I WANT TO PUT A CAMSHAFT IN MY 390 I WANT IT TO HAVE SOME GOOD GET UP AND GO POWER. WHAT DO YOU THINK ABOUT A COMPETITION CAMS 268H SERIES 268 ADVERTISED DURATION,218 DEGREE DURATION @ .050" THIS IS IN SUMMIT 35TH ANNIVERSARY CATALOG. WILL I BE ABLE TO USE HYDROLIC LIFTERS AND WHAT ELSE WOULD I HAVE TO CHANGE? I HAVE PERFORMER INTAKE WITH 750 CARB GOING TO DO HEADERS AND 2.5" EXUAST.

 

I would not use this cam in a stock headed engine. The dual pattern cams are definitely the way to go to wake up your stock. FE. THe exhaust on the FE head flows poorly. A dual pattern cam will help remedy this. I think the 268H would be great for a mild FE with edelbrock heads. Take a look at the Crane 343901. It isn't really any hotter and will give you better results. Welcome to FTE.

BTW, please do not type in all caps. It makes posts hard to read and is against the guidelines for posting here. Thanks.

 

Sorry bout the caps guys i got a little crazy with those. how much horseys and torque do you think the 343901 will give me ratsmoker? guestimation?

 

With the intake, headers and carb you have you should be good for about 275+ HP. Torque should be about 425ft lbs. Compression is killing your performance. Just a guess.

 

Thanks for your help ratsmoker. It would probably help if I had a 1/2 ton shortbox to drop my motor in!!!! They seem easier to fix up and weigh a lot less.

 

Hey Rat:
Would the issue be too little compression on this motor with the factory heads? Sounds similar to where I am at currently with my build. The thought of a set of taller 360 pistons is looming in the future... Of course a 14 second grocery getter is the best idea I have heard!

 

I think between the pistons, heads, and stroke length, you end up with the shortage. Domed pistons or smaller combustion chambers -- early 60's hi-po heads would be nice -- should bring it up. Standard CR on 360's is 8:1 which is hard on performance. There's another thread in here nearby about 360s and cams, has some comparisons between cams and compression ratios.

John

 

What pistons would you suggest?
I want something with about 10:1 or so
Still streetable but higher compression
I have a stock 2 barrel 390 that was rebuilt right before I got it
I will be adding a cam, and im porting some heads as we speak. (going to order heads eventually tho) and im looking for a manifold also.

 

Most people veiw the idea that more compression gives you better performance becasue the air/fuel mixture is compressed more to give a bigger bang when it finally ignites. This is true but higher compression also brings in more air/fuel to give you better volumetric efficiency. When the piston goes from TDC to BDC in a high compression engine there is less atmospheric pressure inside the cylinder than you would have in a low compression engine which in turn makes the atmosphere force the air in at a higher rate. I would not go over 9.5:1 in a iron headed FE for the street. You can run at 10:1 but you will only be happy on the best premium you can find. You won't be able to advance your timing to the optimal point either. You might loose 5 - 10HP by going down this 1/2 point but you can gain that back by getting enough advance out of the ignition. If you port the iron heads out and build the engine around a pretty big cam then you can get by with more compression. Bigger cams lower cylinder pressure and don't require the octane. I am fairly confident that with the edel heads and the RPM cam you should be able to use almost 11:1 on the street. My engine is very happy with the smaller 801 cam and a little over 10:1 right now.

 

Thanks
Im porting heads, but want to buy some aftermarkets later on.
I wont be adding a cam until I can atleast port some heads and get a 4 barrel manifold. Id settle for a stocker 4 barrel manifold right now... but cant find one.

 

Measure the stroke! You may have a 360. I say that because a 390 will have plenty of get up and go. If the engine is a 390. Do the Crane 901, a good ignition, and a smaller carb (650 CFM is plenty). Forget headers for now! After you have these modifications in place and if you need more power improve the heads (bigger valves, port matching), an aftermarket intake and true dual exhaust with equalizer tube. I like 2 1/4 inch tube. Then post back and let us know how you are doing. Take small steps, improve the engines performance with components that will work together later and still be useable on a higher performing engine.
William in Atlanta

 

Hey.
It's a 390. I haven't measure stroke but I talked to the guy that put the motor in my truck.
As for headers... I know where a used set are free. so Im getting them. I already have true dual exhaust w/ Glass packs on them, but no H or X pipe on it. I'll replace the glasspacks with most likely Flowmasters and put a H or X pipe in it after I get the motor like I want.
Thanks for the input.
THis project is coming along faster than I thought.
Its already been converted to duraspark ignition, new timing set, new carb, etc and Ive only put about 100 bucks in it. (nice to know friends at part stores. lol )