273 302 318 340 build

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DCR is a computed value; hand computations are complex as it involves the crank stroke and rod length, and computes the remaining stroke left on the compression stroke when the intake valve finally closes.

There are various DCR calculators: I use the Pat Kelley calculator (free, online), as it will do both SCR and then use that result along with cam entry data to compute DCR, all in one tool. Wallace has a DCR calculator but you have compute SCR separately first.

The big variable in the intake closing angle is the cam duration and the cam timing. With a solid, like your 270, you also back off advertised duration a bit to compensate for the effect of valve lash, which makes the intake closing angle a bit earlier.

FWIW.... Going back through the Pat Kelley calculator, using:
- the unmilled 302 heads (64 ccs)
- a .028" thick head gasket
- a 265 intake cam duration (shorter than the 270 advertised to account for the lash)
- 106 ICL
- the 526 pistons
I get 8.9 SCR and 7.4 DCR; that DCR is fair to decent for low RPM torque, But I would like to be up near 8.

Going with the 285 pistons, I get SCR/DCR of 7.8/6.6. That DCR is not going to be good for low RPM torque. The Wallace DCR calculator shows that 6.6 DCR translates to around 120 psi.... stone stock 318 numbers...ooops.

With the the SCR pushed up to 9.4, by milling the heads for 59 cc chambers, and using the 526 pistons, you get an SCR of 9.4. Now DCR is 7.8, and cranking compression will be 150-155 psi. THAT is gonna have good low RPM torque!
 
Here is weights of 70 318 piston and con rod.
Pistons are not stock. They are TRW L2373.030 basically truck pistons 30 over and approx .150" in the hole.
Specs
Total weight of assy (less bearings) 1530 grams(with bearing 1577.5)
Con rod #2406782 (no bearings) 723.7 grams
Pins and locks (floater) 156 grams
Pistons with rings 650.3 grams
Hope this helps. Pics coming

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Well another opportunity popped up so here is my latest acquisition. I pretty much have most everything else I will need for the build.
Gotta sell at least one of the others to free up a stand.
Can't wait to get started!

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I see two stands now!
And looks like new pistons.
Ima guessing you're going 318 then?

.150 in the hole is a lot, too much for a 270* cam, if I'm reading that right. Guys are on here often enough complaining about the soggy bottom ends of their teeners with 268* cams. That .150 is 30cc on a 3.94 bore. You can't make that up somewhere else. So I hope those pistons come in closer to the top; a lot closer.
A 270 cam wants about 9.8 compression ratio. for a total chamber volume of 75ishcc; you just can't afford to gain 30cc like that. You more or less need a zero deck to get close to that 75cc, in order to enjoy that 270* cam with a reasonable powertrain behind it, like a 904 and 3.23s minimum
Of course with 4.10s and a 2800, you can drive around the soggy bottom end, but the 270 won't pull very hard in a 7.4Scr engine.There's just no cylinder pressure.
Ima lil worried for you.....
 
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Pistons are used forged. All new rod n main bearings. New rings, new cam bearings. Fresh machined block. Basically put my heads intake carb oil pan. A bit off yet but could use cam n lifters from 273
Havent done any math yet but should be approx 10:1 compression.
 
Thanks. With help from good people on here, Im trying to minimize mistakes as best I can. Better be safe than sorry.
This new setup I just bought came from a machinist Ive known for years. Everything is to be within spec but I will dbl chk to be safe.
Need to make room on a stand 1st lol.
Thanks ABB
Abodybomber said:
Damn ,Steve: No one ever actually, checks crank end play. Good Move.
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4spdragtop said:
Havent done any math yet but should be approx 10:1 compression.
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If these are the .150" in the hole truck pistons that you showed above, then this wont 'be anywhere close to 10:1. I am in agreement with AJ.... 7.4 SCR, with your 64 cc heads and a .028" thick head gasket. Am I missing something that leads you to believe in a 10:1 SCR?

Not a surprise.... truck pistons were always lower SCR than car pistons, and those are low-ish to begin with.
 
Thanks ms9, this is a totally different short block. I dont think compression is going to be an issue, but no math done yet
Thanks!
nm9stheham said:
If these are the .150" in the hole truck pistons that you showed above, then this wont 'be anywhere close to 10:1. I am in agreement with AJ.... 7.4 SCR, with your 64 cc heads and a .028" thick head gasket. Am I missing something that leads you to believe in a 10:1 SCR?

Not a surprise.... truck pistons were always lower SCR than car pistons, and those are low-ish to begin with.
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AH, that is indeed different LOL. Good deal..... so this is a 340 block? THAT's quite a change too.

Now, what head is being used?
 
Yes different route altogether. I have a set of X heads. They were freshened up to stock specs by same machinist that sold me the short block.
I might tear them down and redneck/diy port them myself when I get to that point.
Or I have 302 heads that need a valve job or 2 other sets of 318/360 heads.
As of now I plan on using stock adjustable 273 rockers that are in cuda now.
Basically a set of gaskets and motor mounts should be all I need to buy. (For now).
Block is a 340 70 date code, so I will have to get a 70 FSM to get those specs. I have a 69 but there might be variations. I think crank is drilled for 4spd as well.
Gotta get one of those 318's off the stand lol.
Cheers!
nm9stheham said:
AH, that is indeed different LOL. Good deal..... so this is a 340 block? THAT's quite a change too.

Now, what head is being used?
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I'd use the X heads, 302s might be good on a 340 if you port the sh** out of them and put in bigger valves lol. 273 adjustable rockers too, sounds like a nice traditional build with all the factory "good stuff"... really looking forward to how this turns out, best of luck! Should be a lot of fun and pretty bulletproof with all the factory parts.

EDIT: BTW I have a 1970 FSM I could copy the pages with the specs you need and send it to you? Let me know which ones you need...
 
Stopped by machinist today, to drop crank off for a polish. He said to go with X. Let it breathe. I mentioned tearing them down and a diy port job. He said absolutely. But to leave exhaust ports alone besides the casting flash. So I'll try to make garage time on the heads thru the winter.
Thanks for encouragement.
Oh gotta check for pilot bearing, ill get that drilled while its at shop if it hasnt already.
MOPEkidD-3 said:
I'd use the X heads, 302s might be good on a 340 if you port the sh** out of them and put in bigger valves lol. 273 adjustable rockers too, sounds like a nice traditional build with all the factory "good stuff"... really looking forward to how this turns out, best of luck! Should be a lot of fun and pretty bulletproof with all the factory parts.

EDIT: BTW I have a 1970 FSM I could copy the pages with the specs you need and send it to you? Let me know which ones you need...
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You really changed directions.... good for you! Yes, use the larger heads for the compression ratio to be in the mid 9's; I get 9.6 or so with .028" thick head gaskets and the rest stock. (Deck height, rods, etc.)

DCR is coming out to a bit over 8:1 with the 270 solid cam installed at 106 degrees ICL, and .028" head gaskets, so you are as far up as you can easily go with that. Hope you have a good budget for tires! LOL
 
Lol yes a "slight" change in direction. When I started tallying up everything for the 318, and my machinist was offering up some of his stash (the 340), it made total sense to go this route. Ive already got intake n heads and hipo exhaust manifolds. Carb (possibly) Eddy 1405's and orignal 69 340 carb. So basically my "to get" list is head gaskets, oil pump bronze distributor gear(opinions? ?)
I have stock pump but looking to upgrade. Opinions?? Im thinking Melling HV with hardened shaft?
I appreciate all yours and everyone's help so far. Looking fwd to leaning on you and other for advice.
Yes I do see tire changes in my future(a few possibly) lol
Thanks!
nm9stheham said:
You really changed directions.... good for you! Yes, use the larger heads for the compression ratio to be in the mid 9's; I get 9.6 or so with .028" thick head gaskets and the rest stock. (Deck height, rods, etc.)

DCR is coming out to a bit over 8:1 with the 270 solid cam installed at 106 degrees ICL, and .028" head gaskets, so you are as far up as you can easily go with that. Hope you have a good budget for tires! LOL
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Are you doing a roller cam? If not, then a standard gear is appropriate.

The HV pump pumps about 20% more possible capacity but once you reach the pressure relief point both will deliver the same oil into the engine. It will keep pressure up better at low RPM's with hot oil than the standard pump; that is of value to me. The hardened shaft never hurts.

Let me know when that machinist has some more 340's to get rid of LOL!
 
Lol, yeah it came outta his personal stash. I shoulda took pics of a couple really nice Dusters that he has.
Initially I was going to use the 270S cam and lifters from the 273, but will consider my options when cam time comes.
Going with HV pump to me is "insurance" and allows for flexibility. I dont believe its a pricey purchase either (hopefully)
Thanks again!
nm9stheham said:
Are you doing a roller cam? If not, then a standard gear is appropriate.

The HV pump pumps about 20% more possible capacity but once you reach the pressure relief point both will deliver the same oil into the engine. It will keep pressure up better at low RPM's with hot oil than the standard pump; that is of value to me. The hardened shaft never hurts.

Let me know when that machinist has some more 340's to get rid of LOL!
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So got a call from machinist and crank was done being polished. I figured I would take one of the X heads he redid for me 25 years ago. He said looks good to go. All stock. Gonna diy port them when the time comes. Good to know I can go with stock adjustable valve train. While he had the crank I asked him to check for pilot bushing as this engine will ultimately be in my 69 once its done and its a 4spd car.
$20 for bushing installed. ..no brainer.
While I was in town I swung by one of Dads fellow coworkers place as he had a super sturdy cart he offered to me. Came in handy to put the 70 318 on. Even a fold up/down shelf on it.
I did my 273 heads with diy porting and cleanup. im assuming same technique? Stupid question but is there a difference 273 vs 340 heads?
#'s stamped on front drivers side right below head. FW340P32130104
Vin# 0B349476
Cant wait ti get started! Ultimately I would like to dress it up the same as itis now. Kinda wolf in sheeps clothing theme. I think Dad would be good with this.
He woulda loved putting this together.
Thanks all

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Tried to run numbers off the block to find out more specifics. Best I can tell so far is that it is a 70 model year, with a build date of May 15 1970 and was built in Hamtramck.
I'll flip thru 70 Plymouth service manual for specs. I would imagine the Dodge specs would be the same for the same model year.
I dug out my drum and sanding rolls rolls I bought a while back to see what grit they were. 80 and 120 on drum rolls and 80 on flap rolls. Got lots if anyone needs some lol.
Chased all of the threads in the bare block today. No issues. Used lard on the taps, read somewhere its good for tapping and cheaper than oil.
Gotta pick up a bottom end gasket kit(oil pan, front and rear main seals). Not sure what make yet. Probably go Felpro for oil pan, any perference for front and rear seals?
3 pipe plugs at back end look like new installs with sealant.Loctite maybe? Its red
1 pipe plug below distributor hole new install as well.
Am I missing any?
Baby steps, but its still progress lol
Thanks
Steve

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There's a drive in plug in the rear main bolt hole. It is recommended that it be replaced if the block has been boiled. Loss of oil pressure if it's loose. Let me look for the picture I have.
 
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