I need some help on the 225 cid engine for my '73 Dart Swinger I just had rebuilt to "stock" specs. Did this come with a cast or forged crankshaft? I'm aware that the '73 340 cid V8's had cast cranks, but did other motors (incl. the 225 /6) for the '73 model year have them as well?

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Cherry Bomb

'73 is forged. Slants went to a cast crank in mid '76. Did you have your engine rebuilt or was it an exchange? If it was an exchange there's no telling what you have without looking at the block casting number.

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Joshua

Hi Josh,

I appreciate the quick response. Upon first inspection of my rebuilt short block (original motor with the '73 Dart), I discovered a cast crank. The machine shop supposedly ordered a "master" rebuild kit which included an oil pump, etc., but I was unaware that any crank was included in the kit. The machine shop owner ordered the kit and took care of the whole job. He first "rough bored" the block to determine the 0.030" over-size pistons and 0.010" machining for the crank bearing journals. Based on what you told me, my guess is that he messed up machining the journals and found a "cheapo" cast crank on e-bay. It's too bad because if he just told me I had a spare forged crank from a '72 motor I would have just given him. I already stopped payment on the check and I'm waiting for the big argument when the guy returns from his vacation. Someone else told me that if you don't have a high performance application (< 6,500-7,000 rpm) a cast crank should be OK. Since a /6 is a "stump puller" anyway (I've never seen mine go > 4,000 rpm with a 2bbl carb & intake), do you think I should just live with it, or should I stick to my guns on principle and make him do it right with the forged crank? He's only standing behind the short block for 6 months - and if he gets "cranky" about this - I'm wondering if he might just do a bad job out of spite. What would you recommend here, Josh? Any advice would be greatly appreciated.

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Cherry Bomb

This basic topic was just covered in a thread last week (Proper procedures for machine shop, or something like that). If it were me, I'd want it done right. Keep in mind that the block itself does not interchange between the cast and forged cranks, so if you have a cast crank, that means you've got a different block too. While like you said, the cast crank probably isn't going to break, I most certainly wouldn't accept a cast crank engine back if I had given them a forged crank core. Time to start talkin to the builder...

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You can't put a cast crank in a forged crank block. The main bearings on the cast crank are narrower and won't fit your '73 block. So he either gave you a different block or you still have a forged crank. How did you determine you have a cast crank?

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Joshua

Hmmmm.....the plot thickens and my ignorance is showing itself here. First off, I did a visual comparison (along with my uncle who is a mechanic), and there are what looks like "foundry spots" on the bottom of the crank. It also looks "fatter" than the one from a '72 block, which looks rounder and more fully "machined." Since I didn't take the oil pan off and look at it before I dropped off the motor for rebuilding, I'm just assuming that the rebuilt block from my '73 Swinger (modified with a 2bbl intake) was the original motor for the car. Can I relate the casting block number to the VIN of the car to accurately match these? But if the crank is indeed cast (starting in the mid '76 model year as Josh says), then it should be obvious that the block isn't original to the car. I really don't think the guy who sold me the car ever replaced the motor - the odometer read about 90K+ miles when I bought it about 2 years ago - but again, I can't be absolutely sure. What makes me kind of suspicious (now that I think about it) is that the motor wasn't done by the date the rebuilder originally promised, but I had to wait a couple of more weeks for the machine shop to have it ready. I wonder if he pulled the old "switcheroo" here. Are there any Mopar Perry Mason types out there to help me solve/ resolve this dilemma?

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Cherry Bomb

I guess I'm replying to myself here - does that mean I've "popped my cork"? Well, life is a learning experience, I guess! I talked to one of the guys in the machine shop who bored the block, and he told me they sent the crank out to another shop for the grinding. The crank grinder recalled that the crank was indeed cast, not forged, so it appears the guy who sold me the car replaced the block at some point. (The fact that he added an "aftermarket" tach and a line-lock - along with semi-bald bald rear tires - should have been a dead giveaway!) Anyway, I'll wait to talk to the shop owner when he comes back from his vacation and discuss exactly what happened, etc. If there were some problems going on with the rebuild (e.g., wrong kit ordered based on a different motor), I'm kind of surprised he didn't let me know what was going on.....

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Cherry Bomb

If the crank grinder knew it is a cast crank engine, then they most likely gave you the correct bearings.
Everything else about the cast and forged crank engines is the same... unless it is a 1980 or later hydraulic cam SL6
DD

I'm somewhat confused by the last reply from DD. If "everything else" except for the bearings is the same for the SL6's made before 1980 (year of hydraulic cams), then was Josh's earlier assertion that "you can't put a a cast crank in a forged crank block" correct or not? I'm fairly sure now that there was a cast crank in the engine I dropped off at the shop. The question that now remains is: Did the guy who sold me the '73 Swinger rebuild the original motor incorrectly with a cast crank, or was it a completely different ('76 or later) cast crank block? I think I need to verify the casting stamp # on this motor to tell for sure....

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Cherry Bomb

The main journals for a cast crank and forged crank are different sizes. Therefore if you have a block with 1 size journals, it will only fit that one size crank. Forged or cast. What is the # on the block? I am sure someone in here will be able to tell you what block/ crank you have.

Sorry for the confusion, I should have said: "all the other rebuild parts are the same".

As already noted, the block and the crank for forged and cast crank engines must be kept together, you can not "mix & match" cranks with the other type of block.
DD

The numbers on the left side of the rebuilt block read: 2806830-3 2832: BH AAWJ. Does this indicate the year of manufacture or a cast/ forged crank? Comparing the number from the /6 motor in my '72 Dart (which I'm pretty confident is original) I read: 2806830-3 2291: BF AAWJ. The only differences are the 4-digit (serial?) number and the "BH" (cast crank?) instead of "BF" (forged crank?). I need to call the machine shop guy first thing tomorrow morning so a fast and accurate answer would be appreciated.....Thanks!

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Cherry Bomb

I thought I read somewhere here, if the rib behind the waterpump housing on the block is tapered, it is a forged crank block, if it is not tapered, it is a cast block.

hope this helps some.

That's a '68-'75 forged crank block. A cast crank won't fit that block. Read this:
http://www.slantsix.org/articles/dutra- ... blocks.htm

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Joshua

Hmmmm.....the plot thickens more. Good article on the /6's - thanks for the tip and timely info, Josh. By the engine stamp # on the block, then, it appears quite likely it is the original motor for the '73 car. I see 2 possibilities explaining the dilemma: 1) Either the guy who sold me the car rebuilt the motor (or else had it rebuilt) incorrectly with a cast crank, or 2) The machine shop botched the job and tried to fit the block with a cast crank (and different bearings). The engine bore technician told me last week there was some problem with fitting the bearings (which had to be reordered), so I'm betting on #2 but I'll hear what the shop owner has to say tomorrow. In either case, though, I don't think I should accept the work. If there were issues/ problems/ questions encountered during the job, he either should have done a little homework and/ or let me know what was going on before he went ahead and did any "creative engineering." The fact that he was "incommunicado" lends me to think something went seriously wrong here. I'll keep you posted regarding the outcome.

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Cherry Bomb