Looking for a cam

[Honky Kong jr]

Yeah figured that's what ya were getting at. Maybe the only difference between the heads is the intake or exhaust runner. If they vary, my guess is they aren't much different.

For a daily you will be fine. If you were trying to squeeze every drop of hp out of it runner size differences would be more of a concern.

 

[MikeB]

Any good cam grinder will ask you this: At what RPM range do you want to make the best power? With a flat tappet hydraulic cam, that's typically a 3,000 RPM range. So take the truck for a drive, watch the tach, and determine the answer. But be realistic about it.

And seriously, with those heads, I don't think a cam any bigger than the one you have will do anything other than reduce torque at low-to-mid RPM. You might want to try some accurate 1.6 rockers, like CompCams Magnums, but I doubt you'll notice much difference. Just be sure you have pushrod-to-head clearance and have a .060" safety margin before coil bind.

On another note, does your truck have a dual exhaust system with at least 2-1/4" pipes? And are the mufflers free-flowing? Is the muffler internal piping the same diameter as your exhaust pipes, or is it necked down?

How about ignition timing. What are you using for intiial, mechanical, and vacuum advance? And at what RPM do you get full mechanical advance?

Getting these things right can have a much bigger effect on engine performance than a cam swap.

 

[Honky Kong jr]

So it doesn't get warped? Hadn't thought about that.

Correct. I usually do that spray them with lube and tie them fast so they don't get knocked over. Also when you install your crank don't be spinning it before all the caps are on and torqued. The retards on tv are always doing that and it makes me laugh. The bearing journal is not truely round until the cap is on and torqued that's how they align bore it with every thing torqued. When the caps are removed there is a bit of deflection and you could mess up a bearing while spinning it.

 

[theblindchicken]

Any good cam grinder will ask you this: At what RPM range do you want to make the best power? With a flat tappet hydraulic cam, that's typically a 3,000 RPM range. So take the truck for a drive, watch the tach, and determine the answer. But be realistic about it.

And seriously, with those heads, I don't think a cam any bigger than the one you have will do anything other than reduce torque at low-to-mid RPM. You might want to try some accurate 1.6 rockers, like CompCams Magnums, but I doubt you'll notice much difference. Just be sure you have pushrod-to-head clearance and have a .060" safety margin before coil bind.

On another note, does your truck have a dual exhaust system with at least 2-1/4" pipes? And are the mufflers free-flowing? Is the muffler internal piping the same diameter as your exhaust pipes, or is it necked down?

How about ignition timing. What are you using for intiial, mechanical, and vacuum advance? And at what RPM do you get full mechanical advance?

Getting these things right can have a much bigger effect on engine performance than a cam swap.

Definitely appreciate all the help guys.

Mike, currently the engine is all torn apart and hopefully going back together soon.

Truck is equipped with TH350/NP203, 4.10's on 35's.
At 65-70 mph, engine was turning around 2800-3000rpms. That was with fouling plugs, burning oil, low compression from a chipped cyl wall, flattened intake lobe and a cracked head all on cyl. 5. So, easy to say I was definitely down on power. Was

Honestly, my goals for the truck in the future are around 400hp and 450tq at the crank (after a head, intake, and probably a carb or FI swap as well). To the wheels would be awesome, buuuut we both know that a ton of power is lost through the trans and transfer case.

Truck will be running stock intake, quadrajet carb, HEI distributor, high amp alternator, dual electric fans, 1-5/8" long tube headers, currently dual 2" pipes (planning on going to 2-1/2" exhaust all the way back) into a pair of 2-1/2" I/O Flowmaster 40's.

I wanted to try to have peak torque and HP at a bit above cruising speed. I wanted to be able to have room in the powerband to be able to put my foot down and actually pass someone when needed versus stepping on it and having no more power left in it.

 

[shiftpro]

About decking the block...
Most good builders will deck the block to clean up the gasket surface and verify the deck is aligned with the crank.
It's not a one shot deal. When the block gets bored and honed, a cleanup deck job should take place as well.
Pre assembling the engine will determine the valve to piston clearance as well as the opportunity to learn where TDC leaves the piston to deck relationship.

Now I don't know or can't remember (been years and I'm just getting back to it) the point I'm about to make regarding small blocks, but as far as big blocks go, man you can deck the **** out of them. For example my current build is a stroked BBC. My builder decked off .020 - .025 and were still not near zero deck height.

I need to install the crank and at least one rod and piston (without rings) to measure deck height. My block all cleaned up will be going back to the mill to cut more off. My pistons will sit .010 proud when I'm done.

It's a small detail, but it really adds up.
Of course there small details that may be barely noticeable on a small block become more pronounced with higher power big blocks.

We all need to learn more about deck height and squish zones...
To a point, we can build power and fuel economy together.

 

[MikeB]

Honestly, my goals for the truck in the future are around 400hp and 450tq at the crank (after a head, intake, and probably a carb or FI swap as well).

Truck will be running stock intake...

That manifold is probably tuned for peak TQ at 3000. The only way you're going to make more torque and 400 hp with a 350 is by using a manifold like the Performer RPM Q-jet.

I wanted to try to have peak torque and HP at a bit above cruising speed. I wanted to be able to have room in the powerband to be able to put my foot down and actually pass someone when needed versus stepping on it and having no more power left in it.

So, based on your 2800-3000 RPM cruising speed, that means a combo designed to make peak torque at around 3500 or so. Here's a Chevy Performance crate engine that fits the bill. I'm not saying you should buy one, but take a look at the parts list to see how it makes that power. You can also see your 450lb/ft goal is attainable only by going to a 383.

http://www.chevrolet.com/performance/crate-engines/sp350-385-base

Chevy says it all with this statement: "In fact, the SP350/385 Base Small-Block engine produces at least 405 lb-ft of torque by only 3600 rpm for a thrilling feeling of immediate performance." That's exactly what street-driven vehicles need.

Looking at the parts list, the cam is the old ZZ4 roller, and the heads are revised Fast Burn models. I'd say a comparable flat tappet cam would be around 212/224 duration @ .050". The lift won't be there, but you could get close with good quality, 1.6 rocker arms -- and I don't mean stamped steel. A cam larger than that would move the powerband up to a higher RPM range.

Finally, keep in mind that even 25% increases in torque and HP over the stock engine will be a noticeable kick in the back during acceleration!

 

[MikeB]

On another note, I think those domed pistons have to go. Otherwise you're limited to 76cc heads and have very few choices. Also, from what I've read, flat top or D-dish pistons make for a more complete burn vs. domed and smog era "full circle" dish pistons.

 

[MikeB]

Just looked at the specs for your current Isky cam. Small world, because I always thought that would be a good upgrade to a basic GM Goodwrench 350 crate engine cam.

In addition to having much more lift, the cam's 208/208 duration would be a step up from the stock 195/202, and the 108 LSA would close the intake valve quicker than the typical 110 or 112 LSA, preserving cylinder pressure with the lame 7.8:1 compression (actual). But overlap still would be within the street/street performance range.

 

[gpmorgan]

There are some good vids on youtube concerning valve shrouding. Take a look and you'll see what I'm talking about.