Finally decided yesterday to start the process of replacing my 882 heads and cam on my 78 with 66,000 miles on the motor and after getting the passenger side head off first since that is the bank with the weak #6 cylinder (90 PSI on compression test versus 160-165 on the others) which I thought was a leaky valve and or valve guide, I found a #6 cylinder missing a 1/4 inch sliver off the piston at the perimeter where the piston meets the cylinder wall. The 3 other pistons were heavily carboned on the piston tops with lots of white residue on all the exhaust valves. It does appear the valve guides were worn as well. Disaster!

The good news is that Distributor gear looked great-very little wear. The lifters on the stock cam were shockingly in great shape-They look brand new. I have used a synthetic since 1985 in the motor. I expect the cam to look perfect as well.

Besides the tedious nature of the work, all went well except 2 broken intake manifold bolts on the L-82 aluminum intake, one on each end front and back on different sides. I drilled out the broken studs relatively easily.

So here is the plan-PULL the motor, what's left of it. I don't have the expertise to rebuild the bottom end BUT a good friend who rebuilds wrecked Volvos now and who was an owner of a high performance parts store for 20 years does. He has not seen the block yet but is willing to come and pull the engine with me and do the rebuild with me. He did ask if there were any ridges in the cylinder at the top (NO!) or if the cylinder walls were scored (NO). The tentative plan is to rebuild the bottom end with new bearings, new pistons, rings, etc. I guess I will finally get to the rear main seal leak, new oil pump, fuel pump etc. Any thoughts on Sealed Power Forged pistons-engine will not rev above 5,500 RPM and then only very occasionally? I also plann to replace the motor mounts and may do the clutch at the same time. So much for the heads and cam change only!

At least I know what the problem is now! I have owned the car since 1983 (25,000 miles when I bought it) and it has been very reliable, making good power. Oil blow has been a problem forever and I suspect that detonation early on in its life doomed the engine to the inevitable today. When the car was bone stock with all emissions, it routinely ran 225-240 degrees when I bought it in 83. I have never heard it ping since I have owned it but that does not mean it was not pinging at some point. It should be stronger and better after the rebuild with the AFR 180 65 CC head and the Howards roller cam (.525/.525). Hopefully no more surprises!

I have been working on my cars for 30 years but this stuff is NOT for the faint of heart!! LOL

 

Sorry to hear this.

Now you will be able to upgrade the whole motor and be "comfortable" with it when you step on it.

 

When you're up to your *** in alligators, it's hard to remember your initial objective was to drain the swamp.

So true

I have put off doing my heads for fear of alligators

 

I put off the head and Cam change forever for this very reason as well-swimming with the alligators now.

 

oh well, you'll have a fresh motor and be glad you did it later on....

 

Here is the story:

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yeah, it looks tired!

 

While your at it..... Yep, a good time to do a complete rebuild. Buy quality parts even if it takes more time to save up for them.

 

Looks typical of a 35 year old engine. You will be best off boring and torque plate honing it. They usually have some taper and are a little egg shaped even with no or minimal ridge.

 

Thanks for the tip 63mako. Any suggestion on the brand of forged pistons, nothing radical, just a good forged piston?

 

A good time to bump to a 383.

 

Man I'm sorry to hear that. I have been following along since you posted your head and cam choice. You picked the cam and heads I wish I could have so I am eager to hear the results.

I think this stuff is par for the course. I had installed a set of Edelbrock Performer heads and a cam about 3000 miles ago. At some point after that, the cooling system would not stay pressurized. I removed the motor to begin a rebuild and sent the heads to be pressure checked. Each head had cracks in the seats of the center two cylinders.

I did not know to use the performance Fel-pro head gaskets that had been reengineered to direct more coolant to those center two cyls which is genius.

This will also give you an opportunity to really dial in your quench area and compression ratio to the new heads and cam. Try to stay positive because that combo sounds trick!

 

That's not happening. Keeping the OEM bottom (block, crank, connecting rods, etc) end with new pistons and the OEM L-82 Aluminum Intake, with the OEM dual snorkel air cleaner housing. Retaining (storage) the oem cam/lifters/pushrods (for posterity) and the OEM 882 heads, just in case someone may want everything in the future when I am long gone-probably not but you never know.

 

I can understand that. My original engine ran good with 102,000 on it when I swapped it out for my stroker engine. I have it sitting on an engine stand in the back of the garage, with boxes of original manifolds, carb, control arms, and several other original parts.

 

Go with the VMS-75 or 4032 alloy, high silicon, low expansion forged. I like Mahle. they run a little more money but mine weight matched within less than 1/2 gram. I think Probe, Speed Pro and SRP make them too. Look at the compression height and shoot for a gasket, in the hole combination that nets you as close to .040 as possible. They are available in 4.020 or 4.030. The 4.030 are usually cheaper and have more options in compression height.

Edit: Sealed Power (Speed Pro)I believe makes a VMS or 4032. Again, check compression height and gasket combo to get close to .040 quench.

 

Well that is bad news and good news. Bad in that you now have to rebuild the entire engine. Good in that you can go roller cam, have nice fresh cylinders and a squared up block fi you want.
Mine started out as a top end last winter and ended in a full rebuild. The only original parts are the block, oil pump and distributor. virtually every other component of the engine has been changed.
It's a much better engine now that likely makes near 400 hp and performs excellent.
Any reason in particular you're looking to go forged pistons instead of Hyper?
Get the quench nice and tight for good detonation resistance. Mine is at .038 and no deto despite a 10:1 CR and a 270 duration cam with a 3.08 read end in front of a Th350.

 

http://www.ebay.com/itm/MAHLE-SBC-CHEVY-350-FLAT-TOP-POWERPAK-PISTONS-4-030-Bore-3-480-Stroke-5-7-Rod-/200823243075?pt=Motors_Car_Truck_Parts_Accessories&hash=item2ec1ff8143&vxp=mtr
Remember you also have to buy rings with most pistons you price. These come with low drag file fit ring pack and free shipping. Downside is with a felpro 1094 gasket you have .050 quench which is not the end of the world and still much better than stock.

 

Not a catastrophic failure, but it's never fun to find out a "quick top" is going to be a bigger project.

I personally wouldn't just replace the bearings and pistons - I think you'll find that the bores are well-worn and tapered, and you'll find the crank is worn as well. Don't cheap out on the bottom end even if it hurts - take the time to measure everything and count on doing the shortblock. If you're careful and smart, with the right shop you can get through a quality bottom-end overhaul to stock capabilities relatively inexpensively.

As noted, if you have to touch the crank it's usually about a wash to do a cast-crank 383...same for the rods; if they need to be resized with new bolts often a set of Scat 27000's are about the same price as the machine work. A 383 is invisible from the outside...but if you want to keep it all stock, I get that completely.

I personally use nothing but SRP pistons both hypereutectic and forged - they've always been perfect, and they've been great to deal with on a few custom orders I've made. But any good brand will work.

You'll know more after the teardown - I'd set aside any plan you have until you're through measuring what you have. As you've seen, no battle plan survives first contact with the enemy ;-)

 

I appreciate all the suggestions and comments. I will wait until the engine is out and a complete teardown will be the tale of the tape, as they say. I don't know when I will getting the engine out at the moment but hopefully soon.

 

Ya never really know until you crack it open and look at it. Well, all you can do is do what needs to be done, no use crying over spilled milk, right? Do what ya gotta do, then drive it like you stole it. Good luck!

Scott