408 build

[darth720]

Hi. I am a big block guy and have had 4 big block Darts. Three factory 383 GTS cars that I put in 440s. I have a 72 swinger now with a mech roller 500 stroker.

I want to build a 408 for my sons Duster street car (around 450 Hp). I am going to use ported aluminum heads.

My Question is Magnum or LA heads? I like the stabilty of the old shaft rockers but the Magnums are nice heads also.

Also which block, 5.9 1989 mag oils la rockers right ? Can the 90s magnum oil LA rocker if drilled or should I just go all magnum. Wanted to use the magnum block for the ease of roller lifters.

I have two 360 LA blocks from the 70s also.

Was going to use Comp Cams pro Magnum rocker arms.

Thought I might go with ported Edelbrocks.

 

[Brian Hafliger]

The edelbrock Magnum heads are nice especially when ported. Either head will make great power after porting. The LA head has a slight advantage, but if your not looking for every ounce of power the Magnum version is nice.
I would use the LA heads and Hughes rockers. Best quality for power. You can get a 1.6 ratio from hughes and only 1.5 from comp.
Actually with our RHS head, you can get 450HP easy and not have to spend the extra $$ on the eddy heads and porting.

A nice little build we do will make 440Hp roughly, using comp 275HL cam and RHS heads/hughes 1.6 rockers and rpm intake.
Brian

 

[darth720]

Hey Brian . What block with LA Heads if I want to go street roller cam?

 

[stroked 340]

You won't need to do any serious port work to the Edelbrocks to flow for the power level your shooting for,my mildly and i do mean mildly worked Edelbrocks help crank 520 h.p. out of my 416 stroker..if you already have 2 la 360s go with one of them,my stock strock 360 puts out 406 h.p. using the same Edelbrock heads..the comp cam magnum rockers are just fine,i've been running a set on both my motors with zero issues..

 

[Brian Hafliger]

Hey Brian . What block with LA Heads if I want to go street roller cam?

Are we talking solid street roller or hyd.? The only time I use LA heads on a magnum block is if we're running TD rockers because they can oil either way. The comp's are meant to oil from the head.

I have the RHS head in Magnum version and you can use Hughes 1.65 rockers coupled with hyd. roller you can really make some steam.
Or you can use edelbrocks magnum head and stud mount works ok just can't get real aggressive with the cam unless you go to a better rocker (td) which are costly.

The retrofit hyd. rollers are ok, but you need to grind clearance for them in the valley. So no real easy answer I guess sorry!
Brian

 

[moper]

Best bet IMO is the pre-magnum LA 360s from about 89-91. I think those are the only ones with the castings for the spiders drilled and the shaft oiling provision. If you have Magnum blocks I'd use Magnum heads (Brian's) and just oil thru the pushrod. If you have early LAs, you can go conversion lifters but you want to be careful which lifters you choose and make sure they work in your block with your cam choice. Some lifters will bleed off oil pressure at full lift. Not good.

 

[POS Dakota]

I have the RHS head in Magnum version and you can use Hughes 1.65 rockers coupled with hyd. roller you can really make some steam.

Brian

Getting ready to fire mine up soon! Definitely a good combo with the mag heads and hughes 1.65 shaft rollers as brian says.

I'm a little over .600 lift with these. IMO for the money, you really cant beat these rockers. Best ones out there for the magnum until you want to squat and cough out the money for jesel sportsmans which very few will even need.

Go for it! The magnum engine is a great motor to work with, and while some disagree, I much prefer the pushrod oiling setup and the block being all ready to go for a roller cam and factory roller lifters. You can get a new set of factory mag roller lifters for a little over 100 bucks instead of the much more expensive retrofit roller lifters. That frees up money to do other things. Just my two.

 

[71dustar]

i used a magnum engine for my 408 stroker. i have unported eddys with hughes rockers, 0.545" lift comp cams with 241 in and 247 ex. ross racing pistons, stock magnum rods with arp bolts, and eagle cast crank. 750cfm holley 4160 carb and rpm intake.

I only have about 175mi on the motor since i fired her up and i can't stop smiling. I have a 727 manual valve body w/ cheetah shifter and m/t 29x12.5x15 tires in the back and it can chirp second staying under 4,000 rpm

 

[darth720]

Thanks Guys!
I would like to use a street hydraulic roller . So I thought the 360 roller magnum block would be easier. I would like to use Eddy ported LA heads and a shaft rocker system.
Can the 360 magnum roller block oil the rockers on a LA head? If so what years? Do i have to modify it or should I just use the old LA block and a good hydraulic cam with ported Eddy LA heads? I am not big on non shaft rockers. I want good power and low maintenance cause I aint driving it.(sons car)

I have a nice 3800 Neil Chance Converter and lots of tranny parts and a back braced 8.75 with 4.10 gears , detroit locker ,MW caps and Moser Axles for it. Should be quick in a city block. Or I could just drop a 500 hp 440 in the car (have one sitting in the garage), but I really like the way the 408s run at the track. I would like to build one with my son.

The comp cam pro magnum rockers I have on a 440 motor ran for 10+ years with no problems with the 557 X 296 MP Mech. Cam.

Iam running the Hughes rockers (cryro Treated) on my 500 stroker 12.3 comp, Victor heads and Victor intake with a comp cam drag race mechanical roller cam RX296R-8 (650 lift 263 duration @.050 intake) on the street and bracket . SMR 5000 stall & SMR Mega Torque tranny. SMR makes nice stuff! So far real nice.

I figure 10.0 to 10.5 compression ratio with decent cam and I can burn premium pump gas with ported aluminum heads and make 450 + hp.
When I get an idea what parts I am going to use I could figure out a and Static CR and Dynamic CR and make sure it all works for 92 octane.

I just am not up on the magnum stuff and the tricks to getting a roller cam magnum block with Shaft Rockers and parts to make it all work with out unecessary machine work and hassels.

Thanks

 

[70aarcuda]

magnum oil thru pushrods...no shafts....
LA oil thru block/head to shafts..

have to figure out out to oil shafts....in other to get LA heads to work on Magnum blocks...

it will take some drilling to get it to work....

 

[1wild&crazyguy]

why not drill a shallow hole in the position of the standard LA oiling hole on the deck, and then go in from the side of the valley , plumb it to meet another tap at the cam journal and use a feed through cam? as in

Maybe if I had a mag block laying around I would know have a better idea, I do however thing some plumbing can be made to keep out of the way of the push rods.jmo