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Cam Swap info Needed

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four50NCalif

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Hey guys I am going to do a cam swap in my 1981 K5 Blazer, has stock 350 motor put long tube headers on that dump into true dual exhaust, also an edelbrock air filter, lifted 6in on 35s, but am running some form of gears in the rear, I have the th350 trans and it runs out of gear real fast on the highway or even big backroads. Im on a budget an so would like to use the stock heads and carb. I want as much horsepower as possible while still remaining streetable. I was looking at the comp thumpr cam (smallest one) or one of the comp extreme 4x4 cams. Will one of these kits work? Any help appreciated! flagwaverflagwaverflagwaverburnout

http://www.jegs.com/i/COMP-Cams/249/K12-239-3/10002/-1


http://www.jegs.com/i/COMP+Cams/249/CL12-256-4/10002/-1


http://www.jegs.com/i/COMP+Cams/249/CL12-600-8/10002/-1
 
I know for a fact the x4262h is too much for a stock converter, I used that cam in my 72 and had to swap to a 2100 stall and that was even border lined, it's an awesome cam but the motor should be at least 9:1 if it was me I'd go with the smaller of those three. You will be a lot happier.
 
I've got the comp 12-231-2, smallest 4x4 cam in my 83. 305 HO heads gasket matched, intake, holly street avenger. Runnin stock valve springs/stock bottom end.

It's a solid motor, torquey right from idle to 4-4500.


Not overly a fan of the thumper line of cams. Though they do have a juicy idle :haha:
 
Bowtie85 said:
I've got the comp 12-231-2, smallest 4x4 cam in my 83. 305 HO heads gasket matched, intake, holly street avenger. Runnin stock valve springs/stock bottom end.

It's a solid motor, torquey right from idle to 4-4500.


Not overly a fan of the thumper line of cams. Though they do have a juicy idle :haha:
Click to expand...

So there is a noticeable difference than the stock motor even with the small 4x4 cam?
 
Yes the cam lobes on those cams are much quicker opening than a stock lobe, you should see more tq and power vs a stock cam.
 
what else will i need? a gasket set? any special tools? Do I need to get the whole kit with the valve springs lifters and timing chain/sproket? or can i get away with just the cam?
 
I' did just the cam. The motor I put it in had a double true roller timing chain in it.

Up here I couldnt get the cam/lifter set. The speed shop guy sold me on the comp magnum lifters, said they had a few issues with the cheaper lifters.

Also spend the money on some good assembly lube.


stock smogger cams hardly run .400 lift from what I've read.
 
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I'd stay with the Xtreme energy cam you have listed...your heads (if true 81 stockers) will probably run out of flow about 4500 anyway, you might as well build as much flow at lower rpm as you can.
The heads/intake are really the limiting factor here...they just don't flow enough air to support anything bigger
 
Basically what zimmer is saying, the lower rpm and lift limitation tend to sway a cam into the tight lsa and longer duration, if I use my example the make I could have used was 210/210 once you start to get into the longer duration cams they don't make any vaccum idle rough etc. the closer the lsa is also causes this, old school cams are like this because cam tech was well old..
The 4x4 cams have the xe lobes, split duration and tends to have more on the ex side helping with the crappy port flow, keep it open longer helps. But not so much you need crazy springs etc to run it. The engine should all things being equal be much more responsive than a stock cam.
 
I've got the 254 4x4 Xtreme cam on mine. It's one level less aggressive than the one you're looking at. It had a smooth idle and ran fine on the smog heads, and does well with the Vortecs that are currently on it. It's torquey and not much for high RPM, but my truck doesn't rev over 4k anyway.
 
paratrooper307 said:
I've got the 254 4x4 Xtreme cam on mine. It's one level less aggressive than the one you're looking at. It had a smooth idle and ran fine on the smog heads, and does well with the Vortecs that are currently on it. It's torquey and not much for high RPM, but my truck doesn't rev over 4k anyway.
Click to expand...


Hey thanks for all the advice!! I am going with the 4x4 254, for the reasons everyone has stated about the limiting heads, but also because I am on 35s and plan to wheel it! Are there any good "how to" threads that are K5 specific? All the youtube videos are with the motor already out of the car.
 
four50NCalif said:
Has anyone used the "spin" technique to get the lifters out of the way or just better to take them all out?
Click to expand...

So far you're talking about using another flat tappet cam. Lifters should be replaced with the cam as the cam and lifters wear together. If you were running a roller cam and lifters you could reuse the lifters. Pulling the intake is not difficult anyway. I have heard of the spin technique being used in LS motors that have lifter trays, but I think you'd run a risk dropping a lifter on an SBC.
 
You can't on a sbc the lifter will not fit out the pushrod hole.. You must pull the intake off.
 
Ok thanks for the advice am going to start working on it tomorrow, I went ahead and got some good crower lifters, I will post pics once I get into it!
 
Hey have got most of the motor apart what is the best way to get the harmonic balancer off and on? I am at a stopping point today since it looks like I will need one of the specific tools to get it off.
 
Ok just a quick update: I have the new cam and lifters in, going to put the intake back on tomorrow! Fingers crossed everything works. Just for future reference, an aftermarket intake manifold will get decent power gains?
 
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