Think I spun a bearing - rebuild time. Need advise.

[EvanZR1]

Well, looks like I'm going to accelerate my mod plans. Was backing the Z out of the garage tonight for date night with the wife, and it started knocking, blowing white smoke and threw a low coolant light. Car had been running fine last weekend, but I had been hammering on it pretty hard. Given that I don't really know history on the engine, how it was driven, and the fact that it's got 100K miles on it, I can't be too upset. The question now is what to do, and who to take it to. Obviously we'll need to get into it before making final decisions, but here's what I'm thinking.

Option 1: Rebuild keeping stock displacement. Do full porting (top end & heads) and long tube headers. Maybe go ahead and do cams as well, would like feedback from those that have done cams on stock displacement. Would love to have a motor that could rev to 7500-8000 rpm.

Option 2: Go big. I know Haibeck lists a 415 CID, but I've seen some posts of people going even larger. What are the experiences of those that have done this, both for power and reliability? How does it impact the ability of the motor to rev past 7K?

Of course, cost is going to be a factor (don't have a huge money tree in the back yard ;) ), but I want to do it right and plan on keeping the car for a long time once this is done.

For the work, I'm thinking either Corey Henderson or Haibeck. Since I'm in Dallas, Corey is definitely closer and a LOT easier to get to. However, while I've used him for tuning in the past and I know he does a great job with porting and tuning, what's the experience been from those that have used him for rebuilds? Obviously Haibeck has a great reputation, but would be a pretty big pain in the *** to haul the car all the way up there. Having said that, I only plan on building it once, so I don't mind the effort to get the best. Any other options/recommendations? There are a few other things I will want to get addressed while doing this (AC needs troubleshooting, want to have the seat motors rebuilt, install a custom stereo system and lower the car), so don't know if that might impact recommendations as to who to use.

Thanks in advance for advice.

[Top Toy]

Very sorry to hear about your spun bearing (or whatever let loose) but glad you're thinking of it as an opportunity! I have no experience with Corey but can certainly vouch for Marc's work. You would not regret the haul to Chicago. He's very meticulous with everything he does and can do it all from building that 415 (or larger!) to changing a light bulb in your dash. And he backs it all with his personal guarantee! He may try to discourage you from putting cams in a 350 but I say go for it. Tuning for big cams is a little tricky but, when you get it right, the sound and power are awesome!

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[Demps]

Evan,
Sorry to hear. Both Corey & Marc are very credible and you wouldn't go wrong with either. I'd ask Corey if he's still doing major LT5 mods. He can tune cam'd cars very well. Also consider Pete in Chicago.

Here's my take: assess the damage--Spun bearing, head gasket, more, less, etc. If you have cause to get into the bottom end, go with an offset crank engine with the goal of 500rwhp. Marc's site has detail on it and others on this site (Phil-->Jagdpanzer) have built them from ~378-402 cid.

Cams are awesome if sized, timed, & tuned correctly. There's a lot experience here but I'd recommend not oversizing the exhaust cam for your application. I have a love--hate with one of my cars as it doesn't have the best drivability...but boy does it love to GO! I also have another with equal intake & exhaust cams that coupled with timing falls flat above 6,500 rpms...but boys does it get there fast.

I'm not the build expert others are but I can relay personal experience with an SGC ported 350, SGC ported/cam'd 350, cam'd LPE 385 & LPE B-cam'd Haibeck 415. All are better than stock :-D

Ted

[DRM500RUBYZR-1]

100k, even a rough 100k is child's play for an LT-5.
Not many LT-5's need a lower end rebuild at that break in mileage.
If the car was running fine when put into the garage, then upon days later re-start, you observe the listed symptoms, then the only thing that occurred between the two events was heat soak after being run.
Might just be a blown head gasket, which certainly doesn't warrant a lower end rebuild.
Oh, sorry, yes it does ( wink, wink ) if cubes are what you really want.
Keep us posted.
Marty

[EvanZR1]

Marty, would the blown head gasket account for the knocking as well? That was the thing that made me think something more serious.

[We Gone]

I assume you have checked the oil for coolant? yes I would think a head gasket could cause the knock as a coolant will not compress. I say this because I had a 90 that had a few very bad injectors and was putting a lot of gas in the cylinder/s and a very bad knock.

If you pull the heads just go for a full P&P great bang for the $ plus you still have a great driver.

[DRM500RUBYZR-1]

Marty, would the blown head gasket account for the knocking as well? That was the thing that made me think something more serious.



Sorry Evan, I answered that earlier on Corvette Forum, forgot to cross post.


Here you go:


https://www.corvetteforum.com/forums/c4-zr-1-discussion/4111822-spun-bearing-build-advice-needed.html




Marty

[grahambehan]

I agree with checking oil for coolant, but would also remove and section the oil filter, it's contents will give a good indication of potential damage.

Graham

[WARP TEN]

If you want to do an engine, I agree with Ted (demps) that either Corey or Marc would be great choices. I do not have personal experience with Corey but he has a fine reputation and is nearer you. I do have experience with Marc, as he has been servicing my ZR-1s since before he was actually in business as Haibeck Automotive Technology. He and son Bob are experts at the LT5 engine and are meticulous in their work. And Marc always stands behind his work. If best value for your money is a goal, I think you would be well served with Marc's 510 HP package on the stock block. Perhaps with a 4.10 rear axle, a short shifter like Hurst or Bill's (ZFDoc) and electric cutouts. My 510 package (which was really closer to 490 HP because I chose not to do some package components) ran 12.4/116 at Beech Bend and was very easy to drive around town. If you want a bigger engine Marc has done plenty of them and can offer sound advice on cams, displacements and value. His website is pretty clear on a lot of options. I have always loved the work he has done for me. Shipping is an expense but not a huge one compared to your overall expense. You cannot go wrong with either. --Bob

[EvanZR1]

Marty, that makes a lot of sense. As I said, the car was running perfectly the last time I drove it, but yes I had been hammering on it on the drive home. It ran great into the garage when I shut it off. When I started it last night, it was completely normal for the first couple of minutes while I was waiting on the wife, and then started the behavior when backing out of the garage. I pulled the dipstick, and there's no evidence of coolant, which I would take as another indicator of head gasket.

[EvanZR1]

I assume you have checked the oil for coolant? yes I would think a head gasket could cause the knock as a coolant will not compress. I say this because I had a 90 that had a few very bad injectors and was putting a lot of gas in the cylinder/s and a very bad knock.

Now that you mention it, I remember the same thing happening on my previous 91. Had an injector stick open and I remember it making a very similar knock. Changed the injector and the car ran great again.

[Demps]

As an easy diagnosis at this point: pull plenum & check injector housing to head security & plenum too. There's a water passage there. Possibly that or injector stuck open.
Ted

[32valvesftw]

If it was a stuck injector would there be a noticeable fuel smell out of the exhaust?

[jss06c6]

Pull your plugs and put a borescope in the cylinders and take a look. Check your plugs to see which cylinder(s) are causing the issue. Blown head gasket would show it's ugly head immediately upon startup and would have been there when you parked it in my opinion. I would say spend some time doing some good diagnostics before you tear into it..

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[Mr Blue]

There are other options. If you have indeed spun a bearing, Pete had a high mileage short block for sale@ $1350. He also could upgrade it to a closed deck 391 CID for $6995. That would be a great upgrade. For that matter, he may be able to do the same for your short block. Offset grind the crank and use small journal rods would get you to 400 CID.

[lfalzarano]

A failing dual mass flywheel will make a similar knock. Put it on a lift and use a stethoscope to isolate the noise while it is running. I blew my flywheel once and it sounded like the motor.


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