360 Magnum

[Bruceynz]

Hi Guys,

Well I ordered a stroker kit and it required pistons to be made, so I waited and waited and icon never came through, been waiting since March! I had paid for the kit and everything. As time moved on something very rare came up for sale here so I bought it, a 360 magnum engine, I should get it in a few days, I have now cancelled the 408 stroker idea and will go for the 360 magnum.


The magnun will consist of the following

Engine Quest Heads
Air Gap intake
Holley 770 Street Avenger
Cam is a roller 262/270 .496/.496 on 110LSA

So thats where things have been at as you haven't heard from me for a while, just been waiting and waiting but plans changed

See You
Bruce

 

[kkritsilas]

Somebody who is very versed in cam specs for the Magnum will need to comment on the cam in detail, but a stock Magnum 360 is rated at 275 HP vs. the 140 for the original 318. The Engine Quest heads should be worth at least 30 HP above that. I am wondering about the power band, as it seems to be higher rpm oriented, from the cam specs and the Air Gap manifold. Are you still looking to optimize for low RPM torque? On the other hand, with the Magnum 360 you many already have all the low end torque that you want.

 

[Bruceynz]

The stock magnum cam was under .4" lift, its was low lift, it would seem the engine had so much more potential but Chrysler handicapped it with a poor heart, they gave it good lungs! Typical of Chrysler though, they did that for so long until they did the hemi. I reckon if they had given the 360 a bit more cam like they did to the hemi it would of been a pretty stout machine as well. At 50thou my cam is 209/217 degrees, so a bit bigger in duration that a stock 6.1 hemi cam but not as much lift as a hemi cam. My car is a custom grind cam for my setup, so see how it goes, the LSA was tighten up a bit as they said carb cars don't need 114, so they had the weight of my car, intake, rear end ratio, trans, wheel size, intended use of car etc they said could go more than .480" lift but limited by the heads. So I just decided to stop there.

 

[kkritsilas]

If the cam was custom ground to your specs, then it will work really well for your purposes. I don't really understand the "...they said carb cars don't need 114..." as LSA is a major factor in idle quality and in general, the smaller the LSA, the rougher the idle. I could be wrong without a doubt, but that is the way that I understand it. Point is, I think that the carb'd cars, being as dependent as they are on vacuum signal, do need as much vacuum signal as they can get, and a wider LSA generally lowers vacuum (duration does as well). EFI cars don't depend in vacuum to mix fuel, the vacuum only produces a signal from a sensor that the computer uses to fire the fuel injectors.

The Magnum was the last, and probably the best, iteration of the street LA engine family. The Magnum heads themselves flowed better stock than most of the ported LA heads. The EngineQuest heads are better than the factory Magnum heads. The new Hemi is a clean sheet design, and can incorporate all the things that have been learned in the last 40-50 years, whether it be longevity, fuel efficiency, or even performance. The other thing to keep in mind, is unlike the 60s to early 1970s muscle car engines, the Magnums were never car engines and were never put into cars (think back to the cars that Chrysler was making in the early 1990a). The Magnums were truck engines, tuned to deliver maximum torque for carrying loads and pulling trailers. So the cam choices that the engineers made were designed to fit the engine's purpose. If Chrysler was making Road Runners, GTXs, Chargers, 'Cudas, etc., at that time, you would have seen hotter Magnums with better cams. The only reason that we can use the Magnums in our cars is because they use the same block, and bell housing bolt pattern (with a very minor change) as the LA blocks.

From some of the build up articles I have seen, the maximu lift the Magnums will allow is .512", limited by the valve guide height.

 

[Bruceynz]

LSA has quite an effect on the engine, this is quite interesting from comp cams

 

[kkritsilas]

This is why I was wondering about the "...said carb cars don't need 114..." statement. From the Comp Cams list, it does say that idle vacuum is increased, and idle quality improves with a larger LSA. It may be that all of this is so minor that it may not make a difference for your engine (larger displacement engines are known to tolerate more cam duration and narrower LSA just from the large air volume that they draw in) as it is a 360, not a 318. I just found the statement they made to be at odds with what think I know and understand. Like I said, the engine will probably do all that you want, and probably even more, which I am not questioning; I am only questioning the LSA statement.

 

[Bruceynz]

Well to me it would seem its all a fine balance, the perfect cam would be square

 

[kkritsilas]

I love that.

 

[Bruceynz]

Bruce in NZ develops the first perfect camshaft. The square cam instant open, perfect duration and instant close time! That reminds me of a joke my father use to tell, why are poo's tapered? Answer - To stop your arse hole slapping together

 

[kkritsilas]

There ARE cams specifically designed to have faster opening and closing "events" (i.e. rates) than would be considered normal. You do need to be careful as to how fast a rate you can try to get. That is set by things like lifter type (flat vs. roller, solid vs. hydraulic) and diameter, valve spring design and pressure, reciprocating weight, and so on. It is actually best to try and get as fast an opening rate as possible, as long as the valve train allows it.

 

[Bruceynz]

So what kind of idle would you expect for a 262/270 or 209/217 @ 50thou roller cam in a 360?

I wouldn't of thought it wasn't a big cam, any one played with roller before?

(You can get some with mega lift rollers, very common to be well over .5" lift)

 

[kkritsilas]

The lift at the cam is easy to get. How much you can actually make use of without having to do machining or get into geometry problems is the issue.

In the case of the Magnum, anything above the (what I remember to be) .512" lift means that the valve spring retainer/locks will hit the end of the valve guide. If you machine that down, you will eventually cause coil bind (the valve spring gets compressed enough that the coils touch each other) , and then geometry (rocker arm angles and/or push rod geometry issues). All of that has solutions, of course, but the costs start to add up really quickly.

 

[Bruceynz]

My Mag finally arrived, I dropped the exhasut manifolds off it, all the stuff around the front and popped the intake manifold, looks clean inside, need to get rid of the dirt before I go any further. Pulled the dip stick out which was a mission on its own as the tube had been kinked and the handle broken off right at the tube. There was no oil in it but what was on the dip stick looked clean! So far so good, will pop the heads off next. Which will also make it lighter for me to get off my trailer onto my engine stand as I don't have an engine crane/hoist.

 

[Bruceynz]

 

[Bruceynz]

Cleaned things up a bit, may have just got away with it! Number 7 was the one that had water in it.

 

[Bruceynz]

Making progress, I had a stock early 1970s 904 non lockup and I know people are going to give me a hard time because I should have used the weaker later model gear set out of my lockup 904 with the better ratios, but I had opted to go for the stronger gear set and my stall converter, the trans had a Oregon Performance Trans performance rebuild kit, with a transgo TF1 shift kit, should be good for 450hp they said it could handle more HP if I have gone to the TF2 kit, but its a road car, prob more line pressures or something but would end up with harder shifts. Waiting on some parts to come in from USA now and then I can get the mag together! I am so jealous of you guys having all the parts you want at the local junk yards or parts stores! I have to wait a couple months to get bits!

Going to fit the kick down cable system, does anyone know any off the shelf speedo cables I can buy that will go off the dash and straight to the trans and miss out all the cruise control stuff? I think the connections are different on speedo between the non lockup trans and lock up

New water pump, new idlers and tensions, aircon delete serp belt, EQ heads, head gaskets, car oil pan, oil pick up, valve cover gaskets and prob more I have forgotten

 

[kkritsilas]

Bruceynz:

Build the car that you want to. Don't worry about other people's opinions.

The A904 with the lower first gear is an A998 or A999. The weaker gear that you are probably referring to is the lock up sprag clutch, and it has been an issue in the past for high power drag cars. However, the A998 has 4 clutch disks, and the A999 has 5m the regular A904 has 3. The lock up clutch will net you some better highway mileage, but if you don't do a lot of highway miles, it really doesn't make that much of a difference (main benefit is lower trans fluid temperatures and slightly lower RPM at highway speed). I don't know what the trans shops are like in NZ, but if you do have a good trans shop in the area, you may want to ask them what it would cost to move the first gear cluster over to your own A904. There is significant improvement in getting the car moving from a stop with the 2.74:1 first gear vs. the 2.47:1 gear. I'm pretty sure that it swaps right over.

Even in North America, the small block LA/Magnum engines don't have anywhere near the parts availability (and low prices) like the small block Chevrolet and Ford engines do. However, you have to deal with shipping times and customs charges when you order stuff, too, so you are definitely having a more difficult time of it.

 

[Bruceynz]

Thanks for the info, trans is rebuilt now and won't pull it apart again for some time! Since I am not drag racing I am ok with loosing a 1/10th of a second in the 1/4mile But agree it would have to be better. Yeah just the way it is with parts unfortunately, with exchange rate and taxes and shipping. A $1000USD costs me $2500NZD and just remember I gota work just as long, at $25/hr I have to work 100 hours but in USA only have to work 40 to buy the same thing. Makes the hobby expensive, but what do you do when Mopar is in your veins, you soak it up and just do it

 

[Bruceynz]

BTW I fitted a late model deep dish pan to my trans! That should help keep the thing cooler!

 

[Bruceynz]

Took oil pan off today, slotted flex plate and mounted kick down cable on trans, that trans cable is a super nice way compared to all those rods!