340 or 360 for hp

[Cranky]

Thats kind of what I always thought.....although the steel crank in the 340 contributes to some HP gains, doesnt it?

My thought is that when it comes time to replace the 318 I have it will be a 360 stroker crate engine.....keep my headers, tranny , rad, etc......

If I were starting fresh I would go big block...but tossing tons of parts to go big block makes the big block swap as expensive as a 360 stroked I would think......

No, the forged crank really doesn't help produce any extra horsepower. The 360 cast crank is a good piece like the rest of mom's parts. GM is the one that gave cast cranks a bad name....and cast cranks are usually lighter than a forged piece so it'll generally spool up faster.

Is there any issues concerning the rv engines and transmission? I'm figuring the heads to be good but the cam and possibly intake needing replacement. The tranny should be heavy duty right?

The internals of the trans should have the larger drums and 4 planetary gear set but the tail shaft is usually the short version but the pistons in the engine are usually down in the hole so compression is somewhat low.

trans probably won't have the boss for the floor shifter.

Intake is most likely a 2bbl.

its the RV Big Blocks that have a weird head arrangement

The older big blocks have the weird head arrangment which is simply a high mount water pump housing. It connects to the block and to the heads and the ports in the heads can be blocked off in the same way that the back of the heads are done and use the standard automotive housing. Also, no big blocks came with a 2bbl in an RV. The only 2bbl setup I've seen on an RV was on a 318 and yes, you could get one that way but it was a very small RV.

 

[74 challenger]

i dont think the k-frame has to be changed a 440 drops right in,did it with my b-body

 

[bad440]

A 440 is a drop in, just use 440 engine brackets, will need 727 for big block, doesn't get much easier.(did it myself) If the car had a 318 in there, easy to do; you will need of course bigger radiator, and a few simple wiring changes(extending wire to front for distributor. If car was originally equipped with a 904(most 318's) driveshaft will have to be shortened, that goes for smallblock or big block.
I was convinced when I realized rebuilding a 318 or a 440, the costs were very similar except you end up with a much larger, more powerful engine.

 

[Rob C]

Lets start with a few facts;

The 360 is a little bit cheaper, produces more torque, will peak in HP a few hundred RPM's before a 340 and use every last HP trick the 340 will use. There cheaper to start with. Slugs are a slight cheaper in general. After that, it'll cost the same to build.

Once built, it will make just shy the same amount of power a 340 will and more torque. (Considering both are built the same way as close as possible)

As far as tranny's go, a decently built 904 will hold a good bit of power. The word, "Upgrade" to a 727 is not an upgrade. It will actually slow you down and cost you gas. However, it in the long run, it will hold more power, just not enuff to justify it's usage at this stage of the game.

A word on a 318-390 stroker

Doing a stroker is a GREAT idea. Though the cost of doing one will soar over a basic rebuild and performance slugs for a stock stroke engine. You may also consider an upgrade in con-rods over a general replacement rod. It all add's up real quick.

The 318-390 stroker is a little more pricey than a 340 or 360 stroker. Due to the pistons really. It is not as popular as a 340/360 stroker kit. Your gonna want to have to do it in order to be OK with it.
(Oh, then there's a set of heads to make it work really well. IMO, a set of ported Edelbrocks to start with at a min. Edelbrock heads as cast are excellent to or around 370 cubes.)

Use the same trans that the car came with to keep costs down. One thing in changing from a 904 to a 727 is cutting and re-balancing of the driveshaft. It can be done cheaply. Probably about $60 - $70 bucks. But then again, that could be in your pocket.

IF you plan on a TQ carb, that '76 is not a great year carb, but workable. Just understand, there a pain to learn and get tuning parts for. Jets to be exact. Rod? I bend AFB rods to fit. It's only 3/4 of an inch shorter and done in my vice. (Carefully)

 

[btceng]

Update....I purchased a 340 and 727 off of Craigslist. Turns out not to be as described. Its wearing small valve j heads that need rebuilding, has been bored. 040, but has flat tops, and has a can of unknown grind. The bottom end looks fair with a small amount of flash rust in a couple cylinders due to a missing valve cover. I've got to have the block checked out and am probably looking at a. 060 bore.

Not sure what to expect with the 727. It has a reverse valve body that will have to be changed. Supposed to be built for racing.

I probably should have spent the money on the 318 and a set of gears.

 

[Rob C]

Well, it matters not now, just forged ahead and have at it. And, have fun!

 

[btceng]

Can that 340 block take .060 over and be reliable? Looks like if I'm going to use it, I'm going to have to bore it and start from scratch. Any ideas on a recipe for reliability and nice street performance? Wait a minute, that would be the old 318.LOL

 

[bad440]

That kind of overbore can cause problems down the road, have the block sonic checked, if that proves OK then that block should be good for another overbore. The factory recommends no more that 40 over. If it turns out the block can't handle a 60 over there is also sleeving, but again more money.

 

[burntorange70]

I think they have stroker kits for the 340 with a .060 over and 4 inch crank that will give you 416 cid. Have seen 340's and 360's that are 60 over but willwant to soic check it for sure first.

750 carb, some thing like an E-brock RPM or Airgap intake, cam some thing like a Comp 268 or 275 would be good for reliability and nice street performance, and headers.


That should get you around 380-400 HP. A little more if you do some head work.

 

[Rob C]

AGAIN, SONIC check it. IF the cylinder walls are thick enuff, the machinist will tell you it is OK to do.

However, I'd give up the few inches of displacement for a thicker, stronger longer lasting cylinder wall that doesn't flex as much so I can make more power and reliably make more power over the long term.

IF your 340 is all ready at the milt and this would be it's last overbore, go for it.

 

[pisser]

Depends on power output that you want. You can use the 360 crank in the 340 block for a few more cubes but it will be a cast crank. For higher power output use the forged cank (if it is and not the cast crank that came in some 340's). Use the 904 (about 50 lbs lighter than 727) that has been beefed up some with bigger drum for more cluthces and steels and change aluminum planetary to a steel one. I have both, a 360 with cast crank and a 340 with a forged 360 stroke crank both backed up with 904's and manual valve bodies. Drag race both 360- 3000lb challenger w 14/32's @ 6.90's and 340- 3600 lb challenger w/ stock suspension @7.30's in eight mile. If you still want to go with a bigblock I have for sale a 504c.i. 10.4 compression ratio that you can drive on the street all day. Need carb. and oil pan(depending on application). Everything new but block 7500.00.

 

[bad440]

Just to correct this one, a 360 crank does not fit in a 340 block, 360 has larger mains, as well as main bolts spread further apart.

 

[burntorange70]

Just to correct this one, a 360 crank does not fit in a 340 block, 360 has larger mains, as well as main bolts spread further apart.

You can have the 360 crank turned down to fit a 340. Thats what they used to do before all the aftermarket stroker cranks came out.

 

[pisser]

Yes it can be turned while at machine shop since it will be there anyway for magnafluxing and balancing.

 

[btceng]

You can still see the hone marks in the cylinders but as mentioned earlier, there is a slight haze of rust in the #1 hole. I guess I should play it safe and take it to the machine shop. I hate to spend the money for nothing.

 

[moper]

If you're not an engine guy, have it looked over. That's cheap insurance, and most shops won't charge you if they get a rebuild out ot if. If it's .040 over, then it should be sonic tested. If your shop doesnt own a tester, or tells you it's fine, fine a more modern and educated shop. I've built several 060 over strokers and they perform great. But... I test my own blocks withn a good tester. A note - Any pistons for a stroker larger than 4.07 (4.04+.030) are special order and extra money. Personally, with any E body, more stroke is better. teh 340 is short stroke. I'd have recommended the 360 in a heartbeat. (sorry, I dont get over here as much as I should)

 

[Rob C]

Just to correct this one, a 360 crank does not fit in a 340 block, 360 has larger mains, as well as main bolts spread further apart.

As mentioned above, I'd like to add, MoPar Performance has 3.58 360 stroke cranks that all ready have the smaller 318/340 main. This old trick of a 360 crank into a 340 yields 367 cubes w/a stock bore, 372.6 cubes @ .030 over, 378 cubes @ 060 overbore.

A 318 with a 3.91 bore is a 343, (!!!) 349 @ 030, 354 @ 060. Some 318 blocks have been sonic tested and bored to a 4.00 for a 360. It is possible. :toothy12:

 

[Cranky]

Another good thing about a 360 is it's 4" bore and just about everyone built an engine using a 4" bore as it's standard size so 'shelf' pistons are available from nearly every aftermarket manufacturer. If you want to play games with rod length, there's probably a piston that will work sitting on a shelf somewhere but I'm not positive on that because I've never played around with small blocks like I have big blocks. Also, when buying a used engine, I like to at least pull one head off and take a look or see paper work on it's build.

 

[btceng]

Thanks Cranky. Good advice for next time.

Rumble, got any experience with the 318 stroked at stock bore?

 

[BIGSHCLUNK]

Intresting thread, as I'm looking at an a-bod w a motor issue. Dont know yet if its a 318 or 340 and I got a (74) 360. HMMMM cool