I have an 86 c-10 shortbed. I rebuilt the 350 with a .030 overbore, flatop pistons 9.5 compression, comp cam 268 high energy series, aftermarket heads. not sure what brand the heads are, all I know it has a logo with a D inside a circle., it has 2.02 1.60 valves, edelbrock performer manifold, edelbrock 600 cfm (1406) and some headers. my question is, what cranking psi should i expect, i get a reading of 150 psi, motor has not been on the street yet. i also am running 2 1/4 inch duals with flowmasters. should i step up to 2 1/2? What kind of power do you think i am making? is my cam to big for my application.  it has a th-350 with 2.73 rearend . i am planning to step up to 3.27 or lower. it runs good except when i get the vacuum reading the needle jumps from 16-13 in-hg back and forth. there seems to be no vacuum leaks anywhere.  And the carburator  is working fine any suggestions i would really appreciate. i am only 16 but am doing all the work after school including body work

This engine configuration should be good for 320 to 350 horsepower and 400-430 ft pounds of torque.

16 inches of idle vacuum with this cam sounds pretty typical, 150 pounds of compression is about what to expect with flat tops and this cam.

The ticking 16-13-16 inches of vacuum would indicate that either there's a missfire with the ignition or a valve not quite closing quickly enough. The latter could be a missadjusted lifter or a sticking valve. Listen for a bit of a click comming from a rocker box. The missfire could also reflect a cylinder that's running rich or lean due to a distribution quirk of the intake system.

All-in-all, it sounds like a pretty nice engine.

The rear axle ratio is probably too high for the cam timing. I'd pick a late 700R4 or 4L60 (no "E") with a lock up converterr before a TH350. The lower low and higher OD 4th gives a better selection of power range to overall gearing than a stiff rear axle ratio and a 3 speed auto. The OD would work well with the 3.27 rear axle and the lower low will make it drive off low more like you were running a 4.11 rear. The big problem will be the jump from low to 2nd. But the cam you chose has a pretty fat torque cuve so even that may not prove to be an issue. 

Bogie

well thanks for the advice. how do i adjust the lifter with the motor running. do u think i should keep the 2 1/4 pipes. the lifterds sound quiet but ther is a little ticking, i thought maybe the headers made that noise  

the easiest way to adjust a lifter is to first get a set rocker arm stoppers.  They can be had in the Help section of your neighborhood parts store.  Another thing that really helps is to cut the top off of an old valve cover so it resembles an open rectangular hoop.  You then start the truck and let it warm up with the rocker stoppers and open vavle cover. See if you can locate the ticking rocker and tighten slowly until it stops, then go another 1/8th to 1/4 turn further.  Bogie probably has better input on how much further to tighten it but that's always worked for me.  If you don't have the valve cover and stoppers you will get your headers and arms covered in hot oil in short order.  Hell of a mess if not a fire hazard. If you cannot find the offending rocker just back them off one at a time until they start to audibly tick and tighten them back as I mentioned earlier.

Hydraulic lifters should not be making any ticking noise unless these are Rhoads or some other variable duration lifter. Headers can make a ticking nose, you're going to have to figure out the source with careful listening.

I don't see a problem with 2 1/4 pipes. There's all kind of effects that affect exhaust pipes. If the truck runs catalytic converters then keeping the pipes slightly large after the converter helps because the converter puts more heat back into the exhaust. If the muffler is toward the front a smaller pipe like 2 inches after the muffler helps keep the energy level and speed up in the pipe since the muffler reduces temperature and energy which contracts the flow which slows it. This is probably more important when dumping the exhaust all the way to the rear of the truck than if you dump ahead of the rear tire. It's also more important with a quiet reverse flow muffler than a glass pack as the former takes more energy and temperature from the exhaust gasses, hence quieter. Where the muffler is rear mounted, running a larger dia pipe such as 2 1/4 or 2 1/2 inch is desireable since the gasses in the pipe are hotter and more expanded till they get to the muffler. Obviously a 383 can use a proportionally larger pipe than a 350. Same can be said for gear ratios, and engine turning into a 3.08 gear set doesn't put out as much exhaust as an engine turning against a 4.11 gear.

You can also use exhaust wrapping tape to hold heat in. This can be used to trim the exhaust system's performance. This material can be used anywhere on the pipes where you find it necessary to keep temperature up. So if you find your tail pipes are too large, if you wrap them, more heat will be held in which will keep the gasses expanded and velocities up which may help to purge the engine.

I have to laugh at these kids with Honda Civics running gigantic Borla mufflers, it may look cool but it's a waste of energy that reduces power from an engineering stand point.

Bogie 

i very much agree with the "heat retained equals energy theory... i do not however agre that exhaust wrap is the way to go. it captures condensation and promotes rust on expensive precious exaust componets.

as for as the lash adjust let the engine cool. remove the valve covers and bar the motor over with a breaker bar on the crankshaft pulley bolt. the method recommended by many cam manufacturers in e.o.i.c. as you turn the motor observe the valve actuation. as the exhaust valve leaves its seat loosen the intake, till slop is felt. tighten the intake until the slop just dissappears. and add 1/4 to 1/2 aditional turn depending on which cam manufacturer ground the cam (they all like something diferent) with the intake taken care of, bar the motor over further till you observe the intake valve on the same cyl enter its closing cycle ( intake valve opens, passes peak lift, and begins decent on closing ramp.) once this occurs use the loosen/ tighten method on the exhaust valve again adding the 1/4 to 1/2 additiional turn to set preload as discussed previously. do one cyl at a time till you really get a feel for how all the cyl's jive  before too long you'l do 3,4 maybe 5 cyl's at a time.  good luck, keep the sport alive!

I also have aan 86 C10 but I have a TH400 tranny and wondering what rear gear would work best with my tranny, as I'm at the point of cam selection for my LT1 taht I'm swapping in