Edelbrock Magnum Heads on Early LA 360 Block

[65RoadRacer]

I've searched the forum and have not come up with any threads on this, has anyone done this setup? What did you find out, I'm doing a bunch of research, and hoping I'm not missing anything.

 

[dukeboy_318]

I've searched the forum and have not come up with any threads on this, has anyone done this setup? What did you find out, I'm doing a bunch of research, and hoping I'm not missing anything.

its been done. The biggest thing is that you'll have to either drill and tap the magnum heads for an LA intake or use a magnum intake, thus limiting selection a tad.

 

[91r/t]

I built a 360 for my truck using the Indy 360 LA-Max heads. They use the magnum port style and a closed chamber design with LA bolt patterns for heads and intake. Only difference was I had to use Magnum style head bolts, as the bolts are all small head long bolts like the Magnum engines. Also had to use the small 5/8 spark plugs like the magnum. This way you can keep the bolt pattern for the intake, valve covers, etc. but get the flow of the magnum head. Also, these heads have a closed chamber design to build compression over the open chamber design of the LA heads. This also helps to achieve a good quench pad area when building the engine and helps reduce detonation. My motor is about 10.3:1 and it runs great on pump gas. I love them and they build great power on my Power Wagon for an iron head with a stock-ish look.

 

[BeepBeepRR]

Found a interchangeable write up on the magnum http://www.hotrod.com/articles/hrdp-9809-magnum-and-non-magnum-parts-exchange/

 

[Darter6]

Steve Dulcich writes for Hot Rod,Mopar Muscle and other mags.I think he did a article on doing this. Just a thought.

 

[65RoadRacer]

Thanks, I'm familiar with the interchangeability of the Magnum heads, but what I'm trying to address more specifically is what parts were used where they are going to matter most: valvetrain. I know, I didn't really elaborate that. Since I'm using the Edelbrock heads on a 73 block, I had the heads drilled for the LA intake so I can use a port injection system, a good friend at Edelbrock took care of that for me.

The Edelbrock heads use the SBC rockers (1.6:1 ratio, 3/8" stud mount) and I'm using a set of roller lifters for the LA with an LA cam. I'm aware of the way oil is delivered to the rockers (LA vs. Magnum) so my lifters do have the oiling hole and I know I need to use the hollow pushrods, but I'm curious about the length. I've seen a couple of different part numbers and lengths, and since this is a conversion, I'm wondering about the pushrod length and what was used.

Comp has a set (6.8"), as does Edelbrock (6.936"), but they are different lengths and neither kit addresses the head swap issue. Edelbrock has a couple part numbers to use for roller rockers (Comp, Crane) but I don't know if their pushrod recommendation is for the head swap or just for the magnum engine - or if it matters. Or, perhaps I need to have it assembled and measure for length because this is a head swap. This is the information that I have not found on any of the sites that I've checked... they talk about the oiling differences, but none of them actually list part numbers used.

Thanks!

 

[wyrmrider]

for that question we are getting into rocker geometry what's an LA cam- are you talking about the nose and fuel pump lobe? or flat tappets? or
get a couple of adjustable test pushrods and do the half lift optimization -plenty of write ups on how to do it
I take it you have standard 3/8 rocker studs- no stops or anything and enough threads for some poly locks
what lift cam are you considering?
do not buy a cam till you can get cam and rockers that work together (ratio wise on the 1.6 rockers)( I usually use 1.5 on the ex- your cam grinder will want to know
is this a solid or hyd roller?
The goal is to take the valve stem and in your mind extend it
then have the center of the tip roller and the center of the fulcrum roller in a tangent to the valve line at 1/2 the valve lift
you can use a machinist ruler on the retainer and line it up with the centers or there are other methods
raise or lower the fulcurm till you get it right
then measure for your pushrod length
If your motor is apart and you are going solid roller go 3/8 pushrods and guide plates
caveat- different brands of roller rockers take different pushrods
hint you want the adjuster to be back close to the rocker body not adjusted out very far if you do not have adjustable fulcrums/ studs (like shafts)
glad you asked as my 92 Magnum is getting tired and I have an already machined LZ 360 block, balanced crank, pistons etc ready to go- thinking about heads

 

[65RoadRacer]

The Edelbrock Magnum heads have the 3/8" stud mount and they suggest the 1.6 rockers. I'm going with a roller cam, and spoke to someone at Comp Cams and got the cam from them. For the cam, I basically said what our goal was for the engine and what compression we were planning, and that the block is a 1973 360.

I told him everything I was doing and even sent the link to the Edelbrock heads so he could have the specs, but somehow they sent me a rocker set for the LA head (1.5:1), not the Magnum head (1.6:1). The cam is a roller cam for an LA engine, it's what he recommended. I've heard quite a few people say to use the Magnum heads as they flow better than the LA heads, and even Edelbrock said "lots of people do this", but it doesn't seem like lots of people have listed what actual parts to use, just what's interchangeable and what isn't.

I've read three articles from Hot Rod on Magnum heads, but they don't list what they did about cam or pushrods. The Edelbrock Magnum heads utilize the SBC 1.6 roller rockers with the stud mount, so there's no choice there. I'm starting to get curious if I went the wrong direction now.... One builder specifically told me to use Edelbrock's Magnum heads on this, I might have to give him a call and find out what he uses, if he'll tell me.

 

[wyrmrider]

I think the confusion is that Edelbrock makes a Magnum head drilled for the LA intake manifold
you could use 1.5 or 1.6 or 1.7 on either head as both oil through the pushrods and use stud rockers
If you are running a carb the "LA" cam has a fuel pump eccentric and the Magnum cam does not
there are also differences in the nose length so make sure you have the right thrust system and timing chain
You can run a LA core cam in a magnum or a Magnum cam in a carb motor with an electric fuel pump
what specs on the cam? what compression did you say what intake and exhaust, converter, gears, etc?
anyway time for the detail work of dialing in your pushrod length
Comp should be able to get you close if you are running their rockers
HOWEVER I DO NOT TRUST ANYONE on this and would double check via the half lift method
your valve stems and valve guides will thank you
THis is a hyd roller aftermarket kit not factory- right? you do not have a factor roller block, right? even more reason to check everything
if you are on your engine stand when you dial in your pushrods send some pics
best bet is to get an adjustable pushrod and DIY

 

[rumblefish360]

I haven’t seen an Edelbrock offering of Magnum heads drilled for LA intakes but other companies will do this mod for you.

As far as what cam to use or what is used in particular builds combined with whathe parts, it becomes a mix bag of parts due to the numerous variations that can come about.

Choose the cam style
Choose the cam specs
Choose the lift you want at the valve
Equip the heads with the rocker ratio needed.

Intake choices are;
M1 single or dual plane
Edelbrock RPM/AG (best all around choice)
Indy single plane. (Race)

 

[wyrmrider]

good choices rumble The AG seems good
given head flows, manifold, exhaust, compression, gears, usage the cam will spec itself- it's a result not an input
then you may have to adjust the compression for the cam rev range (duration) wanted and go around again
don't know exactly what he means by ", but somehow he sent me a rocker set for the LA head (1.5:1),"
anyway he evidently has cam and pistons so just trying to get it dialed in
I never trust the cam help desk guys

 

[65RoadRacer]

I haven’t seen an Edelbrock offering of Magnum heads drilled for LA intakes but other companies will do this mod for you.

I have a good friend at Edelbrock who intercepted a pair of heads for me and had them drilled to fit the LA intake instead of the magnum intake. I'm going with a port injected LA intake from Edelbrock and a FAST XFI system, but wanted the better flowing Magnum heads. I gave the specifics of what we are doing with this engine build, and the guy at COMP (who is good at this sort of build) determined what cam I needed based on the parts being installed and the goal for the engine.

don't know exactly what he means by ", but somehow he sent me a rocker set for the LA head (1.5:1),"

What that means is that I ordered a cam for the 360 block, which he got me, but when I gave the specs for the heads the sales guy sent me roller rockers that fit the LA head, not realizing that they won't fit the Magnum head (just an oversight on his part, he was going by what block I was using, I suppose).

I realize some of you want to know more details about what cam and how we're setting it up, but I have to keep some of this hush because it's still a project car for the magazine and we don't want to give too much away right now. Everyone and their brother is doing LS stuff, or Ford stuff, but not much Mopar going on lately unless you're talking Gen III hemi swap. I'm just trying to keep this old school for the sake of the build, but show there are some options for the LA. Some of it is experimental and we're using some cool components.

We have a sort of 'unveiling' that we're doing once the final process takes place. I was mainly asking if others have used the Edelbrock Magnum on an early LA and what they came across when choosing pushrods - if they had to measure for them or if there was a set they used that was for this application. I want to be able to share some of this info in my article that I'm working on to discuss what others have done and found successful. I hope that helps explain some things. Thanks

 

[rumblefish360]

65road racer, glad to here you got friends at Edelbrock. If Edelbrock doesn’t do this mod for regular people like me that know nobody, then it’s not a help. I have not gotten an answer if they do this mod as a normal offering or is it a special order? If even orderable in this manor.

I would guess that a place like Hughesengines would do this mod. If you asked for it.

 

[65RoadRacer]

I think if it was something more people requested it might be worthwhile, but you know how it is with any big company, at least when it comes to Mopar stuff. I once looked up crankshafts for an LA on Summit racing. There are 13 for the LA (priced $319-$1252), and 190 choices for the SBC (priced from $190-$2,800). When I started looking at available intakes for the LA, I was surprised there, too. A total of 56 for the LA (some including carburetors and air cleaners) and 486 for the SBC.

Hopefully, if this build works out then it might encourage others to get creative and build an old school LA. Incidentally, Edelbrock does do some stuff for Hughes, and they seem to be a good place for LA/Magnum builds with a lot of options. I bought my stud girdle from David, but I kinda got the impression he didn't like me much so I didn't want to bother him with any questions.

 

[rumblefish360]

Yup! 1 guy from Hughes is ... well...
a dick.
The other guy from Hughes is, well,
Freakin excellent. Wish I could remember HIS name.

Your build sounds cool. Ma MoPar had a “Replacement LA head for awhile. What they never said was, it is the same head as the Magnum R/T head only with LA drilled intake holes. They will port to over 300 cfm. That line is the only iron headed line to stand toe to toe (Or as close as possible) to the W2 & at a fraction of the total cost.

 

[ckessel]

I was going to suggest Hughes also as they are pretty hip on these questions but it looks like they already shut you down. Bummer. For pushrods, check out Manton. Not sure if they already have something but I know they do make them and maybe can help with measuring. They are in Elsinore just off the 15. Small blocks can be interesting on the roller lifters if the units are not Mopar specific and the groove is not in the right place. If its wrong you end up with no oil pressure. Back in the day, they would punch out the rh galley, if memory serves me, and sleeve it thereby blocking the normal oil pass through then you used a rounded off lifter to peen the sleeve protrusion in the lifter bore. From there you punched in specific holes through the tubes and can't quite remember what was done on the lh side. The other methods involved a crossover tube at specific points between the two sides and I believe there were further block offs. Both of these are covered in the old DC books and the old SA Design book on the small and big blocks. Supposedly you don't need to get this drastic on mods since current lifter offerings are supposed to be better but you need to check to be sure.

 

[rumblefish360]

Correct. You do not need the cross over tube. There is a method to the madness. I’m not mad, just a wacko.
I follow the DC/MP book. It worked then, it’ll work now.

For surely watch the oil band on the lifter for rollers or any high lift cam. The band can rise above the top of the lifter boss and cause LOW oil pressure.

 

[wyrmrider]

Sometimes you have to bush the lifter bores tall to prevent the oil hemorrhage- correct lifters should work though
I must always get the "dick" from Hughes

The peened tube in the oil galley only works with solid lifters in an oil the rockers through the block build- not a magnum
I've usually done the x over in the block
Do the half lift drill from scratch- base circle also makes a big difference in pushrod length
just too many variables to risk buying pushrods from a catalog

 

[rumblefish360]

LOL! True. To many variables.

 

[moper]

I'll save my comments on the logic of using these heads or keeping "details to yourself... because this is a magazine build..." for another time. So I want to make sure I understand where you are...
You're doing a combo that's been done a thousand times over, right? You know you need hollow pushrods, and some sort of non-shaft rockers. So you're good there. You're up to "what pushrods?"
Anybody that's done any performance building more than a couple times will tell you: you get it all together, measure for the pushrods, then either order a shelf part number if one matches what you need for length, size, end type, and end radii... Or order custom ones (which is what I do 80% of the time). It was suggested earlier - order some checking pushrods, and then measure for what you need. Manton or Smith Bros will make exactly what you need, or Comp may have a set but you have to do the diligence. There is no "use this pushrod" when nobody knows what the block is, or the gasket, or the rocker, and this is all "Code 5" so you won't tell.