Thread: camshaft for rebuild in 85 chevy truck?

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I have an 85 k1500 with a previously rebuilt 350 that i know very little about. I am planning my own rebuild as the old beast is kind of a dog.

Here is what i know i have goin on
350 with nice edelbrock 650 carb and intake
factory 193 heads
hooker comp headers with 2.5in straight pipes
sm465 granny low muncie
big ass goodyear 33's

want to install msd hei ignition, flathead pistons, and a new cam setup.
I am considering this:

Comp Cams K12-234-2 Comp Cams 'Xtreme Energy' Hydraulic Flat Tappet Camshafts

any thoughts?

I NEED HELP ON CAM SELECTION FROM YOU SMART GUYS THIS IS MY FIRST REBUILD
i drive this beast on the hwy everyday, as well as in town. i just want to boost power/ mileage to the old dog for around 2k.

That looks like a nice, mild cam for a truck. Without knowing all the specifics on your engine like what the compression ratio, etc. is kind of tough to be real specific on a cam... Might also want to try the Cam Quest program, it's a free download at Comp Cams. Just punch in all the information it asks for and see what that recommendation is....

This is a flat tappet cam, so make sure you follow the manufacturer's directions on lubing the cam when you put it in, break in procedure, and oil recommendations.... Today's oil is missing the zinc and because of that flat tappet cams can lose a lobe or two very quickly if the proper procedures and lubes aren't used!!!!!

Cam should work well with ~9.5:1 static compression ratio. Heads are crack-prone and will sign off at around 4000. Personally, with those tires, I'd rather use 8.5:1 to 9.0:1 and a little less cam. I'd want power right off idle and would use this cam if I wanted to use the XE series, which I would not do. I don't like the fast ramps, but apparently you do, so here is the one I would choose for you to match with your combination....
12-230-2 - XTREME Energy

Also, get yourself wrapped around this tutorial if you want to run a flat tappet cam.....
http://www.crankshaftcoalition.com/w...ips_and_tricks

thanks for keeping it civil guys, like i said first rebuild.
after rebuild should be about 9.72:1 compression (advertised) with flatheads and 64cc edel heads (decided to bail on the factory "smog heads", that do NOT have 193cc runners) but i could lower CR with dished pistons?
to much cam? not big on comp XE? im not starting this build till janruary and am still doing LOTS of research so by all means i am open to suggestions.
BUT those edel heads are going to seriously up my rebuild cost, so lets keep it reasonable too.

Originally Posted by Gilligan2591

after rebuild should be about 9.72:1 compression (advertised)

Written properly, this would read....after rebuild, should be about 9.72:1 static compression ratio.
The word "advertised" applies to camshaft duration, not static compression ratio.

Originally Posted by Gilligan2591

with flatheads

This should be written as flat-top pistons. The word "flathead" refers to an engine design made famous by Ford Motor Company and also to a tribe of Indians in Montana.

Originally Posted by Gilligan2591

and 64cc edel heads

You're on this forum asking for help. That means that full disclosure will be necessary. We have no idea what heads you have chosen, therefore cannot comment further on your combination. You should post here everything that Edelbrock has to say about them or provide us with a link so we can see what you want to use so that we can help you....or not.

Originally Posted by Gilligan2591

(decided to bail on the factory "smog heads", that do NOT have 193cc runners)

Where did that number come from? I'm unaware of any such runner size on Edelbrock or any other heads.

Originally Posted by Gilligan2591

but i could lower CR with dished pistons?

Yes, you can lower static compression ratio and dynamic compression ratio by using a larger combustion chamber or by using pistons that have a dish, as opposed to being flat-top or domed. Use caution when selecting a piston though. Standard 350 Chevy pistons have a compression height of 1.560" (measured from the centerline of the piston wrist pin to the crown of the piston). Rebuilder pistons have a lesser compression height of 1.540" (or some other height shorter than 1.560") to compensate for cutting the block decks (resulting in a shorter block deck height). If you use these cheapo rebuilder pistons in a block that has not been decked, the piston will be further down in the bore at top dead center than the correct 1.560" compression height piston. This will make it very difficult to arrive at a close "squish" figure and could make the motor more detonation-prone, depending on cylinder pressure and fuel quality. Use caution when selecting the crown configuration of the piston. Many pistons have a shallow dish in the middle, with very little raised area (the actual piston crown) around the perimeter of the piston and will offer insufficient flat area to mate up with the underside of the cylinder head with the piston at TDC to create turbulence in the air/fuel mixture. Here's an example of a "D-cup" piston. See the large flat area on the piston crown on the left side of the photo?
http://www.kb-silvolite.com/kb_car/p...tails&P_id=154
That's the part of the piston that will mate up to the underside of the cylinder head to "squish" the air/fuel mixture out of that area as the piston comes to top dead center to fire the spark plug. This squishing of the mixture "jets" it across the chamber, homogenizing the mixture and eliminating rich and lean pockets of mixture that may not burn when the plug fires. This squishing of the mixture will allow the use of a lesser grade of fuel without detonation than if there were little or no squish at all. A squish of 0.035" to 0.045" is considered by many builders as optimal. Squish is the sum of the piston deck height (how far the piston is down in the bore with the piston at top dead center) added to the gasket thickness. Here's an example of a dished piston that has no squish pad and is made in the rebuilder compression height of 1.540".......
http://www.summitracing.com/parts/sl...make/chevrolet

With aluminum heads, you will want to use the head gasket that is recommended by the manufacturer of the heads. Most head gaskets have a fire ring built into them and if the ring has not been pre-flattened at the time of manufacture, then the ring can brinell the aluminum heads and they would have to be re-surfaced in order to be used again in another build. At any rate, the correct gasket will probably be on the order of 0.039" compressed thickness, so you would want to cut the block decks for zero piston deck height in order to achieve a 0.039" squish, for instance.

Originally Posted by Gilligan2591

to much cam? not big on comp XE? im not starting this build till janruary and am still doing LOTS of research so by all means i am open to suggestions.

Here's where most guys get into trouble on their first build. Too much cam. The camshaft is not a stand-alone piece. It is one of a number of components that must be matched-up in order to present an orchestrated result. You must take into consideration what you will do with the truck THE MAJORITY OF THE TIME, as well as the transmission used, the torque converter used, the rear end gear ratio, the weight of the vehicle and the desired operating range of the final product. Those big tires will change the overall gear ratio, going the wrong way for a performance camshaft. The more cam you use, the numerically-higher you will need the rear end gears to be and you have the double consideration of big tires in the equation. You will need more gear for the cam and also more gear again for the tires. In other words, if you decided you could use a 3.73 gear with standard size tires, you would need to move up to 4.11 or 4.56 gears with big tires. You have to understand that any cam you install that is hotter than stock will move the power band up in the rpm range and you must change gears to allow it to work in the new rpm range that it was designed for. A hot cam with a stock gear will be a dog and you'll hate driving the truck. Depending on cam timing, you may also have to use a torque converter that stalls at a higher rpm than stock, so keep that in mind. If, for instance, you were to choose a cam that makes power from 3000 to 6500, there would be little power from the motor until revs would reach 3000, so you'd need a looser converter to allow the motor to rev past the rpm's where the cam begins to make power. If you used a stock converter with such a cam, the truck would be a dog until you reached 3000 rpm's and it would be the same way at every stop light. Can you see how this works?

I am not big on XE cams or any other cams with snappy valve action for everyday driving. It's just some "high-helix, double-throw-down" bullshit that the marketing guys have come up with to sell more cams to unsuspecting hot rodders in my opinion. There is a mechanical limit to the speed at which a lifter can be lifted by a camshaft lobe and these guys are right up against the wall with the numbers. This is insanity for a street-driver. If you were in an engine shoot-out against other competitors and needed a few more hp to win the event, then you could justify quick ramps. But on a street-driver motor, it just means less longevity and more chance for failure compared to a camshaft with gentler ramps. To compare the ramp speed of one cam to another, deduct the 0.050" duration figure from the advertised duration figure. Comp uses a 44 degree difference on their Fosdick XE cams, which is probably at or near the mechanical limit. The name for this difference was coined by Harvey Crane many years ago as "hydraulic intensity". Here's a Melling shaft for instance that is cut on the intake lobe at 204/278, for a hydraulic intensity of 74 degrees. Can you see how this would be much, much easier on the cam and lifters, by raising the tappet much more slowly?
http://www.summitracing.com/parts/me...make/chevrolet
Try to understand that the average hot rodder does not need radical hydraulic intensity. Also please understand that the pin point of contact between the lifter and the cam lobe on a flat tappet camshaft generates in the area of 250,000 lbs of pressure per square inch, so everything you can do to help these pieces survive will be to your advantage.

Originally Posted by Gilligan2591

BUT those edel heads are going to seriously up my rebuild cost, so lets keep it reasonable too.

Nobody said you have to use expensive aluminum heads. There is nothing wrong with cast iron heads, particularly for a street-driver, and they will come at a somewhat reduced cost compared to aluminum.

To do a proper rebuild, you'll want to align-bore or align-hone the main bearing bore in the block, cut the block decks to square by registering off the main bearing bore and to the block deck height you want to use with your particular stack of parts, then bore and hone the block for the piston type and ring material using a deck plate.

One last thought. If I were you, I'd seriously consider going with a roller cam. There are just too many hoops to jump through with a flat tappet cam in today's world.

Oops, one last-last thought. In your opening post, you made mention of mileage. Please be advised that if it's mileage you're looking for, find a 305 long block with 416 heads, install a bone-stock cam, stock intake manifold mounting a Q-Jet and sell those tires in favor of a set of 27/28" tires.

.. Sounds like you have quite a bit of load for a 350 engine to deal with. I'd seriously consider finding a complete SBC 400 engine with Q-Jet 4bbl. carb. It'll look just like your current engine and most things just hook right up to it. Rebuild it with KB 2-eyebrow hypereutectic flattop pistons and Summit 1102 (204/214) cam. Stock 400 heads will work fine. Gives about 350HP and 450 torque for cheap. (Or current intake and carb. will fit.) Requires the special 400" manual flywheel. Might find a 400 out of a truck with the manual flywheel already on it.

Originally Posted by BuzzLOL

Requires the special 400" manual flywheel. Might find a 400 out of a truck with the manual flywheel already on it.

. To my knowledge GM never put a manual transmission behind a 400 small block. The engine is externally balanced, but a flywheel from an early externally balanced 454 will work.

Originally Posted by NTFDAY

. To my knowledge GM never put a manual transmission behind a 400 small block. The engine is externally balanced, but a flywheel from an early externally balanced 454 will work.

they make a stick wheel for a 400 sbc . the 454 is a 454 not the 400 sbc it may fit .it may work .But it is not the right weight .it is not really the same and there is two part numbers we been threw this before 454 wheel will fit .but it not made for a 400 sbc

Originally Posted by pat mccarthy

they make a stick wheel for a 400 sbc . the 454 is a 454 not the 400 sbc it may fit .it may work .But it is not the right weight .it is not really the same and there is two part numbers we been threw this before 454 wheel will fit .but it not made for a 400 sbc

Didn't say it was made for it Pat, just that it would work. I put the 400 sbc in a 62 1/2 ton in the mid 80's and at time the only thing that would work was a flywheel from a 454. I had a 3100 lb pressure plate made for it and the best clutch disc I could find and put a 3 speed behind it and I never had a problem except for rear ends. I'll try to get out in the garage this weekend and dig the flywheel out so I can get the numbers from it and post them on this thread. BTW, I got the info from a hobby stock dirt track racer that learned the hard way that a flywheel from a 350 would not work behind a 400.

like i said there two number for stock use . Auto wheels /flex weights are the same as the sticks for the ex cranks wheels as you can see there numbers for both engines heres Pep are 454#fwfp454l and 400/383fphd400 .Scat400/383scafp-400 and 454scafp-454. Pioneer make s both stick wheels for 400/383 and 454 used some new on both 383 /400s . just did some last summer with new fly wheels on 454/496 i build.i do many more set up for auto trans. so there is really no need to look only at only Gm for the stick wheels but here are the 400/383 numbers gm#3986394 the 454 Gm 3993827 and 3963537 lightweight wheel here is the cheater plates i do not care for them but here the numbers sbc two pc seal 400/383 fbp-2 the 454 two pc seal fbp-3454. we go threw alot of trouble getting the crank mass balanced under 2 grams if at time crank is balanced and is matched for flywheel so we try to used a wheel that is for the engine .like i said it may work but there 400 wheels out there should stick using it