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-   -   Rebuild my 352 or grab a local 390? (http://squarebirds.org/vbulletin/showthread.php?t=19322)

toddgilroy 08-20-2015 11:06 PM

Rebuild my 352 or grab a local 390?
5 Attachment(s)
After pulling my 352 Tuesday, and receiving some encouragement from Mr. Dare (~simplyconnected), I kept going with the disassembly and pulled the rocker shafts, intake and heads. The cylinders are worn smooth, so would need to be honed, but what else can be seen in these photos and what else should I be looking for?

Out of curiosity I searched craigslist today and found this listing for a 390 block about 10 miles from my home.


Contacted the seller and this is the additional info he provided:


Engine was used in a '63 T-bird from 1983 to 2005 then pulled out and placed in storage as original engine was rebuilt to put back in car. I have not pulled heads to check cylinder bore condition but would at least assume a good honing is called for - engine was rebuilt in 1983 and had less than 30,000 miles put on it since then - did not smoke or burn oil. As ad says, will need crank ground and new main/rod bearings.
Or there is a 390 advertised as "professionally rebuilt" a few hours away for $2,300. I have asked for more info on that one.


simplyconnected 08-21-2015 07:20 AM

Todd, whenever I buy engines, it is with the intention of rebuilding them. To me, a 'perfect find' is an old tired original engine. I assume nothing and I politely hear the story, but the evidence speaks loudest. All you want is crack-free castings and all the hardware.

This guy is not in your back yard BUT, check this out:
Offer him $350 and tell him shipping will cost you plenty. With this deal, you get every bolt, a complete C6 trans and a complete 390 FE.

This deal makes the others look terrible. Better deals are out there, especially if time is on your side.
Again, for me, I don't want someone else's failed attempt. A newly overhauled engine with wiped out crank and bearings raises big red flags. "Professionally rebuilt" can mean Highschool Engine Builders did the work, which could go either way. You want an overhaul that will last 250,000 trouble-free miles.

I suggest you spend money on new Edelbrock aluminum heads instead of machining cast iron heads, and top it off with an Edelbrock aluminum intake manifold. All your overheating problems just flew out the window and these parts bolt right on. If you consider the cost of machining your cast iron heads, aluminum doesn't cost that much more and you save a lot of weight. You will need the services of a GOOD FE machine shop to bore and deck the 390 block. You can assemble the engine as a great project if you have a son or grandson who wants to learn.

All of your 352 parts that bolt on the block will fit the 390 but now you have the choice of using the best parts from each engine like rocker arms and shafts, exhaust manifolds, water pump, oil pan, rocker covers, carburetor, distributor, cam, lifters, etc.

You will end up with a new engine and plenty of spare parts to sell.

Take advantage of Rock Auto's discount and buy:
Fel-Pro master gasket set
melling oil pump and intermediate driveshaft
Cam bearings (major brand like Clevite)
Rod bearings "
Main bearings "
Hypereutectic alloy pistons
Moly rings
Brass core plugs
true roller timing set
spark plugs

For many parts, an engine machine shop can buy these part cheaper because they order so many all year long. Talk with them. - Dave

toddgilroy 08-30-2015 12:39 AM

8 Attachment(s)
I found a 1968 390 locally here in Omaha at classic car collector/dealer/restoration shop for $300. Picked it up after work Friday afternoon and tore into it today. Encouraging so far...looks like someone has already done some work. Will finish teardown tomorrow, hopefully.

Sharing any observations would be appreciated.


simplyconnected 08-30-2015 07:16 AM

Todd, I'm excited about your find and the price. I want this job to be top notch, so assume nothing and check everything. FE engines all look alike. Yes, the casting numbers are important but still, measure your bore and stroke just to verify you have a 390. This engine should be sweet when you're done.

I hope you strip it all the way down and send the bare block out for cleaning. Leave the main caps and bolts in it. A good engine machine shop will go through all the oil bores, do the machining, and wash all the chips out. If any of the plugs are left in, cleaning is impossible. Even the smallest metal chips will ruin a great build.

Most of the work you do will take time but very little money. For example, I chase all the threaded holes. That verifies depth, condition of threads, reveals any broken bolt pieces, etc. This engine is an "unknown", so let the evidence speak for itself.

I'm looking at one cylinder that appears to have new crosshatch. There is a reason why someone didn't finish this job. Regardless, if you intend on keeping the bores as is, slide a feeler gauge between the pistons and cylinders to verify correct clearances. Remove the pistons to verify:
the pistons and rods are weight-matched to within two grams of each other,
all the wrist pin 'C' clips are there
measure ring end gaps,
send the crankshaft out to be balanced WITH the damper pulley and flex plate. <--this is money well-spent and will produce a smooth running engine. They need a piston, wrist pin, 'C' clips, a set of rings, a rod with bearings, cap and nuts just to set bob weights.

By all means, if you aren't sure about something, please ask.
What is your timeline? - Dave

toddgilroy 08-30-2015 10:22 AM

Thanks, Dave. I measured the stroke shortly after I got it home and it was right at 3 3/4", and now with the heads off it is just a bit over 3 3/4, and the bore is 4.05.

I will continue stripping it down today and will try to get it to a machine shop this week. The shop where I bought the 390 also referred me to their FE shop and their transmission shop.

As far as timeline, I am not in a rush as I am also trying to get the body to a dustless blaster and then to a body/paint shop. I figure that all will take a while so I can work on the engine and all the other stuff I have to do for the car while the body is at the shop.

And then all those distractions like a full-time job, kids activities, and of course, season tickets to Nebraska Cornhusker football and volleyball!

Short answer, this can be a fall/winter project.

I am sure I will have more questions as this is my first engine teardown/rebuild. Having a lot of fun learning, and would never try it without the help you all provide on this forum!


simplyconnected 08-30-2015 01:40 PM

Most mechanics don't want to be bothered with rotating assemblies because it requires precision and patience. Time is money so they simply want to buy a short block, put it together and get paid. Since 90% of this job is spent in time cleaning parts, they cannot justify charging the customer for all that needs to be done before assembly. Consequently, you either get a 'production' build from the factory or parts that are slapped together without checking clearances, parts that are not detailed etc.

You will learn a lot by doing this engine. Then, you will do another because the end result is very rewarding. The more you do, the better you get. If time is on your side you will get a better job than any engine that came off the line. - Dave


toddgilroy 08-30-2015 01:52 PM

1 Attachment(s)
More encouraging news...removed the first piston and it looks like a Sealed Power H304P Hypereutectic piston. :D

simplyconnected 08-30-2015 03:19 PM

These pistons are heavy. In fact, they are so heavy your crankshaft balance may require extra weight in the throws. They drill holes, then insert mallory metal and weld them in. Mallory metal is half-again as heavy as lead.

This may be the reason why they stopped building the engine. Mallory metal inserts cause the balance cost to nearly double. Get with your crankshaft balance guy ASAP and discuss this with him. You may want to buy different brand pistons that are more like the original in weight.

Keep your compression ratio around 9.2:1 so you can run regular pump gas. In order to determine what pistons to buy, we need to know what your combustion chamber volume is. Then we use the internet calculator to determine the correct piston to use. I found a nice piston company (Silv-O-Lite) that sells reasonable cost hypereutectic alloy pistons.

That piston you pulled, look on top for an oversize number (if it has one). Typically it will say, '+.020, for twenty thousandths oversize. I would find it hard to believe your cylinders are not bored to some oversized value. - Dave

toddgilroy 08-30-2015 09:40 PM

1 Attachment(s)
Looks like .060.

So am I correct in thinking I should have this block sonic tested before I do anything else?

simplyconnected 08-31-2015 06:18 AM

Absolutely! I would go forty thousandths over, max. I would also go back to the machine shop you bought the block from and ask why they didn't tell you about this. Somebody knew, and you need a machine shop you can trust, not someone who is deceitful right from the start.

Now you know the importance of measuring everything and regardless of what the seller says, let the evidence speak for itself. The original bore of 4.050" + .060" = 4.110". The last owner probably did not have the crankshaft balanced and this engine ran real bad. That's why it was returned. The machine shop had a lot invested in this block so they sold it to you.

Pull a main bearing apart, look at the back side of one bearing s**** and see if the crank was ground. It will say, +.020, or STD, or something like that. Now, look at a piston bearing.

Let's say, worst case, you have it sonic tested as 'good' and you must keep the block. Balancing will cost ~$230.00. The engine displacement is now 401.6 cu in. (2.055 X 2.055 x 3.1415 X 3.784 X 8), which is great if you're looking for a racing engine on its last hurrah. Or, simply take it back and tell the guy he wasn't honest and you want a full refund. Give him all the pieces without putting them back together.

Keep looking and you will find someone who just pulled the 390/C6 out of their F100. That's what you want. BTW, a guy in CA called me and asked what 390 he should get. I told him the same story and to MEASURE the stroke. He found one, brought it home and discovered he just bought another 352. I suggested he return it for a full refund. He said the seller was a biker dude who wan't about to give his money back. So he was stuck with it. Later found a good used 390. I do all I can to warn our guys about checking before you put money down. An honest seller will help you, so he can make the sale. - Dave

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