360 vs 408

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1994redram

1994redram

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I'm ready to build another engine for my dart. Some of you may have read my last thread where I posted pictured of the destruction. I wasn't paying attention on assembly and I timed the engine wrong.

Gotta build ANOTHER engine.

The heads are supposed to be done next week. They're getting new valves, 3 new valve seats, and needed some welding repair. $$$

I have a spare 5.9 magnum that I tore apart and already got it back from the machine shop. It's. 030 over, decked just enough to get it straight, new freeze plugs, cam bearings, etc. Turn around time on the block was only a couple days. The crank was inspected and they polished it, said it didn't need cut.

My .571/.576 238°@.050 cam survived the carnage. It will be reused along with the edelbrock heads with minor port work.

At this point I'm curious about building a 408. I'm thinking the 10.6:1 360 with that head and cam combo should have been 400-425 hp, correct me if I'm wrong! How much would I gain with a 408? I have an RPM air gap and an M1 single plane intake. 750 cfm carb and would go bigger if needed.

Also if I stay with the stock stroke, would the stock rods be fine? Hyper pistons be fine also? I don't want to do this again anytime soon.
 
ultimate HP is head specific, youll get more torque lower in the RPM range with a stroker. stock rods are strong, youll need shorter pistons.
 
I'd personally be fine with stock rods and hypers for the present stock stroke build plan. Forged are tougher than hypers when you get into detonation but run looser, and I've destroyed forged with detonation, and raced a trubo'd engine a 14-15 psi with both hypers and forged in it with no problems with either. So it's all OK if you use good tuning and care, IMHO. I'd upgrade rods before the pistons... just my take on these things.

With Magnum block milled perhaps .005", those KB107's will stick out around .008". So make sure you use a thick enough head gasket's Felpro 1008's would be getting the pistons clearance from the heads almost down to .030", so I'd be inclined to use the thicker 8553 PT's and push it up around .040".

Making an educated guess on the cam's intake closing angle (Hughes never gives you that info), I am getting 7.9 for DCR so that seems all OK.
 
Agree stock rods are very good. Never heard of failure. I myself stick to stock stroke just for preference. A 408 can give torque sooner and more of it than a stock 360 stroke. Value wise 360 can't be beat! If you plan a large cam the stroker will mellow it out better.
 
If you allready got:
Ready to install crank
Ready to install pistons
Balenced rotating assembly

Then I don’t think its financially worth it.

If you needed to buy pistons and pay for crank polish/grind and balancing... and wanted a little better street manners... then go stroker.

Sound like you already did/bought most of those things...so your decision has been already made.
 
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Sounds like you have everything to support it. If you got the extra cash then why not. But if you want to put money somewhere else (brakes, tires, exhaust, suspension, or other supporting parts) then the 360 would get it done too, just at a higher rpm.
 
Coming from someone who was in a similar situation, I chose to do the stroker.... That being said, if I had it to do over I would have stuck with the 360. I got hung up on the "what ifs" what if I need a new crank? what if I need new pistons? And went ahead and bought the stroker kit. You have good parts so why spend the extra money? I'm not entirely sure that my engine makes more than 400 hp. The specs of my engine are the same as the 360 in roadkill's vanishing paint Challenger with exception of the stroker kit and they have it dyno'd at 400. If you have the money to burn, I say go for it.
 
I was saving up to paint the car. So I do have extra money to burn. But I don't want to spend it for nothing.

I've already upgraded to disc brakes, 11x3 rear drums, 8 3/4, 3.55 gears, have a strip wheel setup with M/T slicks, Doug's headers, 2.5 inch exhaust, big aluminum radiator... I'm pretty sure the car could handle the extra engine at this point.

I figured if I needed stronger rods, forged, pistons, bearings, and rings, for the 360. I might as well spend a bit more and go 408. However, if the stock crank, rods, and KB hyper pistons are fine at my power level I'll probably just build it like it was.

Like I said, I guessed it to be around 400 hp engine. What would a 408 make with the same top end?
 
autoxcuda said:
If you allready got:
Ready to install crank
Ready to install pistons
Balenced rotating assembly

Then I don’t think its financially worth it.

If you needed to buy pistons and pay for crank polish/grind and balancing... and wanted a little better street manners... then go stroker.

Sound like you already did/bought most of those things...so your decision has been already made.
Click to expand...

I haven't ordered pistons yet. The pistons from the last engine are all trashed. I only have the fresh .030 over block, polished stock crank, cam and the heads. I haven't even had the rods checked or resized. They are still attached to the stock magnum pistons.
 
1994redram said:
I haven't ordered pistons yet. The pistons from the last engine are all trashed. I only have the fresh .030 over block, polished stock crank, cam and the heads. I haven't even had the rods checked or resized. They are still attached to the stock magnum pistons.
Click to expand...

You make 400hp with 360 vid. That’s 1.11 hp/cid now

With a 408, very rough guess is 453 hp

With a Scat balanced rotating assy you won’t spend labor on resizing rods and new rod bolts.
 
You need cylinder head to feed those cubes. With the same cam and heads the 408 won't make more power compared to the 360 but shift the maximum
lower (by maybe 500 rpm?) It will also have a boatload of torque down low. A decent 408 needs good flowing heads. My 2 cents, and very general.
 
In your place, I would keep the 360.
 
FWIW I'll be disappointed if my engine makes less than 450 HP at the crank (based on trap speeds not a dyno) and I'm running a bone-stock 5.9L Magnum bottom end, I put in new rod bearings and the special main cap bolts for a windage tray but didn't touch anything else. I've got ported Eddy RPM heads, port-matched RPM intake and a custom-grind Racer Brown cam, 222/226* at .050" with .544/.548" lift hydraulic roller.
 
Well I went with the 340 based .040 over 418 stroker. Costs LOTS-O-MONEY ($13,000) but I bought everything except for the roller rockers, roller lifters and pushrods new. The dyno says 490 HP and 516 TQ (LOTS-O-FUN). The 360 however, will be plenty of fun without all of the extra cashola.
 
I'd do the stroker, big fun in small packages.
 
This interesting!
If it doesn't work Google Engine Masters Episode 18.
Looks like above 5500 rpm the 360 is superior?
url
 
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Strokers are amazing. For the convenience of you already having everything, just build a bitchin 360. My 360 block was toast and not worth savung, I purchased a 408 short block from blueprint, so far it's been damn good. Not bad for $2400.
 
Toluene56 said:
Strokers are amazing. For the convenience of you already having everything, just build a bitchin 360. My 360 block was toast and not worth savung, I purchased a 408 short block from blueprint, so far it's been damn good. Not bad for $2400.
Click to expand...

Wow I didn't realize their short blocks were that affordable, I'll have to keep that in mind for the future... not sure if I'll be up to spending 2 days in a junkyard again pulling another Magnum out of an old truck lol
 
MOPEkidD-3 said:
Wow I didn't realize their short blocks were that affordable, I'll have to keep that in mind for the future... not sure if I'll be up to spending 2 days in a junkyard again pulling another Magnum out of an old truck lol
Click to expand...
yeah.. the blue print engine is going into the womans duster. AND the blueprint engine is a legitimate Roller LA block.
 
Kenny Hensley( Hensley racing) built a 416 eddie headed stroker for me years ago.
I asked him that exact question. What difference would i see going from a 340/360 to a 408/416 at the track assuming same cam and heads.
He said about three tenths, maybe a hair more.
 
I ended up ordering the stroker kit. I was able to get summit to price match and got it for $1790. That's about $160 off. I got the forged crank, forged pistons, I beam rods, and balanced assembly. They also gave me a $100 Summit bucks gift card.

It's going to set me back awhile from getting the car painted. But I'm sure I would later regret not doing it if I stayed with a 360.

The blown up engine can be saved. That block needs to be bored and it will need 2 rods which I have. I now have a fresh polished stock crank that can go into it. And i have a fresh set of uncracked magnum heads. that could be a pretty cheap build.
 
1994redram said:
I ended up ordering the stroker kit. I was able to get summit to price match and got it for $1790. That's about $160 off. I got the forged crank, forged pistons, I beam rods, and balanced assembly. They also gave me a $100 Summit bucks gift card.

It's going to set me back awhile from getting the car painted. But I'm sure I would later regret not doing it if I stayed with a 360.

The blown up engine can be saved. That block needs to be bored and it will need 2 rods which I have. I now have a fresh polished stock crank that can go into it. And i have a fresh set of uncracked magnum heads. that could be a pretty cheap build.
Click to expand...
Glad to hear that you made your decision. Hold on tight, it's going to be an adventure. If there is anything I can help with just ask. My stroker was expensive but it is a lot of fun. Good luck!
 
superchargeddrt said:
Glad to hear that you made your decision. Hold on tight, it's going to be an adventure. If there is anything I can help with just ask. My stroker was expensive but it is a lot of fun. Good luck!
Click to expand...

What is your cam/head specs?

I already have edelbrock heads, 1.6 comp roller rockers, comp pushrods, Doug's headers, mandrel exhaust, high volume oil pump, RPM air gap or M1 single plane intakes, etc. The cam will be the mentioned .571 238°@.050 roller.

Hoping I can be somewhere around 450-475 hp. The heads have had some mild cnc port work and the combustion chambers are cnc'ed and smoothed.
 
1994redram said:
What is your cam/head specs?

I already have edelbrock heads, 1.6 comp roller rockers, comp pushrods, Doug's headers, mandrel exhaust, high volume oil pump, RPM air gap or M1 single plane intakes, etc. The cam will be the mentioned .571 238°@.050 roller.

Hoping I can be somewhere around 450-475 hp. The heads have had some mild cnc port work and the combustion chambers are cnc'ed and smoothed.
Click to expand...
My head's are Edelbrock RPMs with mild port work and 2.05 intake valves. My rockers are Crane gold 1.5 ratio and I gave the Comp solid rollers. My Cam is a Bullet and I've attached the spec card here. This combo was good for 490 HP & 516 TQ (probably over 500 HP now after tuning) You shouldn't have any trouble duplicating this.
I Also have the Air Gap intake. My engine is Fitech fuel injected but you should be close to the same HP with a carb.

ATTACH=full]1715292564[/ATTACH]

Cam_Card.jpg
 
1994redram said:
I ended up ordering the stroker kit. I was able to get summit to price match and got it for $1790. That's about $160 off. I got the forged crank, forged pistons, I beam rods, and balanced assembly. They also gave me a $100 Summit bucks gift card.

It's going to set me back awhile from getting the car painted. But I'm sure I would later regret not doing it if I stayed with a 360.

The blown up engine can be saved. That block needs to be bored and it will need 2 rods which I have. I now have a fresh polished stock crank that can go into it. And i have a fresh set of uncracked magnum heads. that could be a pretty cheap build.
Click to expand...
It's gonna be fun, save some money for tires, they don't last long.
 
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