help with 360 stroker

[daves 72 dart]

hello! i just read in the dec mopar action. that the stock small blocks tend to split their cylinder walls at about 550 hp unless the water jacketsare concreted. im doing a 4 inch stroker h-beam rods forged pistons.this is goig to the same engine that is in engine masters. this is going to be a weekend street car to eat chebs and 5.0 ruststangs.

[eric414]

i think thats what happened to my stroker 360,it took out the whole cyl wall.i bent 4 h-beam rods,one piston was 1 inch in diam.one head it was a mess.the only thing that was good that i could use was the crank,rockers and intake.i have a new R block now.

[rumblefish360]

Thus is the reason to keep overboreing down to a min.
The possabilty is certainly there. Another weak spot that can crack at high HP leves is the cam area, the webbing. A fella here did this while under boost.
Reguardless. 550 hp is pushing the limits. A good block can live past that, but the question is how long. Cranks (Cast) are said to be good till 600 HP. Stock rods can take it, but better be prep to do so.
Eric went the best way although pricey, it'll pay for itself in the long run.
If he did a stock block and blew it up again, theres the pay off for making use of the race block instead of the stock block again.

[daves 72 dart]

well shit! what is a safe hp for a stock mopar small block?

[dust]

Semi unrelated: What’s safe for stock Hemi 426, I’m just curiou

[daves 72 dart]

where can i find R blocks?

[sanborn]

Wish I could give you a definitive answer---but I don't know of anyone who can. All you can do is base the answer on experience.

Horsepower doesn't destroy blocks---torque does(yeah, they are related but I don't know exactly how when it comes to destroying blocks).

Torque tries to twist the cylinder block. The amount of twist is dependent on the amount of torque applied, RPM the torque is applied and the frequency the torque is applied. What am I saying?

Amount of Torque---Stroker cranks increase torque significantly, increased compression increase torque. Modified heads/long cams usually decrease torque.

RPM Applied---The higher the RPM, the less torque applied to the block during each revolution.

Frequency of Torque Application--- A new, stock block may be able to stand 500 ft/lbs. of torque---during the first application. But keep applying that same 500 ft/lbs. to the block and the block begins to fatigue, then flex, then crack, then fail. Said another way, you may be able to run 100 drag races before failure---but only one 50 lap oval track race(because each lap on an oval track is equal to about two drag races).

I know, I haven't answered the question! Still don't know if I can!

Real Life Situation---A friend has a 414 engine, steel crank, race rods, JE pistons, four bolt mains, W2 heads, roller cam, etc. A serious engine used in his oval track car. The engine was prepared in a nationally known shop. He ran it THREE times in an oval track race. Noticed a slapping sound, brought it to my shop. When we took it apart, we found the block had twisted so much that a rod bolt was hitting the block. In addition, the deck was not flat(.003" dip in the center of the block), the bores were not round(.005" out of round even though it was honed with deck plates). In short, the block was ready to fail. What is the solution? Another block, earlier with better cylinder walls---that will buy him a few races. The best solution---a race block. The race "R" block is the only long term solution.

What will a stock block take? A loaded question! A stock block will take a stroker crank---but when you load it with modified W2s, high compression, roller cam, etc. and really abuse the engine in serious racing---it will fail. Maybe not in the first race---but it will fail ultimately. Hard block will help but all that does is give the cylinder walls support so they don't flex as much--- but that too is a temporary help. Four bolt mains do help---a little. But they primarily help to prevent "cap walk" under high stress.

My advice, if using a stock block---use a stock stroke crank! And even they can fail if the engine is really serious.

Cheer Up! GMs and Fords have the same problem. Serious race engines demand aftermarket blocks, regardless of brand.

[DAHEMIKOTA]

The best thing to do to a stock block when you push a lot of power is to use a motor plate to mount the engine. The stock motor mount ears will distort the block enough to seize the piston in the cylinder. This was proven in a Chrysler dyno run. I have a stock block LA engine that run a corrected 547 HP on a dyno. It has 50K miles on it with no broken engine parts ...yet. I beat on it every chance I get. What has failed is Torque conv,Trans,Rear end. Now I will probably blow the engine tomarrow.

[sanborn]

You are correct about the block mount ears! A mount plate is the only way to go---the "R" blocks are beefier but we still use a block mount plate.

[daves 72 dart]

thanks! everyone for the info. im going to rethink my build.

[dodger1]

Logic says to me that thicker cyl walls = higher pressure capacity = stronger block. If so, aren't we better off if we just do a clean-up bore when building a stroker? How much power are we getting from the extra 5 cu. in. gained wih a .030 over 360, vs. lost cylinder wall strength? (I refuse to admit my 360 is .030 over)Comments??

[rumblefish360]

Originally Posted by dodger1

Logic says to me that thicker cyl walls = higher pressure capacity = stronger block. If so, aren't we better off if we just do a clean-up bore when building a stroker? How much power are we getting from the extra 5 cu. in. gained wih a .030 over 360, vs. lost cylinder wall strength? (I refuse to admit my 360 is .030 over)Comments??

Yes, A clean up is better than a .020 or .030 etc... overbore. The amount of extra power from 5 cubes in overbore is to small of an amount to bother with. Lost wall strength is a longevity concern and also a current running problem. When the walls flex, theres lost power. To what tune? I don't know. But any blow by is bad.

[George G. Leverette]

"The LA blocks weigh about 160lbs. They are strong enough to handle output up to about 430 HP in high-endurance applictions. Output can be slightly higher for low endurance applications" This is a direct quote from Jim Sziligyi a Chrysler engineer who has worked at DC since 1989 and currently works in the Dodge Motor Sports division and is the author of BIG-INCH Mopar Small Blocks. Other potential problem areas mentioned in the book was the oiling system and head bolts. I have a standard bore 1968 340 engine and it appears the Mopar cast 4.00 stroker crank, Eagle SIR Rods and Keith Black pistons will be adequate for the HP levels of the engine, it also appears 2 1\2" exhaust will be plenty for this power level.

[daves 72 dart]

what heds are going on your 340.

[eric414]

Rumblefish,Ryan at shadydell found this R1A 48 degree block for me that was brand new for $1500 which i didnt want to pay that kinda of money but i know i wont have to worry about the block giving out.plus i will be making about 760 hp so i dont want the stock block with that kinda power.This is one reason i got the R1 block,a friend brought a 340 block that was 30 over ready to go.the car ran 10.30s than the crank was walking on him.dont know how true but he took the engine apart and add the 4 bolt mains that cost when another $1000.so he has in between $1400 and $2000 in a junk block that not going to hold in his car.i drove the car to the first ever 9.90@136 but he also has a 200 shot of nitrous that he has been using so for best with that is a 9.60s.the car slow down running a 10.20@132 when he use the NOS to a 9.60@131.look at the mph.he didnt use the NOS when the car ran 9.90s,anyway changing the subject.he wants me to drive on the NOS and i wont do it cause when or if that block comes apart while i am behind the wheel isnt going to be funny,plus he wont come up to me saying i owe him a engine/block.His stock will/might hold up on motor but with the NOS i dont think it will.oh the R block doesnt need to be filled and weigh 40 pounds more that a stock block.

[rumblefish360]

Eric;
Glad to here that the block is a good one at a good price. I know there expensive suckers from MoPar. Your bottom end sounds like a very good foundation. Best of luck with it.
Your story is one worth reading. A very good lesson.

[eric414]

If you guys need anything small block call ryan.he got me a set of lemans w8 heads,new T&D rockers and sheet metal valve covers for $2500 also the block as i talked about early

[George G. Leverette]

daves 72 dart, I have a set of eddy RPM heads, cam and carb need some detail advice and careful consideration.

[daves 72 dart]

that is what i was going to put on my 360. then i read that x or j heads with a good valve job and a good port job will out flow the eddys out of the box. i understand the eddys with a good port job will be much better. but i have the j heads.i was looking for 550 to 650 hp.now im looking at something around 400 hp.do i even need the stroker kit to hit 400 to 450 hp.

[rumblefish360]

do i even need the stroker kit to hit 400 to 450 hp.

No. For a 400 HP engine, you'll need a 750 cfm, dual plane ot torker II pocket oported heads, headers, a off the shelf 280 comp, Crane, Iskaderian cam and a little compression.
Another 50 hp is a bit more porting and a 292 duration cam.
This is a basic recipe for a 340 or 360 engine. More power can be had with extensive porting, not crazy work, just a full port job.
The stroker will add lots-o-torque to the engine.

[daves 72 dart]

thanks for the info all i have to do is come up with a different build for the 360.the bad thing is when i bought my 72 dart swinger.the man i bought it from did not know anything about the engine.he lost all the papper work.what i do know is it has a toker ll manifold,800 holley double pumper,headers.electronic ignition with the chrome box. and j heads with adjustable rockers not rollers.i can tell the cam is bigger just by the way it sounds.the reason im rebuilding is when i took a compression test every cylinder was 115 psi.and sense i dont have a clue what i have i figure its time for a rebuild so i know what i have.i wont a high 11 low 12 sec car.i need 400 to 450 hp at the crank to get there. any ideas on how to build a 360 with out a stroker kit to hit 400 to 450 hp would be great.i know you guys can help

[rumblefish360]

Originally Posted by daves 72 dart

any ideas on how to build a 360 with out a stroker kit to hit 400 to 450 hp would be great.i know you guys can help

Please re-read post #20.

[daves 72 dart]

rumbelfish thanks i didnt read your post that helps alot.

[kl89360]

lemans head you say????????

[michaelmopar]

Ok, I was told by a good racing shop that if i wanted to beef up the cylinder walls i could bore out the block. Then install a set of high strength forged sleeves. They state with the added strength i could get 550 to 600 hp stroker motor with a long life expectancy. They did state i needed an engine oil cooler and also a two filter system and then after break in use full sythetic oil and it would keep oil temp down. They tell me that oil temp is the number one enemy of high horsepower then weak cylinder walls.


Now here is another question if i want to build a stroker to be a good torque motor for street applications also for the pony express 130. I want it to have a mild cam and be a solid motor. Cam would be like a 212/224 dur and 320/327 lift. Compression would be a max of 9.5:1. What would you all suggest.

[George G. Leverette]

A split level cam in th 480-500 lift range with the same duration numbers you quote would be a better choice. Hughes, Straight Line and Comp Cams should be contacted to confirm the best choice for your application.

[rumblefish360]

I don't know a whole lot about sleeveing a engine. I would not do it on purpose. I'd hard block half the block for strength.
Heat is bad, oil cooler is good. Twin filters I haven't done. I run syenth when I can. Almost allways on all cars. (At least the ones that don't leak.)

The larger the engne, the easier it is to swallow a large cam. A 400+ cid engine with an iron head could use 9.5-1 well. Now depending on cam and intended useage of the engine, comp ratios can go up or down.
Whats the stroker going in, it's weight, gear ratio, tire size, tranny being used and useage of the ride.