nitsuj Posted July 6, 2007 Share Posted July 6, 2007 I have a question I'm pretty sure already know the answer to, but I'm going to ask anyhow. I'm looking at buying a 73 Z with a smallblock already installed. The owner didn't know which engine it was, so I set out to try to find the engine number on the front of the block. It must be covered by the valve covers or something, because it's no where to be found. I did find the casting number on the rear just forward of the transmission. Can the engine be ID'd by the casting number? Just in case, here it is GM 39700200 Does that tell me anything at all? I'd settle for CI. I don't care what plant it was made in or what year it is. Thanks. Quote Link to comment Share on other sites More sharing options...
nitsuj Posted July 6, 2007 Author Share Posted July 6, 2007 Let me add to my question. I've been googling. The closest I came to finding the casting number was 3970020. One zero short of what this one said. According to one site and Wikipedia, it's a 307 Ci motor, the lowest hp rating of any of the small block Chevy's. So, is this accurate or is that missing zero cauing me to lose something in the translation. Should I run screaming from this car? Quote Link to comment Share on other sites More sharing options...
deja Posted July 6, 2007 Share Posted July 6, 2007 I have a question I'm pretty sure already know the answer to, but I'm going to ask anyhow. I'm looking at buying a 73 Z with a smallblock already installed. The owner didn't know which engine it was, so I set out to try to find the engine number on the front of the block. It must be covered by the valve covers or something, because it's no where to be found. I did find the casting number on the rear just forward of the transmission. Can the engine be ID'd by the casting number? Just in case, here it is GM 39700200 Does that tell me anything at all? I'd settle for CI. I don't care what plant it was made in or what year it is. Thanks. I think you wrote down too may numbers. http://www.mortec.com/castnum.htm 3970020....307...69-73 Quote Link to comment Share on other sites More sharing options...
jasonZ Posted July 6, 2007 Share Posted July 6, 2007 This web site lists #3970020 as a 2 bolt main 307 1969-73. Not the best Chevy ever made but it will run fine while you build a BIG motor. Heres the link: http://www.mortec.com/castnum.htm Jason Quote Link to comment Share on other sites More sharing options...
nitsuj Posted July 7, 2007 Author Share Posted July 7, 2007 I guess maybe you guys are right, maybe I did write down too many numbers. I'm a little bummed now, I was really hoping it was a 350 in there. I'd never heard of a 307 before, but after looking it up, I can't really find much good about them. Something about the block material being softer than normal. Plus, it's rated at 200hp. Sheesh. For 200hp, I'd just as soon leave the 6 cylinder in there! It does have a 4 barrel on it and a cam, so maybe it's been given a few extra ponies, but probably not what I was looking for. I began my search for a Z thinking I'd do a V-8 swap. This car jumped out at me because it already had a V-8 in it, so I could put all my money into the body work and interior it needs. Sounds like if I got it, I'd still be putting a motor in it, so I screwed either way. Anyhow, thanks for the help guys. Quote Link to comment Share on other sites More sharing options...
280zwitha383 Posted July 7, 2007 Share Posted July 7, 2007 If the price is reasonable you should buy it. It will be cheaper in the long run and you can have something to drive while you build the motor you want (as stated earlier). Quote Link to comment Share on other sites More sharing options...
nitsuj Posted July 7, 2007 Author Share Posted July 7, 2007 Yeah, you might be right. Price is 2 grand. Body is as good as I've found. Ugly, but solid. I was pretty pumped about it when I thought it had a 350 in it, but I guess a 307 isn't the worst thing in the world. I think I'm going to make an offer and see if he takes it. Then I can drive it around the rest of the summer while I gather parts for the winter. Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted July 7, 2007 Share Posted July 7, 2007 I guess maybe you guys are right, maybe I did write down too many numbers. I'm a little bummed now, I was really hoping it was a 350 in there. I'd never heard of a 307 before, but after looking it up, I can't really find much good about them. Something about the block material being softer than normal. Plus, it's rated at 200hp. Sheesh. For 200hp, I'd just as soon leave the 6 cylinder in there! It does have a 4 barrel on it and a cam, so maybe it's been given a few extra ponies, but probably not what I was looking for. I began my search for a Z thinking I'd do a V-8 swap. This car jumped out at me because it already had a V-8 in it, so I could put all my money into the body work and interior it needs. Sounds like if I got it, I'd still be putting a motor in it, so I screwed either way. Anyhow, thanks for the help guys. I've never understood why the 307 gets so thoroughly dissed... sure, it's down on cubes, but how well it runs depends on the parts added (heads, cam, intake/carb and exhaust), and how tired it may be. Still, not a great choice for hot rodding as parts are same price (or more) than the more popular 350s. The 'soft block' tale is BS: I've run across 307s with high nickel blocks. Sort of depends on how GM was feeling the day it was cast. If it runs well, leave it there and enjoy driving it while you build a killer 383 or 406. Actual engine codes should be stamped on the block's deck surface in front of the (US) passenger side head. If the engine has been decked, could be gone. Chilton's manuals used to list these codes. HTH <> Quote Link to comment Share on other sites More sharing options...
nitsuj Posted July 8, 2007 Author Share Posted July 8, 2007 See, thats just the thing A.G. I my mind, theres no sense in buying a car with a V8 when I know I'm taking out the V8 to put in a different V8. And heres why. Locally, I have 2 Z's I've looked at that I'm considering. Both are in about the same shape. Interior is shot, exterior is ugly, but salvagable. Neither is rusty, both have terrible shade tree paint jobs. One has the stock motor which runs, but badly. I suspect one carb needs attention. The other has the 307 in it. I can't tell which kit is used to mount the V-8 or even if it is a kit. It may be a home brew. The tach isn't hooked up, which makes me think maybe they didn't buy a kit. Now, heres my snagging point: The one with the V-8 is $2000, the one with the stock motor is $700. So, do I want to pay $1300 extra bucks for a motor I know I'm going to be taking out anyhow? If it had a nice 350 in it, and I knew it was a proper conversion, it would be a no brainer. I was really sure I wanted the one with the V-8 already mounted. But now I've had some time to think a bit, the $700 car seems really attractive. I'd get to pick and mount my own motor, so I'd be sure to be happy with the results. I'm just damn glad I found this forum full of folks that knows what I'm going through. My wife is getting sick of hearing me whine about the choice. Quote Link to comment Share on other sites More sharing options...
HICKL Posted July 9, 2007 Share Posted July 9, 2007 I'd say it all depends on what is in the V8 car. You can spend $1300 real quick getting a trans, headers, exhaust, custom driveshaft, motor mounts, tranny crossmember, etc. If those parts are decent then you could almost call the motor free. All depends on the quality of the swap. Jeff Quote Link to comment Share on other sites More sharing options...
Guest jeremiahbell Posted August 16, 2007 Share Posted August 16, 2007 The 307 produced 300 ft-pounds of torque at 2400 rpm stock, and 200 horsepower at 4600 rpm in 1971. This may not sound like a lot, but when you consider the short stroke and small displacement its not bad. It was not a performance motor, though one of the best 307 blocks is the 3970020 because it should have a high nickel content (check under the timing chain cover). A well built 307 will run circles around a well built 305 especially in a car. I suggest build it up, and enjoy having a unique ride. Oh, and as a side note. If you still have the crank from the 3970020, it should be a forged steel crank that will also work in a 327. Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted August 16, 2007 Share Posted August 16, 2007 first Id point out theres alot more than just an engine envolved in a (Z)v-8 swap and ALMOST ANY (Z) in GOOD CONDITION (BODY, SUSPENSION, INTERIOR),with a running v8 car with a chevy engine will be a no brainer to swap in a replacement engine and is easily worth 2k next Id point out that while a 307 is far from ideal its possiable to pull 400 flywheel hp from one with the proper parts added Quote Link to comment Share on other sites More sharing options...
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