Hey guys,

I am going to be running a 10.5:1 compression N/A 340 in my 71 scamp and turbo setups have really attracted me lately...Im just trying to do as much reasearch and planning ahead of time (this setup with a turbo wont happen for probably about a year) that way i can execute the plan right! what i was wondering was which smallblock platform do you guys recommend for a turbo? When i do the turbo motor i was hoping to have the car into the mid 11's, maybe faster, and still VERY streetable...I realize the compression in my 340 is too high for a turbo...Does it make sense to get some pistons that will help lower the cr, or should i just move up to the extra cubes and lower compression of a 360? or should i go 318? Id think the extra cubes would be better for more power obviously, and i wouldnt have to run as much boost...My 340 has a forged crank and pistons (obviously id change the pistons) and ported x heads so if i could reutilize this motor for the turbo setup that would be great, but if its better to move to one of the other smallblocks i would do that instead...Interested to hear what you guys have to say on this...also, i saw a thread about how much power stock blocks can handle, but it was on the b/rbs..how would can an LA block handle before having to upgrade to an aftermarket block?

 

well i ran 11.5 to 1 on my turbo setup, but i ran race gas all the time. was fine without issues for me. id say you should be able to get by with it on racegas, but i dont know what the piston crown looks like or if the rods are up to the challenge. camshaft has a bit to do with compression aswell as the pistons.

 

I'll need race gas to run 11.5's in the quarter? the whole reason i was attracted to boost was being able to make good power with lower compression and therefore pump gas....guess i need to reconsider my options since this will be a daily driver summer car and race gas is out of the question for sure...the cam I am running is an old comp extreme energy grind specing out at 480 lift/ 280 duration...Im not sure what the pistons are (motor was built by my dad quite a few years ago but they are forged)...thats why im wondering if moving to something like a 360 or 318 which has lower compression would be better since i can run boost on pump gas (or so i thought? )

 

That was 11.5:1 compression on boost. Needs race fuel.

 

so obviously as boost increases or comes in fully so does compression...how low of compression would the motor have to have so that when full boost comes in I am still able to run pump gas and mid 11's...sorry if thats a real noob or stupid question, i aint the smartest on this

 

i think a water/meth kit would be best if you wanted to not rebuild the 340 and try to get away with pump gas.

 

im not dead set on the 340...in fact, i think its actually straying from my goals of streetable power to have to run the turbo with the 340...thats why im asking what you guys think about the 318 and 360's potential for my goals..I forgot to mention that this will be blow through, and will be fabbed my me...I can find a running 360 in decent shape around here for 500 bucks if im patient (and like i said this isnt happening right away)...Im not familiar what the stock compression of 318's and 360s are (I know they probably changed in certain years, same with 318's) but i know they are obviously lower than my 340's current cr, which is why i thought they would make a great platform for the goals im planning

 

if you want to break cast pistons use the other engines. as long as your tune is safe you should be fine with either, but going to need more boost to make the 318 run with the 360.

 

i know thats the downfall of the other two, but i would more than likely try to upgrade the rotating assembly (or atleast the pistons to forged ones)...How much boost would i need to be able to achieve mid 11's on pump gas with a boosted 360? and how much boost do you think i could run on the stock internals before im really pushing the breaking point?

 

dont know. but to get in the 11's your going to have to do some suspension work to handle it.

 

I realize that...its a whole other section of the car that ive not reserved for discussion...a good chassis and crap motor are better than good motor and crap chassis...I feel as though im asking for too much help here ive looked through many different threads but im just trying to figure out which motor will be a better base for my goals and if they will actually help me attain my goals (mid 11's on pump gas)

 

dont get snippy here or ill stop capeash. attitude will get you the big 0 for help from the members here.

like i said either will get you what your after, just up to you on which one suits you best. the 360 will get you closer to the power needed at a lower boost cuz its larger to take in more air from the get go. there for easier to acomplish your low octain goals.

 

I would search all of Duner's posts for info on his baaaaddd 5.9L Truck. It's surprisingly stock. Based on his results, you should be able to eclipse your 11.5 goal if you play your cards right....

 

If that seemed snippy then i guess ill just have to treat this board like moparts too then....you answered my question perfectly with your last few sentences about the 360..thats all i was looking for, just a rough idea from the guys who have done it before on what will atleast start to head me in the right direction as well as your personal opinions on these motors

as far as duner's posts go, i will have to search for more...i have seen tidbits about his truck but have not really delved into his setup..thanks for the tip

 

Mshred look into turbocuda, topfueldart and rdakota for information as to what you are trying to do. They have been very informative on this site. Brian W.

 

the whole, "i feel like im asking for to much help here " comment. no thats not snippy. to think anyone of those engines is better then the other is kinda....well ill keep it pc. they will all do the job, but you seem to think ones better then the other. if its the same design only size is the difference. then i would guess the large being the better of the 3.

 

hey man the little emoticon was supposed to be me not understanding...I was looking more for info on block strength, factory cr and rotating assembly material not size as i realize size makes more power...it just felt like you didnt want to contribute because i lacked knowledge...its all good man, im here to learn so im all ears to any suggestions

 

its all good then.
i dont think any is stronger then the next. maybe the newer magnum engines are, but i think thats more for the roller cam option for its liking. i think with only 11's you should be fine for your et goals.

 

cool man! did you ever decide on a front crossmember for it? i remember you made the post about it over on BBD...

 

I have no testing of my own, but it is said the 340 and early 360's (through 74) are stronger. If nothing else, they are cast with different water jackets than post 74 360's, so they are _different_ at least. I don't think I've ever read anything that put them to the test. All the BB myths have been tested fortunately. I would agree that with your stated goals any OEM block should be fine.