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i just redid my static compression and it came out to about 9.76 with the Dish pistons and 10.32 with Flats tops with 4 reliefs.
Out of curiousity, what specs did you use to calculate your compression ratio?
Head gasket thickness and bore,
piston deck height,
piston dish/valve relief volume,
The rest would include a 4.030 bore and 64cc Vortec heads.
Out of curiousity, what specs did you use to calculate your compression ratio?
Head gasket thickness and bore,
piston deck height,
piston dish/valve relief volume,
The rest would include a 4.030 bore and 64cc Vortec heads.
I said .018 thick gasket as ill be buying one that is supposed to be that small compressed. Deck height i used .025. dish volume i put 10.00 b/c i was told a typical dish piston is about +10.00. Did i do it wrong?
No. Not at all.
I was looking at the 10.3:1 with the flat top pistons. I use a Speed Pro piston with 4 reliefs and my CR is 9.9:1. However I'm using a .026" thick gasket which brings the CR down a few tenths.
You'll want a fairly long duration cam to go with 10.3:1 should you go with flat top pistons.
My XR276HR gives me a DCR of nearly 8.5:1. I find that's about the limit with iron heads. Without 94 octane fuel, I have to pull my timing back and the performance goes away somewhat.
No. Not at all.
I was looking at the 10.3:1 with the flat top pistons. I use a Speed Pro piston with 4 reliefs and my CR is 9.9:1. However I'm using a .026" thick gasket which brings the CR down a few tenths.
You'll want a fairly long duration cam to go with 10.3:1 should you go with flat top pistons.
My XR276HR gives me a DCR of nearly 8.5:1. I find that's about the limit with iron heads. Without 94 octane fuel, I have to pull my timing back and the performance goes away somewhat.
I'm running 93 octane anyways so that's not a problem....
I just figured out how to set my bore guage i think, i set it to read 4.030. And what i got was...... in the wear zones on cylinders 8+4 the gauge read one line to the left of 4.030. so it has a small wear i think.
Here is a pic of the one line past 0....
And here is a pic of most of the other pistons reading..... They read right about 0 and a little to the other side of the gauge, which would be under 4.030....
Also would it be better for a flat top with 2 or 4 valve reliefs?
Nothing inherently better with one or the other (as far as I know). It comes down to a couple of factors. Price and availability vs compression ratio difference. Seeing that a 4 valve relief piston has a minus 5cc volume ( like Speed Pro ) I can't see where 2 valve reliefs will impact things very much regarding your final CR.
Nothing inherently better with one or the other (as far as I know). It comes down to a couple of factors. Price and availability vs compression ratio difference. Seeing that a 4 valve relief piston has a minus 5cc volume ( like Speed Pro ) I can't see where 2 valve reliefs will impact things very much regarding your final CR.
What about my bore measurements? What do you think?
What about my bore measurements? What do you think?
I'm trying to find the out of round tolerances and maximum taper for a small block chevy and haven't found it yet. I may have to go back to my old text books to get the info.
So far from what I've seen with your dial bore gauge, I can't determine if you are within spec.
This web site gives a little insight into what to look for regarding those specs.
This is one of those things where you just have to be there to figure it out.
Not at all.
I wish we were in the shop and going through this on the block itself. I enjoy the work , it's just difficult to work it out in a forum like this. Maybe that website link will provide a little info on what the bore gauge is capable of and what you're looking for.
Perhaps one of our engine building savy friends can provide the out of round and taper data that's needed.
I would just say screw changing the pistons and just stick with the dish pistons but idk if it will have enough compression to run properly... it will be very close if i'm calulating things right....
I wish i could just throw new pistons in there! haha
.. find a shop where you know somebody, and offer 20 bucks to a mechanic to show you how to use it. Any mechanic worth a damn should be able to use it, and show you how.
You might be at this point.
I have taken projects to local high school shops and used them as teaching aids. Any connections?
I would just say screw changing the pistons and just stick with the dish pistons but idk if it will have enough compression to run properly... it will be very close if i'm calulating things right....
I wish i could just throw new pistons in there! haha
That's an option for sure provided those cylinders aren't really out of whack.
I've seen more than one rebuild (a couple of mine included) that involved nothing more than cylinder deglazing and re-ringing. Can't say they lasted forever but they were reasonably durable.
Just double check your DCR measurements to make you're not building a dog.
Well i figured out from one of my friends that they know a machinist who does work but is not a big business. I am going to call and ask how much for a cylinder hone. But i want to take my block to him to ask if i can just have him hone it and put new pistons in it. Basically have this guy check the cylinders to see if they are wore ok or not.
Assuming that you have set up the gauge right, I would venture to guess that you are going to be ok with a deglazing and new pistons and rings. If you are not showing wear at the thrust point of the cylinder walls then I would be surprised to find any taper at all on the cylinders. You do need to turn the gauge and measure 90 degrees from where you are now. You must verify that they are all still round. If they measure the same that way, I think you will be ok with new pistons and rings.
Assuming that you have set up the gauge right, I would venture to guess that you are going to be ok with a deglazing and new pistons and rings. If you are not showing wear at the thrust point of the cylinder walls then I would be surprised to find any taper at all on the cylinders. You do need to turn the gauge and measure 90 degrees from where you are now. You must verify that they are all still round. If they measure the same that way, I think you will be ok with new pistons and rings.
I did measure crossways on the cylinder and they all same out about the same. didn't vary more than a line on the gaage either way. How do you deglaze a cylinder? Thanks
I did measure crossways on the cylinder and they all same out about the same. didn't vary more than a line on the gaage either way. How do you deglaze a cylinder? Thanks
You use what the older guys would call a dingleberry hone. Its a hone that has a bunch of balls on the end of it. Its also called a ball hone. You chuck it up in a cordless drill and use a lubricant(I have always liked using ATF) and have at it. Your goal is to break the glaze on the cylinder walls to help the new rings seat properly. The crosshatch pattern will depend on you and the speed you move the hone up and down the cylinders. I greatly prefer a dingleberry for this over the stone mounted honing tools, though that is just me.
They look like stock pistons. A internet search (or someone on the forum) should have the dish values. What I did find was a Goodwrench 350 that has a dished piston which looks similar to yours. With a 76cc combustion chamber it yields only 8:1. Check out this article to see how similar your build is to start with.
They look like stock pistons. A internet search (or someone on the forum) should have the dish values. What I did find was a Goodwrench 350 that has a dished piston which looks similar to yours. With a 76cc combustion chamber it yields only 8:1. Check out this article to see how similar your build is to start with.
Well i have a deck height of .025 i think, 5cc flat tops(when changed), .018 head gasket, 4.030 bore and 3.48 stroke. That where i got my 10.32 static and 8.09 dynamic.... That's with the XE274 figured in.
Another question, changing to flat tops will i have valve clearance issues? Or does all that have to do with the lift from the cam?
k, i have to say this. from the questions your asking, and the knowledge that has been given to u, i think its in your best interest to just take your shlt to the machine shop and have him tell you if you can get away with a hone.
as for clearance issues, that would be a problem if u have a big cam, witch i dont think you have to worry about
k, i have to say this. from the questions your asking, and the knowledge that has been given to u, i think its in your best interest to just take your shlt to the machine shop and have him tell you if you can get away with a hone.
as for clearance issues, that would be a problem if u have a big cam, witch i dont think you have to worry about
I don't much appreciate the underlying message that i'm stupid, i can see that's what your saying. I am making sure i am doing this right, i'm not too brainy on the engine building side, i can fix whatever i want to, but when it comes to the complicated and touchy insides of a motor i get nervous and want to make sure i'm doing it right. Thats all.... I called a machine shop, they said $110 for a hone.... is that too much?
not trying to be a dik, just saying it might be in ur best interests to have a pro's opinion/guidence.
110 for a hone i assume they are checking tolerances, and what not, prolly worth it. but like skinny said, this is something that u need to be guided on a personal basis, not via the web.
I am planning on having the bore checked and honed if its ok, If so i'll have the machine shop hone it and i'll purchase the pistons and have them press them on b/c i'm assuming they are press fit. Than i think i will have them machine the rod bolt holes to fit the ARP bolts.Thats my idea so far....
the out of round limit is .001 for a new block or one major division on that gauge you have... and is a total measured dimension. start by taking measurement at the same height around the bore find the measurement that has the needle farthest to the left of zero then move the zero to line up with the needle... that will be the smallest point of the cylinder now continue taking measurements around that height any measurement that goes past one major division to the right of zero is out of tolerance.
taper is a more dificult measurement do to the assumtion that more wear occurs on the thrust side however you can assume that the cylinder wall is straight except for the thrust side again you need to find the smallest diameter and zero your indicator then take measurements perpindicular to the thrust side done the bore the limit is one minor division for the length of the stroke
the out of round limit is .001 for a new block or one major division on that gauge you have... and is a total measured dimension. start by taking measurement at the same height around the bore find the measurement that has the needle farthest to the left of zero then move the zero to line up with the needle... that will be the smallest point of the cylinder now continue taking measurements around that height any measurement that goes past one major division to the right of zero is out of tolerance.
taper is a more dificult measurement do to the assumtion that more wear occurs on the thrust side however you can assume that the cylinder wall is straight except for the thrust side again you need to find the smallest diameter and zero your indicator then take measurements perpindicular to the thrust side done the bore the limit is one minor division for the length of the stroke
Just so you know i set the bore gauge on the cylinder head to try to get it flat b/c i don't know how to hold it straight... but if you look at the picture of the cylinder gauge when i tried your idea in cylinder #4 i got 2 lines right of the 0.. and i also tried it on cylinder 7 and i got just under one line to the right.... Does it need a bore? What do you think? I think i will take it to a machine shop i'm terrible at this haha.
it is hard for anyone to give you an answer without actually being there to take the measurement... your best bet is to take it to a shop and have it measured... if you decide that it needs a bore wait until you purchase pistons that way they can get the piston to bore clearance inspec.
I also figured out my piston deck height is .035... a lot higher than i thought... Should i try to have the heads shaved a little? or will i be ok with flat tops, vortec heads, .018 inch head gasket, etc.?
again no way to say for certain if the wrist pin sits a bit lower on the new pistons you might be in decent shape or not... however you could always have the block decked... much simpler than having the heads worked on especially if you are going to have the block honed
I also figured out my piston deck height is .035... .?
I'd double check that piston height measurement.
I've been told that factory specs can be anywhere from around .025 to almost .050 below deck however I've never seen much more than .025 firsthand.
That will be a significant factor in your CR calculations.
my first block was a 4bolt mexican block those pistons sat at .042... i was very depressed... but when i installed my scat rods and KB hyper flattops they were only .028 in the hole which worked out perfect with 64cc vortecs and a .015 gasket
I also ordered forged connecting rods with ARP bolts already installed,ARP main bolts, Summit brand 4.040" pistons, and rings. They will be delivered tomm. (3/17/09) and i will be taking the engine to get re-bored tomorrow.
you need to hook up a return to the secound outlet it should say return somewhere... you dont want to just plug it as it will greatly shorten the life of the pump
Not the bolt holes, but the bore of the 'big end' that fits over the crank journal. Once the bolts are pressed into the rods, that can distort the big end a bit - resizing it just 'trues' the hole, more than anything. Sorta the same idea as line honing a block.
I just noticed... that block in the pics has all the provisions and machining for a factory roller cam setup. Why not get the spider and factory type lifters (they are pretty cheap) and get a roller cam instead?
Not the bolt holes, but the bore of the 'big end' that fits over the crank journal. Once the bolts are pressed into the rods, that can distort the big end a bit - resizing it just 'trues' the hole, more than anything. Sorta the same idea as line honing a block.
I just noticed... that block in the pics has all the provisions and machining for a factory roller cam setup. Why not get the spider and factory type lifters (they are pretty cheap) and get a roller cam instead?
B/c a roller cam is about 3 times as much as a flat tappet. With little gains over flat tappet from what i hear.....
you need to hook up a return to the secound outlet it should say return somewhere... you dont want to just plug it as it will greatly shorten the life of the pump
Won't it not really matter due to the fact that the reg will be downing the pressure, won't all that will be returning to the tank very low pressure? Or does it really help that much? Not judging just curious. Thanks
Also is it easier to just stick with the in tank pump then getting a FPR/guage/adaptors vs putting in a pickup line and using an external electric fuel pump that designed to be low pressure already?
the regulator will be cutting the pressure to 1 port only down to 7psi or so once that preassure is meet it needs to do something with the rest of the fuel as the pump is running constantly so the best thing to do is return it to the tank where it can be cooled and help prevent vapor lock and premature pump death
