RustyRatRod
Well-Known Member
Exactly. Rob gives great advice. The main thing is don't over think it and have FUN.
318 Performance Mods
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A few notes that I feel will help make a good package run good. Some say a larger port intake mated to a smaller port head really doesn't matter. I disagree. Air and fuel (especially fuel) doesn't really like to go up over steps but falling off a step isn't as bad but the smoother the transition, the better the flow. You're not really looking for more flow but you're looking for good quality flow. Fuel likes a good quality of air stream to maximize suspension in the air stream. Air will follow dang near any port configuration but fuel isn't so forgiving.
Don't think anyone mentioned cleaning up the back cut in the bowls under the valves or pocket area. The factory back cut really sucks and spending some money in this area will really help the quality of the flow into and out of the heads. It's known as pocket porting. Don't know what a shop charges to do that but it's not hard to do it yourself with a die grinder. Practice makes perfect and a junk head is great for that.
I think someone did mention that power is in the cam and heads. That's pretty true but the cam won't do much good if it's not in the right 'place' so to speak. Yeah, degree the thing! When you degree the cam in, you know EXACTLY where it's at and you also know exactly where your TDC mark is on your balancer. They go hand in hand. Yeah, lots of folks just line up the dots and the majority of the time it's good enough but I've seen way too many that chased their tails for days or even weeks trying to get their engine running right if after things were not on spec. Even seen some end up with bent valves because of this. I degree all my engines....bone stock rebuilds included. Production tolerances can stack up against you too. For example if the cam is ground a couple of degrees off and then maybe the sprocket key ways are a couple off and maybe even the crankshaft key way is off a degree or so and all of a sudden, you're 6 or so degrees retarded and that can make your engine act sluggish off the line. I know this sounds like it pertains to a high end build but it's really not and look at it as cheap insurance to a good running engine.
Don't think anyone mentioned cleaning up the back cut in the bowls under the valves or pocket area. The factory back cut really sucks and spending some money in this area will really help the quality of the flow into and out of the heads. It's known as pocket porting. Don't know what a shop charges to do that but it's not hard to do it yourself with a die grinder. Practice makes perfect and a junk head is great for that.
I think someone did mention that power is in the cam and heads. That's pretty true but the cam won't do much good if it's not in the right 'place' so to speak. Yeah, degree the thing! When you degree the cam in, you know EXACTLY where it's at and you also know exactly where your TDC mark is on your balancer. They go hand in hand. Yeah, lots of folks just line up the dots and the majority of the time it's good enough but I've seen way too many that chased their tails for days or even weeks trying to get their engine running right if after things were not on spec. Even seen some end up with bent valves because of this. I degree all my engines....bone stock rebuilds included. Production tolerances can stack up against you too. For example if the cam is ground a couple of degrees off and then maybe the sprocket key ways are a couple off and maybe even the crankshaft key way is off a degree or so and all of a sudden, you're 6 or so degrees retarded and that can make your engine act sluggish off the line. I know this sounds like it pertains to a high end build but it's really not and look at it as cheap insurance to a good running engine.
For what it's worth. I used a stock short block 318, .484" Mopar cam, stock w/no valve job 360 heads, intake , and T/Q, 2 1/2" exhaust system. 4.10 in a Dart. 14.0@101. Street tires, due to no low end torque it never spun. Personally it had to low a compression ratio and too much cam, just shows what you can do if your willing to spin the motor up and not spend any $.
Doug
Doug
RustyRatRod
Well-Known Member
But Doug, you did good with that. I've always been of the opinion that he MoPar cams were ground to take advantage of stock, unported heads. Sounds like you used it for its exact intended purpose. I bet that was a fun car.
rumblefish360
Well-Known Member
The MP cams are designed to take more advantage of the larger lifter diameter vs. the competitions cams. While they do not max out in there effort, they were sizeable by compare to what was being offered back in the day.
Single pattern cams work best when the head flow is in that golden area always preached about. This is not to say the engine will perform better with a split cam.
Unported heads, anybodies as far as I know, (as in old iron we run) do not flow that well as cast.
The MoPar head will take to porting well and the single pattern cams will work just fine.
I ran just a bit shy bit of Doug's ride in My low comp 318 when I was a kid. Less cam, a 600 Holley DP and a 4spd E-body missing some weight.
Single pattern cams work best when the head flow is in that golden area always preached about. This is not to say the engine will perform better with a split cam.
Unported heads, anybodies as far as I know, (as in old iron we run) do not flow that well as cast.
The MoPar head will take to porting well and the single pattern cams will work just fine.
I ran just a bit shy bit of Doug's ride in My low comp 318 when I was a kid. Less cam, a 600 Holley DP and a 4spd E-body missing some weight.
vexner
Member
Hey, I just built a pretty nasty 318 after doing a lot of research on this sight, used a old edelbrock ld4b , 1406 carb, milled the heads .050 with a .020 mr gasket head gaskets , a comp cam xe268h , went up one size on both intake and exhaust valves, had to use custom length pushrods from hughes, the heads are the 1967 closed chamber , matched ported to a 318 gasket, and a lot of time blending ports a cleaning up the runners, cc the heads and of course degreed the cam which was off, summit headers and exhaust, it seems like most of the info i found was don't match it to the 340 gaskets or use the larger port intake , the ld4b is for a 318 and had to shave .025 off the intake. it has a 3.23 gear also. I would like to thank all the guys who's post i read ,the motor runs very well
satellite66
Well-Known Member
Does anyone have a link to a manual or something that explains cams and/or rockers? I'd like to be able to know not only what I have (or will have) but also why. I have yet to figure out what "lash" is, among other things.
73coupe
Active Member
the edelbrock ld4b is 318 majic ,,, matches the ports ,,, they are becoming harder to find.
rumblefish360
Well-Known Member
I'll start with rockers and lash:
Lash is the space between the rocker tip and the valve tip. It is set with the adjusting screw and lock nut on the pushrod side of the rocker. Hyd. rockers do not have this.
The amount of lash is dictated by the instructions/suggestions of the cam manufactures.
Cams made simple, or the K.I.S.S. method to choosing a cam for your street ride:
a cams duration is the time it opens and closes the valve in terms of degrees. The longer it is open, the higher the RPM range of the cam is. Choose the cams duration in the performance RPM your looking to operate in.
Lift: choose the amount of lift your heads can take advantage of. If your heads are stock, they flow good until approx. .500 lift. Going beyond this point is pointless a d just adds stress to your valve train without any bennifit.
If your heads are ported, you should have had them flowed to know where the air flow stalls at and how much it flows.
Often you'll see a set of cam specs that end in a common number of 110. This will signal to you it has a muscle car chop to its idle. A 112 is smooth, A 114 sounds stock. Going the other way, a 108 has a nasty chop to the idle, 106 sounds radical, etc.....
Going lower than a 108 isn't really needed for street, street strip road driven cars.
Take note from the Crane cams web site that they also have a recommended cruise RPM for there cams.
That ought to do it for cam basics. Each cam company has a few pages in the beginning of there catologs to help explain things better. But I figured a Basic starter was good.
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