86 350 cam question

[jlmohr76]

Just wanted to get some input here. I have an 86 350 engine in my 81 k10. The engine is bone stock except for edelbrock performer intake, holley 650 carb and headers. The truck has 4.10 gears and a 350th with stock converter. I'm looking at upgrading the cam . So far the two cams I have in mind are the summit 1102 and 1103 cams. Just looking to get more lower and midrange power. This is a daily driver so I don't want to go over board. Any thoughts on these cams?

 

[jlmohr76]

Specs for the cams are: 1102- intake duration at 050 , 204. Exhaust 214. Lift is 422,444 lobe separation is 112. The 1103 - 214,224 duration. Lift 444,466 with 112 seperation.

 

[RangRayy]

Comp cams 12-300-4

 

[jlmohr76]

Wondering if the 1103 cam would be too much

 

[1987 GMC Jimmy]

I would say the K1102 is more of a towing/RV type cam. I'm gonna spice up a 305 at some point in the future, and I'm doing that one because it's a nice little improvement over the L69 cam that's in it. Plus, it sounds nice, and the idle quality is stock level. I'd say the K1103 is venturing more into street cam territory. You'd probably be wise to do a spring job with that one, and I really think it's a cam that just getting the cam isn't gonna cut it to net any worth while gain. You have the intake, the carb, the short gears, but what's the exhaust looking like? What are the heads looking like? The exhaust in its stock form is mediocre at best, and the heads aren't anything to throw a parade over in their stock form either.

 

[yevgenievich]

I have used 1103 before on a 350 with 305 heds, air gap intake, headers, and 600 carb. It had a bit of a cam sound and would run best around 1800-5000 rpm range.It made for a fun street light to street light truck, but was quickly out of breath mostly due to 305 heads.

 

[jlmohr76]

I do have 2 1/2 inch dual exhaust. Plus I was thinking about gasket matching the intake and heads. Maybe try to clean up the ports on the heads as well.

 

[rich weyand]

12-300-4 or 12-235-2.

The Summit cams are old school, with 74* ramps. Ramp time is wasted time. You dump the pressure when the ramp starts, but don't get good flow until the ramp is done and the valve is open.

The Comp Cams cited are modern grinds, with 44* ramps. That 30* means a lot. It means more compression time, more expansion time on the ignited charge, and more flow time both in and out.

P.S.: Ramp time is the difference between the duration and the .050" duration.

 

[jlmohr76]

Checked out the 12-235-2 I like the looks of that cam

 

[1987 GMC Jimmy]

12-300-4 or 12-235-2.

The Summit cams are old school, with 74* ramps. Ramp time is wasted time. You dump the pressure when the ramp starts, but don't get good flow until the ramp is done and the valve is open.

The Comp Cams cited are modern grinds, with 44* ramps. That 30* means a lot. It means more compression time, more expansion time on the ignited charge, and more flow time both in and out.

P.S.: Ramp time is the difference between the duration and the .050" duration.

And I'm really liking the Comp 12-300-4. I saw your YouTube video of that truck idling, Rich. Sounds nice. What kind of improvements are you seeing/feeling over stock?

 

[rich weyand]

The horsepower is up from 175 to 275, and comes on sooner, but the torque is the big thing. Big difference between 275 lbft and 425 lbft. I am running the BFG 31x10.5R15 with 3.73:1 gears and a G80 on a TH350, and if you punch it from a stop on clean, dry pavement -- no brake torquing -- it'll break both rear tires loose. I usually ease the throttle in over the first 5 mph for the best hook-up.

With that much torque in the bottom -- like 320 lbft at 1000 rpm -- it runs out of breath around 4600 rpm, so I modded the governor to move the shift points down 500 rpm by putting one size thicker flapper on one side only. This keeps it from holding gears too long.

So I gave up a few rpm on top, where I don't drive anyway, but it has tremendous stones out of the hole, with stock valve lift and decent mileage.

You can get more on top out of the Gen 1 350 with the stock smogger heads, with the 12-235-2, 12-231-2, or 12-230-2 cams, but not with stock lift. I didn't see the need to push the valvetrain that hard. Going to modern quick ramps was about all I wanted to push it. I got the torque I wanted, without compromising valvetrain life.

 

[1987 GMC Jimmy]

It sounds like you're doing great with it. The specs show a lot more versatility and modernity compared to the Summit/Edelbrock cam, and the price isn't that much more. Thanks for turning me onto this. I know I get a lot more out a cam purchase than I would have with a K1102.

 

[jlmohr76]

Thanks for the info! I knew the 1103 was going to be too much but oh that sound lol.