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Old 01-11-2018, 12:43 AM   #1
Steeveedee
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Rebuilt engine

OK, the 402 in my truck was rebuilt about 20 years ago, and is smoking and using oil. I'm looking to replace it, since another overbore may make it unusable. I just don't know. I'm looking at this power plant as a replacement. Does anyone have any input with what they have experienced with this (if they have bought one) or warranty issues?

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Old 01-11-2018, 07:33 AM   #2
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Re: Rebuilt engine

Looks like a nice engine. Is your current big block the original? If so, it might be worthwhile pulling it apart and seeing how much it has already been bored. You could have it sonic tested to see if you had enough meat to go further and then the machinist could decide whether or not the walls would clean up within the safe range. Probably not going to end up with the power/torque of that crate engine but it would be kept original which is usually valued the most.
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Old 01-11-2018, 05:17 PM   #3
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Re: Rebuilt engine

That crate motor puts out nearly 450 lbs of Tq just off idle! That is something!

You could spend less than half that $$ though refreshing yours if the block is still good. It's not as fun as a new crate motor but... saves you plenty.

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Old 01-11-2018, 05:21 PM   #4
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Re: Rebuilt engine

Are you sure it doesn't just need some new valve stem seals?
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Old 01-11-2018, 05:24 PM   #5
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Re: Rebuilt engine

Yeah, I'm not in love with losing the original engine, that's for sure. Or dropping that kind of hard-earned money. The truck has been in the family since '73, so I'm pretty sure that it is the original engine. Same for the trans (rebuilt at the same time the engine was out). Even the carburetor is the original.
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Old 01-11-2018, 05:38 PM   #6
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Re: Rebuilt engine

Keep it, if you can

I have just rebuilt mine (402 in a Cheyenne Super 1972), It runs super fine and I am proud to keep the sense of historical conservation.

(Crossing wire over air cleaner is an AFR cable, removed since)
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Old 01-11-2018, 07:04 PM   #7
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Re: Rebuilt engine

How much is it bored out already?
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Old 01-11-2018, 07:14 PM   #8
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Re: Rebuilt engine

As stated above... keeping the original power plant is just a better idea. Your engine may only need a very minor refurbishment with oversized rings and all new seals... then be good for another 20 years or more.

If It's not broken, why fix it? (Just my $0.02 worth).
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Old 01-11-2018, 07:29 PM   #9
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Re: Rebuilt engine

just alittle food for thought. the truck motors of our era do not have the vin number stamped into them like the cars do. if you tear the original engine apart and find that the block is indeed toast, find another block with the same 3 letter suffix from another truck of the same year. and presto, you are still original.
you can't do that with a camaro or a vette but with a truck you can kinda get away with it. just sayin. whatever you decide to do , best of luck to you, tony
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Old 01-11-2018, 07:51 PM   #10
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Re: Rebuilt engine

Original engines in trucks won't gain you any value. Sentimental value to you maybe.

I'd rip it apart and see how much it was already bored out. If it has been bored .020 or .030 already, pretty sure a BBC will take .060 just fine.

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Old 01-11-2018, 11:02 PM   #11
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Re: Rebuilt engine

The big questions haven’t been answered. What do you want? Power? Warranty? Looking to save money? Originality? Personally, I would tear the 402 apart first and see if the cylinder walls are still in good shape. If the 402 is rebuildable, you’ll save some $$$. You can also throw some performance parts in there to wake her up and still be cheaper than the crate engine. If money isn’t and issue and saving time is, go with the crate engine. You’ll have a warranty and only be down the time it takes you to R&R the engine.
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Old 01-11-2018, 11:24 PM   #12
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Re: Rebuilt engine

WE have had this conversation around here a lot lately.

That crate engine is impressive, but I think you can build one for a lot less.

That said, you can build a 454 for the exact same money as a 402.

If I were building the original 402, I would use a better cylinder head. With the right heads and cam, even using the original intake, the engine will be perky.

I have nothing against the original engine, but, If I pull the engine from my Longhorn again, it will get a 454 back in it.
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Old 01-11-2018, 11:33 PM   #13
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Re: Rebuilt engine

I'll just repeat what a few others have said. There's a good chance you can rebuild your (original) engine for a good bit less than you'd have in the crate 454. The original engine isn't a big selling point like it is in collectible passenger cars, but it doesn't hurt its desirability and keeps the truck more authentic. And, even if your block is bored too far, it's not big chore to substitute another block.
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Old 01-12-2018, 01:34 AM   #14
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Re: Rebuilt engine

Rebore at 4.155 compared to 4.125 original. It was performed in... 1995.

I just put some new rings and honed the chambers (plus new crankshaft, bearings and camshaft)
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Old 01-12-2018, 10:00 AM   #15
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Re: Rebuilt engine

Tear it down and check it out.
You never know what you’ll find.
I had a 396 once. Always burned oil. 500 miles to a quart. Checked the bore. No ridge, minimal taper. Ball honed it to clean it up and put in new rings. The correct ones. It turns out it had 30 over rings in a 40 over block.
Cured that oil problem.
All done with a like new motor for less than 500 bucks.
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Old 01-12-2018, 12:24 PM   #16
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Re: Rebuilt engine

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Rebore at 4.155 compared to 4.125 original. It was performed in... 1995.

I just put some new rings and honed the chambers (plus new crankshaft, bearings and camshaft)
You can most definitely bore it again if you have to, going to .40 over is perfectly fine. Rebuild that sucker.

Anything past .60 over is usually when it's questionable.
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Old 01-12-2018, 01:17 PM   #17
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Re: Rebuilt engine

There is a good chance that your 402 block started life as a 396 reject because core shift spoiled the chance it would clean up as a standard bore 396. If that is the case you now have .030 overbore and if it was rebored to .030 over 402 with the rebuild 20 years ago you now have a 396 bored .060 over. If you choose to have it bored to the next oversize without checking cylinder wall thickness you may be setting yourself up for a serious engine failure. Buy the crate engine and enjoy it.
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Old 01-12-2018, 04:33 PM   #18
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Re: Rebuilt engine

I'm leaning towards the 454, mainly for pulling torque. The truck slows quite a bit pulling hills with my 26 foot travel trailer. If I do this, will all my ancillary equipment fit? Seems like all the holes would be threaded metric, nowadays. It also looks like I'll have to run headers or get bolts with shorter head heights on the bottom row. I prefer not to run headers.

The claim is that these now have the boss for the mechanical fuel pump, but then in the detailed description it says you need to buy an electric fuel pump.

I've done tons of engine work, but not so much in the last 15 years, so I'm full of questions. I tried to chat with a tech person to get answers, but the application wouldn't come up, for some reason.
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Old 01-12-2018, 10:04 PM   #19
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Re: Rebuilt engine

I think davepl may have used a crate motor in his restoration. You might check him out.
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Old 01-12-2018, 10:12 PM   #20
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Re: Rebuilt engine

I'm pretty sure all the bolt holes on the block will be SAE.

Wiring a fuel pump is not a big deal, with the ethanol content these days I'd prefer electric.

A good (thick flange, coated) set of short headers will work nicely to make power and last.

You could get a newer 454 or 8.1(496) core and build a copy of the crate, it might be cheaper and you get the same benefits of roller cam and one piece rear main. You could build an 8.1 for a similar price to the 402.

I had a 68 396 truck a while back and figured out it was the same $ to build a 454 so that's what I did. It was 2004 and had the 8.1 been available like it is now I would have built one of those.
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Old 02-16-2018, 10:01 PM   #21
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Re: Rebuilt engine

BTTT. My wife wants minimum downtime for the truck, but when I told her the price for the crate 454, she balked. I'm pretty sure if you checked her coin purse, one of the first nickels she ever earned will be in it. Don't get me wrong! She'll spring for what is necessary with repairs on our vehicles, since I was a mechanic when we met, and trusts me not to do stupid stuff. I don't even ask generally, when repairing or maintaining our vehicles, but this is a huge expense.

I'm also looking at a stock new 454 (to fit an '84- that is as far back as the menu goes) from Chevrolet that is about $4400. I don't actually want to go there, either. I'd really rather rebuild my seasoned block, but again, she doesn't want too much down time, and my hands haven't really recovered from the surgeries last year to just dive in and get it done. The days when I could get an engine out, pop the pan and replace the oil pickup screen, and have it back in in 2 hours are gone (that was on my '64 Impala, anyway, which is long gone). The big question is whether the rest of the stuff from my engine will fit on that 454. I quit my mechanic job in '84 when I went to work as a mechanical engineer, and have never dived into a BBC. So, I don't know what fits, over the years. Will all my parts, such as intake and exhaust manifolds, water pump, AC, PS, fit the new engine? If I go part metric, I won't be happy, but that's just bolts and nuts.
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Old 02-16-2018, 10:09 PM   #22
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Re: Rebuilt engine

GM has an awesome warranty and it comes with great parts all at a premium price. Have you considered any other reuilds? Blueprint engines have a good rep and like someone said above, no more expensive to build a 454 than a 402 and anymore that is true with a 496 as well.

https://www.speedwaymotors.com/BlueP...ine,52469.html

Why not get a long block? ATK 454 for $2400.

https://sdparts.com/i-24075971-atk-d...iABEgLaMfD_BwE


One reality is that big block Chevy's are expensive. I just went through a 427 from a boat and spent WAY more than I wanted to, but that's the nature of the beast. Rebuilding stock cylinder heads one of the largest expenses.

I don't see any reason you can't pull it, check it, and then make the call. It may just need valve lapping, valve seals, ball hone and new rings and bearings.
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Old 02-17-2018, 12:10 AM   #23
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Re: Rebuilt engine

Quote:
Originally Posted by Mike C View Post
GM has an awesome warranty and it comes with great parts all at a premium price. Have you considered any other reuilds? Blueprint engines have a good rep and like someone said above, no more expensive to build a 454 than a 402 and anymore that is true with a 496 as well.

https://www.speedwaymotors.com/BlueP...ine,52469.html

Why not get a long block? ATK 454 for $2400.

https://sdparts.com/i-24075971-atk-d...iABEgLaMfD_BwE


One reality is that big block Chevy's are expensive. I just went through a 427 from a boat and spent WAY more than I wanted to, but that's the nature of the beast. Rebuilding stock cylinder heads one of the largest expenses.

I don't see any reason you can't pull it, check it, and then make the call. It may just need valve lapping, valve seals, ball hone and new rings and bearings.
You may well be right. Here's my situation. We moved to this house based on the agreement that I would have a woodworking shop. For a number of reasons, this never happened. It also means that if I want to rebuild the engine that is currently in the truck, I will have no place to do it unless I rent a storage facility to put all the wife's crap in until I'm done, because the garage is full of it. I've done some vehicle engine and transmission replacements in the street in the past, and leaving the truck in the street may be OK if it doesn't get towed for overstaying its welcome. Our city and HOA gets all kinds of hissy about vehicles left in the street for too long.
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Old 02-17-2018, 10:36 AM   #24
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Re: Rebuilt engine

Your intake would not fit the crate engine because that one has rectangular intake ports so you would have to do a different intake manifold with it at least. Your stock engine should be oval port.
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Old 02-17-2018, 11:26 AM   #25
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Re: Rebuilt engine

Go big! You'll love the torque. Pull your engine & stash it until "some day" comes along. You can always re-build it down the road. (as I've said before, it's real easy for me to spend your money!)
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