318 stroker -> Mopar Performance A8 build guidance needed.

[SOMMS]

Hello, long time lurker - first time poster here.

I'm looking for some small block stroker wisdom. I am building a track car out of a 72 cuda for 50% track days(twisties...not drag)/50% grocery getting/mopar events. I occasionally want to put the wife and kids in it so Im not planning on caging it. One of the primary focuses of this car will be handling and trying to get it as light as possible.

To this end I have decided to go the small block stroker route - particularly the 318/340 setup as the 360 blocks weigh 50lbs more. I already have a roller 318 block to start the build with.


The goal of this motor is to: be reliable, make 500-600hp, run on pump gas, be light-weight.


My initial idea was to get the car on the street/track with my 318 block, and then later upgrade to a Mopar Performance A8 block (Mopar Performance A8 Aluminum Blocks & Components - JEGS) as these motors weigh in at roughly 350 lbs (compared to 525 lbs of the 318/340)


Okay - so now the question:
Is there a good stoker crank/rod + valve train + head + carb combination that would work well in my 318 block, but then could be later transplanted to the A8 block?
Or is this just a crazy idea? (Would I need to start with W9 heads on my 318)?



The budget for the initial build is $5-6k, but then later ponying up the money for the A8 block.



Thanks for any help!


S

 

[TT5.9mag]

You’re talking about building a fairly serious piece of hardware and using it for a purpose it’s not necessarily intended for. Like using a 10lb sledge to drive in a staple. But to each their own. If you’re stuck on the A8 w8-9 combo, find a sprint car or roundy round team selling a complete engine and pony up the cash for it. You’ll be years (and $$$) ahead. For a more reasonable approach to your goals, refresh a magnum and stick a turbo on it. Done and done.

 

[67autocross]

I know of one A8 running…. Probably cost $40 grand Canadian… you “might “ be better off getting a Ritter aluminum LA block up front and forget about the A8

 

[sireland67]

The price of the support hardware for the block is not cheap, $1100 for head studs????????

 

[toolmanmike]

Hello, long time lurker - first time poster here.

I'm looking for some small block stroker wisdom. I am building a track car out of a 72 cuda for 50% track days(twisties...not drag)/50% grocery getting/mopar events. I occasionally want to put the wife and kids in it so Im not planning on caging it. One of the primary focuses of this car will be handling and trying to get it as light as possible.

To this end I have decided to go the small block stroker route - particularly the 318/340 setup as the 360 blocks weigh 50lbs more. I already have a roller 318 block to start the build with.


The goal of this motor is to: be reliable, make 500-600hp, run on pump gas, be light-weight.


My initial idea was to get the car on the street/track with my 318 block, and then later upgrade to a Mopar Performance A8 block (Mopar Performance A8 Aluminum Blocks & Components - JEGS) as these motors weigh in at roughly 350 lbs (compared to 525 lbs of the 318/340)


Okay - so now the question:
Is there a good stoker crank/rod + valve train + head + carb combination that would work well in my 318 block, but then could be later transplanted to the A8 block?
Or is this just a crazy idea? (Would I need to start with W9 heads on my 318)?



The budget for the initial build is $5-6k, but then later ponying up the money for the A8 block.



Thanks for any help!


S

Retrace your steps and form a new plan.

 

[rumblefish360]

Hello, long time lurker - first time poster here.

I'm looking for some small block stroker wisdom. I am building a track car out of a 72 cuda for 50% track days(twisties...not drag)/50% grocery getting/mopar events.

The goal of this motor is to: be reliable, make 500-600hp, run on pump gas,
My initial idea

Up to 600hp and no cage…. Stop, give me all of your money, then say it’s the same thing, I threw it all away for nothing doing the dumbest thing I could think of.

50/50 track/grocery getter equals a stock block and not 600hp, back it down to 500, 500 and change & it’ll live a while. Use frame connectors. A cage would really help in many areas including but not limited to a bent up and twisted car, everyone is safe inside when shot goes sideways & it will.

The A8 block is not what your thinking it is.

 

[Cuda416]

Second 50/50 use case 550+hp stroker 318 post in two days from new accounts. Almost like someone is stirring up dust.

 

[rumblefish360]

Second 50/50 use case 550+hp stroker 318 post in two days from new accounts. Almost like someone is stirring up dust.

I don’t think that’s correct. 318 now, A8 (Highly Discouraged!) later. Though he did mention “318/340”, the 340 block is the way to go if you can!

It’s his first post…. Have mercy!

 

[Cuda416]

I don’t think that’s correct. 318 now, A8 (Highly Discouraged!) later. Though he did mention “318/340”, the 340 block is the way to go if you can!

It’s his first post…. Have mercy!

Ha, well, we'll see. Just an odd turn of events after the other guy got trounced.

 

[rumblefish360]

 

[junkyardhero]

the A8 build would be its own entity, basically nothing from a LA stroker could be used or, more aptly, should be used when building a piece like that.

a roller teener with a stroker would be a good starting point for a pretty stout engine combo, but like @TT5.9mag pointed out a fresh mag with a turbo would be the easy button.

that would easily meet your power goals, live on the street and leave a little money in the coffers for all the suspension work you're going to need, and a trans. definitely a trans.

 

[273]

Hello, long time lurker - first time poster here.

I'm looking for some small block stroker wisdom. I am building a track car out of a 72 cuda for 50% track days(twisties...not drag)/50% grocery getting/mopar events. I occasionally want to put the wife and kids in it so Im not planning on caging it. One of the primary focuses of this car will be handling and trying to get it as light as possible.

Race track you can build for any rpm you gear it for streetability idle to 3000 rpm is your daily
driving range so you got to keep that in mind when trying to extend the powerband to 5000-5500+ rpm with deeper gears and higher stall 6000-6500 rpm are possible, but you still want a decent idle-3000 rpm which how much cam overlap is gonna be the biggest factor.

To this end I have decided to go the small block stroker route - particularly the 318/340 setup as the 360 blocks weigh 50lbs more. I already have a roller 318 block to start the build with.

Why would a 360 block weigh that much more?

The goal of this motor is to: be reliable, make 500-600hp, run on pump gas, be light-weight.


My initial idea was to get the car on the street/track with my 318 block, and then later upgrade to a Mopar Performance A8 block (Mopar Performance A8 Aluminum Blocks & Components - JEGS) as these motors weigh in at roughly 350 lbs (compared to 525 lbs of the 318/340)

With the money it seems you plan on spending, build an all aluminum 500+ cid big block it will make the most hp/tq in the street friendly rpm band of idle to 5500+ rpms.

Okay - so now the question:
Is there a good stoker crank/rod + valve train + head + carb combination that would work well in my 318 block,

I have Nothing against the 318 and if you really want to, build it. You want power & drivability which a 390+ cid could be decent at that and the smaller bore will allow enough flow for 500-600 hp but a 360/340 is gonna breath better and make like 20+ more cid for a slightly better idle-5500+ rpm.
Giving you more driveability.

but then could be later transplanted to the A8 block?
Or is this just a crazy idea? (Would I need to start with W9 heads on my 318)?



The budget for the initial build is $5-6k, but then later ponying up the money for the A8 block.



Thanks for any help!


S

You don't need that for 500-600 hp that's more for a 700-800+ hp.

 

[SOMMS]

the A8 build would be its own entity, basically nothing from a LA stroker could be used or, more aptly, should be used when building a piece like that.

a roller teener with a stroker would be a good starting point for a pretty stout engine combo, but like @TT5.9mag pointed out a fresh mag with a turbo would be the easy button.

that would easily meet your power goals, live on the street and leave a little money in the coffers for all the suspension work you're going to need, and a trans. definitely a trans.

I didn't know I was going to need a Nomex flame suit for all of this - so thanks for the kind reply.


I'm actually trying to go the otherway - the horsepower goal is not the problem - the weight is. From all the reference data I can find on the web...360's are about 550 lbs, the 318/340s run about 525. Now there are gen III hemi's that are 485 - but I'd prefer the older school approach. Not sure how up-to-date it is but Jegs is listing the A8 for 8k and legend is the motors clock in just under 350lbs.


Fwiw - tranny will be a tremec 6 speed unit.


S

 

[SOMMS]

I don’t think that’s correct. 318 now, A8 (Highly Discouraged!) later. Though he did mention “318/340”, the 340 block is the way to go if you can!

It’s his first post…. Have mercy!

Hey there rumblefish,

I do have two blocks - the 318 roller and a 67 340. I'm just on the fence as to whether or not I should build the 'period piece' 340 instead of using the endless supply of 318's.

S

 

[273]

If you got a 340 and want build a serious engine why leaning towards 318, build the 340 is a no brainer with it's .140 bigger bore, besides efficiency, tq is air flow per stroke (CID/VE%) and hp is air flow over time (revolutions per minute). Bigger bore = CID/AIR FLOW (CFM).

 

[SOMMS]

If you got a 340 and want build a serious engine why leaning towards 318, build the 340 is a no brainer with it's .140 bigger bore, besides efficiency, tq is air flow per stroke (CID/VE%) and hp is air flow over time (revolutions per minute). Bigger bore = CID/AIR FLOW (CFM).

It's .60 over already so leaning on like I want is probably not the best use of it.

 

[GTX JOHN]

Sonic test the 340 = It might be fine
for you purpose.
I would forgot the A8.
Overdrive trans would be way simpler 500/518.

 

[TT5.9mag]

As @ratbastad would say don’t step over donuts to pick up dog turds. I doubt the 360 is 50lbs heavier than a 318/340 but even if it is, the bigger engine will more than make up for the weight disadvantage with torque production. Loose 50 pounds somewhere else. The gen3 hemi idea is solid as well and can make good power. I’d go that route far before trying to find (or machine) everything you’ll need to put an A8 together. Just for ***** and grins, call a few cam companies and ask if they have a core for an A8 engine.

 

[273]

It's .60 over already so leaning on like I want is probably not the best use of it.

it's up to, depending on your idea of streetable you might be asking too with this 50/50

396 500 = 1.26 hp per cid with a peak hp around 6000 rpm , 600 = 1.52 hp per cid with a peak hp around 6500 rpm. For a weekend burnout machine probably streetable enough but seems like your going for a more balanced sport/super car pro touring thing.

What about and centrifugal blower?

Your best bet is to build higher efficient engine power more like 1.3 to 1.4 lbs-ft per cid than the more standard fair 1.2 to 1.29 lbs-ft. Which your should find a good builder and work on a game plan together. Higher lbs-ft will make the power at a low rpm for a given hp and cid.

 

[273]

As @ratbastad would say don’t step over donuts to pick up dog turds. I doubt the 360 is 50lbs heavier than a 318/340 but even if it is, the bigger engine will more than make up for the weight disadvantage with torque production. Loose 50 pounds somewhere else. The gen3 hemi idea is solid as well and can make good power. I’d go that route far before trying to find (or machine) everything you’ll need to put an A8 together. Just for ***** and grins, call a few cam companies and ask if they have a core for an A8 engine.

in his example it was only 25 lbs heavier 550 vs 525 lbs

 

[Killer6]

I didn't know I was going to need a Nomex flame suit for all of this - so thanks for the kind reply.


I'm actually trying to go the otherway - the horsepower goal is not the problem - the weight is. From all the reference data I can find on the web...360's are about 550 lbs, the 318/340s run about 525. Now there are gen III hemi's that are 485 - but I'd prefer the older school approach. Not sure how up-to-date it is but Jegs is listing the A8 for 8k and legend is the motors clock in just under 350lbs.


Fwiw - tranny will be a tremec 6 speed unit.


S

I don't know where You're getting these engine weights, but engines & blocks are two different things, and the weights You've listed don't add up even a little. An assembled Slanty is like 390#, an LA is only 450-475#, and in case You don't know the iron heads & intake on the LA are a good 30#+ heavier than B/RB ones. Replace the heads & intake with Al-U-minimum & an LA is close to stk. Slanty weight.

 

[junkyardhero]

worrying about engine weight should be your last concern. i think that 50lb difference between the small blocks is hogwash. and that 200ish or so for an A8 when you break down for $ per pound is a poor investment in weight reduction. your return for dollars spent in lightening something up would be so, so much more on a fiberglass front clip, gutting the interior, lightweight wheels/brakes, aftermarket K setup, manual steering, alum radiator, that sort of thing.

TT5 had the answer-- lose 50lb someplace else.

unless you have or are planning on getting a car that is "correct" for that 340 and you care about "numbers" then i wouldn't even consider it as an option and sell the thing to finance another aspect of the build.

also, "8K for an A8" is not even close to being a reality. that's just for the block man. then, before you can even thing about putting stuff into that block you're gonna need sleeves (i don't think the block comes with them) so there's another 1K, a timing cover (1,300), headstuds (1,100), misc. block hardware/cam bearings, waterpump drives, plates and **** (1,000), dry sump oiling system (2K WAG) so that's about 15K before we're talking about machine work, heads, intake, and a bottom end (cranks are what, 5K?)...

random question, what's your overall budget for this build? what do you project the timeline to be?

 

[Killer6]

Sonic test the 340 = It might be fine
for you purpose.
I would forgot the A8.
Overdrive trans would be way simpler 500/518.

He's talking Road Course "track" car, so the trans is what I'd use, but the engine plan is flawed.

 

[TT5.9mag]

in his example it was only 25 lbs heavier 550 vs 525 lbs

I’m not sure what you read, but I read this from the original post;

To this end I have decided to go the small block stroker route - particularly the 318/340 setup as the 360 blocks weigh 50lbs more.

 

[SOMMS]

I don't know where You're getting these engine weights, but engines & blocks are two different things, and the weights You've listed don't add up even a little. An assembled Slanty is like 390#, an LA is only 450-475#, and in case You don't know the iron heads & intake on the LA are a good 30#+ heavier than B/RB ones. Replace the heads & intake with Al-U-minimum & an LA is close to stk. Slanty weight.

Lessee - I'm using the one posted at Hughes Engines (https://www.hughesengines.com/TechArticles/5engineweights.php). And aluminum heads are going to be used no matter what (trick flow v W9).

That puts the 318/340 in the 475lb zone(with alum heads).