Thread: 454 rod bearings

Tweet

howdy folks,i have a 12 to 1,square port,balanced,external oil & heat,fuel injected,ect.. in a boat.rebuilt it 3 times,it keeps spining rod bearings,three thousenths clearance at assembley.any ideas as to what i am doing wrong?

What has it got for oil pressure? Does it vary much before the rods go? How many RPM is it turning? Exactly what kind of "external oil" system?

oil pressure does not flucuate,60 + @6500,oil system is external,it hase a pre heat & pressure tank,for initial startup,buzzed up to 8500,everything felt good,let off throttle,she came apart.

r pope,thats alot of rpm for a big block?she hase all the good parts.should'nt she be able to twist that tight?

if you have good set of rods you can get to them rpms 7800 that is hi. 8500 is to hi .003 is good for the clearance but what rods are you useing? and bearings ? the big end of the rod will want to move and this may be some of the problem the bearings will grab the crank and at this rpm the oil may have to much air in the the oil .so you need a good pan the a aero-wing conterweigt crank this will cut down on windage .and the mass will have to be very light why do you think you need to run it this hi??to go this hi you you need the very best rods steel billets or titanimum or a set of alloyed rods very good pistons and a light crank at 8500 rpm s a crank that is 80 pounds this hard on the bottom of the block with good parts 7500 rpms is much better the lower the rpm the longer it will live and you valve spings will last a lot longer

.003" is kind of loose. .0015-.002" is ideal. Have you considered cross drilling the crank? Normally, the rod bearing is only lubed for half of a crank revolution.

here is some thing to think about were is the size on the housing bore of the rod? you want this on the small side this keeps the bearing bedded in the rod housing hi crush and i see this is dry sump you could go up to .003.5 to.004 on the rods and turn up the oil psi to 75 psi to 80 and go up on oil 50 weight at 004 on the rods

no it is not lose built a lot of big blocks 002.7 003.5 you can not run them as at 0015 to 002 they will srue come a part i built a lot of them the bore on the rod moves and the main caps you need more room for this

Are you saying you took it to 8500 on initial startup? Yes, 8500 is a lot of rpm for a big block, or anything else,actually. For that kind of revs, you want to break it in good, and have top drawer components (which you seem to have). The crossdrilling idea would help, but in your case, failure seems to have come too soon for that to help. Are the rods distorting? Like, the ones that don't spin the shells, do they need resizing again?

8500 on startup?no sir.the first time she gernaded,it looked like it streched a rod bolt,or lack of oil to rod bearing,i'm not sure yet.(i'm leaning towards lack of oil).the second time,pulled the rod bolt through rod cap.do they need resized?boy howdy!!!!!! do they ever,she twisted em up like a predzel.here are the parts,4340 lunati,h-beams,je pistons,arp 7/16,childs & albert.

there is no break in on race engines . the rings seat in the walls and you are ready. and i hope your are useing a cross drilled crank and 3/4 groove main bearings i use the federal moguls and the rod may be moveing and the main caps and the crank is flexing i would bet on it at 8500,thats why you need move clearance on every thing and run the small end pin boss to 0001 at least i not a big fan of the lunati rods great for lower rpm the crower is better they have the clover pattern on the big end of the rod puts more steel where you need it and you should be using L19 bolts or 2000 or better your mass is to heavy for the rod to keep on the crank. and this WORKS ON THE BOLTS AND THATS why YOUR RODS LOOK like predzels and try to turn up the oil psi this will not hurt