So I've built a few car engines, but never did my own shortblock. I'm a pretty decent mechanic and while I make plenty of mistakes, I always catch them since I triple check everything!

I put together this LS1 shortblock using an LS1 block and crank from a high mileage C5 I had as a track car. I currently roadrace a Stock Car in the V8 Stock Car roadrace series, but my old Lingenfelter ASA engine was tired and needed replacing.

I initially dropped the crank and block off with my usual machinist back in November but I was waiting on a ton of parts from a buddy who promised me he could get everything at dealer cost. Turns out he couldn't and I waited 2 months for nothing. In January I got started but then machinist #1 was super busy, and is already semi retired so he passed off my stuff to another local shop with machinist #2 for balancing of the bottom end components. I finally got everything back around March and started assembly. I nicked rod journal #1 but polished it all out. When I got the engine completed and ran it, we had very high oil pressure. The mechanical gauge pinned at 110 PSI at 3k rpms. Took the car out at Pocono Raceway to test, and over 4k RPMs the oil was smoking out the breather so we took it home. I figured the problem was the Melling 10296 High Volume High Pressure oil pump. When I drained the oil it was full of metal so I tore it down. Pictures are below but basically Rod Bearing #1 failed. I initially thought this was related to the nick I polished out but when I pulled it apart the rest of the way I found that all the rod bearings were damaged, and the rods were blue from the heat, starting with rod #6 and getting worse as you went forward with rod #1 being the worst. I have a feeling that with all the shuffling around, the rod clearances were never checked. This was supposed to be done by machinist #1 and I remember seeing tooling marks on the main bearings but not sure about the rod bearings.

Failed rod:





Mains look OK





Rod journals all look bad.



Another thing is the thrust bearing. I checked endplay and it was ok, but when machinist #2 looked at it today he suggested that the input shaft could be putting pressure on the crankshaft. He suggested I push the pilot bearing in a few more thousandths. There is no unusual wear on the pilot.



The car is an ASA Stock car, Gforce G101A transmission, 7.25" Quartermaster Clutch. Engine is an LS1, GM LS1 Crank, Callies Compstar H beam rods, Calico coated Clevite bearings, Melling 10296 HVHP oil pump, Razor Scavenge pump with Moroso Dry sump pan and 10 quart sump tank.

Any thoughts or comments are appreciated.

 

What oil weight were you running? Seems like clearances were very tight .

 

Conventional 10-30 for break in. Same as I've always used.

 

I think you already know the issue. I'd bet it was the rod bearing clearance, or at least lack thereof. The high oil pressure would support that too. At least the damage isn't too bad. Looks like maybe a new rod or two and new bearings and have the crank turned .010" or so.

 

Couple of issues here as KCS said "tight rod bearing clearances" without question !!!!
New rods absolutely have to be checked and often need both ends sized for custom clearancing. Usually the pin bushing gets honed a bit to set the pin clearance and then the big ends come at the low limit of size. Most of the shops I deal with here in the Milwaukee area will hone them lightly just to open them a few tenths as well as put a clean, consistent cross hatch finish in the bore. They also check and recheck that the bearing shells when installed in the rods will measure consistent ID" time after time. Repeatability of torquing
Lastly, from what I understand, the coated bearings NEED additional clearance. Like .003" rods and .004" mains (at operating temp) I say that cuz your aluminum block application will open up by at least a thousandth.....so even .003" at room temp on the mains would not hurt anything. Specially with 10 quarts of oil and high volume pump that you run.
Take that crank .010"/.010", have the shop that grinds it size both ends of the rods as well as hone the piston pin bores to set that clearance at .001", and buy yourself an inexpensive bore guage to not only check their work but check the mains. IMO a quality Speed Pro Federal Mogul bearing is all that is needed and leave the coated stuff to the pros who have doezens of sets of them and can play around with mixing and matching to get the perfect clearances

 

Thank you for the advice! I bought most of my stuff from Brian Tooley racing and the coated bearings were all they had. Like I said this is my first short block and I'm in the dark as to what I need. So I'll go with uncoated bearings. Got a forum vendor for them?

 

A lot of LS engines suffer from main bearing clearance issues, but we never see a rod bearing clearance issue.

Could the 10296 pump have sucked the oil pan dry? For 700 HP and less engines we run stock GM pumps, that's what I had on my 705 hp 454 LS7. Even for some applications up to 1000 HP we'll remove the high pressure spring from the 10296 pump and run the lower pressure spring.

 

I think it's unlikely I sucked a 10 quart sump tank dry, and my total capacity is somewhere around 13 quarts. Oil pressure never dropped or wavered. I put in that 10296 pump again because I just didn't know any better, it was just ignorance on my part. I used it on the last 2 motors I built off Thompson shortblocks with no issues but they were both wet sumps. The way the ASA dry sump system works is the engine pump pulls straight from the sump tank, and the scavenge pump sends oil from the pan back to the tank. 2 different machinists had these parts for months and there was allot of confusion. I was also busy completely rebuilding the chassis on the stock car so my attention was elsewhere. When I asked the second machinist yesterday if he checked the rod bearings he said he was under the impression that machinist #1 was going to do it. Both of these guys have been rock solid and great to me over the years, but I think it just got lost in the shuffle.