Brugge
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PostPosted: Sat Feb 24, 2018 11:09 am    Post subject: Re: 1st engine build need help Reply with quote

Pruneman99 wrote:
Your deck height is right where it's supposed to be. Get heads with some chamber, and your golden.

Measurements take practice and a light touch. I still have to measure 3-4 times to get an acceptable measurement. Notice I said acceptable, not accurate lol


So what do you do, average them?
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Pruneman99
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PostPosted: Sat Feb 24, 2018 11:14 am    Post subject: Re: 1st engine build need help Reply with quote

I just keep measuring until I get three readings within a thou.
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modok
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PostPosted: Sat Feb 24, 2018 2:26 pm    Post subject: Re: 1st engine build need help Reply with quote

Put a 1" or 1/2" parallel across the cylinder and measure down from that right in the center. Set on flat surface and zero, move to cylinder.

You can't measure well at the edge because pistons rock.
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SRP1
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PostPosted: Sat Feb 24, 2018 5:10 pm    Post subject: Re: 1st engine build need help Reply with quote

Bottom line, set the deck to .050" and buy 52cc heads. Puts you right at 8.0:1 and with that deck and stock cam it will be set up perfect. Anything else is just going to be a headache. I know it's going to cost more, but in the long run it's the only really good solution.
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Bob Brugge
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PostPosted: Sat Feb 24, 2018 11:20 pm    Post subject: Re: 1st engine build need help Reply with quote

Modok, I don't understand. Can you explain please?

SRP, like using the caliper I can't get the same measurement twice with cc'ing the heads. I can't get the head flat in both directions to get the chamber to fill evenly + surface tension screws me up too. I tried making a disk to put in the chamber and that really confused things. Thinking about seeing if lowes has a 6x6 piece of plex I can get and make a disc for it.

Any other suggestions to get more accurate readings and measurements? If I can't get this right I am rally leary of doing the bottom end. I know all the how to theory for the last 45 years, done very little of it despite busting knuckles as a pro for 5 years.
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Pruneman99
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PostPosted: Sat Feb 24, 2018 11:41 pm    Post subject: Re: 1st engine build need help Reply with quote

Sounds like you might be struggling due to not having the right tools. For CC measurements, use something like this:

http://carcraftstore.com/headccmeasuringkit.aspx

Decent calipers help over the bargain basement cheap ones. You don't have to get crazy. I think I got mine a HF and they are usable.
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66brm
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PostPosted: Sun Feb 25, 2018 12:11 am    Post subject: Re: 1st engine build need help Reply with quote

Use an old CD as a disc for ccing heads, they still have them right? Something by Mariah Carey, or similar, just grind it down till it sits flat in the cylinder register
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modok wrote:
I am an expert at fitting things in holes, been doing it a long time
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modok
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PostPosted: Sun Feb 25, 2018 12:39 am    Post subject: Re: 1st engine build need help Reply with quote

I mean you need to measure in the center of the piston, so you need a thing to set across the top to measure down FROM, and the thing needs to be flat and parallel. Set on a flat surface and set dial to 0
Image may have been reduced in size. Click image to view fullscreen.

Set on what you want to measure and read the difference.
Image may have been reduced in size. Click image to view fullscreen.

In this case .047", the dial indicator is read backward in this application. I must say it is FAR easier to use the dial indicator in the block than it is trying to use the calipers. Those calipers are very good, about 80$
indicator is 20$ in a 10$ block of material, and works FAR better.
Good tools don't have to be expensive.
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modok
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PostPosted: Sun Feb 25, 2018 1:26 am    Post subject: Re: 1st engine build need help Reply with quote

Even better. You can use calipers as a step gauge like THIS
Image may have been reduced in size. Click image to view fullscreen.


Get the same answer three ways now you KNOw you got it!
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Bob Brugge
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PostPosted: Sun Feb 25, 2018 7:53 am    Post subject: Re: 1st engine build need help Reply with quote

Mpdok I got it Brother, thank you.


66 I will see if I can fin an old cd and give that a whirl Thank you too!
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PostPosted: Sun Feb 25, 2018 10:45 pm    Post subject: Re: 1st engine build need help Reply with quote

Tell me if this is horribly wrong?
I measured the deck height as Modoc suggested In the center, using a stand off
For cyl 1 I get .103
cyl2 .0928
cyl 3 075
cly 4 .082
I added these numbers and averaged them at .082 deck height. With a 46cc cyl chamber I show 8.2:1 comp
Is that any where in the realm of close?
I got the numbers for the deck height by measuring in the same place 5 different times, never got the same numbers twice, but they were close, so I averaged them.
I used a cut up cd that fit snug in the head and filled it w/ water, can't believe how slick that works! My heads CC within a CC or two of each other So I am guessing thats easier to not screw up than a device you have to know how to use.
Am I close?
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Danwvw
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PostPosted: Sun Feb 25, 2018 11:41 pm    Post subject: Re: 1st engine build need help Reply with quote

It's a lot what is it supposed to be? I would install the studs and then some spacers don't over tighten then measure.

Image may have been reduced in size. Click image to view fullscreen.

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Pruneman99
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PostPosted: Mon Feb 26, 2018 12:29 am    Post subject: Re: 1st engine build need help Reply with quote

Bob Brugge wrote:
Tell me if this is horribly wrong?
I measured the deck height as Modoc suggested In the center, using a stand off
For cyl 1 I get .103
cyl2 .0928
cyl 3 075
cly 4 .082
I added these numbers and averaged them at .082 deck height. With a 46cc cyl chamber I show 8.2:1 comp
Is that any where in the realm of close?
I got the numbers for the deck height by measuring in the same place 5 different times, never got the same numbers twice, but they were close, so I averaged them.
I used a cut up cd that fit snug in the head and filled it w/ water, can't believe how slick that works! My heads CC within a CC or two of each other So I am guessing thats easier to not screw up than a device you have to know how to use.
Am I close?


The deck heights in that range are in the no-no range. You need longer rods, or get the cylinders turned down. Those measurements are twice the measurements you stated before, but now I see the first measurements you were measuring of the side of the cylinder on the edge of the piston. Definitely need to measure in the middle, right over the pin.

The measurements the second time seem a bit odd, where the rods rebuilt, or new?
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Bob Brugge
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PostPosted: Mon Feb 26, 2018 8:03 pm    Post subject: Re: 1st engine build need help Reply with quote

Pruneman99 wrote:
Bob Brugge wrote:
Tell me if this is horribly wrong?
I measured the deck height as Modoc suggested In the center, using a stand off
For cyl 1 I get .103
cyl2 .0928
cyl 3 075
cly 4 .082
I added these numbers and averaged them at .082 deck height. With a 46cc cyl chamber I show 8.2:1 comp
Is that any where in the realm of close?
I got the numbers for the deck height by measuring in the same place 5 different times, never got the same numbers twice, but they were close, so I averaged them.
I used a cut up cd that fit snug in the head and filled it w/ water, can't believe how slick that works! My heads CC within a CC or two of each other So I am guessing thats easier to not screw up than a device you have to know how to use.
Am I close?


The deck heights in that range are in the no-no range. You need longer rods, or get the cylinders turned down. Those measurements are twice the measurements you stated before, but now I see the first measurements you were measuring of the side of the cylinder on the edge of the piston. Definitely need to measure in the middle, right over the pin.

The measurements the second time seem a bit odd, where the rods rebuilt, or new?


Neither, I am using the same short block that started as a stock 1600 sp when I bought the car, then became a 1641 sp and now is becoming a 1679 dp, but only because I have all the parts.
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Bob Brugge
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PostPosted: Tue Mar 13, 2018 8:44 pm    Post subject: Re: 1st engine build need help Reply with quote

I am still having a hell of a time getting consistent readings.
I bought a brand new digital caliper.
I got the kind with the depth gauge.
I drew a dot dead center of the piston
I am making sure the cylinder doesn't ride up when i move it.
I was using a pushrod as a stand off since they are about as uniform as anything else I have and thought maybe the curve of it was causing incosistencies.
So I got a piece of angle Iron I have and marked a dot on it to line up with the pistons dot and tried measuring again
push the piston down a little in its bore, hold the tool so that when the piston rides up it will push the depth gauge up, let the piston go past tdc. Check the measure ment, reset the tool, re roll the engine past tdc and see what it says.
I have tried re zeroing the tool after every measurement, I have tried closing the jaws with no re zero and I tried just opening the jaws back up. I get about a .031 difference between highest and lowest number. I even tried drawing a center line on the angle Iron in case I wasn't holding the tool square.
What am i not doing right here? Do I need to bolt the cylinder down to get the most consistent readings?
What do you guys do when you take the deck height measurements?
Does it matter if the rings are not installed? I am hesitant to install them as I am not super skilled at using a ring compressor. I already broke one or two rings and had to get a new set. I am operating under the premise that what ever tiny bit of rock the piston would have would be offest by measuring dead center of the piston. one set of rings already set me back $65.00 and I am not super excited to tell the wife I need yet another set when I break another one trying to get the cylinder on the piston yet again when I figure out if I need a shim or a turn down.
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Last edited by Bob Brugge on Tue Mar 13, 2018 8:52 pm; edited 1 time in total
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PostPosted: Tue Mar 13, 2018 8:49 pm    Post subject: Re: 1st engine build need help Reply with quote

are you sure your cylinders aren't hitting the case nuts?
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