Need some help with high torque 408 build

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greenweenie

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Hello everyone.

I had originally purchased a complete '74 360 to build into a 408, but I found a sand casting flaw in the block so the block is junk, but I've retained everything else, including the 974 heads, Edelbrock intake manifold, and Edelbrock 600cfm 4bbl carb (1406 I believe, it looks like the intake and carb were a package).

I'm looking to build a budget high torque 408. The only machine shop I trusted packed up shop recently, so I want to purchase a 408 short block and build the rest from there. I've been doing a lot of research and I'm leaning towards a 408 short block from Muscle Motors. Places like Blueprint and ATK have short blocks for a grand less, but I'm seeing too many negative reviews.

So basically here's what I'm looking at doing:

Muscle Motors 408 short block - shooting for 9-9.5:1 static cr
Rebuilt 974 heads - maybe some minor porting/cleanup?
XE256 cam
Eddy intake and 600cfm carb
1 5/8 headers

Does this seem like a good combination? Is it worth investing in porting and larger valves in the 974 heads with this combination?

Any other feedback/advice regarding this combination would be much appreciated. This is my first engine build, I've spent hours looking all over the internet trying to gather as much info as I could before posting.

What kind of power would this combination make?

Thanks
 
I was at Mopars at Garlet's 2 years ago. Indy cylinder head had a nice short block for $2800. It was cast crank but that's what you'll get for a budget.
 
Honestly, the OE iron heads will fall short. For the price you'll put into them to have them perform, your better off with a set of Edelbrock heads prep'd and use a RPM & a 750 carb.

While this combo on a 360 is a bit more so in the higher rpm performing range, it is much more at home on a stroker. Remember your going up 40+ inches and it's almost all in stroke which creates torque. From 3.58 to a 4.00, this is a big torque maker. The big inches will gobble down the carb like a 600 on a 360.

Your cam is also ridiculously small.
Simply choose the cam to operate in the rpm range your going to be in most. Cane cams for example list a cruise rpm there cams operate in best for there intended purposes and cam size. Ask what ever company you intend to look at what there cruise rpm range is for a given cam your looking at.

The cam need not be big. You'll peel the pavement back.
 
I picked up a 415 small block stroker from INDY in 2004. This was just the short block internally balanced, mopar cast crank,SIR rods, weisco pro true dish pistons for $2800. No cam or timing chain. just assembled block with crank,rods and pistons. I used my edelbrock heads with slight mods and they told me what cam to use which was a custom grind from comp cams. Engine is still in my street car 1964 Dart Gt. Hundreds of passes at the track 11.50's , and plenty of street miles too. Very happy with the engine and would buy another from them. Jayson
 
greenweenie said:
Hello everyone.

I had originally purchased a complete '74 360 to build into a 408, but I found a sand casting flaw in the block so the block is junk, but I've retained everything else, including the 974 heads, Edelbrock intake manifold, and Edelbrock 600cfm 4bbl carb (1406 I believe, it looks like the intake and carb were a package).

I'm looking to build a budget high torque 408. The only machine shop I trusted packed up shop recently, so I want to purchase a 408 short block and build the rest from there. I've been doing a lot of research and I'm leaning towards a 408 short block from Muscle Motors. Places like Blueprint and ATK have short blocks for a grand less, but I'm seeing too many negative reviews.

So basically here's what I'm looking at doing:

Muscle Motors 408 short block - shooting for 9-9.5:1 static cr
Rebuilt 974 heads - maybe some minor porting/cleanup?
XE256 cam
Eddy intake and 600cfm carb
1 5/8 headers

Does this seem like a good combination? Is it worth investing in porting and larger valves in the 974 heads with this combination?

Any other feedback/advice regarding this combination would be much appreciated. This is my first engine build, I've spent hours looking all over the internet trying to gather as much info as I could before posting.

What kind of power would this combination make?

Thanks
Click to expand...

How much power are you looking for? RPM? What are you doing with the engine, towing?
 
Not enough cam, not enough carb. You cannot build a 4" stroke engine and not have high torque. Add another 15-20° duration at .050, and another 150 cfm, and you'll be fine.
 
I run an xe272hl it idles at 600 pulls to 6000 all day long I run a Holley 850 dp on a single plane m1 . Cam is plenty mild brutal torque your cam is too small & 600 carb will run out of air around 4000 your talking less than a 340 cam which isn't much . A 404/416 needs lots of air bigger cam helps make up for heads
 
I agree with what the others have said "BUT" we need to know the intended use.
Will it be in a 2500 lbs A body? or a 6200 lbs 1 ton truck that will seldom see 4500 RPM. When I first read this my thought was "Sounds like the perfect combo for my 88 D350 truck".
 
My 426 stroker I run eddy heads with a stage 2 port work( I've done a bit more on my own) 850 carb and a custom cut cam and it dynoed at 612 570ftlbs at 4200 rpm. Its real important to get the lungs workin because like they said above you won't make chit for power with small heads and carb. Strokers demand a lot of air and fuel.
 
Darter6 said:
I agree with what the others have said "BUT" we need to know the intended use.
Will it be in a 2500 lbs A body? or a 6200 lbs 1 ton truck that will seldom see 4500 RPM. When I first read this my thought was "Sounds like the perfect combo for my 88 D350 truck".
Click to expand...

85 W150 :-D

Sorry for the confusion guys. I should have shed some light as to what the motor this is going in...

It's basically a toy truck, for weekends, messing around, hauling my snowmobile and driving logging roads. I want to build a motor that's going to generate tons of torque but I also want to have the edge on new trucks that are rolling off the assembly line with 400hp. It seems like most 408 crate engines are re in the 400-450HP range.

Here's the thing, I'm doing a lot of other work on this truck this year, and if the aforementioned combination will work reasonably well, I'll probably go that route... then when my bank account recoups I'd already have a good bottom end to work with, I could just slap a new top end on the motor and down the road I go.
 
Then Just use what ya got. Why even ask?
 
rumblefish360 said:
Then Just use what ya got. Why even ask?
Click to expand...

Well, the posts above have let me know that this combo is not all that great. Now that I know that, my plan has shifted and I'm wondering if this combo will work well enough to assemble and run for a while so I can save money for a better top end. Does that make sense?
 
I built a 422 for my 72 Duster. Stock Eddie heads Hughes hyd flat tappet cam 236*244*/550 ish lift/11.2:1 compression. Could not believe the torque. So much I had to swap from 4.30s to 3.23. At wide open throttle from 2100 rpm up there is significant vacuum 1 inch trending upwards to 4+ at 6000 RPM the 750 must be too small.
My point to that is, strokers demand allot of air that a stock head will struggle to support. Quench is also difficult to build for two seperate heads unless both heads are closed chamber and similar CCs.

I am now in the process of building a 408 like you are describing. High torque yet 6000 to 6500 rpm is needed.
I had Hughes choose my cam for this build 228*236*/544. lift hyd roller the heads are the 2.02 valved RHS X heads by Brian at IMM who seemed to approve of the cam selection for this build. Compression will be 9.7:1 with. 039 quench.
Having said all this i would've liked a recipe book to choose builds from. I think anyone wanting to can screw one together but a well planned build will net better results. I am learning this now the hard ways time and money.
 
My 408 is on an engine run stand already broke in and I have no idea what its going to do. Sounds good but so has any other mopar engine I've built. Forged eagle crank, scat rods, srp dish pistons, stock eddy heads, rpm air gap, voodoo cam, quick fuel 750. Cam specs Intake Duration at 050 inch Lift:226

Exhaust Duration at 050 inch Lift:234

Duration at 050 inch Lift:226 int./234 exh.

Advertised Intake Duration:268

Advertised Exhaust Duration:276

Advertised Duration:268 int./276 exh.

Intake Valve Lift with Factory Rocker Arm Ratio:0.494 in.

Exhaust Valve Lift with Factory Rocker Arm Ratio:0.513 in.

Valve Lift with Factory Rocker Arm Ratio:0.494 int./0.513 exh.
I'm using 1.6 rockers to add a little more air. My goal was 500+ ft tq and 500 Hp. At the end I ran out of money for port work and now I think I may fall short on the power but I believe my big tq will be there. It's my first stroker and I don't think you can really call a 408 build a budget build. Re ringing a 440 is a budget build.LOl
 
My truck is a W250, D60/D70, NP205. It's got custom spring packs and can carry about 3500lbs in the bed... Right now it's set up to plow but I also run wood and scrap with it and tow a car trailer. The 360 in it has an EX262, Performer 750 carb, MSD, and cheap headers. It idles for hours, rarely goes full throttle, and never goes over 4200rpm. There's "will rev" and "makes steam". This 360 will still make power at 4200.
I would expect you to have issues with detonation and making any power over about 2500 with that cam. Think about it this way: the stroke of a 440 is .370" or about 10% longer than a 383. The same cam in the 335hp 383 that made great midrange and top end was a stump puller in the same 375hp 440. The 4" stroke crank is .690" longer stroke or about 18% longer. Given everything else was the same, a 4" stroke engine should have 18% more cam and 18% more carb. In this case that would be 708cfm carb (assuming you run a 600 carb on a 360...) and .483 lift with 240° @ .050 (assuming you have the stock '77 4bbl cam that is 203° @ .050 and .409 lift going off Rock Auto). That should give a similar power curve to the smaller 360 but will have higher peak figures and those figures will be lower in the rpm range than that of the bone stock 360.
 
Sounds like I'd be better off leaving it on the stand and "doing it right the first time."

As I read through everyone's comments it became clear I didn't pick out the right cam! I realized that the cam torque curve I was looking at was for a mild 360, and that a 408 can use a lot more cam and still have a similar torque curve.

Thanks for helping me understand!
 
Hey, that's what the MoPar brotherhood is all about. Helping out. That cam in a mild 360 would be great! But not in the 408. :(

greenweenie said:
Well, the posts above have let me know that this combo is not all that great. Now that I know that, my plan has shifted and I'm wondering if this combo will work well enough to assemble and run for a while so I can save money for a better top end. Does that make sense?
Click to expand...

YES! Absolute! Do what you can when you can as you can. As time and money allows, work your way towards your goal.

Moper is a bright guy as well. He understand things pretty well.
OU812 builds MoPars on a regular.

For a truck, doing some work, I kind of like that cam above in the 226 @ .050 area myself.
 
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