I have a 1986 Pontiac Trans Am with a donor 350 block and the original lb9 heads and intake. Long story short is that the computer acts up every now and then and it misses or don't want to accelerate. I am pulling the engine to put a new oil pump in, rings, bearings, swap out my 700r4 for a T-5, and pull all the tpi off and go with a carb instead. figured now would be a good time to upgrade the stock cam that has unknown HARD miles on it. (was a figure 8 trailer race engine before i got it)
Any info on What kind of cam would work with the 305 heads and 350 block would be helpful.

 

Summit k1103

 

Would I need new pushrods, rocker arms or valve springs?
Sorry, I don't know to much about this part of an engine.

 

That summit cam is pretty mild I think it's the 214/224 @ .050" cam, it has nice slow ramps so it's easy on the valve train , you would at least need some z28 springs they are around 25 bucks give or take, stock rockers will still work, but don't be surprised down the road you might break a stock rocker or two with the new higher spring pressures, the z28 springs are around 110 lbs on the seat they very a little at installed height about 10 lbs at most for the sets I have checked anywhere from 109 to 118 lbs installed.

Anyways, you will need to measure for pushrods once the heads and cam are in, every engine is different and you won't know what pushrods you will need til measured. it would be a good idea to upgrade pushrods anyways to .080" walled pushrods to help with deflection- those would cost about 50 bucks on up on ebay.

before you order a cam check to see what your compression will end up to be, if you compression is on the low side it might be worth stepping down a little on cam just so you won't have a dog of an engine per say.

good luck and post back

 

I really doubt his compression ratio could be under 9:1 with those 58cc chamber 305 heads on it.

 

Yup, that's "The Mild" cam. Just a bit more than "The RV" cam.

As far as compression, a .030" over 350 with 12cc dish pistons, .039" gasket, .045" deck clearance (.025" stock plus the added .020" of "rebuilder safety"), and 58cc heads, should be just at 9¼:1. Should work OK with such a cam.

If the motor has the roller setup, use the Comp "502" instead.

Always renew the valve springs with an aftermarket cam change, no matter how "mild". Even the "mildest" aftermarket makes about ANY stock cam look like all it needs to make its lobes disappear completely, is some Clearasil. Prior hard use should be an immediate red flag that you're not even getting out the stocker, whatever little it has to offer.

 

I know it's worn out (305 had more even with the spun bearing) but I didn't have the time or money to rebuild it compleatly. (Only vehicle I had at the time) I did clean everything I could without taking it to a shop, replaced all seals, and sensors, timing gears and chain, and ran short on time and money to finish with bearings, rings, cam, and oil pump. I'm doing the rest when I have it out this time.

 

The reason the combo doesn't work well is that the PO swapped out the original 305 bottom end with a 350 without doing ANY tuning or changes to support it at all. The 350 probably has the typical "pickup truck" -191 cam, which is bigger than the cam in the original 305 and, of course, it's got 45 more cubic inches. Will it run? Yep. Will it run well? Nope (as you have discovered).

If you're going carb, I agree the K1103 cam kit from Summit is a good "entry level performance cam" for a flat tappet engine. I happen to run that cam in my very mild roots-blown 383 and it's a real pussycat until the blower starts shoving some serious atmosphere into it. Totally drivable, even off-boost.

I just wish you would put on some better heads. Those 305 heads are good for building some compression on top of a smogger (dished-piston) 350, but that's all they're good for. They don't flow worth a damn by modern standards.

Since you need to buy an intake manifold anyway, why wouldn't you swap out those 305 heads for some bolt-on Vortecs? They will absolutely blow away the original 305 heads despite the fact they will lower compression ever so slightly. They will make a lot more power EVERYWHERE.

 

I changed it over planning on going to a carb but didn't have the intake carb or distributor so I put the tpi on it. I used the 305 heads because of the center bolts angle. My 86 tpi are angled the same as the front and back, and the heads that were on the 350 tbi had the straight up center bolts. And one was warped.

 

those 305 heads are ok on that setup if you put some larger valves in and port them.

 

I am not going to Vortec heads because i already have an Edlebrock Performer intake and a brand new quadrajet that i got for $50. Bad news is i opened the box for the carb and its a quadrajet but its computer controlled.