SuperMacDaddy

So I pulled a 350 out of a 91 z28 and I’ve been putting it together to swap with the 305 in my 86. I have vortec heads and I ordered Alex’s spring kit so I should be at .550 lift. I have shorty headers, the stock computerized carb, or a regular 650 non computerized q-jet, and i don’t have a clue about anything to do with cams since this is my first engine build/swap. The shop rebuilding the heads said I need something that will provide enough vacuum for the power brakes. I would really like to get 300+ to the wheels. I emailed comp cams but never got a reply, so I’m hoping you guys here can help me get the cam sorted out. I want something with a modest chop at idle not super aggressive, and will get me the power I’m trying to reach

Abubaca

iTrader: (3)

I'm not the right guy to give advice on a carbed set up, but I WILL say that I had a not so helpful customer service experience with CompCams. Lunati on the other hand was super helpful. ...and with a 383 running TPI, I needed to be careful NOT to over cam it. I had specs in mind, but wanted a professional opinion. Lunati recommended a custom grind within 1 degree of duration and withing 2 hundredths lifts from what I had thought. He really understood the engine was built for quick low end torque as opposed to peak, obviously, based on the cam specs. I was happy with it, and would recommend calling them.

midias

http://www.compcams.com/v002/Pages/395/XR270HR-10.aspx

This is a great roller cam. Not too wile will make good power and good vac. Probably work well with your 9ish:1 car

You can go one step up to this but you will probably want to go with a bigger stall.
http://www.compcams.com/v002/Pages/396/XR276HR-10.aspx

Ja85z28

Assuming near stock vehicle weight, please tell us about your compression (head volume can deduced from casting number), converter, and rear end gear.

If the aforementioned is stock an xr262h-10 would work nicely.

Here's my current set in the video link below. Unfortunately, my 85 has a flat tappet cam block.

https://youtu.be/Fle9A6RC1E8

Good Luck and Merry Christmas

QwkTrip

iTrader: (22)

Here is a pretty good article to read.

http://www.hotrod.com/articles/0607phr-camshaft-basics/

Short story is that you don't want to choose a cam based on duration numbers. A carbureted 350 usually likes 108 degree intake lobe centerline angle (LCA). The overlap is chosen based on how you want the engine to run. And those two things come together to dictate the duration.

fstarocka

most cams under 300 duration shd have plenty of vac - the higher the overlap the less vacuum.

I installed the GMhotcam in my 350 roller - https://www.summitracing.com/parts/nal-24502586

Excellent all round 350 roller cam, wide rpm range and I had about 18" of vac @ idle with power brakes, same carb / intake / headers - except I put on a true dual 2 1/4" exhaust with a 18" collectors up front..

you might want to look at the 268 roller variant cams - good for lower comp / stock piston builds..

I dont know what the deal with power brakes are - unless they leak they only use vacuum when they are being filled (after braking) for probably no more than a full second if that.. only when u have "lope" cams that waste low end torque on overlap and have low idle vacuum..

stick in the 260-290 adv duration and 100-112 LSA and ull be fine.. 108 lsa and 290 = worst, 108 lsa and 270 = better, 112 and 270-280 best compromise..

however with your build id stay at 270 and 110-112 - that will build up real nice dynamic compression, good vacuum and economy/power

SLEEPER 86

Never had a problem with vacuum when I had a comp XE274 in a 350, hell, I had it running strong in a 305!
Maybe not the XS 282 solid lifter I have in my 383 now, but the 274 in a 350 is a blast!
If you want to improve mileage a tad, go with the XE 268
Be sure to match your springs!!!
Iirc, the 274 springs are stock diameter