318 Mopar rebuild and modification questions!

[drobertson]

Ok. So I bought a 1973 Dodge Charger for $500 last month. I have pulled the motor and transmission, and I plan on doing the rebuild. The motor had 150 hp from the factory.... but I want more; with the same motor. I plan on buying a performance cam, or a cam kit if necessary. I would also like to raise the compression ratio if possible.

What I ALREADY HAVE : a remanufactured crankshaft (from napa, with pre-machined main and rod bearings), 4bbl intake manifold from with an edelbrock 600cfm carburetor, all engine gaskets, spark plug wires, spark plugs, lifters, and that's all I can remember for now.

What I still need: High compression pistons ; 9.5:1 would be perfect with stock cylinder heads. I have bored the block 30 thousandths as well, so the pistons must be 30 over. I'm also finding a Camshaft and timing chain assembly, oil pump, fuel pump, and cylinder valve guides. Headers would be nice as well, and dual exhaust.

THE BUDGET: So far $650.keep in mind that I already have half the parts I need.


SO here is the real question: What is the highest lift, longest duration camshaft I can use with stock valve springs??? Where can I buy x8 high compression pistons at an affordable rate? $100-$250? I've been looking at summit racing... but cannot find compression specs. What kind of power will I be looking at? I want at least 250 horse. Is that realistic from a 318? and can my 904 transmission withstand this? Thanks for help. I will try and post pictures. (I have rebuilt the transmission to factory specs.) Keep in mind that I'm young, and still in high school; with every tool imaginable to assemble it. And thankfully lots of energy! Thanks!!!!!!!!!!!!!!!!!!!!!!!!!:headbang:

 

[Bb70charger500]

I'll be the first to say it .don't just shove a huge cam in it ,it will run like crap and fall flat on its face . I understand the budget deal so why not for now do the carb a rpm intake from eld a set of cheap headers "summit is great " a pair of flowmasters (full duel exhaust) grab a $100 shift kit for the 904 to help get the power out . And get a set of rear end gears 3.?? Something is better the the stock 2.71's this will wake that car up a lot you will be very happy with this and in the meantime why your driving it save up your money for a set of heads and cam in the future the stock 318 heads are not performance orientated in any way there door stops.
And if you still have a few bucks throw some fancy plugs and bigger 8 mm wires in it and maybe a better then stock coil but just doing the things I listed should stay under budget and get you moving a bit better I've done a lot of these charger s and I love my small blocks if you set them up right there great little motor s
Don't forget the gears those are very important and don't just but 4.10 gears those are useless especially for a driver race car yeah that's a start but be realistic you want to drive the thing right? Not sure if this is your first mopar or what but if you need help p.m. me I'll gladly help you out .By the way you probably have a 8 1/4 rear in it if it has a rear cover with bolts then 8 1/4 if the rear of the rear is smooth then it's the bigger 8 3/4 (witch would be great ) take a picturev if you need more help I.d. ing anything . Good luck with your project post some pictures up I'd love to see your charger here's a picture of one of my older cars eng 360 View attachment 277655

 

[coronet68mx]

The Mexican versión of the 318 output 270 up with forged crankshaft. 340 cilynder heads a better camshaft. ... In 1968

 

[drobertson]

What about a reproduction camshaft from a 340? I know some mopar guys in my area that got a good power gain from them. I have a pair of 1976 360 cylinder heads... but I'm not sure if they'd help the HP at all. What about pistons????

 

[451Mopar]

You will need to cc the cylinder head combustion chamber to really figure the true compression ratio.
The valve springs might be able to handle a slightly larger cam if you shim them for more pressure, but you really need to measure the springs pressures and coil bind to know what you have.
For a mild performance daily driver, 250+ HP, a cam like the Lunati Voodoo 10200701LK would work nice. It is 213/220 @ 0.050" lift, 0.454"/0.475" lift.
The standard pistons with a 1.741" compression distance will be about 0.080"+ below the deck height and be lucky to get over 8:1 compression, but they cast ones are cheap.
The KB 167 Flat top had a 1.81" compression height which puts the piston 0.012" below the block deck at TDC, and with a 65cc head and 0.040" head gasket gives right at 9.0:1 compression.
Your heads may have smaller chambers? that would increase the compression ratio, as would a thinner head gasket.

 

[747mopar]

I'll be the first to say it .don't just shove a huge cam in it ,it will run like crap and fall flat on its face . I understand the budget deal so why not for now do the carb a rpm intake from eld a set of cheap headers "summit is great " a pair of flowmasters (full duel exhaust) grab a $100 shift kit for the 904 to help get the power out . And get a set of rear end gears 3.?? Something is better the the stock 2.71's this will wake that car up a lot you will be very happy with this and in the meantime why your driving it save up your money for a set of heads and cam in the future the stock 318 heads are not performance orientated in any way there door stops.
And if you still have a few bucks throw some fancy plugs and bigger 8 mm wires in it and maybe a better then stock coil but just doing the things I listed should stay under budget and get you moving a bit better I've done a lot of these charger s and I love my small blocks if you set them up right there great little motor s
Don't forget the gears those are very important and don't just but 4.10 gears those are useless especially for a driver race car yeah that's a start but be realistic you want to drive the thing right? Not sure if this is your first mopar or what but if you need help p.m. me I'll gladly help you out .By the way you probably have a 8 1/4 rear in it if it has a rear cover with bolts then 8 1/4 if the rear of the rear is smooth then it's the bigger 8 3/4 (witch would be great ) take a picturev if you need more help I.d. ing anything . Good luck with your project post some pictures up I'd love to see your charger here's a picture of one of my older cars eng 360 View attachment 277654View attachment 277655

Agreed, just throwing a big cam in is a recipe for disaster! Step back and ask yourself "what is the intended use for this car" now put a package together to match. When going to a "big cam" you move the rpm range where the motor makes its power up meaning more stall and lower gears are needed to get it in that range plus you needs heads that will deliver the added demands of the cam. It's a slowball affect so take your time and do your homework. Good luck


You really should already have your pistons when having a block bored so they can hone to match, make sure to check the clearances.

 

[Seventy]

I have to say the 318 is a great engine, no real reliability short falls BUT plenty of them when it comes to performance. I personally ignore the motor unless its for a farm truck. IMO you can grab a later model 360 out of a junk yard, toss in a cam, a slug with a bit more compression, a tiny bit of port matching and call it a day, not a rocket ship but it will get you sideways with the right gears and a snappy automatic...

Besides the 318 your other hurdle is going to be your budget. $650 is tight, considering rings, bearings, and freeze plugs can cost you $200+ of it..

So since rebuilding a motor is not easy I would say ignore the budget vs the performance, but that is going to be your call.

Here is what I would do...
Find a set of junk yard 302 heads, they will be sitting on pretty much any mid 80's to early 90's small black chrysler. Should be able to get a set for $20 if not for free, I know I have to have 2 or 3 sets somewhere around here unless they already made it to the junk pile, but they will cost more to ship than you can get them for locally...

First order of business would be to get your self a 360 intake gasket and a set of 2.02/1.60 valves (I know hearing 202/160 from a guy who builds chevys is a surprise, lol). Fit the valves in there (they will easily go) and port them heads to match the 360 gaskets (intake should also be matched to them), plenty of meat to do your porting.

The 302 heads are going to be the best head you can afford, and they are a nice head, believe it or not. Has a vortech style (I know chevy wording) chamber and they are around 58cc's with a thin gasket you will get some compression with a set of basic 4v relief cast pistons (probably $80 a set).

As for a camshaft, that is just as important as the heads, I would look into the purple cam, mopar has one that is something like 430/450 that I used before, I scored it on ebay for $90 new with no lifters (make sure you are using new lifters)...

I say with silvo lite/sealed/speedpro/etc 4v or flat tops (sp has a set with 1.790 height that is affordable, the KB 166s are like $500 a set, but they will obviously make more compression, even cheaper than the sealed powers is a set of speed pros they are 1.755 but again less compression and they save you $80 or so from the sealed powers which save you $250 from the KB's), a set of ported 302 heads with the 2.02/1.60 valves, 360 intake gaskets, matched aluminum intake, 650 to 700ish cfm carb, that mid lift purple cam, an ignition system capable of burning the fuel, and an exhaust capable of getting the chambers clean with out too much back pressure, you will get the HP you are looking for plus some.
Use the thin mopar head gaskets and the 360 felpro intake gaskets, put in the time with the grinder, do a really nice valve job and you will have one heck of a 318...

Falcon will have the best prices for all the parts, I have the part numbers for the valves and head gasket since I bought them at summit and can look up past orders pretty easily, if you need them. I can not stress enough that the heads are the most important part of your build, I know the valves cost me around $200 alone, if you had some extra money decking them heads will get your compression even higher but most shops charge $150+ to do it...

Good luck, I know some satisfaction comes with building a budget small cube engine that has some sack to it, I LOVE my 302 chevy and destroked small block builds, something about shifting a v8 at 8500 rpms just makes me smile... ALthough I will be the first to admit an all aluminum -500 cubic inch 800hp mill that weighs as much as a 5.0 ford is even more fun... They all have their place...


PS- I take it your block is bored but not honed since you do not have pistons yet? There is nothing worse then spending your budget on a build and having it not right. Take your time do some research then spend your money. I would get on the phone and find a set of 302 heads, buy the valves, get the heads all together and ready then move on to the next part which would be your short block. So when that is done you bolt the heads and intake on and go to town...

 

[Cranky]

A buddy and I threw a teen together with spare parts and ended up running 13.50 with but the car only weighed 2950 and we had a ton of gear in the back. It also had pocket ported 360 heads which we figured the CR at 7.8-1. With a 480 lift cam, no converter, it was dead until 3000 rpm then ripped like crazy to 6200. Didn't need to do a burnout because it wouldn't but on street tires, it would flat out blow them off on the 1-2 shift so we had to run slicks just for that reason. People used to ask us why we were running slicks lol. The car ran 102 mph with a 2.2 60 foot. Talk about a bad combination. Your car is much heavier so keep it mild and don't use the 360 heads. You want to keep your smaller ports and valves for better low end and add some compression. You will see a difference with just a good intake, carb, 340 cam and good exhaust. Headers will help too but the car will still not be quick.

Seventy mentioned his 302 and going to 8500 with it. That right there is the key for a small motor making great power. More rpm means more air flow and fuel through it. The teen I mentioned had the next step up in Mopar springs and heavy duty stamped steel rockers but this engine flat out hauled butt from 3000 to 6200, but it was like someone just backed off the gas and kept it at 6200. Valve float? You can make any small block scream if you know the combination and have the money but it's not doing to perform all that well in the lower rpm ranges and especially so in a heavy car. If you want to see some killer small blocks, go to the track when the Comp Eliminator guys are running. You'll see them there. There will also be some in Super Stock....at least they used to be. Another buddy ran in SS/O with a 56 Chevy and a 265 and that thing ran low 11's. It was all steel too with a stick. He launched it at 9500 and shifted at 9k! Yeah, he used up rings pretty fast lol

 

[GinoX]

I endorse the 360 heads and their mods on the 318, the mildest Purple shaft cam with its lifter set and matching springs (I know, over your budget already), Offy or a more modern Edelbrock street master intake and 700~ish carb., MSD ignition and dizzy.... phew!!!! And I didn't touch the shortblock yet, because in my built I didn't have that much moolah way baxk when.

 

[Seventy]

Here is what you are looking for in a head. see that heart shaped cumbustion chamber, no useless space behind the valves. This is a modern style head, vs what you see in a 60's head, cams and heads have changed for the better (cranks and rods, not so much lol, ask me how I know what a PM rod looks like sticking out of the side of a $9K LS motor, lol) ... Find your self 302 casting heads, 85-91 318's, adding the larger valves and porting the snot out of them will get you more power, but even just gasket matching them and leaving the small valves in will be heads and tails better than any other head I can think of for the price... Junk yards used to be loaded with these things, diplomats, police cars, any of them 318 late 80's powered cars will have them heads, I wish I saved them all, I saved a few sets, but watched hundreds of them motors get crushed over the years...

 

[drobertson]

I have not bored the block yet. But it is ready. I'm not building a race car... but just want some oomf under the throttle. My auto class teacher had redone plenty of these motors; and He's showing me how to do it right. The crank is dinged up a bit... So i bought a remanufactured crank kit from napa for 250 bucks. (has the crankshaft, and pre-sized main bearings and rod bearings.) I already have all the gaskets for the motor; so I ordered a custom rebuild kit from napa that only includes the timing set, camshaft, lifters, pistons (30 over), freeze plugs, oil pump, water pump, piston rings, wrist pins, etc. Keep in mind that I'm in wyoming --- one of the largest states, and the lowest population. we consider a 10k people area as a 'big city'.---- Or in other words: there's limited recources and no race tracks. I got a 4bbl intake for 20 bucks at a salvage yard, and a brand new edelbrock 600 cfm carburetor for 40 bucks, and a few other parts. So far so good! I have decided not to raise the compression, for saving money. All that only cost me about 600 bucks. After the motor is ready, I'm going to redo the 904 automatic, tires, side glass, and differential. Thanks yall! I will post pictures soon!

 

[Bb70charger500]

Soundsb good so far keep it up ,hands on is the best way to learn. If it doesn't work out keep trying you'll figure it out . Yeah let's see those picturesi ts a shame your not closer I'd set you up with a good motor (it's not fast but ready to go)good luck and keep us posted

 

[rumblefish360]

Deck the block for some compression. Yield at 9.0-1.

 

[drobertson]

Deck the block for some compression. Yield at 9.0-1.

Not a bad idea! I might deck the block a little now.

 

[451Mopar]

Not a bad idea! I might deck the block a little now.

Most of the time the block is decked to square up the block so the pistons sit the same distance in all the cylinder bores, but decking the block can create other issues, mainly the intake won't fit correctly unless the intake side of the heads or manifold is milled. You may also need shorter pushrods.

 

[rumblefish360]

Correct to a point and that point depends on how much is milled. FWIW, I'd start with the KB piston because it is taller and has valve reliefs for high lift cams. This will require less decking of the block.

If your staying with stock Pistons, the amount of decking needed for a reasonable compression is a bit more and the heads and intake should be brought to the machine shop to be checked for fitment and alignment.

 

[niteshift70]

Have the block zero decked and shave the heads. Should not have intake fitment issues unless you shave .060 or more. If you do shave that much, shave the intake face the same amount.

 

[niteshift70]

If done in this fashion, use standard intake gasket just don't use the rubber end seals (intake to block seals.) Use RTV instead.

 

[Seventy]

All that decking work is not free, most shops to cut heads, block, and fit intake will charge $600 or so... At that point, just build something with my cubes and save the trouble... There is a 340 hp core, taken from a running car on c-list near me for $1000, complete motor... they are out there and the 340 short stroke made a real nice mill

 

[niteshift70]

Shaving the heads in that manner is a cheap deal. For a budget build I wouldn't touch the deck. Following the guidelines, you can plop the intake back on with no issues.