Engine Builders - Are these the Engine tolerance specs you use?

[fullahotair]

Are the specs on the gntytype.org site the ones that all the engine builders use? Or are there values on here, you like to "tweak" a little? This engine would be for a 10 sec range bottom end. My apologies in advance if this is too broad of a question....

Piston Clearance Limits .
Top Land .046 in. - .056 in
Skirt Top .0008 in. - .0020 in
Skirt Bottom .0013 in. - .0035 in
Ring Groove Depth .
#1 - Compression Ring .185 in. - .194 in
#2 - Compression Ring .186 in. - .194 in
#3 - Oil Ring .188 in. - .196 in
Ring Width .
#1 - Compression Ring .077 in. - .078 in
#2 - Compression Ring .077 in. - .078 in
#3 - Oil Ring 183 in. - .189 in
Ring Gap .
#1 - Compression Ring .010 in. - .020 in
#2 - Compression Ring .010 in. - .020 in
#3 - Oil Ring .015 in. - .055 in
Piston Pin Length 2.900 in
Diameter of Pin .9391 in. - .9394 in
Pin Clearance in Piston .0004 in. - .0007 in
Pin Press Fit in Rod .0007 in. - .0017 in
Pin Direction and Amount Offset in Piston .040 in
Major Thrust Side

Connecting Rod Specifications
Bearing Length .654 in
Bearing Clearance (Limits) .0005 in. - .0026 in
End Play .003 in. - .015 in
Crankshaft Specifications
End Play at Thrust Bearing .003 in. - .011 in
Main Bearing Journal Diameter 2.4995 in
Crankpin Journal Diameter 2.2487 in.
- 2.2495 in
Main Bearing Overall Length .
#1 .864 in
#2 1.057 in
#3 .864 in
#4 .864 in
Main Bearing to Journal Clearance .0003 in. - .0018 in
Camshaft Specifications
Bearing Journal Diameter 1.785 in. - 1.786 in
Journal Clearance in Bearings .
#1 .0005 in. - .0025 in
#2,3,4 .0005 in. - .0035 in
Valve System Specifications
Rocker Arm Ratio 1.55 to 1
Valve Lifter Diameter 8420 in. - .8427 in
Valve Lifter Clearance in Crankcase .0008 in. - .0025 in
Minimum Valve Margin .025 in
Intake Valve .
Head Diameter 1.715 in. - 1.705 in
Seat Angle 45 degrees
Stem Diameter .3412 in. - .3401 in
Clearance in Guide .0015 in. - .0035 in
Exhaust Valve .
Head Diameter 1.505 in. - 1.495 in
Seat Angle 45 degrees
Stem Diameter .3412 in. - .3405 in
Clearance in Guide .0015 in. - .0032 in
Valve Spring .
Valve Closed 90 lbs
+or- 4 @ 1.727 in
Valve Open 245 lbs
+or- 10 @ 1.340 in

 

[Just a Six??]

It's a good guide but anyone that builds a lot of them will have their own preferences of course. Definately a good starting point. Don't think too many guys are going to give away all their secrets on the really fast cars that they spent hundreds of hours testing to get exactly what they like. Also one guys secret may be old hat to others. This is where an experienced builder of the Buick V-6 comes into play & is all part of the price cuz you gotta pay for that knowledge!

Get a copy from the net of the Buick Powersource Manual & they give you many tips & tricks!

 

[$1987 GN$]

Actually it has a lot more to do with what parts you use.

Later AJ

 

[fullahotair]

Thanks for the replies...

I realize certain people will prefer tighter tolerance here and looser ones there, for various reasons based on their experience and superstitions, but just wanted to make sure that even those variances are within these ranges provided by gnttype.org.

Or in other words, would an engine built within these tolerances generally yeild you a sound motor??

I don't know that any two engine builders would agree on all the specs, but I was curious if these ranges post above encapsulate most/all builder preferences...If not, I would like learn about which ones don't....

Thanks,
Nate

 

[fullahotair]

Actually it has a lot more to do with what parts you use.

Later AJ

Fair point. It makes sense that aftermarket parts and their specs would govern over a stock item.


Thanks,
Nate