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Discussion Starter · #1 ·
Ok i have an 85 silverado with a:
350 cast#3970010 50k miles on it
882 heads
comp 280 magnum cam
performer rpm intake
edelbrock 600 cfm carb
long tube headers
truck has 3.92 gears

it just feels like my truck doesnt have alot of power i bought it like this and i am wondering if the cam is too big and is actually making me lose power
it sounds real mean and loud but it just doesnt act like it i cant even think about getting my tires to spin it just seems bogged down please help
 

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Discussion Starter · #3 ·
duration
advertised intake 280 exhaust 280
@50 intake 230 exhaust 230
valve lift .48 intake .48 exhaust
lobe seperation 110 degrees

i have my timing set at 10 degress inititial
 

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It is a little big. You need to set your distributor curve to match it. Get a curve kit and run 16o initial and 18o mechanical.

The Holley 600 is a little too small. I would go with an RPM intake and a 750 vac. sec.
 

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Discussion Starter · #5 ·
what im saying though is should i just buy a smaller cam like a xe268 would it run better? it would be cheaper than buying a new carb

and im already running the performer rpm would the regular performer be better or did you just miss that
 

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Discussion Starter · #7 ·
duration
int.268 ex. 280
@50 intake 224 exh 230
valve lift .477 int. .480 exh
110 lobe sep

i just suggested that cam because it seems to be a pretty popular one right now
 

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With that 280 Magnum, you got a definite mismatch of parts. Not knowing what compression ratio you got make's it tougher to recommend a cam. For that 280, you'll need at least 9:1 and around a 2000-rpm stall. Since it looks like you are wanting more low end, I'd go with a XE262 or XE256 along with a Performer.
 

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Discussion Starter · #9 ·
so youre saying i will be better off with the performer instead of the performer rpm too right? should i change the lifters? when i change the cam?
 

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id go with the performer on a street vehicle and a smaller cam. that is a common story with the RPM and spinning the tires (with a small stall). its of idle pull is iffy. what compression are you running? a 280 cam will need higher compression.

if you already paid for the RPM, thats a good manifold too. with a 280 cam ,and 3.91 gears,3000 stall ,it should work just fine. also the holley 600 carb on the larger intake will keep the velocities up. so i guess thats ok too. check your tuning .
 

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Some of you guys will have him making less power than he is now.


Here's what you do.

Switch to an XE268 and new lifters, keep your performer RPM intake, buy a converter with a stall speed around 2200-2400 rpms. Keep your 600 cfm carb.

That is the set up, and stall (TCI Break-A-Way converter) I have in my 3800 lb Caprice, 350. And you know what, from a dead stop, with 2.73 gears, it burns the back tire.
 

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too much cam

With your stock heads and 9:1 compression, you do have too much cam. Your carburetion is fine. were I in your shoes, I would go to the Performer intake over the RPM due to the RPM is geared more for higher RPM, and I would go to either the Comp Cams XE268H or even down to the XE262H, and regain the bottom end torque you are losing. I think you would be much happier with this setup.
With this setup you wont have to change converters.

A little bit is good but a lot isnt always gooder.
 

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Discussion Starter · #14 ·
still not sure if i would be better changing the cam and the convertor or the cam and the intake which one would give me more power?
 

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leastbay said:
Ok i have an 85 silverado with a:
350 cast#3970010 50k miles on it
882 heads
comp 280 magnum cam
performer rpm intake
edelbrock 600 cfm carb
long tube headers
truck has 3.92 gears

it just feels like my truck doesnt have alot of power i bought it like this and i am wondering if the cam is too big and is actually making me lose power
it sounds real mean and loud but it just doesnt act like it i cant even think about getting my tires to spin it just seems bogged down please help
With those heads the 280H Magnum cam will not work well. I agree with several other posters that an XE268H cam will work much better with the stock small valve heads that you have.

Keep the Performer RPM intake! A regular Performer intake isn't much more than the stock cast iron intake.

Keep the carb. It is better suited to your engine and heads.

If your rear gears are really 3.92, then keep them.

The long tube headers are killing your bottom end. Even more if you have 2 1/2 inch pipes.

You do not need a higher stall with the XE268H cam but I would suggest a slight increase and suggest using a TCI Saturday Night Special. I have used that converter with that cam and it works excellent. I had 3.80-1 rear gears and 28" tall tires.

After you get all your parts sorted out, post back as to your timing specs. If you are running somewhat retarded (4-8 degrees initial and less than 30 degrees total mechanical ) you won't have much power.
 

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too much cam

The current cam and intake you have are hurting your bottom end torque without appreciably boosting your upper end, due to the limitations of your stock heads and compression.

What you are needing is more torque, to haul around that heavy vehicle. The power gains you need are below 4000 RPM. You can always over wind an engine if you want to hear it scream, but you will never be able to underwind it.

You need to concentrate on where you need the power. With either of the Comp Cams I mentioned earlier, as well with the Performer intake you will be well able to turn your engine up over 6000 RPM, but I doubt that is the rpm range it lives in. In the real world, most of the time, your engine is running at below 3000 RPM, especially when pulling or hauling stuff.
 

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Car Craft did some dyno testing comparing the Performer, Performer Air Gap, Performer RPM, Performer RPM Air Gap. The Performer RPM made more power from the base line up that the Performer. So in reality there's no reason to spend more money on another intake manifold.
 

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It is great to have a cam that really sounds off but if you can't even burn the tires it's useless. With your basically stock engine a small comp xe cam would work nice and I would not get a bigger carb than a 600 for your engine. Unless you are turning major rpm's the big carb will just bog you down even more. Too much cam with too little compression doesn't work.The intakes will not make much difference if you are sticking with a dual plane. Try reducing you're timing in 2 deg incriments untill your engine feels like it isn;t improving. Too much timing is as bad as not enough. :pimp:
 

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Well I don't see why that combo you currently have won't just smoke the tires or at least "burn rubber". The cam seems like it is a tiny bit big but not big enough to really hurt anything too bad....unless it is not tuned or you have a stock converter.

If you have a stock converter you really need about a 2500rpm with the smallest diameter you can find(http://cgi.ebay.com/ebaymotors/ws/e...tem=7941991654&category=63692&sspagename=WDVW). If you really want it to run a 3000-3500 stall will allow it to almost double torque on launch. Note that the 3500 is entirely too big for daily use.

First make sure it is tuned well. Check the timing, pull the plugs and make sure they are light brown, not white(lean or too hot) or black(rich or oil). While the plugs are out check the compression, if you don't have a gauge at least do a finger test If it won't pop your finger off the hole somethings wrong.
 
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