What is minimum safe piston-to-head clearance for a stock rod 455 with forged Federal Mogul 10:1 pistons (.040") and std weight pins? 6000rpm max.
This link suggests more clearance http://mywebpages.comcast.net/jholthenrichs/weightsn.htm Here are the Blueprint Specs for the big block Buick BLUEPRINTING SPECIFICATIONS 400/430/455 Total Mechanical Timing 32* - 34* Plug Gap .035" Main Bearings .0015" - .002" Rod Bearings .0015" - .002" Cam Bearings .001" - .002" Piston to Valve - Intake .080" Piston to Valve - Exhaust .100" Valve to Guide .0015" - .002" Lifter to Guide .0008" - .0015" Pin to Piston .001" Rod End Play .006" - .010" Crank End Play .004" - .008" Minimum Deck Clearance .000" - .030" Cam to Cover .002" - .004" Retainer to Guide .060" Oil Pump Gear .003" - .006" Pump Gear Side .002" - .005" Lifter Preload .045" (With adjustable pushrods you want 1/2 to 3/4 of a turn past zero lash.)
I would stick with the blueprint specs. The exhaust valve expands due to the heat that passes it therefore a larger clearance is required. Royden
I just inspected my main and rod bearing clearances last week, on a 455 block based Buick 462. The 1970 "All Series" Chassis Manual I have, under Group 60, Section B, paragraph 60-3, Engine Dimensions and fits, states that: b. connecting rod specifications Bearing Clearance (limits).......................0002" - .0023" Section 60 paragraph 60-2, b- Checking clearance and selecting Replacement bearings, subparagraph 6 says: 6. The desired clearance with a new bearing is .0002" to .0023" In case that seems like a typo, under "engine dimensions and fits" In the same section, paragraph 61-3, crankshaft bearings and seals, has a sub-paragraph under 'a. replacement of crankshaft bearings', which is sub-paragraph 13, wich says: 13. the desired clearance with a new bearing is .0007" to .0018" (455 cu. in.) In the engine dimensions and fits section, 60-3, it calss for the same clearnace limits, .0007" to .0018" for the main bearing to journal clearance. I am not trying to call anyone a liar or anything, please understand. It's just that I did this last week with the chassis manual as my guide and these numbers for blueprint specs in this thread are nothing like what the manual calls for. The manual calls for tighter tolerance. Where did these 455 blueprint specs come from?
Guys, he is looking for piston to head clearance aka quench distance.. and the answer given first is correct. With steel rods you should be fine with .030-.040
Roger that, Jim Can you shed light on those blueprinting specs? I hate to say this, but don't some of those clearances seem too sloppy? Are those 'optimum' clearances? How can they be so different from the manual's numbers? I'm really confused by that spec list
Chris, Put your motor together at .002 on the mains and rods, and you shouldn't have a problem. I will go as high as .0027 on more of a race motor, but don't rarely build anything under .002. The factory specs were designed for the factory electra motors mainly, and that's a very different application than we have here. If you find a copy of the Buick "Specs for Hi Performance and Heavy Duty" applications for the 455, dated around '71, you will see that the recommended rod spec was .002, if I recall correctly. I have not read my copy in a while, but I remember it stuck out to me when I first read it, because it was very different than the "book spec". .002 to .0025 works just fine on the mains/rods of Street Driven Hi-Perf 455's.
Hmm, I never knew that. Electra motors! As things turn out, .002" is exactly what I got on all rod clearances, and right on the "hide side" at .0018" on the mains, which is right where my machinist put things 5 years ago. I think I should be all set. Thanks for the confirmation :TU: I may even get to drive it with the new cam and Stage 1 heads before I put it away!
