Thread: 355 cam choice

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Hey guys, im a noob lol and have a question about picking a cam.

First off i have a 1979 4 bolt 350 sbc crate engine, it was bored .030 over to 355, has original crank and rods but everything else in the block is new/balanced, 10.5:1 flat top pistons, my heads are 76cc 2.02/1.6 and i was wondering what is a good choice for a cam (F/T)? pretty new to engine building so any suggestions would be appreciated?

Thanks
Joe

your engine may not have 10.5.1 with 72 cc heads most all flat top with 64 cc heads will be 10.3 or so . you never said were and when you want the cam to come in it and what your doing with this engine .drag. street . street /strip .RV. boat. mud . WHAT?

Sorry lol, i am going to be using it for street/strip in a camaro, Not sure what the cr will be in the end i was just told the pistons were rated for 10.5:1 cr and my heads are the 624 76cc heads also have a set of 882's. I just don't want to buy a cam that is too big for my set up because I'm not to knowledgeable when it comes to that. Also where i am i dont have to worry about smog laws or emmissions

well if there flat top pistons and its a 350 not a 383? it 10to3 or so with 64 heads no way with 76cc head as for cams roller hyd .roller solid . hyd flat lifter . solid lifter?

Hydraulic flat tappet

if you use a 64 cc head and have 10to1 then you can look at some thing in the hi 220s @ 050 cam and hi 400s to 520 lift .alot of cams out there .how much gear ?and stall are you willing to use ? your heads may stop you from going to of a big cam the power will move up the power band and you may not like it much on the street

so i should look for another set of heads then?

Originally Posted by 80ZJoe

so i should look for another set of heads then?

Yes. Those large chambers will not help performance. If you are looking at iron heads, take a look at Iron Eagles.
www.summitracing.com/parts/DRT-10121111
For less money, you could use S/R Torquer heads, but they do not have the new combustion chamber design that a lot of people prefer.
www.summitracing.com/parts/WRL-042660-1
If you prefer aluminum, then you have numerous choices--it all comes down to how much you are willing to spend. Edelbrock RPM series is a great head for the money.
www.summitracing.com/parts/EDL-60899

I know a guy who is selling a old set of cammel humps (64cc) needing rebuilds for $200 CAN and he has a set of vortec 305 heads for $300, he said they are also 64cc and should work good on a 350? should i even bother?

Hi Joe and welcome to the forum.
Let's address some of the aspects of engine building.

1. Piston deck height. This is the dimension from the crown of the piston to the flat deck of the block with the piston at top dead center. Nominally, with a premium 350 piston, this dimension will be about 0.025".
2. Squish. This is the dimension from the crown of the piston to the flat deck of the block with the piston at top dead center and adding in the thickness of the compressed head gasket. Current thinking is that a squish of 0.035" to 0.045" works best.
3. Compression height. This is the dimension from the centerline of the piston's wrist pin to the top of the piston's crown. With a premium piston in a 350 Chevy, this dimension is about 1.560". Lesser quality rebuilder pistons will measure out at around 1.540". This will increase the piston deck height and the squish and make the motor more sensitive to detonation.
4. Stack. This is the combined dimension of the crankshaft radius, rod length and piston compression height. A common stack with a 350 Chevy would be about 9.003". That would be with a crank radius (half the stroke length of 3.480") of 1.74", rod length of 5.703" and piston compression height of 1.560".
5. Block deck height. Nominally, this dimension would be about 9.025" on a virgin small block Chevy cylinder block. So, when using a stack of parts equalling 9.003", this would result in a piston deck height of about 0.022". Combined with a steel shim head gasket thickness of about 0.018", this would result in a squish dimension of about 0.040", just in the middle of the desired range of 0.035" to 0.045" to help prevent detonation with a reasonable (nominally, about 10.0:1) static compression ratio on pump gas. Alternately, a builder might cut the block decks down to the height of the stack and use a more conventional composition gasket that specs out at around 0.040" compressed thickness. If you had a stack of 9.003", cut the block decks down to 9.003" and used a 0.040" gasket, then the piston deck height would be 0.000" and the squish would be 0.040".

Sorry, but it was necessary to explain the above in order to get to what I am trying to explain to you. Presently, with my best guess of the parts you have in the motor, the static compression ratio is about 8.60:1. This is calculated with 727cc's in the cylinder, 76cc's in the combustion chambers, 4.6cc's in the piston deck height (@0.022"), 6cc's in the piston eyebrows and 9cc's in the composition gasket. If you used cheapo rebuilder pistons with a reduced piston compression height of 1.540", then the static compression ratio will be even less (8.29:1). If you used quality pistons and a shim head gasket, it will be a little higher (9.03:1). If it is currently 9.03:1 and you change to 64cc heads, the static compression ratio will be 10.26:1. You will then have to use a camshaft that makes power from about 2800 to about 6200 rpm's. This will require a looser than stock torque converter and a shorter rear gear to work properly. At 9.03:1 static compression ratio, you could use a street-friendly cam that might make power from 1200 to 5000 rpm's and would work with the stock torque converter and stock or slightly shorter rear gears.

The point is, you need to know what the static compression ratio of the motor is before you can intelligently choose a camshaft. The intake valve closing point, which is ground into the camshaft at the time of manufacture, is designed to work with a certain static compression ratio. If the valve closes too late, there is insufficient mixture trapped to make good cylinder pressure and the motor is a turd. If the valve closes too early, there may be too much cylinder pressure and the motor will detonate and destroy itself in short order.

Now, do you have any idea what piston compression height was used in your build? Do you have any idea what the block deck height is? Do you have any idea what the piston deck height is? Do you have any idea what the squish is?

270-h comp

or once you get some stall, gears and compression a 280-h or 305-h all great street/strip cams.

id go for the camel humps if you dont have any accesorys PS etc, if you do go for the vortec 305 heads and have your local machine shop drill them for regular bolt pattern intake OR get a vortec intake. not sure what kinda machine shop deals you can get. around here its about a $50-100 deal to drill and tap them

Thanks for the info guys, im not sure what the heights are on my build i'll have to check it out. I never heard of the squish before is that the same thing as a quench? But i have a stock converter in the car right now but i will need a new one once i finish the motor. I had a good converter but someone stole it out of my car when it was being stored at a friends house. Not sure what gears i have but i know it's a th400 with a B&M shift kit and the rear end is a limited slip. Again sorry i'm just learning lol.

The 305 heads will not breathe effectively enough to make a 350 run efficiently. Now 350 Vortec's would be a good choice as they breathe very well and make excellent horsepower.

You know guys and gals,I am just going to repeat what has been said many times before.By the time you make a used set of heads right is right and spend good money to do that,you still don't have the aftermarket heads that flow better,have thicker passages,are a better product to work with and really in some cases don't cost that much more and most importantly are a brand new set of heads.But that is my two cents worth and what direction this old boy is taking with his project.

I am constantly baffled by folks who seem to think their project has some deadline date.If only they would just wait and save alittle more money,they would get it right the first time.Also get it the way they would want the first time spending once and not twice.

Gary makes an excellent point. My philosophy may be a little more extreme than others, but I make it a point to use all new parts in a build. The only things I will re-use are the block and possibly the crankshaft. That's it. If I am spending thousands on an engine, I want the best and most reliable parts available. If I cannot afford to do it right, I wait until I have the money (or put it on my credit card--I don't recommend that).