Factory Magnum Heads

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BJR Racing

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I was talking to Rumblefish360 a few days ago and he sent me a set of factory Magnum heads just to play with. So I have to Thank him for his effort in these findings. I told him that I would post the results as soon as I had the time to mess with them a bit, well I had time today and this is what I found and what they flowed on my bench. Modifications will be listed as we go and per the flow #'s listed.

Stock out of the box heads:
Intake valves are 1.925 and exh.valves are 1.625
Flow is as follows

Int. Exh.
.100 84 80
.200 132 118
.300 201 134
.400 226 134
.500 235 134
.600 236 134

Then I went and Bowl Blended the heads and did a multi-angle valve job and this is what they flowed:

.100 86 81
.200 137 118
.300 201 140
.400 224 143
.500 239 148
.600 246 149

Well now I went and backcut the valves and narrowed the valve guides and lowered the floor .050 on the intake side. As for the exhaust side I ported the port and narrowed the guide.

.100 88 84
.200 144 130
.300 204 190
.400 226 192
.500 239 190
.600 245 190

As we can see that it really liked the exh. port to be ported and the work on the intake side helped a bit in the low lifts, so I figured that it may need a good gasket match as the intake port entrance was untouched. So this was the next step. I didn't figure that the exh. would have any need to be any stronger, so it was left alone at this point. So after gasket matching was done this is what I found.

.100 84
.200 139
.300 201
.400 231
.500 246
.600 252

As we can see it wasn't much gain for the amount of time it took to do this work. The HP gain by the SF #'s is only 4 HP more. The gasket opening was opened as far as the head would allow, and the port was all but ported at this point. As only the port walls about 1" was left untouched. So as far as these heads go, and against other LA style heads, I had to do more to these than the older factory iron LA heads to get the same amount of airflow. They do have great low lift airflow #'s and are very, very close to the Edlebrocks with just bowl blending and narrowing the guide, and a good VJ, also doing the short turn radius helped.
This is what a 915 head flowed with a 1.88/1.60 valves done with the same amount of work.

.100 91 89
.200 184 133
.300 222 176
.400 239 191
.500 283 196
.600 276 201

The only thing that I can see as a advantage is the style of combustion chamber, otherwise I would prefer the older style LA heads for the amount of work and effort that has to be done to both. The Edlebrock heads are only slightly better than the 915 1.88 valve heads when they are fully ported, and they the (Eddys) would cost more than a $1,000.00 to get in this condition.

These are just my findings, and THANKS! again to Rumble for the heads to play with.
 
Adam; Yes you did and there making there rounds across the country even without an engine beneath them. LOL

The story behind this;
Since I got stalled in every project from house to car while I paid for the wifes schooling (She's a now a RN ! ) and the kids extras, Baseball and soccer etc.... I'm screwed from doing anything until the wife turns in a pay check. (She has an interview the 18th, woo - hoo!!!!)

While taking with Bobby, he mentioned he never had a set to mess around with.
"Well, I do and there just collecting dust, wanna play with them and see what you see?" I told him if he wreck if need be LOL. Cut'em in half! I said.

What this means for street bound guys like me;
Being that I'm mostly a street bound driver, the gain in the heads is very nice. Knowing that MoPar used these heads, as cast with a tougher spring as the only upgrade for the cam used, they were rating there crate engines at 380 HP. Then the magazines were grabing these engines and doing there own dyno runs with them. And they all moved right on past that 380 HP level right on out well passed 400 HP every time.

The stock OE heads are showing a nice gain and great street potentail for alot of fun and power. This curve as listed above will really comploment the power curve and if you have a roller cam engine, this is going to have a great torque curve. A stout fast ramp solid will show excellent results as well without being a race cam.

I think this is a good bang for the buck. Thanks for the work and posting the numbers up here BJR.
(Now I'm going back to my morning coffee. With some extra thoughts in my head. He he he.)
 
so here's a question, are the 1.88's better than the 2.02 in the 915's? curious for a future build
 
They make more port velocity and stronger low lift flows while the high lift flows are within a couple of cfms when done the same. The 2.02's really help in the upper RPM ranges above 6500 rpm's, so if your build is going to be turned this high then I may give them consideration, but if most of your driving is going to be at a lower rpm than this then I would stay with the smaller 1.88 valves. As you'll have more Tq and power due to better port velocity.
 
BJR Racing - Thanks for posting those numbers, very good data. What did you do with the pushrod "bump"? Did you thin it up alot or just clean it up? What if a person sleeved the pushrod hole and ported to the max? My guess is the pushrod pinch is the most restrictive part of the port after the bowl clean-up. Also what did you do to the part of the intake port under the rocker arm mount. There seems to be alot of iron there. But does that lump under the rocker mount help with swirl? Sorry to bombard you with questions.

Also what kind of flow bench are you using and are you measurig flow at 25"WC or 28"WC?
 
340,
I use a superflow flow bench and use 28".
As for the stud bump in the port, you can remove alot of it but the more you remove the weaker the stud or rocker bolt support will be so I left most of it in there and I thinned the pushrod pinch as much as you can and still have material there. It's actually thinner at the bottom of the port than it is at the top, so be careful not to cut through or the head will have to be welded up. If you look at the flow #'s most people wont use a cam in the .600 lift range and use this type of head, so you only have a 7 cfm gain at .500 lift from the gasket matching and the lower lift flows arent as good so if your going to use a cam smaller than .600 lift I wouldnt gasket match the heads. The trade off isnt worth it. The velocity was better before gasket matching, but you just dont know unless you try something new.
So in this case the pushrod pinch area was helpful and removing any of it actually hurt the low lift flows, where the bowl made gains the pinch area took them away, so unless you have to have these heads for class rules or some other reason and custom ground cams in the size of the max flow at .600 lift then I would use a different head or run a smaller cam. Your combination dependant. But for the street these heads would be a very good choice for lifts under .500 lift and some mild porting being done.
 
Im a bit suprised at the low exhaust flow #s. There is a lot more flow in those heads. The exhaust will flow 210-215 without too much work.
 
Hey Bobby, I'm glad you finally got a chance to work on a set of magnums. The numbers you posted aren't bad, but I was wondering what would happen if you opened up the intake's to 2.02.
I noticed the same thing as you as far as port shape. After you gasket match, the port seems to narrow and restrict flow to some extent. this being the case, the laws of physics dictate that the flow would increase in velocity and if you had a bigger valve then maybe they would flow more. Just a thought.

Jack
 
BJR: Great stuff! I really like seeing this kind of information. How much time did you have into the Magnums when all was said and done?
 
BJR Racing said:
340,
I use a superflow flow bench and use 28".
As for the stud bump in the port, you can remove alot of it but the more you remove the weaker the stud or rocker bolt support will be so I left most of it in there and I thinned the pushrod pinch as much as you can and still have material there. It's actually thinner at the bottom of the port than it is at the top, so be careful not to cut through or the head will have to be welded up. If you look at the flow #'s most people wont use a cam in the .600 lift range and use this type of head, so you only have a 7 cfm gain at .500 lift from the gasket matching and the lower lift flows arent as good so if your going to use a cam smaller than .600 lift I wouldnt gasket match the heads. The trade off isnt worth it. The velocity was better before gasket matching, but you just dont know unless you try something new.
So in this case the pushrod pinch area was helpful and removing any of it actually hurt the low lift flows, where the bowl made gains the pinch area took them away, so unless you have to have these heads for class rules or some other reason and custom ground cams in the size of the max flow at .600 lift then I would use a different head or run a smaller cam. Your combination dependant. But for the street these heads would be a very good choice for lifts under .500 lift and some mild porting being done.
Click to expand...


Thanks for the info. I have ported two sets of magnums. I used the MP templates on both. On one set I also opened the exhausts and worked the intakes a little too. I installed 2.02 intakes as well in the more ported set. I also did some port molds of the stock magnum ports as well as some w2s. That was kinda interesting. Next week I will post some pictures of the molds (they are on my work computer). Oh yeah....And I did cut through the pushrod area in one spot. Brazed it up and it seems to be holding.
 
GTXperience said:
BJR: Great stuff! I really like seeing this kind of information. How much time did you have into the Magnums when all was said and done?
Click to expand...

About 3 hours in 1 cylinder, and this included porting the exhaust and the work on the intake side.
 
needsaresto said:
Im a bit suprised at the low exhaust flow #s. There is a lot more flow in those heads. The exhaust will flow 210-215 without too much work.
Click to expand...

needaresto,
True they very well could get over 200 cfm's but then your getting very close to what your intake flow is. The more air flow on the exhaust doesnt generally mean more HP, and you only need 70% of the intake charge to be efficient.
Things that I've found before when the exh. flow was higher than the intake flow was that a large overlap cam sucked the intake charge out and created a lean condition in the engine. This is why SF says to get 70-75% of the intake charge and theres no more to be gained. And we've actually seen anything more than about 62-65% and the gains become minimal.
 
Can 2.02" intake be installed?
I was thinking with the larger intake valves and some port work these would be a good inexpensive upgrade.
 
I'm sure they can, it would just be a matter of getting the valves and enlarging the valve seats.
 
The biggest problem with Magnum heads is finding good valve springs for them.
 
BJR,thanks for the info. How much do you think the intake could be made to flow? And if I dont have a large overlap cam will this improve or eliminate the lean condition?

Im going to slap the mags on a 318 and will be building a very streetable,hi torque, good mileage motor for a 4000 lb car with 2:94 gears. I planned on a small cam under .450 like an xe262. The heads are fresh and have brand new stock springs, and stock 1.6 ratio magnum valve gear. I will port them with the template kit from mopar. Shooting for about 9.5:1 but may need to get K.B pistons so 10:1 with them.With that small of a cam I may not bother porting. Was thinking of that in case of a cam upgrade
 
One of the bigger advantages of the magnum head is the closed chamber. IT allows you to run a lot more compression without detonation issues.

I am running 10.6:1 (180 to 185 cranking psi) on my 360 with magnum heads, it runs fine on 89 octane fuel. It may even be fine with 87, just haven't tried it.
 
The orignal magnum crate motors came with stock magnum heads. The 380 HP verison of the 360 will dyno consitently in the 410 HP range.
 
I guess I should have stated that the heads are worth this much with stock componets. The crate engines have larger cams and better intakes and better exh. so with the mods done with these heads you could increase these #'s about 30%.
This is also RWHP not engine HP as the crate engine are advertised.
 
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