Now that's good stuff right there! lol
318 cam
- Thread starter 65Dart270Sedan
- Start date
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Now that's good stuff right there! lol
Owen 340+6
Bang em till it breaks
That's the way I break my cams in to. I dont do that 20 minutes and 2k non sense. Fire it up idle for 15 seconds and let it rip. Haven't lost a cam in my life (yet) and yes its hydraulic flat tappet.
I totally agree. That is a good cam for stock when wanting to use all your factory parts over. New lifters are a must. Should replace the springs on a 50 year old head. Kim
Dale Davies
Well-Known Member
You have not purchased the cam yet. Better take a step back and think about this a bunch. On an engine rebuild you need to define what you want to accomplish as an end result. That is a lot of cam for using as much stock parts from 1974 as possble. Those year engines had low compression and open chambers. Open chamber heads are somewhat prone to detonation as compared to quench heads. Do not choose a cam solely on price. If a cam fits your build specs and will give your expected performance and you get it on sale, good. But purchasing the wrong cam just on price is a lesson in frustration.
Describe on here exactly what you expect for an end result and budget. Then people on here can give relevant advice.
With looking at using as many stock parts as possible, you probably need to look at an "RV" style cam. 210° to 220° @0.050" tappet lift. If your valvespring installed height is aboit 1.800", beehive springs can be used to control spring harmonics. You will need different retainers and probably locks. For valve lift, if you do a little pocket porting and port match, the 0.475" lift at the valve is probably good. Build the engine for 0.525" valve lift to clear the pistons. This way if your cam is a bit less on lift you can later upgrade your rockers for a higher ratio. Intake is more sensitive than exhaust, so you can just replace the intake rockers. Remember you are likely telying on atmospheric pressure to fill the cylinders. The exhaust has give or take 100PSI at EVO pushing the exhaust out. Then the piston on the exhaust stroke is pushing it out.
Careful consideration must be given to the intake and exhaust manifolding. Stick with a dual plane intake for low RPM torque and driveability.
Dale Davies
Well-Known Member
Emissions OEM small block cams for the smaller displacements wer short on intake lift. Valve was in the way of vacuum up to the carb resulting in low power and fuel economy.
A fairly stockish short duration but high lift cam will aid performance immensely. Do like the factory 5 liter displacement high output engines and use the 5.7/5.9l cam. Going to higher ratio rockers will also benefit performance, but clearances between the retainer and guide and the PTV clearance must be accomodated during the build.
I've been doing it for 50 years. It is easy and not a secret. See post #17, #48, and #56. What was factory 340 hp, 275? What times did they run, low 14's? Looks like it is doable... I used to take a pair of milled rebuilt 360 heads, drop a 340 cam, springs, double roller timing set, high pressure oil pump relief spring, a windage tray, a hardened tip oil pump shaft, 340/360 4 barrel intake and rebuilt 340 carb that others were swapping for a slower combination, a Direct Connection electronic conversion kit for around $100, and 360 or 340 exhaust manifolds with dual exhaust. You think that combination would not run with a 340? And what's more, it works with a 273 or 360. Add a custom solid lifter cam and add "64-67" 273 rockers, and you are now faster than a 340. One can do a lot better than stock 318 performance with just a different cam and valve springs with no dependability problems.
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Did you install the cam @ 102 ICL? and if so have you checked the cranking compression?
I would be curious to know what the cylinder pressure is like.
Owen 340+6
Bang em till it breaks
It's a derby motor. I didn't check anything. Stuffed it in and stuck some old nos lifters in it and impacted rocker shafts down and fired it up and revved it a few times and took it out in the Pasture and held it wide open doing donuts for 8 to 10 min and called it good. Definitely nothing fancy here for this secondary hobby of mine. I did run it on a 50/50 mix of VP 110 and 89 pump gas and never had an issue. Doesnt seem like it has a ton of cylinder pressure by any means. Its to tight for my use it point had 40k original miles but the more times I get it so hot It won't even shut.off, it'll loosen up in no time. Love derbying absolutely the best testing of products ever
junkyardhero
Well-Known Member
exactly this.
if you're not trying to shoot the moon, you can build a reliable, stout 318 that will absolutely run with the pack. the combo isn't some super secret mix of high dollar and proprietary parts. heads, cam, and a little compression is really all it takes.
it's been proven several times over that you can easily and reliably make a rip snorting 318. can you make more and do it easier with a 340 or 360? sure, that's just basic fundamentals.
and i can already hear the mewling from the great unwashed massed: wHaT aBoUt vAlvE sHrOuDiNg?!?! Durrr rOd rAtIoS mAtTeR!! sMaLl pOrTs wOn'T sUpPoRt hOrSePowErrr!!
honestly, it doesn't matter at these power levels. you're not building a super stock motor. knock that **** together with decent stuff, size the cam and carb appropriately, gear it right and ship it. it'll be plenty good enough to do a burn out in your ice cream cruiser and probably run 13's at the track.
The posts I cited used 318 heads. I used 360 heads for the better ports. I don't like 360s. I did most of my engine work in the 70's and 80's. It was cheap to buy a 70's C-Body and scarf up the 727, 8 3/4 pumpkin, and a 360. I'd sell or scrap the 360 block and crank and rebuild the heads, and use the connecting rods, and electronic ignition. You can absolutely make good power with 318 heads. Like every engine ever made, a 318 responds to better breathing. It can be a cam, valve springs, and a 4 barrel carb and intake. It can be all out, but that is not what I did. People need to read and respond to an OPs question instead of constantly going down the same rabbit holes without being any help at all. @273 nailed it, post #17. It is easier for most people to swap an intake, carb, or a cam. It is more complicated to swap a 360 than it would appear. Even a 340 has a different mounting bracket and exhaust. Also a 340 will start to break parts that are not up to the task. Go back and read post #1. I used to rebuild engines. I kept my favorites, the rest are all gone. I only rebuild engines for myself now, but I know you can make reliable power from a 318. Does anyone really think .13 of an inch in a 4 in diameter bore makes any sizable difference, all else being the same?
Dartswinger70
Well-Known Member
How would all else be the same when it isnt...? what are you going to do scrounge up 3/4 of a 340 and bolt it to a 318 block? whats the point...? Hav e you ever disassembled a 68-71 340 and a similar yeaR 318 SIDE BY SIDE? NONE OF IT IS THE SAME...
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True that parts aren't the same. Most are interchangeable but not the same.
I have three 340s, and have built many more. One 340 has been machined and sitting on an engine stand, and is still there after 20 years, waiting for me to get tired of my HP 273. What is your point? The OP asked:
What are you helping him with? Post #17 gave him 2 cam recommendations, one put out 280 hp using his stock 318 engine. You answer with get a 340 or 360. I don't see where he asked what engine he should swap in.
This thread started out great. Way more informative than almost any other "318 cam" thread on the first 2 pages.
Unfortunately it has now degenerated into the same old thing of bashing, and "max performance" talk.
I just wish someone, anyone with more smarts than me could be bothered to take a look at the dozens of cams available in the "one step" or two steps" up category, IE doesn't need a converter or headers or final drive gear numerically higher than say 3.23 and compare them and explain what qualities make them different and how those qualities affect what the results might be like.
I've seen that done with high lift, high duration cams (OK, maybe medium in the 480 to a bit over .500 range) for both big block and small blocks, so I know the knowledge is present here.
However, that request is usually met with "who has time for that?" type responses.
Unfortunately it has now degenerated into the same old thing of bashing, and "max performance" talk.
I just wish someone, anyone with more smarts than me could be bothered to take a look at the dozens of cams available in the "one step" or two steps" up category, IE doesn't need a converter or headers or final drive gear numerically higher than say 3.23 and compare them and explain what qualities make them different and how those qualities affect what the results might be like.
I've seen that done with high lift, high duration cams (OK, maybe medium in the 480 to a bit over .500 range) for both big block and small blocks, so I know the knowledge is present here.
However, that request is usually met with "who has time for that?" type responses.
If you look at post #17 stock 318 with 4bbl headers and comp xe262h cam, it ain't hard to imagine how a xe250h and xe256h or similar cams would respond, the down low rpms 3500 and under probably pretty similar, above probably a drop of 10-15 ish hp for each step down and a loss of peak hp rpm by around 100 or so. An xe250h to me is similar to a 340 cam which is still a decent size over stock 318 so there is still a couple steps in between. Going up to a xe268h plus will gain top but will start to take away from bottom. Going wider lsa will tend to drop under the curve performance by a bit for each step wider. It all moves in relatively small steps.
Dartswinger70
Well-Known Member
Well my point is/was ( with regard to the OP) use the stock 318 cam because installing a performance cam into an otherwise stock early 70s smogger 318 doesnt gan you much in the top end... I beleive its mainly because of the small port heads and small valves,
THat would be good until someone posts a Summit cam and someone else will down talk it and say how junk it is. Same with Comp except about the quality. (or lack of) (or not). THere is no win. I would just use baselines. No duration @.050 any larger than 225° It's interesting how the old grinds are heavy on the duration side and have a @.050 around 210° but have 280° advertised. One thing good about those types of cams is the max lift is relatively low and can use stock type springs (like Comp 901's) THey still make power at lower rpm. Take this one for example. and they have a couple that are steps up. This one would work fine with stock exhaust and converter. A 4 barrel would be a plus.
204°/214° 278°/288° .421/.444 112° 12-5000 rpm
DODGE Summit Racing SUM-6900 Summit Racing™ Classic Camshafts | Summit Racing.
WHIPLASH 
Dartswinger70
Well-Known Member
good mention about the springs, it gets where you are modding a 318 why not just start out with the good 340 360 heads with spring dampers etc. this is what gets me people say "there the same..." 318 and 340 arent the same.its in the details. The blcok isnt even the same there reinforcement near the drivers side motor mount ears...i get tired of the argument myself and hearing that they are the same...or "what difference does the bore make..." the bore doesnt make the 340 its a small part of it though. i beleive its more in the ability of the 340 to rev and the stout bottom end and the flow of the heads which allows for a bigger cam ...thats all the things the 318 doesnt have going for it. again this brings me back to my point why put a big cam in a 318 when the heads cant fully support it. OR I'd say do it but eventually youll add heads...porting a 318 head isnt going to make it a 340 360 flowing head.
I know, but meant mores as comparing the tq curves of one another, 318 would be lower overall tq numbers and probably at a slightly higher rpm, but still useful see how those cams effect the tq curve and wouldn't be to hard to imagine how they would compare to the xe262h tq curve in the 318.
Got the work with what we got, be nice if someone dyno every mild cam in a stock 318.
I guess you are wrong. Post #17 has a 100 horse power gain with just a cam change.
Do you or have you built engines? Airflow makes horse power. It does not matter what size the ports are. 318s are plenty strong enough.
jpl572103
Well-Known Member
Good old friendly advice on this forum from a few. but some of the others wow.
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