Best cam for combo?

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64physhy

64physhy

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I recently got a got a couple 318's with my Duster, one with 302 heads. I plan on building one up. I'm going to use either the 302 heads or a set of magnum heads on the build. I'd rather stick with the 302's since I have them, but can get a good set of Magnum heads for about $400 shipped (probably less if I look around). I also plan on using KB 167 flat top pistons.
.040 over bore
decked to zero deck height
KB 167 pistons
fed mogul rings
M-1 or Performer RPM air gap
2000 or 2500 stall depending on cam
3.91 gears
Demon or Eddy 750 carb
Headers (TTI or Dynomax)

Now for the cam, which of the following?:
Comp 280H (230 @.050, .480)
Comp XE268H (224/230 @ .050, .477/.480)
Purple Shaft P4452992 (238 @ .050, .474)
Purple Shaft P4120231 (241 @ .050, .484)

Overall combo is based on various builds I've seen on theis forum and elsewhere on the internet, I'm just looking for a compromise between some of more elaborate builds and basic builds.

I know the best will vary depending on what heads I go with (most likely the 302's). I plan on using it for mostly street use and take it to the strip from time to time. I don't have power brakes, and will probably use a lean burn plate, so vacuum is not a big concern. Please help me out with the best combo. I'd like to do a stroker, but not really in the budget right now.

Input appreciated. Thank you.
 
What do you plan to use for an exhaust system? The early A manifolds were not all that great. If you plan to run them, pick a dual pattern cam which gives some extra exhaust duration.

Your combo seems quite similar to what I am putting together. I will be using an old LD4B intake, an Edelbrock 1406 carb, and probably a Hughes HEH1928AL cam, but otherwise the same.
 
I'd go with a Lunati 60402 or 60403...

60402- 262/ 268, Lift .475/ .494 (220 int./226 exh. at .50)

60403- 268/ 276, Lift .494/ .513 (226 int./234 exh. at .50)

Lunati uses a faster ramp design than the mopar cams. The purple cams were good, but the more modern grinds will give you more power. Lunati recommends 2400 RPM stall, 700 cfm carb, dual plane intake and headers for the 60403, so you're fine with your build. If you're worried about over camming it, you can go with the 60402, but I know a lot of folks that run the 60403 on the street with success. (I have a 60404 going in my 340 build)

If you're not a Lunati fan, I'd say go with the Comp, either the XE268H you chose or the next step up at the XE274H (274/ 286, Lift .488/ .491, or 230 int./236 exh at .50). The only thing is that the Comps have a little more duration and less lift, so you can get into some of the problems of running more duration (choppier idle) before you see the added lift bonuses.
 
Thanks. I had been looking at the XE274H, but I guess I forgot it from the list. Haven't looked at the Lunati's. I like the wide RPM range on them, especially the 60403, but I'm worried with that much exhaust lift, the valve might be really close to or contact the flat top pistons, especially if I end up using magnum heads with the 1.6 rocker ratio. Are the stock valve sizes in the 302 heads big enough to support these cams?
 
I think you were the guy that was asking about building a 273 that you have in the car ?

I'd strongly consider pulling the 273 heads off and putting 1.88/1.60 valves in them with hard exh seats and pocket porting. The old 273 heads were a closed chamber like a 302, and will be similar to the 302's except that you dont have the huge pushrod bulge to contend with in the intake port. I would think they should be able to flow more than a 302 head ported the same way.

If you are going to build a 318 - consider taking the 273 apart and using the crank from it, it should be forged. Use a set of rods from one of the newer 318's you have - they will be the heavier duty rod compared to the 273 which are lighter. Balance the whole mess together along with a good set of pistons to get you into the 9-9.5:1 CR ratio. With the correct cam selection and compression ratio you should be able to achieve your goal.

Use a dual plane intake and a 600-650 cfm carb, with one of the cams being suggested. Also think about using a set of shorty headers from spitfire. Order them now as they take a long time to get.
 
Yeah, I was inquiring a while back about building the 273 in my Barracuda, but now that I got the duster with the 318, I'm going to build it instead. I'm keeping the 273 in the Barracuda, so I'm not tearing it apart to build this engine. I see 273's on craigslist quite a bit anywhere from free to $100. I've thought about getting one just for the crank and adjustable rockers. Depending on how much I have to spend on machining and parts, I may just go with a set of the new castings of the Magnum heads (supposedly, they don't have the problem of cracking that most magnum heads have). If the Magnum heads are going to put me too much over budget, then I'll just use the 302's for now, and can upgrade later. Thanks for the advice so far.
 
302's are 1.88/1.60 right? If that's right I'd say you'd be ok with the 302's, otherwise I'd go up to that size for sure. I've seen differing opinions on going to 2.02's with a 318, some say its good as it will free up top end power, others say it kills the bottom end and is overkill for the small bore.

Forgot about the 1.6's with the lift, since you zero decked it I'd check into the clearance with the larger cams, it might be close.
 
Based on inputs and further reasearch, I think I'll probably get a set of Magnum heads. I can get a set for under $400 rebuilt, decked and 3 angle valve job. I've read that you can go up to a .510 cam lift with stock magnum springs, so that narrows my cam choices to the Comp 280H, Comp XE274H, or Lunati 60402. I'm leaning toward the XE274H. I believe I can achieve my power and torque goal with any of those cams.
I was wondering something esle. How much power do I stand to free up by going with an electric waterpump? I found these from aerospace components.
http://www.aerospacecomponents.com/...iew=article&id=115:rmwp&catid=29:ec&Itemid=31
I have no experience with electric waterpumps, how would this thing mount.

I'm going to end up so overbudget on this :shock:
 
For street use I'd skip the electric water pump. I've heard you can save 10-15 hp by ditching power steering, I'd assume its the same ballpark for the water pump. But in terms of reliability I'd just go with the mechanical. You don't really have a need to be turning the water pump on and off unless you're seeing a lot of strip time, and its just an added expense.
 
I've been trying to figure the compression ratio I'll end up with a .040 overbore (3.950"), Magnum heads (60cc), stock con rods, KB-167 flat top pistons with zero deck height, and various head gaskets. I've come up with 9.97:1 with a .080" HG with 4.155 bore, up to a 11.4:1 with a .050" X 4.060" HG, and everywhere in between with various gaskets. I was thinking I would be a little lower, like around 9.8:1.
Did I error somewhere in my calculations?
Is 9.97:1 too high for pump gas at sea level?
Suggestions?
 
Your head gasket will typically be .043 thick and have a 4.060 bore. This should give you about 10:1 compression. About he upper end of pump gas, but certainly doable with the magnum's modern chamber shape.
 
You should be ok, keep in mind that the 60cc chamber is an estimate too, most heads I've seen are a little bigger and that'll make a difference. Typically actual compression tends to be a little lower than the calculators.

With the calculator I use I came up with 9.97:1 with the 3.95" bore, 4.060 on the HG bore with a .043 compressed thickness and a 60cc chamber with the +5cc for the dish on the 167's.

A +1cc difference in the chamber volume puts you at 9.85:1! Also, a change to a .060 head gasket should put you at 9.55:1, even with a 60cc chamber.

Although because you're in Ca I'd say you're definitely toward the upper limit of our pump gas here. I'd check the actual cc's on the chambers when I got them and then decide whether to go .043 or a little bigger on the head gasket. If all else fails, head gaskets are pretty easy to change if you have to.

This is the calculator I use...

http://www.mopar1.us/compratio.html
 
The formula I was using didn't have piston ring height or piston skirt clearance. I can't find that info on them. Thanks for the calculator though, it's a lot easier than figuring out the long way. Oh, when I was doing my calculations, I was using 3.91 for the stroke instead of 3.31, so that's why it kept coming up so high.
 
So, here's where I'm at with my planning so far:
-318 block bored .040 (haven't seen if it's already bored, so this could be +/-)
-square decked to zero deck height (anyone know how much this will cost in So Cal?)
-Magnum heads (stock, 3 angle and resurfaced)
-.050 head gasket (9.79:1 compression, if chambers are 60cc)
-KB167 flat top pistons
-Stock connecting rods
-Comp cams XE274H cam (230/[email protected], and .521/.524 with the magnum 1.6 rockers)
-7.650" pushrods
-M-1 or Performer RPM Aig Gap intake
-725 or 750 cfm carb
-36 degrees total timing
-headers (probably TTI)

I read somewhere that stock magnum valve springs were good up to .530" lift. I know I'm pushing it, but I'm going to try it with stock springs.

I'm thinking I should be able to get really close to 400 HP and 380 LB/FT of torque with this combo, and a good amount higher if I port the heads.

Also planning on:
-2500 RPM Toque Converter
-3.91 gears

Any comments or suggestions?

The mission I was on in Iraq is over, so I have nothing to do all day other than Physical Training and figuring out what to do on my car when I get home.
 
You could easily run higher compression than that with Magnum heads, probably around 10.5:1 no sweat on pump gas. I know dgc333 is running 10.6:1 in his Magnum 360 with a XE268 cam on 89 pump gas with no issues at all. You should also run around 34* total timing with those high-efficiency closed chamber heads; more timing will just cause problems. I'd recommend running a smaller cam too, that thing is pretty big even for a 360. One last thing, if you have the time you should at least go through the combustion chambers and smooth down all the edges. Magnum chambers are full of sharp edges.
 
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