340 and Engine 101
#1611823
04/25/14 03:33 AM
04/25/14 03:33 AM
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Joined: Dec 2010
Posts: 12,375
SoCal
MuuMuu101
OP
I got lucky at Woodward!
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OP
I got lucky at Woodward!
Joined: Dec 2010
Posts: 12,375
SoCal
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I found a guy who's selling his 340 engine and this is the description he's given on the engine when I asked about a compression, oil pressure, leaks, cam, and heads: Quote:
Its a 1970, dated 1-5-70, .040 bore, Thumpr cam kit, double roller chain, U casting 2.02/1.60 heads, has about 2000 miles on it, does not have a intake or exhaust manifolds, nor a water pump.
I bought it from a older gentleman here in town when he pulled it from his Plymouth street rod with the intention of putting it in a Duster I was trying to get...didn't happen.
The history on the engine..has been in his Plymouth since 1974, had it rebuilt at R&E Racing in 2010 I think, doesn't drive the car a lot, other than car shows etc. He decided he wanted to go more modern and is installing a 5.2 Magnum with EFI and a overdrive, that's when I bought it.
I know it ran well, good oil pressure and no smoke, the cam has a shorter lobe separation, so it doesn't make tons of vacuum, the Thumpr cams are made to sound fairly nasty without having big lift and duration numbers. I may be able to get a hold of him to see if he ever ran a compression test on it, being rebuilt,not sure he would've though. It had a minor oil leak on the pan, so I removed it fix, but decided to leave it off in case someone wanted to look inside.
My question is how do I know what a good majority of this information means. Were U heads common on 340's? What exactly does 2.06/1.60 mean? I'm assuming it has something to do with porting. Now, does a cam with shorter lobe separation attribute to a longer duration thus more incoming air entering the cylinder?
Now, would you recommend this kind of engine for a street engine that might see some time at the track (corners) a couple times a year? Do you think it will run on 91 octane? If so, what kind of intake/carb setup would you recommend? He's asking $2k obo if anyone's wondering.
Thank you for your help. 
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Re: 340 and Engine 101
[Re: Kern Dog]
#1611825
04/25/14 03:47 AM
04/25/14 03:47 AM
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Joined: Dec 2010
Posts: 12,375
SoCal
MuuMuu101
OP
I got lucky at Woodward!
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OP
I got lucky at Woodward!
Joined: Dec 2010
Posts: 12,375
SoCal
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Quote:
The 340 has the "street reputation" that many people like but a 360 built with similar specs will be cheaper and stronger.
Unless you are trying to build a clone or something like it, skip the 340 and look for a 360 or a 5.9 Magnum engine. The cubic dollars people want for a 340 isn't worth it IMO.
I don't mind either. Just trying to find a decent engine that will be for the most part "bolt-in" and "running" with minimal issues and a known history of some sort is getting difficult to do.
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Re: 340 and Engine 101
[Re: MuuMuu101]
#1611826
04/25/14 03:47 AM
04/25/14 03:47 AM
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Joined: Aug 2003
Posts: 12,291
Kent, Wa
340SHORTY
Truck Nut
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Truck Nut
Joined: Aug 2003
Posts: 12,291
Kent, Wa
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A friend bought a 70 340 Duster. It had "U" heads. 2.02 intake valves/1.60 exhaust valves.
Personally a 6 pac/ Edel Performer or Perf Air Gap is what Id run.
I am truckless..
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Re: 340 and Engine 101
[Re: MuuMuu101]
#1611827
04/25/14 03:49 AM
04/25/14 03:49 AM
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Joined: Jan 2008
Posts: 4,258
Canada
WO23Coronet
master
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master
Joined: Jan 2008
Posts: 4,258
Canada
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Not to up on SB's but I'll take a stab. U code heads are an early 70's casting, they had a giant letter U cast into them. I think they're a 915 casting number (last 3 digits of the casting number). X heads were the ones that the SB guys went gaga over before the advent of readily available aluminum heads, but I think U codes are basically the same head. 2.02/1.60 refers to the size of the intake (2.02")/exhaust (1.60") valves, it's pretty much the standard size for a performance small block. Also pretty sure U heads are an open chamber, prone to detonation with to high of compression. The Thumpr cams seem like a decent performance cam from what I've read on here, I think they have alot of exhaust duration for that "muscle care sound". A tight lobe seperation also gives that musclecar sound (choppy idle)as your exhaust and intake lobes are closer together (less degrees of seperation) and have more overlap, but they also give more power usually, but aren't efi friendly.
As far as price, if you could confirm what was done to it by talking to the machine shop that built it, that would be a good thing. A bad thing is you can't hear it run. You could give it a leak down test to see how the rings are. Alot of guys will probably chime in that it's worth a little more than a core price, cause you can't confirm it's health.
340's have a good reputation as a performance engine, 400 HP is pretty common with a healthy rebuild
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Re: 340 and Engine 101
[Re: MuuMuu101]
#1611829
04/25/14 10:28 AM
04/25/14 10:28 AM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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Quote:
I found a guy who's selling his 340 engine and this is the description he's given on the engine when I asked about a compression, oil pressure, leaks, cam, and heads:
Quote:
Its a 1970, dated 1-5-70, .040 bore, Thumpr cam kit, double roller chain, U casting 2.02/1.60 heads, has about 2000 miles on it, does not have a intake or exhaust manifolds, nor a water pump.
I bought it from a older gentleman here in town when he pulled it from his Plymouth street rod with the intention of putting it in a Duster I was trying to get...didn't happen.
The history on the engine..has been in his Plymouth since 1974, had it rebuilt at R&E Racing in 2010 I think, doesn't drive the car a lot, other than car shows etc. He decided he wanted to go more modern and is installing a 5.2 Magnum with EFI and a overdrive, that's when I bought it.
I know it ran well, good oil pressure and no smoke, the cam has a shorter lobe separation, so it doesn't make tons of vacuum, the Thumpr cams are made to sound fairly nasty without having big lift and duration numbers. I may be able to get a hold of him to see if he ever ran a compression test on it, being rebuilt,not sure he would've though. It had a minor oil leak on the pan, so I removed it fix, but decided to leave it off in case someone wanted to look inside.
My question is how do I know what a good majority of this information means. Were U heads common on 340's? What exactly does 2.06/1.60 mean? I'm assuming it has something to do with porting. Now, does a cam with shorter lobe separation attribute to a longer duration thus more incoming air entering the cylinder?
Now, would you recommend this kind of engine for a street engine that might see some time at the track (corners) a couple times a year? Do you think it will run on 91 octane? If so, what kind of intake/carb setup would you recommend? He's asking $2k obo if anyone's wondering.
Thank you for your help.
I would not buy it because it is .040" over bored. That's a ton for 340, .010" is what mopar recommended years ago as the max.
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Re: 340 and Engine 101
[Re: RUNCHARGER]
#1611831
04/25/14 12:58 PM
04/25/14 12:58 PM
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Joined: Sep 2004
Posts: 6,906
IL, Aurora
ademon
master
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master
Joined: Sep 2004
Posts: 6,906
IL, Aurora
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Guy sounds pretty honest in the description, see if you can get a hold of the guy he got it from, check the plugs for color and oil, check intake runners and exhaust runners for oil film, Plenty of 340's that are running strong at .030 .040 over, your probably not going to rebore it ever if its a weekend cruiser that see's a thousand or two miles a year. most stock bore bare 340's go for around $500 or more and then its a gamble on the sonic check.
Last edited by ademon; 04/25/14 01:01 PM.
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Re: 340 and Engine 101
[Re: MuuMuu101]
#1611832
04/25/14 02:08 PM
04/25/14 02:08 PM
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Joined: Jan 2003
Posts: 1,255
Columbus, GA
Michael Ecks
pro stock
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pro stock
Joined: Jan 2003
Posts: 1,255
Columbus, GA
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Quote:
this is the description he's given on the engine when I asked about a compression, oil pressure, leaks, cam, and heads:
Unless you can hear it run all you have is his word based off of the previous owners word.
.040 bore - Already at the max, if there is a problem, like rust in the bores from sitting you will not be able to have it bored more.
U casting 2.02/1.60 heads - 2.02 intake 1.60 exhaust valves. Standard 340 sizes. U's are the same as J's 915 casting which replaced the X heads everyone does indeed go crazy over despite the fact that J's are what were used as the basis for 340 T/A heads.
Do you think it will run on 91 octane? - There is no indication if the pistons were changed. Assuming the stock pistons it would probably be fine.
If so, what kind of intake/carb setup would you recommend? - RPM Air Gap or Weiand Stealth with port matching work. I'm fond of Holly Street Avenger carbs.
He's asking $2k obo- That is STUPID money for an incomplete engine, you haven't heard run and have to take someone's word for on everything IMHO. Leave if for some resto guy with a 1970 car and more money than brains.
For two grand you could pull a junkyard 5.9 magnum and put a ring and bearing kit, re-ground camshaft, and the required new balancer in it and still have enough left over for the new carb and intake that you have to buy anyway.
"The happiness of your life depends upon the quality of
your thoughts" ~ Roman Emperor Marcus Aurelius
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Re: 340 and Engine 101
[Re: scatpacktom]
#1611834
04/25/14 02:35 PM
04/25/14 02:35 PM
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Joined: Jul 2010
Posts: 295
Vallejo, CA
ditchdrift
enthusiast
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enthusiast
Joined: Jul 2010
Posts: 295
Vallejo, CA
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Quote:
.04 is not the max. I have a few 340 blocks that sonic tested AWESOME.
I wouldn't go by any blanket statement like that 
yep, my 340 is .060 over and has plenty left to go on the thinnest cylinder. I think it depends on core shift.
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Re: 340 and Engine 101
[Re: ditchdrift]
#1611835
04/25/14 05:33 PM
04/25/14 05:33 PM
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Joined: Apr 2003
Posts: 915
near New Haven, CT
fireeng
super stock
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super stock
Joined: Apr 2003
Posts: 915
near New Haven, CT
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My 340 runs very strong at .040 over
2016 Diesel Ram 3500 Mason Dump
1971 Challenger
2013 Jeep Wrangler
1979 Dodge Ram Power Wagon 400 Mini Pumper
My other car is a Fire Truck.
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Re: 340 and Engine 101
[Re: fireeng]
#1611836
04/25/14 06:07 PM
04/25/14 06:07 PM
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Joined: Dec 2007
Posts: 18,160
Mass
DAYCLONA
I Live Here
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I Live Here
Joined: Dec 2007
Posts: 18,160
Mass
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Quote:
My 340 runs very strong at .040 over
Same here, my 340/6 in my Challenger T/A is actually stroked to 410 Cubes...a .040 overbore was required along with the proper crank/rod/piston assy to achieve this, my block has been in the car nearing 30 years of hard abuse, street and track, without no issues in 3 decades....although I'd want to sonic check any block I'm going to invest coin in, regardless of the bore, stock or not
For the OP if you invest in this engine, have every thing magged for cracks, have the block sonic checked as well, never assume it looks "good", seen to many guys dump money into junk castings because they never sonic checked, or magged the castings
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Re: 340 and Engine 101
[Re: WO23Coronet]
#1611838
04/25/14 10:59 PM
04/25/14 10:59 PM
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Joined: Sep 2004
Posts: 22,873
Chicken coop
dustergirl340
Chicken Little
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Chicken Little
Joined: Sep 2004
Posts: 22,873
Chicken coop
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Quote:
Alot of guys will probably chime in that it's worth a little more than a core price, cause you can't confirm it's health.
I'm in that camp...and that's a lot for a core.
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Re: 340 and Engine 101
[Re: Shoozy]
#1611841
04/26/14 01:46 AM
04/26/14 01:46 AM
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Joined: Dec 2010
Posts: 12,375
SoCal
MuuMuu101
OP
I got lucky at Woodward!
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OP
I got lucky at Woodward!
Joined: Dec 2010
Posts: 12,375
SoCal
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Quote:
Quote:
Quote:
Alot of guys will probably chime in that it's worth a little more than a core price, cause you can't confirm it's health.
I'm in that camp...and that's a lot for a core.
Although you're not a guy you are right. Keep searching Samy. For that money you could do one yourself and know exactly what you have.
Ok, good to know. Anyways, I'm in no rush and the Dart is on the back burner due to work and school. I still haven't touched the drum brakes in over a month. I did one side but have to redo it as I messed up a couple things. I just can't find the time or the energy. And my car isn't going to the mechanics for the Hotchkis TVS to be installed till I get that done.
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