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  #16 (permalink)  
Old 06-16-2010, 12:19 PM
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I'm guessing that your prices are Canadian? which would explain some of the seemingly highish prices.

.001" of cylinder taper is fine for a street car, ie a car that is not raced to put food on the table.

To zero deck a block easily, you have to mock it up. To just index the deck surfaces and cut to a specific dimension does not, and would be fine for most applications. Your pistons have a reduced pin height location, resulting in the .020 clearance even after decking. That much off the deck will not hurt anything.

I would be concerned about the main cap walk issue and would be putting studs in and have the caps tightened up and align hone the block.

The .0006 runout is marginal and I would make my decision based on the specific measurement: is it .0006 under the 2.100, or is it under/over the nominal dimension.

The .0025 number for piston to wall sounds like a minimum clearance so you might want to look at that a little closer.

I only use the Trimetal M77 style cam bearings and would not recommend try to scrimp there.

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  #17 (permalink)  
Old 06-16-2010, 05:28 PM
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No Worries

[IMG] installed the crank and a rod and piston in all 4 corners and measured the differences in piston to deck heights. Well it turns out that one corner was 0.022 in the hole while the other three were 0.020" in the hole.[/IMG]

Hey 383, First no one is hollering at you. We're all just outraged with these machinist, plural...
Secondly, when I read your comment it registered in my head that you were zero zero zero and +.002", Rather than .020" and .022". At most the guy just flattened the deck, Wasn't gauged or really cut...

But you're right, a coated steel shim gasket will give you reasonable quench. And I think the cylinders sound like they would pass. Just don't kick it too hard for 5 or 7 hundred miles, and give it time to fine machine itself; Which we're suppose to do anyway, and you'll be better than all right. Sounds like you've put in your time and done you homework.. It's going to be fine... And now you know you have a hundred techs on the case too! No Worries
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  #18 (permalink)  
Old 06-16-2010, 05:48 PM
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And Another Thing!!!

Just kidding with the all caps...

Did I miss some something BIG.??..

Did the first guy bore this engine to your new oversize pistons? Don't think you said!

Because if you are in an existing bore which may or may not have worn to a 1.540ch, or a 1.56, or 1.563". Not to mention variations in top ring heights from brand to brand and from # to #.
Did I just miss that or is it generally unknown to the whole team?
Duntov
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  #19 (permalink)  
Old 06-16-2010, 06:20 PM
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The second shop does bring up valid points that in the right circumstances can be issues of concern. I would politely tell him thanks for his observations, and only let him deal with the matters you went to him with in the first place. Then you should return to the shop that did the work originally, and point out your finding, especially about the zero deck issue, and see his reaction to this, and then slowly reveal the other discrepencies such as the cylinder taper and see if he is willing to rectify the situation for free, since if it is wrong, he should be willing to make it right.
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  #20 (permalink)  
Old 06-16-2010, 06:57 PM
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Can you give us the bore history?

Quote:
Originally Posted by weedy64
did you just rehone and hope you were lucky or was this bored to suit?
See, I'm not the only one who feels the need to know the circumstances leading up to the current bore condition.
I had the feeling it went a thousand miles on the first build, which included an overbore of some kind.. and possibly, now different pistons? Surely we're not working to a STD bore?
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  #21 (permalink)  
Old 06-16-2010, 08:47 PM
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Thanks again for the help here guys. Ok to answer the first question these are wiesco pro-tru forged pistons. To answer the second question, the original build (that went 1000km) was a true 383 (bored 0.030" to give me a bore of 4.030"). For the rebuild I bought 0.040" over pistons and had the cylinders bored to 0.040" and torque plate honed. So if there is any taper it would be their fault because they bored to 0.040" and honed. I plan in the next few days to measure all of those measurements again MYSELF to verify the second machinists findings. I told machine shop #1 to deck the block to 9.000", which should be zero deck, correct? Regardless of how deep in the hole the pistons remain after that decking, they should all be the same distance in the hole if they did this correctly? I just looked and I was mixed up on my numbers machinist #2 gave me (too many numbers flying around). The left bank is both 0.025" in the hole at both corners and the right bank are both 0.020" in the hole at both corners. Like I said I will double check this as it seemed to me he was doing this very fast and may have got an inaccurate reading. It would seem to me though that if I asked for the block to be decked to 9.000" then both sides should be the equal distance from the crank centerline, not one side 0.005" higher than the other. Do I have a valid point here and reason to pay them a visit because if they didn't do the work properly I am going back asap. It appears the decking issue should be rectified, as well as the main cap issue (you do have to put all your weight on the cap to get it to "SNAP" into place which I don't see unusual. Anyway I'll get back to you guys with MY measurements and if you need any more info please let me know.

Thanks,
Keith
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  #22 (permalink)  
Old 06-16-2010, 09:09 PM
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After all is said and done- Summit sell a fully prepped 383 4 bolt for less than 600 bucks.
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  #23 (permalink)  
Old 06-16-2010, 09:42 PM
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4.040"

Ok,
Now I'm satisfied. Yeah, That deck has to be trued up; That's for certain.
I think first I would check my rod length, and verify the pro tru pin height. A dial caliper from top of the big end, to bottom of small end, checking several times making sure you got the shortest measurement because it's not a precise way to do it, but it'll be close and whatever it reads it should read all eight the same. (I wouldn't be shocked if there was a length variation of .001" to .0014ish)

Rod big end 2.225" /2 = 1.1125"
Small end .927" /2 = .4635"
Add both these #s to the rod length reading.. That's your center to center rod length, or very close.

Next manually check pin height with caliper from piston deck to bottom of pin, w pin inserted. subtract .4635" That's your actual pin height/ch. Maybe quick check 'um all in case there's something weird going on with mismatched left and right bank piston #s.

Add rod length and C/H to get assembled piston rod combo length. Now If your crank stroke is 3.75" half that is 1.875"

Typical #s might be 1.875" +6" + 1.125" = 9"

If your numbers add up to 9" and you are sitting 20 and 25 deep, then I would go ahead and deck it to about 9.005" if it were me, cause 99.99%, it hasn't been cut any more than it appears to have been.

It's easy enough to measure the remaining deck thickness to be sure you don't have a some sort of freak tall deck small block. Never heard of a factory version and doubt it, but I'd check deck thickness anyway.

That' enough for now Duntov s
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  #24 (permalink)  
Old 06-16-2010, 11:33 PM
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Agree^^^^^

The .0025" piston to wall with a nitrous hit on the siamese bore wall 400 bothers me however, I would call Wiseco and make very sure they know exactly how you intend to run it - water temp, cold air package or not, comp ratio, fuel octane so they know the parameters of how it will be existing in the car. If they still feel comfortable with the .0025" figure then run what they recommend.
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  #25 (permalink)  
Old 06-17-2010, 02:28 AM
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383SBC is working w/a 350 block, not a 400 block.

If the slugs are down the hole, the first shop may have decked the block to 9" (the block is stock @ 9.025"), and the piston's CH is the cause of the piston being down the bore instead of even to the deck. It was the shops mistake if the pistons were 1.400" CH and not 1.425" (assuming 5.7" rods)- but if this IS the case, it would have taken a special order piston from Wiseco, all I see from them is a "standard" piston for the 5.7" rod 383/385 (0.040" over) of 1.425" CH.

So, it looks to me like the first shop dropped the ball on the decking.

As for the second shop- if they were to have been instructed to "Check Everything" on the block and reciprocating assembly, the report they gave the OP would be as expected- every deviation from the ideal was noted.

If it was a fishing expedition on the second shop's part, to try to part this guy from his money, that's another issue altogether. It depends on how it came about, IMHO.
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  #26 (permalink)  
Old 06-17-2010, 02:41 AM
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Wiseco says:
Q. What kind of piston-to-wall clearance can I run?

A. The factors that affect this are cylinder wall thickness, whether the block is filled, the overall compression height of the piston, piston material and thickness, and whether a marine engine is to see fresh-water cooling.

Most small blocks get .004 piston to wall clearance and most big blocks get .005 due to the use of our 2618 high-strength alloy.

For heavy blower and nitrous applications, Wiseco recommends adding .001 to the standard clearance.

Special note: Clearance numbers are obtained from measuring the largest diameter of the piston, typically at the bottom of the skirt. All measurements should be taken 90 degrees from the pin centerline."

I see no mention of what alloy is used in the Pro True forged off-the-shelf pistons, a call to Wiseco for P to W clearance recommendations for nitrous use is recommended in any event.
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  #27 (permalink)  
Old 06-17-2010, 05:54 PM
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Thanks for the replies and investigating. A couple things. I am running 6 inch rods so these are the pistons I have. http://www.summitracing.com/parts/WIS-PT017H4/
They have a 1.125 compression height so technically I should be right at 9" (1.875+6+1.125= 9.000"). I will do as you say and measure each connecting rod and piston to ensure they are accurate before raising hell. None the less both decks should be the SAME distance from the crank centerline after I had them decked, correct? For one to still be 0.005 higher than the other means that it couldn't have been done using an arbour through the main caps and a grinder (whatever it is they use) set to 9". I am buying the measuring tools necessary for these measurements tomorrow and will get back to you with my results.

Keith
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  #28 (permalink)  
Old 06-17-2010, 06:20 PM
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Quote:
Originally Posted by 383SBC
Thanks for the replies and investigating. A couple things. I am running 6 inch rods so these are the pistons I have. http://www.summitracing.com/parts/WIS-PT017H4/
They have a 1.125 compression height so technically I should be right at 9" (1.875+6+1.125= 9.000"). I will do as you say and measure each connecting rod and piston to ensure they are accurate before raising hell. None the less both decks should be the SAME distance from the crank centerline after I had them decked, correct? For one to still be 0.005 higher than the other means that it couldn't have been done using an arbour through the main caps and a grinder (whatever it is they use) set to 9". I am buying the measuring tools necessary for these measurements tomorrow and will get back to you with my results.

Keith
The factory machines the main bearing bores slightly off center as a means of quieting the engine as pistons come off their thrust sides. This has the effect of making one side of the cylinder block appear shorter than the other.

Exactly what do you intend to do with this engine? The dimensions you're chasing are inside the purview of a competitive race motor that's expected to win enough to pay for itself. What you're doing gets really, really expensive, really fast and except for guys where a handful of horsepower at 8000 RPM makes the difference of feeding the kids at home or not, these nuance dimensions aren't worth chasing. If you want a balls on race engine, you're going to have to start with something a lot better than a production block. Continuing to shave on it is a zero sum game, as I said a while back the more material you take off, not only thins your wallet, but weakens the castings. You'll soon reach a point where regardless of the precision in machining, the block will never hold on to the dimensions when you start it up.

Bogie
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  #29 (permalink)  
Old 06-17-2010, 07:53 PM
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Every spec you listed is better than mine was when I put it together. My cam has .630 lift, no special cam bearings. No special bearings anywhere. Dynoed 583 at the wheels. Revs to 7800 rpms. Put over 5000 miles on it and still no troubles of any kind.

Just my $0.02
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  #30 (permalink)  
Old 06-18-2010, 12:31 AM
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Quote:
Originally Posted by CNC-Dude
The second shop does bring up valid points that in the right circumstances can be issues of concern. I would politely tell him thanks for his observations, and only let him deal with the matters you went to him with in the first place. Then you should return to the shop that did the work originally, and point out your finding, especially about the zero deck issue, and see his reaction to this, and then slowly reveal the other discrepencies such as the cylinder taper and see if he is willing to rectify the situation for free, since if it is wrong, he should be willing to make it right.
Good advice here, I am willing to bet this new guy has been a little "flexible" with his mic readings. Your original shop can verify whats true and whats not and should only take a few minutes of your time while your present to see the measurements taken.

The wall taper is a non issue and so is the deck height...pistons can easily be out that amount out of the box. The crank should be rounder than 0.0006", that should be addressed but since he "polished" your crank he could have been the one who made them out of round! Polishing means different things to different people but to me it means using a cork based belt and nothing else...it does not remove material. The caps not fitting tight can be fixed in 10 minutes once the caps are torqued on with the crank installed, no big deal...you only need a punch or flat chisel to do this yourself.

No doubt he is covering his butt, although I am skeptical when you look at everything he has an issue with. If it was me I would go back to the original guy and not go back there, he sounds like trouble. I would still verify the measurements though, better safe than sorry...never know he might be doing you a favor. Can you get access to a set of mics and do this yourself? Access to a college/HS machine shop? Would be nice to do the measurements yourself.

Just remember machining anything has to have a tolerance, its not a perfect world. The only measurement that is really bad is the crank out of round, 0.0002" would be a max from me but everytime you cut the journal it gets harder to keep that spec, hard and soft spots show up the deeper you go and it gets harder to maintain them round.

If all you needed was another crank thats not the end of the world, at this point it seems thats the only issue. BTW it will still work fine in a grocery getter but once you get up in rpm it gets to be important, if your staying under 6000 rpm don't worry about it and run it.
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