Keeping a C4 LT1 alive

I'm putting a C4 back together which I purchased from another forum member: the car has an unfortunate history of spun rod bearings.... Due to time constraints, I paid a local to rebuild the current motor (spun one rod bearing with VERY low miles on the rebuild), and would like to ensure this never ever ever happens again....

I intend to use the car as a weekend/semi-daily (no problem there) and as an occasional auto-xer on fresh RA1's. Is there anything I should do to ensure the motor holds together?

I "believe" the car should be just fine auto-xing, and may have suffered oil starvation in high rpm sweepers during it's (extensive) track use, but don't really have any facts to back that theory up. Is this a C4 issue?

Details: stock motor and oil pan, stock suspension with revalved Bilsteins, R-compounds.

Thanks! Nathan

When it spun rod bearings were the rods checked or replaced ?

I've never used one, but it seems an "accusump" type device would be relatively inexpensive insurance. Given the history and presumed cause (oil starvation)...that would be my direction if it were mine...

Clem

Yeah, I think an Accusump would be cheap insurance there. And what was replaced by your "local"? In my non-professional mechanic opinion, that motor would have needed: Turned (at least) crank if not new, new or rebuilt rods, bearings, at least 1 piston (over the bad rod bearing), rings, oil pump, etc. Wanna bet it only got new bearings and a gasket set? That never works (long).

my guess is not machine work just new parts like Dr Hess said. oils starvation in a LT1 is not b=very common and i see a lot of them in time trials events with no issues. a sump device couldnt hurt though!

Replaced the rods?

Different (better) rod bearings after rebuilds?

New or machined crank?

checked bearing clearances?

Break in?

Amount of oil?

Those things don't spin rods for fun - something had to go drastically wrong.

has anyone ever actually checked ALL the specs?

The block might need align bore, the crank could be bent, the rods used may not have been the same mass/construction.

small block chevy (LT1) is a GREAT engine for its time.

Where do you live? Have you looked for a shop with a good reputation? Anywhere near Portland Or? I know Arnie Loyning builds some VERY mean small blocks

The LT1 is a stout motor , I have no idea why he had such problems with his. Between 2 Lt1 caprices We have amassed over 600K without issue, only ever needing Optisparks and normal maintenance.

PS..you got a great car, I loved driving it! I think rob got it due to driving our C4 LOL

I'm glad to hear it's stout. I think the car spun a bearing, got a crate motor which subsequently spun two bearings. ANOTHER crate motor was installed, which spun a rod bearing...at which point the understandably frustrated owner sold the car.

To me. :)

I pulled the nearly new motor out, and took it apart with the rebuilder. All bearings trashed, one spun. We found a loose oil pickup (at the pump)...I don't know if it was loose before I pulled the pan, or if I knocked it. The rebuilder is apparently reputable, and it's a pretty big operation: he gave me a tour before I was convinced to try again. (the motor wasn't covered under warantee) Clean operation, well organized, and 1000's of domestic motors go through there. It certainly ISN'T a "hot rod" shop, however.

Rebuilder: replaced the crank and damaged rod, new bearings all around, new cam bearings, hot tanked block.

I'm pretty excited about the car, but need to ensure there was some other problem lurking: design or other. My next inspection is going to be at the oil filter adapter...and make sure there aren't any wierdnesses to be found there.

It appears the Opti was installed incorrectly at least once (damaged spline?) and I'm told the installers had a few issues, including low oil pressure upon installation (!) and non-starting. (opti?) I cannot verify those stories, and they came from the rebuilder...who had a vested interest in the process.

njansenv wrote: ... including low oil pressure upon installation (!) and non-starting. (opti?)

So it didn't have oil pressure so they cranked away at it instead of fixing it and breaking it in properly?

ding ding!

sounds like somebody did not know quite what they were doing on the previous owner's watch. Three dead engines in a row, especially two brand new crate engines, sounds like they were trying to reuse some damaged parts somewhere.

the LT1 is about as reliable as gravity..

PO here -- one remanufactured engine under my watch. When I purchased the car, it had a crate engine in it installed by a previous-previous owner with about 60 000 kms on it.

I just had the pan off my c4 to fix a crack (I hit something).

There is a nice boxed in pickup "baffle" in the pan. Not quite a race pan but its pretty serious for holding oil in. The only prob I have seen is the oil in the valve covers getting sucked in the pcv system in sustained turns, like a skid pad. Oiling system is most likely not your problem if functioning properly.

tuna55 wrote:

njansenv wrote: ... including low oil pressure upon installation (!) and non-starting. (opti?)

So it didn't have oil pressure so they cranked away at it instead of fixing it and breaking it in properly? ding ding!

Not sure how much the electronics jumped from L-98 to LT1 (assuming same system) but the fuel pump gets secondary power from the oil pressure switch. One pulse for startup, then no more electricity to the pump till your oil pressure switch opens up. So it should not start and run if you have zero oil pressure. As you have seen however this system will not help in a high rpm oil pressure problem.

Hope you get a good rebuild, the LT1 is a great motor.

ZOO wrote: PO here -- one remanufactured engine under my watch. When I purchased the car, it had a crate engine in it installed by a previous-previous owner with about 60 000 kms on it.

Hey Rob. I hadn't realized the previous crate motor mileage was that "high" (loads of track use). (How's the M3 been? I have been missing it.... )

And I'd like to make ABUNDANTLY clear to all that I don't believe this was a PO issue: he's been nothing but straight up about the car, and I bought it in the knowledge that the motor may or may not be guaranteed.

I just want to be sure that there aren't some C4 oddities I need to be aware of: I know that plenty make it to the track and seem to be just fine. Here's to a good rebuild.... and getting it on the road soon! In the meantime, I'm going to investigate the Accusump and perhaps an aftermarket oilpan if that appears to be a good idea.

1.Weld the new pickup to the pump.

2.Make sure any accessories or components that may have been lubed by the old engine are either absolutey clean,or replaced. If there is an oil cooler, replace it. Do not clean it. You will hate yourself.

3.Use the correct weight and specification of oil, not what Billybob the genius says is the best oil for tractors, cars, spaceships and motorboats and also works well as a laxative. Some say not to use Mobil 1 or other good synthetics during break in. I don't think its a big deal with modern rings and cylinder wall finishes.

4.Make sure the new engine is prelubed well before the initial startup, and make sure someone there is smart enough to have everything in time and properly connected so it starts as soon as the key is turned. There is no reason a new engine shouldn't start the second the fuel pressure reaches spec.

5.Watch pressure and temperature, and don't let it idle below 1000 rpm. If its flat tappet, 2000 rpm. Warm it up, make sure there are no leaks, and drive it. Accelerate 10 times as hard as you can it drive for an automatic, 4th for a stick from about 1500 rpm to about 3000, letting it coast down each time without braking. This heat cycles and breaks in the rings.

6.Abuse and enjoy.

Thanks!

The comment about oil pressure and fuel pump solenoid got me thinking: I noticed the oil pressure sensor was epoxied back together at somepoint: maybe the "oil pressure issue" and the no start issue were in fact related to the sensor getting damaged upon engine install.

There was no oil cooler running to the motor, so I don't have to worry about cleaning that: new pickup came with the motor.

I hope to get the manifolds and oilpan on the motor this weekend, and prep it for install. I'll keep you all posted. With regards to the cam, I avoided the (very strong) temptation to put "something bumpy" in.

It was hard....the "while you're in there" Siren was loud and clear, but I stayed the course.

This time.

njansenv wrote: Thanks! The comment about oil pressure and fuel pump solenoid got me thinking: I noticed the oil pressure sensor was epoxied back together at somepoint: maybe the "oil pressure issue" and the no start issue were in fact related to the sensor getting damaged upon engine install. There was no oil cooler running to the motor, so I don't have to worry about cleaning that: new pickup came with the motor. I hope to get the manifolds and oilpan on the motor this weekend, and prep it for install. I'll keep you all posted. With regards to the cam, I avoided the (very strong) temptation to put "something bumpy" in. It was hard....the "while you're in there" Siren was loud and clear, but I stayed the course. This time.

There is an oil pressure switch and an oil pressure sender. Switch for fuel power, sensor for the dash cluster. Your fuel pump should not get power without 4psi (or so, I think) of oil pressure unless someone bypassed the system.

Are you getting an canton oil pan? If so, check for leaks and flatness before installing, some need a little tweaking.

Do you have a budget for a cam+tune? If you can swing $500 for the LT4 HOTCAM kit and a $400 or so for a tune I would highly recommend it. There are better cams/setups out there for the money but IMO the hotcam kit will get you a decent HP boost, some more rpm power without really sacrificing drivability/reliability. If it won't fit in the budget no biggie however it is a MAJOR PITA to do a cam swap with the engine in the bay of a C4. If your teetering just do it. IMO don't go too big, but don't wait for the engine to go back in. I believe GM performance makes another mild cam that requres no re-tune or new hardware, seem to go around $150 new, I would at least stick one of those in.

Don't forget to have fun. I love my c4

I thought I should post a quick update on this thread.
The rebuilt motor from this supplier lasted a few hundred kms. Again. It took some time before I had the gumption to replace the motor again, but I just got it running last week. I have yet to do the post mortem on the "re-rebuilt" motor.

I ended up finding an ironhead LT1 (this time with the vented opti) from a Roadmaster with under 100k miles for $400. I kept it stock in the interest of getting the car on the road, and let me tell you: this thing is MUCH quicker than it was. There must've been something wrong from the beginning with the last rebuild.

In the meantime, I may build up the LT1 that I pulled out, but frankly...the car pulls just fine, and I'm starting to "get it". The targa hasn't been put back on yet this week: yes, the car feels flimsier without it, but it's just too much fun.

the one you pulled out - with its history - i wouldnt reuse any part except the block and heads, i'd toss the entire rotating assembly in the scrap bin. then build a 383.

on a scale of 1(replace brake pads) to 10(hours and hours of swearing and blood shooting out multiple unintended holes in your body) how bad is it to get the engine out?

The engine pull isn't too bad. Time consuming, but technically fairly easy. Maybe a 4 or 5? I pulled the motor with the bellhousing attached to the motor and leaving the transmission in the car: it's very tight, but can be done. The second time, I think it took about 4 hrs to pull. I'm told the auto cars are much easier, and you can leave the transmission/bellhousing/tq converter in place.

Getting the motor back in the first time was surprisingly easy: it slipped right where it needed to, first time. The second try showed me how much of a fluke that was, and stabbing the motor on the trans took way more time than I expected it to.

A stroker is the plan "if" I rebuild the motor, and probably a healthy cam and ported stock heads.