318 Aspen with magnum heads.

[jed_laski]

Hello! I am looking to get more horsepower from my 318 1977. The engine itself runs pretty well. I have currently put a pertronix 3 full set with chineese airgap and edelbrock 1406 600cfm wich is a little too much for the engine. What went with it is a lokar style cable and throttle and throttle plate spring set. The combo works very well, i tested it on numerous trips, amateur races and it really boosted the car from stock 2barrel configuration.

FIrst of all I have to change timing set, and it would be a shame not to replace camshaft and what goes with it a valvetrain.
Now im looking to get something more from the motor, maybe boost compression? What i have in stock is a set of 5.2 magnum heads from grand cherokee wich i could upgrade. I got also a bare block and a bit rusty crankshaft from it. What im looking for is a recipe for a nice choppy sounding cam that will be able to burn rubber. Now the car is quicker but it hardly burns any rubber on dry pavement. From what I know i need other kind of pushrods like magnum has with a hole inside. So any advice what to choose will be greatly appreciated! I am looking to get best bamg for a buck for my heads without swapping entire engine. I am capable of spending some money on speed parts, but I dont want to swap entire engine. The car has a 904, a factory suregrip lsd wich i found out is capable of handling 300hp, a factory power steering and a fake X pipe.

 

[kkritsilas]

There are a number of videos on Youtube on how to make power with a 318, even from well known sources like Power Nation. Just have to do a search on Youtube. Also, Hot Rod Magazine did a 318 hop up video; article may still be on their web site. Those Magnum heads are a really good start (if they are cracked (a known Magnum head issue), get them checked), helping fix a lot of the LA series engine issues (breathing and small valve size, as well as a partial solution to the low compression issues (to get really good compression, you are going to need new pistons)).

 

[brotherGood]

I put magnum heads on my 318, with a summit 6900 cam, headers, Summit (Holley) 600 cfm carb and it was night and day difference. Down the line I also swapped in 3.55s and a sure grip into my 8.25, and it also needed a bit more converter, but it was rowdy compared to the stock AHB I started with.

The magnum heads also don't allow too much on the cam in factory form, due to springs (i believe guides as well, but could be wrong), so the 6900 was pretty close to what I could do without changing all of that.

 

[Mikes5thAve]

What rear axle? If it's a 7/14 it won't handle 300hp, not that you'd get there anyway with a head swap.

What's the rest of the engine like? It might be cheaper and less work to swap something else into it unless it's low miles and well maintained.

 

[Aspen500]

Sticking point of swapping in a 360 Magnum (for example) is, they haven't been made for 22 years. Probably 95% of the trucks that had one are loooong gone, and what's left is worn out junk and needs completely overhauled before use. Multiply all that by a factor of 10, being the OP is in Poland. Just saying.........

 

[Duke5A]

We're going to need a little more information. Others have already asked gear, axle, etc... Add budget and import taxes to that list. We'll try and get you a plan that takes that into account.

I will add that a 318 turning tires off of the line is going to involve a fair amount of gear and a higher stall. Your motor will be living higher in the RPM band. Something to think about from a drivability point of view.

 

[Mikes5thAve]

Sticking point of swapping in a 360 Magnum (for example) is, they haven't been made for 22 years. Probably 95% of the trucks that had one are loooong gone, and what's left is worn out junk and needs completely overhauled before use. Multiply all that by a factor of 10, being the OP is in Poland. Just saying.........

At the same time that could be about the same condition this 47 year old 318 is in.
As they say you start putting new parts on an old engine or trying to get more power out of it and that's when the weakest links start showing up so it would suck to put that much work into into it and not get much if anything out of it or cause some other issues.

 

[M_Body_Coupe]

Czesc, jak sie masz??? LOL

OK, the guys pretty much covered it all, we need to know a lot more about the shape of your 'as-is' combination, meaning: how good has the engine held up? Do you happen to know the cranking PSI right now? Have you done a leak-down test? what rear-end ratio are you running, what stall speed? etc....

Along all that, we probably need a better definition of what your actual TARGET is!

Here is why I say that: "...Now the car is quicker but it hardly burns any rubber on dry pavement...", OK, so do you want something that has that street "showmanship" ability (thus smokey burnouts), or do you want it to sound mean (that lumpy cam sound), or do you want the motor overall to increase hp and you hope that nets you all of the above?

I will say the following:

1) TORQUE
- you could focus on maximing the torque the 318 can produce, which would mean a short/er duration cam (as compared to high-RPM stuff)
- this would most likely work w/o changing too many things (parts wise, thus smaller cost)
- but this will not get you a motor that just wants to rev high and feels like the power just keeps on coming and coming
- in other words, you can build torque, but that engine will stop climbing RPM by the time you hit 5K, it will nose over, done, finished, koniec!!!

2) HP
- sort of the opposite of TORQUE (in general), although if you match all the right parts and appropriately build the motor the torque will be there as well but with the shift to a higher PRM powerband
- this is costly to do though because to make HP you normally need to bring in the high-RPM stuff, that means larger cam, higher compression ratio, parts that are either lighter, or more durable, so costs go up
- the fuel you use will require higher octane rating, again, more expense
- the thing here is that this approach is no longer JUST about the engine, you really need to look at your drivetrain as well, so think about higher stall converter, more aggressive gearing, etc., again, costs!

3) SOUND
- plenty of speciality cams out there offer that nasty 'big cam' sound while not necessairly requiring all the crazy parts and the spend associated with it
- keep in mind, this approach will not get you the BEST torque, nor the MOST hp, rather it focuses on getting you that "too hairy to run on the street" feel
- nothing wrong with this approach, but know your limitations as this is more about the 'show' factor

My advice, figure out what you are aiming to achieve and only then talk about specific parts, be it the Magnum heads, or pulling the motor and replacing it with a higher displacement altogether (318 => 360 is a night & day difference, 360 => 408 provides overabundance to torque and power, etc.).