I got my block assembled by the machine shop and they put my rods at .002 and my mains at .0025 clearance. This is a forged 347 setup (except crank) and I told them it will also be sprayed. Is that too much clearance and will I have any problems? Also what weight oil is recommended?

 

thats what my LS2 418 is clearanced at and runs fine and the oil pressure is at 45psi at idle and 65psi at cruse 55mph. That with a LS6 ported and shimed spring & double o-ringed, oil pump.

 

Your ride is at 45psi when the engine is at operating temp? Which weight/type of oil do you use?

 

Rods are ok. Mains are a little loose. When the oil is hot your idle pressure may be a little low. Machine shops seem to forget aluminum blocks expand more than steel so they should keep the mains at .002 maximum cause when they are at operating temp they are probably at .003. If your oil pressure is ok at higher rpms you will be fine or you could go with a higher volume pump. I would try it the way it is if it was me. Chuck

 

M1 synthetic 15W50

 

Production rod clearance is .0006-.00248, the crank is .0007-.00212, so you are pretty close to what the factory may have assembled. The service limit on the rods is .003, I can't find a service limit for the crank, but it is probably around .003 as well.

 

IF I have low oil pressure, a heavier (40w-50w) weight should cure the problem? Is there anything else I should be concerned with? I used federal mogul main/rod race bearings if that make any difference. Thanks for the help.

 

Oil pressure is largely decided by the rod side clearance, and not so much the bearing clearance. Heavier oil viscosity, will raise pressure a bit, but it is sort of false security because it only masks a larger problem.

 

Bearing clearance and eccentricity determine oil flow as these are much tighter clearances than the rod side clearance. I run rods with as much as .030 side clearance and I can have positively high oil pressure and I also have stock stuff at .012 side clearance that has really low oil pressure because of loose bearing clearances.

 

.030 rod side clearance would be catastrophic in any engine that is not designed and built specifically for that type of oil wash. When I say that bearing clearance is not as much of a factor I am assuming a realistic parameter, such as a working spec of .0009 to .002. With a rod bearing clearance range of .0009-.0020, the side clearance will have a much greater affect on oil presssure than will moving the bearing clearance around within the specified range.

 

Almost every engine with aftermarket rods on LS1tech already has .020-.025 on the rods and they have great oil pressure.

I've built hundreds.

Now you put the rod bearings and main bearings in at like .0030-.0040 clearance and you will see much lower oil pressure especially at idle no matter whether rod side clearance you are running is,even still .010 like it is on some stock LS1s.

Remember as well that the rod journals are not always completely surrounded by metal anyway so anotherwords the oil could leak out much easier than you think at the sides reguardless of side clearance anyway.

Some OEM rods even have "cutouts" in the side clearance area to direct oil spray on the bottom of the piston or the cam as well with no problems maintaining oil pressure either like the new Hemis.

Finally you probably don't know but some Nextel Cup NASCAR engines run over .100 side clearance and they do not have any oil pressure problems whatsoever. They do still run the rod clearances at about .0020-.0025 though.

 

As I stated, if an engine is built specifically for that amount of side clearance you're fine. Nextel cup engines are dry sump systems, apples and oranges. As far as the aftermarket rods coming in at .020-.025 on side clearance, I too have built hundreds of engines, and everytime it pisses me off! 90% of the guys here are street/strip, and I feal that .030 side clearance on a relatively tame LS series engine is too much.

 

These NASCAR engines do not have any excess oil usage with the huge side clearance again though as they DO NOT WANT tons of oil and windage in those engines. They do it to get rid of weight but with the new now rules hardly anyone does it anymore.

The same engines with normal rods and side clearance don't have a different oiling systemn and you don't need a dry sump to run pin guided rods or have normal oil flow and pressure with the huge side clearance setups. The bearing clearance is the restriction in the oil flow like I said.

The oil pressure won't be determined by side clearance unless you had absolutely tiny side clearance and the rods are 100 per cent sealed around the whole journal which they often are not since they have other leak paths as well.

 

I built my lt1 and it was comming out to .002 Two Thousands on rods and mains. High volume pump and a canton 6-quart pan. Runs Great

 

Here is an engine build sheet for an iron block 415 CID stroker that Lingenfelter Performance Engineering auctioned on eBay a while back. Notice that all of the rod and main clearances are set to a target of about 25 ten thousandths.

Steve

 

I think you are misinterpreting what I am saying. Let's exclude exotic race applications. The hydrodynamic wedge that "floats" the crank begins to degrade at anything beyond .004 oil film clearance. 99% of all street/strip engines have less than that amount of bearing clearance. Given that restriction, the rod side clearance will have the most effect on low speed oil pressure. The absolute maximum factory limit on all LSX engines, including the LS7, is .020 rod side clearance. If the side clearance comes in more than .020, the engine is not allowed in service. The factory prefered rod side clearance for ALL LSX engines including the dry sump LS7 is .012". I don't know how else to put it.

 

First of all, it's important to affirm that the oil clearance dimensions that shortdog stated should be fine and give him good oil pressure assuming that other things are within reason (cam bearing oil clearance, oil pressure regulator setting and pump volume at the normal operating RPM's, etc.).

GOaT Cheese - I don't think that you are properly understanding the point that Erik is trying to make. As the oil flows into and out of the crankshaft journals (first to the mains then to the rods) the first (and truly primary) restriction to flow is the cylindrical gap between the bearing and the journal called the oil clearance. Once the oil flows past this "oil clearance", the side clearance has virtually no influence on oil pressure assuming that the side clearance is sufficiently wide for normal operation. I just looked in my GM factory manual and the rod side clearance range is from .0043" to .020". By the time the oil migrates out to the fore and aft ends of the journal bearings and is ready to turn the corner to get slung out, the oil pressure is down to about zero even with an engine oil pressure of 70 PSI or more. If the side clearance is the pressure determining restriction to oil flow, there is insufficient clearance to be operating the engine.

Steve

 

Good luck man. Both of these guys seem to know what they are talking about and both are probably correct on their specifics (I know GoaT is). I just wish they would stick to the subject. The monkey wrench in your set up seems to be the forged verses cast and what impact that has on OEM specks. I would think you could be tighter. Keep asking questions because to much clearance is low pressure and not enough is death.

 

The factory side clearance specs are there so you know if something is wrong with the rods or the crank. There will be no difference in anything and you won't be wider unless the rods are made wrong whereas many engine builders will totally freak out if you have even less than .020 side clearance.

I am not one of them since I have run aluminum rods at .012 and had no problems and at .030 and had no problems either. It matters whether the rod is crank or pin guided as one of the two has to have more side clearance in case the thrust bearing fails so you don't **** all the pistons sideways and blow up the engine when the crank moves forward.

 

You'll be totally fine. Your NOS tune is what you need to worry about. I would have reversed those specs with the rods at .0025 and the mains at .0020 but they are both within range and the crank and rods will live longer than running them tighter even though you may see lower oil pressure than a dead stock engine. Less pressure in your case if from more oil flow through the bearings.