Have a 1993 dated magnum block going in a 1971 dart. Speed pro h116cp pistons, undecided cam yet. Both heads were cracked like normal. Trying to decide if should go with speedmaster aluminum heads or get some magnum replacements. Block has the oiling for la style heads. Would like to be around 400 hp, or little more. What would be the best and easiest route? Is there alot of geometry issues with the speedmaster heads? Is there any good flowing magnum cast iron heads available anymore?
Which heads on 1994 magnum block
- Thread starter milo123
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WHICH Magnum?
Sorry forgot to put that. 360. Came out of a 1994 dodge but is dated 93 on block.
replicaracer43
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Either head will do what your wanting. LA heads will give you more intake choices, and geometry can be a issue with ANY aftermarket head, depending upon which rockers you select.
With the LA heads though, won't he need to make sure the block is drilled for the oil passage to the rocker shafts?
Bobzilla
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He said it was in the first post.
He sure did! I slap missed it. Thanks!
Bobzilla
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Currently, there are only China stock replacement cast iron heads available.
Edelbrock makes and aluminum Magnum head that uses Chevy small block rocker arms. This lowers the rocker arm cost a little but the cost of the heads makes that a factor not worth considering. This head has Magnum intake bolt pattern, so pretty much an Edelbrock dual plane air gap intake is best choice.
The Speedmaster aluminum heads are pretty much a copy of the Edelbrock Performer RPM LA head, so geometry issues are similar on both as stated in post 4. These heads have LA oiling allowing LA rocker arms. they also have LA intake bolt pattern allowing more intake options as mentioned in post 4, but again and Edelbrock dual plane air gap is a good choice.
Editing to add: The smaller chamber of the Magnum style Edelbrock head will give about half a point higher compression ratio with similar head gasket specs used. Again, not a deciding factor at this level, but more info.
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Bobzilla
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It's early. Lol.
replicaracer43
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Your correct! There is also the option of using the PRW steel bushed rockers, they are a LA design, but they can be pushrod oiled also.
Comp cams also has a 1.5 ratio rocker that is OK with pushrod oiling.
So if I went with the la heads and a prw style stainless rockers would I run a oil through pushrod or solid since I can oil through the head? Guess could oil both ways but not sure if that would be too much? Would like to reuse my factory roller lifters.
Since your block has the passages, I would utilize them and run a solid pushrod.
replicaracer43
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What he said
Dan the man
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The OP said that the block has LA oiling to the cylinder heads.
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Nebraska has some crazy changes in elevations with the average being 2600ft, which by itself, from sealevel, is gonna cost you about 14psi of cylinder pressure. If you are at say 3500ft, this will cost you an additional 5psi. So right off the bat, from a performance standpoint, you will never , with a 400+ hp cam, make enough pressure with iron heads, to get any decent low to midrange power, unless you happen to be close to sealevel, and set the pressure to the max. So then, if you are a streeter, and are dead set on 400hp or more, then you are pretty much forced into an alloy head.
If you run alloy heads, you can really bump the cylinder pressure up, which makes for a heck of a peppy engine and can lead to great fuel-economy.
However, on a true 9.600 deck, your speed-Pros look to be ~.027 below deck which at 4.02 bore is 5.6cc.
Adding the 5cc for the Eyebrows, this totals 11.6cc
Adding 8.6 for the .039 FellPros, is 20.2cc
to get to 11/1 would require a total volume of 74.5cc, so then
the heads would have to be, 74.5 less 20.2=54.3cc..
I don't remember ever seeing chambers that small.
But, I do remember seeing as small as 57cc. With these, the total chamber size would come in at around 77.2 and the Scr at 10.6. ... which looks pretty good, until.....
you contemplate those elevation changes again, and the fact that those changes are gonne wreak havoc with your pressures; and so, you can't just stick any old cam into it and expect it to run great, never mind getting 400or more hp out of it. I mean at sealevel you might make the number, at say 5300rpm, but the bottom end will already be soggy, for lack of pressure.
IMO, you are gonna need a supercharger to get there at anything but sealevel.
Now, if you want a strong-running steeter, she don't need to be 400hp. A streeter is a two-gear car, because most times, the top of second gear, with a street-friendly rear gear, is gonna be well into speeding-ticket territory. A couple of those could see you walking, if a cop catches you.
So then
IMHO,
you need to make some serious decisions right now, before you start spending money.
1) what elevation is your car gonna be running at?
2) Are you willing to stay at that elevation, or if not, then are you willing to deal with the consequences?
3) What is the intended usage?
4) What trans-ratios, and what rear gear-ratio, do you intend to run?
5) what grade of gasoline are you willing to pay for?
6) and besides all of that, the biggest tire you can fit under a stock-tubbed 71 Dart is a P255, and a stout 360 at 400+ hp will annihilate those right thru First gear, and most if not all, of Second, in a hurry .... as will 350. Down, in First gear, so will 300hp even 275, maybe even 250 depending on the gearing.
If you run alloy heads, you can really bump the cylinder pressure up, which makes for a heck of a peppy engine and can lead to great fuel-economy.
However, on a true 9.600 deck, your speed-Pros look to be ~.027 below deck which at 4.02 bore is 5.6cc.
Adding the 5cc for the Eyebrows, this totals 11.6cc
Adding 8.6 for the .039 FellPros, is 20.2cc
to get to 11/1 would require a total volume of 74.5cc, so then
the heads would have to be, 74.5 less 20.2=54.3cc..
I don't remember ever seeing chambers that small.
But, I do remember seeing as small as 57cc. With these, the total chamber size would come in at around 77.2 and the Scr at 10.6. ... which looks pretty good, until.....
you contemplate those elevation changes again, and the fact that those changes are gonne wreak havoc with your pressures; and so, you can't just stick any old cam into it and expect it to run great, never mind getting 400or more hp out of it. I mean at sealevel you might make the number, at say 5300rpm, but the bottom end will already be soggy, for lack of pressure.
IMO, you are gonna need a supercharger to get there at anything but sealevel.
Now, if you want a strong-running steeter, she don't need to be 400hp. A streeter is a two-gear car, because most times, the top of second gear, with a street-friendly rear gear, is gonna be well into speeding-ticket territory. A couple of those could see you walking, if a cop catches you.
So then
IMHO,
you need to make some serious decisions right now, before you start spending money.
1) what elevation is your car gonna be running at?
2) Are you willing to stay at that elevation, or if not, then are you willing to deal with the consequences?
3) What is the intended usage?
4) What trans-ratios, and what rear gear-ratio, do you intend to run?
5) what grade of gasoline are you willing to pay for?
6) and besides all of that, the biggest tire you can fit under a stock-tubbed 71 Dart is a P255, and a stout 360 at 400+ hp will annihilate those right thru First gear, and most if not all, of Second, in a hurry .... as will 350. Down, in First gear, so will 300hp even 275, maybe even 250 depending on the gearing.
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Block is a standard bore. Pistons are on back order. Just gonna be a fun weekend driver for now. 355 gears. I was kinda going off the 380 horse crate motor and figured with better and or ported heads, better camshaft should be able to make 400. Was going to call cam maker and go with whatever they suggest for cam.
I think the magnum block has a little shorter deck height also then la. Not sure how much that changes stuff and also was planning on going with a thinner head gasket, mr gasket is .029 I think.
I think the magnum block has a little shorter deck height also then la. Not sure how much that changes stuff and also was planning on going with a thinner head gasket, mr gasket is .029 I think.
mopar65
Well-Known Member
Which pistons are on back order? I have KB107 pistons in the 2000 360 magnum engine thats in my 91 dakota sport..I went with trickflow heads and PRW 1.6 Rockers. Also used 3/8th Smith brother oil through push rods. The crank and rods are stock
The speed pro h116cp standard bore. Thought about the kb107 but heard that they had some skirt issues, and the speed pro are close to being stock weight.
Never heard of a skirt issues.
mopar65
Well-Known Member
What is the issues with the skirt issues? I haven't heard anything about them. I bought the short block off my friend that built it. He was switching to a gen3 hemi. But any way the KB107 have seen a bunch of 6500/7000 rpm shifts and a few 7500. Lol also I thought the KB were soposed to be close to stock Weight. Unless I was told wrong..
Maybe I got told wrong. Guy that told me didn't do much with mopars, mainly chevys. I know that the top ring has to have more clearance. Did they give you a zero deck height or were they sticking out a bit?
mopar65
Well-Known Member
The best I can remember they came in at zero deck. The older I get the CRS seems to get worse. Lol I added the trickflow heads 3 to 4 years ago.
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