I think I need more cam

[Swingin'70]

I have a stroked out 340. Lots of aftermarket parts, well all of them except the block. But for some reason I picked out a cam with .495 lift, 235 duration @ .050, 3000-6000rpm range.

I want more rpm. What kinda rpm is safe for a stroker. And what size lifts are alright for one. I'm having second thoughts before I degree in my cam. Any help or suggestions would be appreciated. -Derek

 

[2shelbys]

That sounds like a decent cam for a street/strip engine. A hotter cam will help you make power higher into the RPM range provided you have all the other things in place to work with it but it will not help the engine survive higher RPMs any better. Is the engine balanced? Do you know the flow characteristics of your heads? Will they even allow you to benefit from high lift? Which rods are you using? If you go much higher than 6000 RPMs it is advisable to go to solid lifters. There are a lot of things to consider when seeking high RPMs. And more importantly, is this a race car only? If it is a street car you are far better off concentrating your power below 6000 RPMs. Everything is a trade off. If you concentrate your power higher in the RPMs you will lose it in the lower RPMs. This is not good in a street car.

 

[rumblefish360]

If you concentrate your power higher in the RPMs you will lose it in the lower RPMs. This is not good in a street car.

Or a stroker. The point of a bigger engine for more power. VIA the stroker route, more torque. A stroker engine has a harder time spinning higher RPM's
(Due to the longer stroke having to travel faster to mantain the same rpm as a shorter stroke engine)
And a harder time making high HP above 6000 rpm's even with some radical street cam shafts.
Alot of what you read on the cam shaft car (RPM range) is out the window a bit on a stroked 340. Since you changed it so around much.

After a Hyd. cam, go solid for more RPM's. Then a roller.
Personnaly, I'd save the cash for a roller and be done with it.

 

[moper]

That cam is the equivilent of an RV cam for a 4" small block. Much more info is needed tho. Wha tdo you have for heads? Any work done to them? What rockers? What springs? Header size? Power brakes? Intake design? Carb size? gearing? trans type/stall speed? Last and most important...What do you do with the car 80% of the time? And what gets done that last 20%?

 

[2shelbys]

Or a stroker. The point of a bigger engine for more power. VIA the stroker route, more torque. A stroker engine has a harder time spinning higher RPM's
(Due to the longer stroke having to travel faster to mantain the same rpm as a shorter stroke engine)

Another good point. It takes cubic dollars to build a long-stroke engine for high RPM's. When I was young and too stupid to understand the true value of "numbers-matching" I used to launch my car at 5000 RPM and shift at 7000 RPM which is what the previous owners did. It is a balanced and blueprinted 383 with solid lifters. They spared no expense when building it but it is not a stroker. It still has the short 383 stroke.

 

[rumblefish360]

OH! You make a good point Moper. (Cam size in a stroker) Though I think "RV" is a bit harsh even for the cam size. ??? I don't know for sure, but since bigger engines tend to swallow up large cams and still idle well by compare to a 318 with the same cam.....
He could step up quite well and be happy still. Combo dependent of course.

2Shelbys An excellent point I should have writin down. LOL, cubic dollors. I love that phrase. It is so true.

 

[408duster]

A small step up that ran fine in my 9.7C.R. 408 was the Comp Cam Xtreme Energy 284-10 (.507/.510?? lift). Mike Ware at Muscle Motors recomended that one for my build when I foolishly envisioned more street use than strip. It worked great, but after couple years I upgraded to a larger mechanical. Gotta go faster , right??
The XE 284 got handed down to our 360 Duster that sees plenty of street use. Its a little large for it, but works well with the 9.5" converter.
Cubic dollars?? Thats great, thanks for the chuckle

 

[Swingin'70]

Thanks for all the responses. But to tell you the truth, I wanna go racing. Im building it all to spec and everything. I mean occasionally I'd drive it on a Sunday when the weathers nice, I'm not very concerned about making it very streetable. It will just happen to be street legal. The place I work it is very good at doing so.

But I believe I have a decently solid engine build, cept the cam. 418 cubic inches. I know I have a strong rotating assembly Eagle forged crank/rods and Diamond Pistons. My heads are Indy Eldelbrocks with 2.05 intakes and 1.60 exhaust valves: 57cc chambers. I'm polishing the stock port castings. Aluminum roller 1.5 rockers, not sure what brand off hand. I was planning on a Demon carb. I kinda want to run two small ones. And I dont know if you'll believe me. But I'm going to build my own sheet metal intake manifold. Thats why I can either go one or dual quads. So I can make it short for low rpm usage, high rise, or crossram. Same with headers. Build my own, whatever size or shape. I bought a barely used Dynamic Trans/Converter, with a ridiculous 4000-4500 stall. And i think its a 3.23 posi.

The cam I have now is a mechanical flat tappet. I like the 110 lobe separation and it seems like it would have enough torque, but It seems like I need more rpm for my combination. I almost bought a roller. But I read somewhere that the angles of them suck in a small blocks. But I want a fast car I have the ablity to set it up for more rpm. I just want to be sure that 4" stroke can handle the rpm. And of course my other concern was piston to valve clearance, what can i get away with?

Thanks for all the help though.

 

[408duster]

Yeah, more cam for sure. Let me know if you want the specs on my upgraded mechanical, a large step up in performance from the hydraulic. Its a custom ground unit from Muscle Motors.

 

[moper]

If you are planning mostly race, then by all means go with a cam more suited to what your plans are. You have large decent ports, and are planning a large plenum high flow induction. You can under cam that too, and it will run decent, but IMO you should be looking into solid flat tappets in the 250-270 @ .050 range. You didnt say what the compression comes to, but with 53cc chambers, I'm thinking in the 11.5:1 range? I would go for something like the Comp TL300S-8. You need not fear to rev that engine to 6500rpm. With 3.23s, you wont be revving higher than 6K anyway. The stroke is 20+% longer. So your power band will be lowered by at least 1000 rpm in terms of what you read for intended applications in catalogs. Plus, your intake will be sized for mid range and hgiher rpms. I dont think that convertor will be good for you, but that you can always address after the egnie is running and you know what it wants. I would be careful if you are making your own intake as far as runner volume and shape, and plenum volume. It's not just a big box up there. You can have some bad distribution issues if you are not very careful. As for carbs, "two small ones" in this case could be a nice set of 660 race center-squirtors. I wouldnt run under 1200 total cfm for a dual quad system. And if you decide to go single, the starting point would be a 930 HP Holley and a Victor 340. I know of similar built flat tappet 416s that make 530-550hp on a regular basis. A solid roller could push that over 600.

 

[moper]

Though I think "RV" is a bit harsh even for the cam size. ???

Well, I built one with a 520ish solid. It idles smooth as glass with tons of vaccum...I admit now, the cam is too small...lol. A good rule of thumb for 4" strokes is: hydraulics start at 235°@.050, with 245 being a nice performance one. Solids Start at 240°@.050 with 250 being a nice middle ground. Head choice is huge. Better heads work well with smaller cams. Smaller ported iron heads will want more cam to make up for the less flow rate. Another thing is, on Mopar small blocks, you will lose about .025" of lift just from bad pushrod angles and factory rocker geometry.