lt4 coupe

Turns out my cyl. 1 noise was rod bearing. We pulled the motor and trans (cuz you have too). Car only has 57k miles, so its strange, but now im going to rebuild the motor and put a new clutch in while the trans is out.

It has excellent oil pressure, and I only run Castrol Synthetic, so im puzzled! Would a higher volume pump be a good idea? Was this an issue on these motors?

If I remember right the dual mass delete is as simple as getting LT-1 Camaro clutch parts correct?

Im going to go with bigger cam and long tubes, but I dont want to go crazy, so thats about it besides the obvious (for me), new pistons and rings (11:1 most likely), valve springs, seals and all new gaskets. The crank is likely turnable, so ill keep it and the rods since both are forged in these no?

Is it still a good idea to get rid of the sodium valves even if they look fine?

A95Y

Don't think the rods are forged. Has the cam been replaced. Seems like it happens in an unusually high rate after a cam. You could have repaired this in the car I think. Maybe just on an auto. You could probably get 11:1 with thinner head gaskets, you are almost there now. Either go all out now and never look back or do as little as possible to get back up to snuff IMHO. A refresh, so to speak. You have a good piece to work with.

Cheers

edit: the crank isn't forged either

good page to bookmark:
https://www.grandsportregistry.com/lt1vslt4.htm

bjankuski

Rods are forged. I cannot tell you why it spun a bearing, that does seem unusual.

rklessdriver

LT4's have Powdered Metal (PM) rods.... not forged. GM did away with forged rods in all SBC after 1994..... The GM PM rods are fine to 450HP or so.....

The bearing clearance is very tight in LTX series engines.... they are well known to spin bearings if pushed on the track or even if slightly starved for oil (such as fast sweeping turns on the street). The pan is better than the regular GM passenger car and truck pans but not the best design for the kind of cornering ability the C4 chassis has with good tires.

No you can not just put the Camaro Flywheel and clutch in a Corvette for the single mass conversion.... You need a Camaro flywheel and will need to have it machined. You can use the Camaro clutch disk because it's sprung hub but you can also use the solid hub Corvette disk but expect some engagement chatter. You still need the Corvette Pressure Plate and throwout bearing.... so summary:

Camaro Flywheel - machined down .090" or so.
Camaro or Corvette Disc
Corvette Pressure Plate
Corvette Throw Out Bearing

Your really much better off just buying a Single Mass flywheel and Stage 1 clutch kit from SPEC.

Will

RichS

I would have the rods rebuilt with ARP bolts. The valves are fine to reuse, I ran them for years in my 397 and only recently replaced them. For what your doing they are fine. A simple cam for the LT4 is the hot cam, it's old technology but is a nice cam, gives a slight lope and a few more hp. I ran a Centerforce Billet flywheel and clutch before swapping to an auto. Be aware getting rid of the dual mass you may get some trans noise at idle out of gear.

DGXR

Small block Chevys in good running condition are known for strong oil pressure, so I don't think a high volume oil pump is necessary... it might even create a starvation issue in some situations.

mtwoolford

LT1 Camaro clutch parts? NO those clutches / flywheels are for a T56 trans, not the ZF6 speed you have; you will need Corvette specific clutch and flywheel.

neither the rods nor the crankshaft are forged'

The crankshaft is cast nodular iron, same as LT1 cranks, but with a more desirable rolled fillets on the rod journals.

The rods are powdered metal and utilize a fractured cap (parting line) on the big end.

I'm not gonna justify this, but my choice, oil system wise was to go with a Canton road racing pan with the recommended Canton recommended high volume pump and dedicated Canton pick up.

If you pull the oil gallery plugs from the front of your engine, or rather when you pull the oil gallery plugs, keep track of them; at least two should have 0.030" holes drilled in them to bleed off air and provide lubrication to the timing chain drive and water pump drive.

Just so you know that low mileage doesn't mean good; my LT4 always had what I considered oil pressure problems, and anyone who says 10 pounds of oil pressure at idle is okay, well its not. My engines problem wasn't he oil pump, it wasn't the bearing clearances, it wasn't a hundred other things, it was that the factory left the middle cam bearing out. Now that WILL cause a noticeable drop in oil pressure.

Kubs

I have been running a machined Camaro flywheel and ZF6 clutch/pressure plate in my 1990 road race car for about 6 years now without issues. It wasnt that hard to source parts and it was a pretty cost effective way to shed some weight.

lt4 coupe

If the crank is salvageable ill keep both. But if the crank is trashed then ill just get a forged rotator from Manley again.

Is there a generally accepted clearance and oil viscosity combo?

Is there a better pan that will fit without crazy mods?

No sprung hub doesnt sound like a good idea on the street, lol.

Where is the machining needed?

Ill look into that brand. I havnt bought a clutch in many many years...lol

lt4 coupe

I didnt think about the trans diff. lol

Well im ok keeping the stock bottom end if its salvageable.

I called them as that link was dead, WOW $450!? For a sheet metal pan? Will that even clear long tubes? Is there anything similar thats not so spendy?

Should I change any of that?

I hear you. But how did this thing make it 57k miles on a bad bearing oil clearance? Ive run nothing but quality full synthetic oil and only occasional, "spirited" driving!

Kubs

You need to have the friction surface machined to reduce the total thickness of the flywheel.

Kevova

Thr snap fracture rods are replaced not serviced. The big end is snapped in half and the surface is not machined. The rough surface will mate to it's partner. The valves are LT4 specific so you want to keep them if possible, don't mix match. Don't replace LT4 valves that are serviceable with LT1 valves unless all 8.

rklessdriver

Generally accepted clearance and oil.... That's a big can of worms and varys with engine builders. I stay in the old .001 per inch of journal rule rule... So .002-.0025 for most SB stuff. Oil doesn't matter I have run 5W20 to 15W50 depending on application.

Oil Pans.... Canton, Moroso and Champ all have pans that fit. The Champ is the nicest pan (better baffeling design and integral louvered windage tray) but requires a minimal mods of removing or relocating the oil level sensor and removing/replacing the factory windage tray/long main studs/bolts with normal length main studs/bolts....

The face of the Camaro flywheel needs .090 machine off it to work with the Corvette PP and TOB.

Will

rklessdriver

This is not true of the SBC PM rods.... Because these rods have the big ends affixed and the cap is located true to the big end with traditional thru-bolts (not cap screws) they can be rebuilt like traditional forged rods.

Remove the bolts, cut the cap and cut the big end until both are flat, bore the big end to size, hone to final size.
Will

lt4 coupe

Just a quick update:

ONLY rod #1 was spun, but ALL rod bearings were in bad shape. All mains looked pretty good. The cylinders dont look great but the piston skirts all still show machining marks. So definitely oil starvation issues (possibly before me?). Drivers side freeze plug with the oiling hole in it is cocked a bit sideways, not sure if this had any effect.

That weird harmonic pulley hub thats balanced has severe seal grooves, is there a better option? Its balanced so im not sure if it has to be mounted to the damper pulley in a proper orientation?

mtwoolford

the sealing surface on the hub can be repaired with any SBC harmonic balancer repair kit; basically a stainless steel sleeve that fits over the sealing surface; no biggie there.

with the crank at the #1 piston TDC, the hub goes back on with the small triangle shaped mark at the 12:00 o'clock position.

lt4 coupe

Ok thanks.

These rods are PM but not fracture split.

With these pan options, how is fitment with long tubes?

Thanks! I would rather convert to internal balance if I can get a suitable damper/pulley? Do you know which keyed traditional would be a bolt in?

rklessdriver

Pan fit is fine with those pans using Exotic Muscle, Hooker and LPE longtubes.... some folks have had problems with ARH longtubes. I have used all those headers with the Champ pan and no serious issues.

A suitable keyed hub is the Pioneer/PB/Jegs billet hub for an F Body same hub length as Y Body..... You have to use the Dorman replacement pulley for Y body thou as Pioneer/PB/Jegs dosen't make the correct one. You will need to pull a small roll pin out of the hub but otherwise they go right together. This combo is what I use when customer didn't have $450 for ATI.
Will

lt4 coupe

Awesome thanks!

Out of all those headers, since you have used them, which do you recommend I get?

rklessdriver

The ARH are the nicest being stainless and having an included x pipe and mid pipes that go all the way to the rear diff. I swapped them on blackharleymans 383 build which orginally had EM when he wanted to go stainless.

The EM are also good headers. I had them on my 92, orginally on blackharleymans 383 build and 93 ragtops 385 build, never had any compliments other than the factory coating.

I'd recommend either of those for most street builds.
Will