I started rebuilding my 318, I messed up doing the ridge reeming, got too deep into the bore. So I'm doing a complete rebuild now. May have a 340 short block available for a good price. My heads are all rebuilt, ported the head. Planning on using the 318 heads. Ya, I know, not the best route but it's what I have. Can change out the heads later. But why not a 340 instead of a 360? I don't have the money to build an expensive engine. I just want a decent hot rod. Already have new 268 cam and lifters. Performer intake with edelbrock 600 (Carter copy). Doug's ceramic coated headers.
Why not build a 340?
- Thread starter MOA
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sure, why not... usually the "why's" are three things: 340 = more $$$ up front; 360 = much easier to find in good running condition; and if your not building a stroker, the 360 is 20 cubes ahead.
The 318 heads on a 340 will have slightly higher compression and should have good port velocity - nothing wrong with it.... Maybe port the 318 heads for a little better flow. There's a good thread on home porting in the small block forum.
Put it together how you can afford now, then improve later as funds are available...
Put it together how you can afford now, then improve later as funds are available...
ScampMike
Despicable Damn Yankee
absolutely - run whatcha brung! go with the 340 block for sure.
nm9stheham
Well-Known Member
The hurdles for 340's are the block cost and fewer piston choices; the 360 has the advantage in both of these areas. In hydraulic roller use, the 340 blocks' lifter bore chamfers can be problematic, but that is not likely your issue to deal with.
In your case, the 360 will have added cost in a different crank and different front damper and flextplate/flywheel. With a 340 block, you can drop in your 318 crank and reuse your flexplate or flywheel, and reuse the damper if it is good condition. Also, IIRC your 318 pan will fit right on the 340 block but not on the 360. So parts re-use will be better for you unless you find a complete 360 short block (should be do-able).
What HP range are you looking at? If under 400 HP, then the cast cranks are supposedly safe.
Stock type 340 pistons for the earlier years set about .018" above deck; this is as opposed to 318 piston setting something like .080" below the deck. So managing the increased CR with those smaller chamber 318 heads is going to have to be solved before you make any final decision. Some options are different pistons choices and a thicker head gasket. If you get this solved for the 318 heads, then you ought to also look ahead to whatever larger heads you are considering, to see if they will drop the CR too low. I think this can be managed with head selection, maybe some milling of the later heads, and changing head gaskets thickness, but I would plan it out now so there is not an unwelcome "Ooops!" moment later.
All of this can be worked out it is a simple math problem and there are plenty of calculator around to make it easy.
In your case, the 360 will have added cost in a different crank and different front damper and flextplate/flywheel. With a 340 block, you can drop in your 318 crank and reuse your flexplate or flywheel, and reuse the damper if it is good condition. Also, IIRC your 318 pan will fit right on the 340 block but not on the 360. So parts re-use will be better for you unless you find a complete 360 short block (should be do-able).
What HP range are you looking at? If under 400 HP, then the cast cranks are supposedly safe.
Stock type 340 pistons for the earlier years set about .018" above deck; this is as opposed to 318 piston setting something like .080" below the deck. So managing the increased CR with those smaller chamber 318 heads is going to have to be solved before you make any final decision. Some options are different pistons choices and a thicker head gasket. If you get this solved for the 318 heads, then you ought to also look ahead to whatever larger heads you are considering, to see if they will drop the CR too low. I think this can be managed with head selection, maybe some milling of the later heads, and changing head gaskets thickness, but I would plan it out now so there is not an unwelcome "Ooops!" moment later.
All of this can be worked out it is a simple math problem and there are plenty of calculator around to make it easy.
I already ported the heads and had .010 taken off the head, surfaced. I increased the bowl size on both intake and exhaust, more so on the intake. Eliminated the humps and raised the roof a bit on exhaust. New valve springs that came with the cam.
I want as much usable hp as I can get. I estimated the 318 would put out between 270-300 to the wheels. Going to have pro trans (local drag racer) build the 904, he suggested putting in a lower first gear and use a 323 rear end, rebuild the stock torque converter. The lower first gear will have a ratio similar to a 355 rear end. Good out of the hole but not be spinning so high on freeway. I trust his opinion on this, he IS the 904 go to guy. This is intended to be a fun street rod, not a race car.
diymirage
HP@idle > hondaHP@redline
IF you can get a good deal on a 340, go for it
But chances are...you can get a good, running, complete 360 for the price of a 340 short block that needs work
You said yourself you can't afford an all out build...so build what you can afford
But chances are...you can get a good, running, complete 360 for the price of a 340 short block that needs work
You said yourself you can't afford an all out build...so build what you can afford
mguner
How many is too many?
Hell yeah I'd do it! Should have great torque and response and work well with stock converter and gears.
Dartswinger70
Well-Known Member
A 340 short block is a good foundation to start with. Go for it.
Finding a 360 in so cal is harder than one might think. A 360 is what everyone is looking for. Guy at cylinder head only mentioned that 360 heads are getting hard to find. I know where I can get a 360 block only for $700. Ya, not as easy in so cal as it is elsewhere, it seems. And the other part of getting a 360, I have no idea what year range is best and or the ECU fuel injection, ignition trigger, etc. So many different 360s. Roller cam, heads, ignition, fueling..
IfItsGotWheels
XS Tech-Anything worth doing, is worth doing in XS
Dartswinger70
Well-Known Member
years ago, I got rid of a 360 just because it was laying around collecting dust. For me, I had 340's and 318's and the 360 being externally balanced was a PITA for me at the time. I wanted interchangeability as far as pulling one engine and dropping another in quickly so I stayed with 318-340 setups. I wish I would have kept that 360. I haven't gotten rid of many things, but that was one I regret. I basically gave it away. But at the time, they were "dime a dozen" I remember 318's being "dime a dozen" Now they are popular small blocks LOL!
Just wanted to make sure I want missing something.
With different numbers from different builds, hard for me to estimate. Initially I felt if I could get 270 to the wheels I would be happy with that. Engine dyno numbers don't really mean much to me, where the rubber meets the road is what I'm interested in. This is going to be a daily driver, I'm semi retired, I have a lot of screwing off to do.
yellow rose
Overnight Sensation
I would step over free 360's to build a 340. I will take th bigger bore, shorter stroke and smaller main bearings all day long.
Even with a 4 inch stroke, there is PLENTY of overlap on the crank throws to not have to deal with those big main bearings.
Plus, when you are induction limited (and most guys are) I detest giving up rod/stroke ratio. But that is a discussion on engine geometry and beyond the scope of this thread.
Even with a 4 inch stroke, there is PLENTY of overlap on the crank throws to not have to deal with those big main bearings.
Plus, when you are induction limited (and most guys are) I detest giving up rod/stroke ratio. But that is a discussion on engine geometry and beyond the scope of this thread.
Main reason the 360 is favored over 340 now is cost and 20 cid. Unlike HP torque is pretty predictable most street performance engines will be around 1.2 lbs-ft per cid so that's 24 lbs-ft advantage or basically one gear size.
So the average gear for a decent 360 seems to be 3.55 which would mean a 340 would need 3.73 gears. Not the biggest deal in the world.
So the average gear for a decent 360 seems to be 3.55 which would mean a 340 would need 3.73 gears. Not the biggest deal in the world.
I'm kind of digging on Yellow Roses post. And while I agree a whole lot, most of the time I pass worn 340 for $700 & better.
For that cost, a better way to skin a cat for your street performance needs would be IMO would be a complete 360 Magnum engine. All it needs is a B&M flex plate if you do not get the factory one, cam, headers, intake and a carb.
The early MP create engines used a dead stock 5.9 and the above parts to make a 380hp 360 engine which routinely dyno'd over 400.
(The recipe was;
1-7/8 headers, MP's roller cam is no longer available, but the duration was 230 on the intake IIRC, there single plane and a 750 Holley on top. Not to shabby for a few bolt on and a cam huh? )
Good luck in your endeavors
For that cost, a better way to skin a cat for your street performance needs would be IMO would be a complete 360 Magnum engine. All it needs is a B&M flex plate if you do not get the factory one, cam, headers, intake and a carb.
The early MP create engines used a dead stock 5.9 and the above parts to make a 380hp 360 engine which routinely dyno'd over 400.
(The recipe was;
1-7/8 headers, MP's roller cam is no longer available, but the duration was 230 on the intake IIRC, there single plane and a 750 Holley on top. Not to shabby for a few bolt on and a cam huh? )
Good luck in your endeavors
nm9stheham
Well-Known Member
Since this is street engine with lower gearing, then go for better torque and a wider torque band. Keep the SCR up above 9. Just a quick exercise:
- 318 head, open chambers of 66 cc with milling
- .051 standard Felpro head gaskets
- KB243 pistons with standard deck height, .030" overbore
- SCR = 9.1
Change head gaskets to .039 Felpro 1008's, and your at 9.3.
It won't be as hard as I thought to keep the CR up around 9 with the larger 360 type heads with nominal 72 cc combustion chambers. And you can always mill them .030" or so and stay well above 9.
BTW the Speed Pro L2316F's are probably a better budget choice as they are close to stock weights for piston & pin and so won't require a crank rebalance.
- 318 head, open chambers of 66 cc with milling
- .051 standard Felpro head gaskets
- KB243 pistons with standard deck height, .030" overbore
- SCR = 9.1
Change head gaskets to .039 Felpro 1008's, and your at 9.3.
It won't be as hard as I thought to keep the CR up around 9 with the larger 360 type heads with nominal 72 cc combustion chambers. And you can always mill them .030" or so and stay well above 9.
BTW the Speed Pro L2316F's are probably a better budget choice as they are close to stock weights for piston & pin and so won't require a crank rebalance.
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Thanks for the info. The 340 is being hot tanked and prepped. Harder to find a 360 than a 340 at a reasonable cost? I would of never imagined it would turn out this way.
The Performer dual plane manifold I bought is a spread bore. At some point I'd like to try a Thermo quad on it. I had a 780 on a 327 and it worked better than anything else I had used on it. Everybody (mostly) says it's too much carb, I found it worked great, the most problem free carb up to that point. Keeping in mind, that was back in the day of problematic Holley carbs, power valve issues using the 600. God those were a pain in the ***!
The Performer dual plane manifold I bought is a spread bore. At some point I'd like to try a Thermo quad on it. I had a 780 on a 327 and it worked better than anything else I had used on it. Everybody (mostly) says it's too much carb, I found it worked great, the most problem free carb up to that point. Keeping in mind, that was back in the day of problematic Holley carbs, power valve issues using the 600. God those were a pain in the ***!
moper
Well-Known Member
340s are nothing special once you view them as cores. Any of these engines, even the "lowly" 318, respond to the usual performance rebuild work, and all will make decent power for the OP. While technically accurrate in terms of reasoning, there is no reason to even remotely consider the main bearing size on a build such as this, or probably 90% of builds currently being done. If you're building an endurance engine, or in some cases a high rpm drag racing engine, then it's probably a worthy considertaion. For a hot rod with a 318 it's a waste of grey matter.
I have heard the "smaller main bearing" thing all my life. I mean no disrespect when I say this, but to me, that doesn't hold a lot of water.
I know the 360 larger journals has more friction area and all, but you will never in a million years be able to tell it with what God gave you . Might not even show up on a dyno.
It's sorta like the Chevy guys arguin over whether a 2 or 4 bolt main is better. IMO, it's not enough difference to know anything about.
Course, I could be wrong as hell. It's happened a time or two.
I know the 360 larger journals has more friction area and all, but you will never in a million years be able to tell it with what God gave you . Might not even show up on a dyno.
It's sorta like the Chevy guys arguin over whether a 2 or 4 bolt main is better. IMO, it's not enough difference to know anything about.
Course, I could be wrong as hell. It's happened a time or two.
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