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Topic Review (Newest First)
03-22-2012 04:01 AM
farna I just remembered something... part of the problem may be the quality of the flexplate IF it's a recent (in the past 10 years) purchase. My brother works on a few of the local farmers and friends vehicles. He recently put a reman engine in a 2002 or so Chevy truck and bought a new flexplate. The flexplate cracked in the center after just a couple months (and over 2500 miles... truck used by a siding company). He'd bought a NAPA "made in China" flexplate. The replacement was purchased from GM, but low and behold it was "made in China" too! Probably the same flexplate, just reboxed by GM and cost $20 more. We figure the one that cracked probably wasn't properly heat treated (hardened). That will happen occasionally even with US manfuactured items -- everybody makes a lemon now and then, though it does seem to occur a little more often for some...
03-21-2012 08:16 PM

Not a lot of people have extra money laying around. I replaced a dozen or more flywheels that looked exactly like the one you pulled out, and they were hammering so loud it would've fooled almost anyone into thinking the motor was blown. It would be prudent to pull the oil filter and cut it open. You don't need any fancy tools. Examine the filter media for the presence of any metal particles. If there is no metal, I would install a new filter and change the oil. Since the motor has been setting for a while, a pre-oiling is mandatory. The pro-form tool is not terribly expensive and does a decent job, but if you have any old distributors available, a nut welded on the top and spun with an air ratchet works very nicely, and they don't heat up. Of course if metal is obvious you will have to make a decision as to the best use of your hard-earned money. Stay away from the cheap crate motors as most are assembled with questionable parts and sometimes questionable labor. If you do choose to go that route, stay with a reputable company that will stand behind their product. Assuming there is no metal, remove the spark plugs and squirt a bit of motor oil into each cylinder. After you have achieved oil pressure, have a friend turn the motor over with a ratchet as you continue to pre-oil. Just a couple revolutions is adequate... you don't want to damage the camshaft. The only other thing that you may want to consider, while the motor is out, is a new set of valve seals. Easy to do with the motor on the stand and very inexpensive.
03-21-2012 12:54 PM
Originally Posted by bsa_bob
The flex plate was tightened down center. not completely flat[fitted]on the crank. before the tightening down sequence began.therefore it just broke out at the shown point hth No other reason to me.
This makes sense to me, I wouldn't have thought of it because when I assemble stuff I always check fitment before and during tightening of the bolts.

I would think that some of the other alignment issues discussed are possible, but not something I've experienced.

Since you had this failure of the flexplate, I would check to be sure your flexplate, trans, etc fits correctly before putting it back in the car.
03-21-2012 08:32 AM
ol'rodder Sorry to join in late. BSA Bob is right, it is a misalignment problem. I have seen this many times but it does not usually progress as far as this example. Either there was some dirt or burr on the crankshaft hub or flexplate preventing it from mounting properly. Or, more commonly, the transmission was not in alignment with the block. Think of tilting the transmission at an angle to the block and not having a U-joint, Something has to give! There could have been dirt or a burr on the engine/transmission mating surfaces. The locator dowels in the block may have had dirt, rust, or a burr which would keep the transmission from pulling in totally flush. Also, and this is not as uncommon as you would think, the alignment dowels on the back of the block and/or the alignment holes in the transmission mating surface are actually out of spec causing the mis-alignment. Check to see how to check alignment or google "transmission to engine alignment", "belhousing alignment" etc. I know they show manual transmissions but it gives you an idea of what to check for. Any speed shop can get offset dowel pins to correct mis-alignment and Harbour Freight has a cheap dial indicator and base that can also be used for many other things such as crankshaft end play, setting differential gears etc. Because the cracking, and in your case, the eventual total failure of the flexplate takes quite awhile to happen, the flexplate is after all "flexible", people have been known to just replace the flexplate and solve the problem. If it was just dirt and/or a burr from a previous sloppy installation and this was taken care of during the new installation, then the problem is indeed fixed. However, if there is actual engine/transmission misalignment and this is not corrected when the new flexplate is installed, then the new flexplate will also fail somewhere down the road. As a side note, any actually mis-alignment will also strain and or fail the front transmission bearing. In either case we are talking about a fair amount of time here, it won't happen over a couple of weeks or even months, depending on usage.
I would clean and check all mating surfaces and the alignment dowels and then just to be on the safe side check overall alignment. As far as the engine goes, you have lots of good advice already. Good luck.
03-21-2012 08:22 AM
rebuild or crate

Personally I would rebuild but first thing I would do is go to a local salvage yard and buy a used but running 350 or 305 check around for the cheapest price. Install it in your 55 and enjoy it while you rebuild the 327. This way you can take your time on the rebuild. Also if you buy a 350 with vortec heads you could put them and the intake on the 327 too.
Then when the 327 is done you simply put the 305/350 in craigslist and get the money back. There is always looking for V8 chevy engines.
03-21-2012 08:21 AM
drs1023 That broken flex plate is almost identical to one that came apart on me in a '64 Impala with 283 I had just done a re-ring on. I was 19 at the time and didn't know to check the flex plate when I re-installed the engine, so I convinced myself the thing already had stress cracks and came apart during a rubber burning start. I replaced it and the harmonic balancer (somebody suggested it, so I did it) and had no more issues with it. I bought a parts truck with a 4-bolt 350 in it a few years ago, and again, the flex plate had shed its center part, sheared off the torque converter bolts and destroyed the transmission housing.

Flush and check the engine, to include dropping the pan and cleaning out the settlings that's bound to be in there as others has suggested. Maybe you are lucky and will still have a good engine.
03-21-2012 08:19 AM
Chopt 48 Ok, I'm a bit late to the party but I have a couple of questions.

How is the engine mounted in the car? Does it still use the factory front mounts and a rear mount on the trans or did who ever put the 327 in it install side mounts on the engine? Also were all of the bell housing bolts in place and were they tight?

It's been common knowledge for a lot of years that a Tri 5 Chevy running a V8 with front mounts and an aluminum case transmission can flex at the Block/bellhousing connection enough to crack the trans case or cause problems with the flex plate. I've also seen a couple of cases where loose bellhousing bolts caused a broken flex plate or knocked out the front seal in the transmission.

I'd do as a couple of the guys suggested and put a new flex plate on it and pull the plugs and run a compression test. You can see if the engine has oil pressure at the same time by connecting a gauge to the engine where the oil pressure line or gauge hooks up. Using a oil pump primer as was suggested earlier would be a good idea though as it gets oil up in the lifters and into the bearings.

You don't need a fancy stand and can hang the engine from a chain hoist or cherry picker to run the compression test as all you are doing is cranking the engine over so that each cylinder hits four or five times on the gauge, checking the reading and writing it down and going to the next cylinder. I've even started a lot of engines sitting on the ground or hanging from a chain hoist.
This is a short video from when I fired up a 500 Cad that my friend gave me for my 71 GMC the engine had been sitting for several years.
I couldn't run it more than about 30 seconds but I did find out that it ran ok. No engine stand or other equipment but as I said I only ran it long enough to hear it run and determine that it didn't knock or blow clouds of smoke.

As far as the 327 goes, if it is in good shape I'd either run it as is or rebuild it and put some better heads on it. 1. it gives the car a lot higher Bubba Factor with a 327 than a crate motor these days as a lot of guys still think a 327 is the Holey Grail of small block Chevy engines. 2. you already have it and can go several ways on it. You could run it as is if it checks out. You could do a complete rebuild with new pistons, new cam bearing, better cam and better heads or you could do a rering and bearing job and run the pistons you have if the cylinder bores are good with little taper.

If the insides of the engine don't look good then you can think about a different engine and think crate motor or rebuilt.
03-21-2012 08:09 AM
Just went through the same thing

I shelled the 350 in my '37 Chevy Coupe about 4 weeks ago. The oil pump failed and the distibutor gear failed, don't know why, never seen it happen before. Anyhoo, I had a similar delemma. Rebuild or buy a crate 383 SBC. Called a buddy and he recommended a shop here in Jacksonville, FL. Called and they told me that they charged $70 to tear down my motor and tell me what it needed. I was happy to oblige as I could do it myself but am way too time short to do so. PLUS, when I bought the car, I was told the car had a 383 and I wanted to know whether it truly was. SUPRISE!!! I have a two bolt main 350. Good news was that it did have some good parts. Forged TRW pistons, Trick Flow twisted wedge heads(67cc) and decent rods. It had a Comp Magnum 292 H cam which was also damaged so I simply bought a new 292 Magnum(LOVE the sound and it works!) The motor was thouroughly cleaned, crank reground, new bearings and reassembled . They checked my heads and they were fine. Bill was $1,150 for parts and labor(I supplied the cam). I added a new Hurricane intake and should end up with a 420 HP 350. So for me, I am happy and I saved about $1800. It is not a four bolt, but it should hold up fine for occasional strip and weekend cruises. Putting it in this week.
03-21-2012 08:03 AM
farna Yes, just check it out and run it. If it was running 5-6 years ago there is no reason it shouldn't run now. The rings could be stuck and give variable compression readings, but it will free up after a couple hundred miles of running. Make sure you drain the gas tank then pull and CLEAN it. Old gas leaves a residue which new gas (especially with ethanol in it) dissolves. The residue gets in the engine and gums up carbs/injectors and even valves. I've had it get into valve guides and cause the valves to stick open and bend pushrods. I've brought many old engines back to life after sitting for years -- you should have no real problems. Pull the fuel line and stick it in a gallon anti-freeze jug (or similar) with fuel in it for temporary running -- until you get the tank pulled and cleaned. Can't go far, but can run it enough to see what condition it's in and run around the block a few times.

The flexplate isn't a big mystery. I've ripped the center out of one on a little 195.6 Rambler six cylinder. Flexplates are a hardened steel, and get brittle with use and age. Cracks usually develop around the bolt holes first, either at the crank (most common, that's where most of the stress is) or where the converter bolts on. The bolts may have not been tightened properly causing excess stress, could have just been age, or the metal may not have been properly hardened.

Engine balance wouldn't affect the flexplate -- that would affect the crank bearings. A bad torque converter can put excessive stress on the flexplate though. A bad bearing in the converter can throw the converter out of balance enough to stress the flexplate, but the harmonic balancer or crank balance shouldn't.
03-21-2012 07:22 AM
Originally Posted by starnest
I'm guessing it is a balance problem. The crank (w/rods/pistons) and flexplate weren't balanced together. - AND/OR - The harmonic balancer is bad (or the wrong one).

The flex plate was tightened down center. not completely flat[fitted]on the crank. before the tightening down sequence began.therefore it just broke out at the shown point hth No other reason to me.
03-21-2012 07:17 AM
ap72 A good USED running 350 can be had for $500 or less, a 305 can be had for $300 or less. Either of these will be a fine replacement. There is no headaches of chasing down problems, its the cheapest option, and you will likely have MORE power. When buying a used one go with one that is fuel injected and is clean under the valve cover, best case scenario one that you can hear run (but that isn't always possible).

I would go the 350 route as it'll have more power and if you should ever sell the car is worth more than a 305. If you still want to add a little something extra I would get a chrome dress up kit, a clean aluminum intake, headers and an RV cam. That's what you'll see a lot of at car shows as its cheap and effective.
03-21-2012 07:04 AM
Originally Posted by starnest
OK - you've got 70 307 heads (small valve, 69CC) on a 67 327 block. It'll work fine for just cruising around. If everything checks out, I would replace the flex plate and put it in the car. If you have problems after that, you could rebuild it and with a few improvements make a hot little 327 with the right heads and cam.

My Vote is for this also!!

While the engine is out check all gaskets and fix all the oil leaks, and maybe replace the freeze plugs in back of the flex plate "If they show signs of rust"

Replace the flex plate front balancer,.................... and maybe look at replacing the transmission with a 700R4 and drive the car like you stole it. until there is a major breakdown. then you can rebuild or replace as the dollars dictate.
What is the condition of the rest of the car?
03-21-2012 06:58 AM
norseman here's my 2 cents and it worth exactly what you paid for it.

If it was me, I'd run it and see!!

Since it's out of the car, I'd do a couple of things before putting it back it.

Compression test as a couple of people have already suggested. If the compression looks good, pull the pan, and check the bearings, pull one main and one rod and see what they look like.

If they look good, replace the front seal and rear main seal , clean the oil pump screen, make sure the timing chain looks OK and then stick the pan back on with new gaskets.

Put it back in the car, and drive it!!

03-12-2012 06:00 PM
starnest OK - you've got 70 307 heads (small valve, 69CC) on a 67 327 block. It'll work fine for just cruising around. If everything checks out, I would replace the flex plate and put it in the car. If you have problems after that, you could rebuild it and with a few improvements make a hot little 327 with the right heads and cam.
03-12-2012 03:01 PM
Silver Surfer
Originally Posted by kevinmack
Here are the heads. the shop didnt have the flexplate so will get that in a day or so.

A friend of mine wants to do a blowback test. So waiting for him on that. Maybe this weekend if its not raining we get the fp and try to drop the motor back in.

Some rust on the heads, ill look for a good way to clean that off...

Numbers on the heads.

Passenger side:
D 27 70
GM 14

Driver side:
D 24 70
GM 12

Why is one GM 12 and the other 14? Why D 27 and one D 24?
Here is info on your casting numbers:

I believe D is April. 70 is 1970. One was cast on the 24th the other on the 27th. Having a discrepancy of a few days is normal, not a big deal.
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