someone972

iTrader: (2)

Previous thread I had, don't think there's anything really important to know from it: https://www.thirdgen.org/forums/tech...-i-expect.html

So I've recently acquired a set of AFR 195 heads (the 1041 model with L98 angled plugs and 72* center bolts). I'll be getting a FIRST TPI intake once they are taking orders again (should hear back within the next two weeks). I'm also waiting on some Dyno Don 1 3/4" headers which will feed into 3" Magnaflow exhaust.

Now one area I know will need upgraded is the cam, but I'm pretty clueless on what would be a good cam for this setup. I do mostly city driving, and it is currently a daily driver. I don't mind some lope as long as it doesn't have to be idling at 1000 rpm to stay running . With the converter I have right now (a 2600 stall Edge) it's usually at or around 2K when accelerating lightly, so keeping some torque down in that range is preferable. Not looking to go over 6000 RPM (don't even know if the FIRST is capable of that). Also, since I'm a newb to cam choices, if you can say why a certain cam would perform well I'd appreciate it.

What compression ratio should I be aiming for to run on 91 octane pump gas (no 93 in my area)? My current heads are 14096217 castings which are supposedly 64cc chambers. No idea on the current C/R but it was suggested to run on 87, so it can't be too high. Most likely it's whatever one of these engines had stock.

With the parts I listed above, will I need to upgrade anything over the stock 350 parts? The engine was a rebuilt crate and has less than 10,000 miles on it. I put a camera down in the spark plug holes, but it was difficult to see. I think I have one of these two styles of pistons, it's hard to tell from the pictures I got:

sofakingdom

iTrader: (1)

I'd suggest a Comp "503" grind. http://www.summitracing.com/parts/cca-08-503-8

Get the UPGRADED springs for it; don't try to cheeeeeeze out with the bare minimum.

Piston454

I see you are from my neck of the woods.

You need to factor in our elevation being at +-6000 feet when you pick a cam. We dont have as much air up here so when you cc your cylinders and heads and compute your compression ratio that is at sea level with most calculators! you also need to compute your DYNAMIC compression. (how many degrees is your crank spinning around before your intake valve closes). we need to run cams with low duration in order to get that intake valve closed quicker to bring up our dynamic compression. unless you are looking for more high rpm torque/hp then go with a little more duration. if you were to contact Crane Cams and have them recommend you a cam shaft you typically want to go 1-2 cams lower (less aggressive) to compensate for our altitude. your dynamic compression should be between 7.0-9.0 for best performance and still able to use 91 octane gas.

i know that didnt answer your question, just trying to give you some info about picking cams.

someone972

iTrader: (2)

Great info, thanks!

EDIT: @sofakingdom the heads will be coming assembled with springs, so should be good there.

sofakingdom

iTrader: (1)

Just make sure they're the UPGRADED ones; not the base model.

someone972

iTrader: (2)

Doesn't say what springs exactly it uses, but it does say it's dual springs per valve with 0.600" max lift.

sofakingdom

iTrader: (1)

That's Comp 986 probably then. Should have OD of 1.45".

If so, they'll be fine. Set them up with about 125 lbs on the seat.

someone972

iTrader: (2)

Took another look and found this info for the springs:

PAC Racing Spring 1.290" OD Hydraulic Roller Dual Valve Spring,
140 lbs on seat, .600" maximum lift, Max RPM 6300-6500(upgrades available)

Sound like a good set of springs?

sofakingdom

iTrader: (1)

Seems suitable. Worth a try at least.

someone972

iTrader: (2)

So how about rocker arms? I'm pretty clueless on this too. Right now my engine has plain Jain rocker arms, should I get a set of roller tip or full roller rockers? What about ratio? I hear a lot of talk of 1.5/1.6 ratio rockers. I assume this is greatly dependent on my cam as well.

Also, are there any other parts in a stock-spec'd block that would need upgrading to safely handle the power (let's say an upper limit of 500 hp)?

sofakingdom

iTrader: (1)

Full roller would be the way to go. NOT aluminum: either Comp or Crower steel bodies.

Those heads can use all the lift you can throw at em, within reason. With the cam I suggested I'd go with 1.6. But with some other cam, it could be different.

someone972

iTrader: (2)

Lets say I were to get some Comp Ultra Pro Magnum 1.6 ratio roller rockers; would they clear stock centerbolt valve covers?

sofakingdom

iTrader: (1)

Don't think so...

The thing where the bolt goes through, won't fit between them.

I don't think any non-aluminum ones will fit. Only ones, used to be, the ones GM bought from Crane. But they were aluminum and as such, not a good choice for a motor that's expected to do DD duty.

someone972

iTrader: (2)

Hmm, I've seen posts where they will fit if you remove some of the support on one side of the tube the bolt goes through, since the tube is offset from the rocker arm centers. No conclusive yes or no on whether that can be done with the Ultra Pro Magnums though. I could always get new valve covers I suppose.

I know there's not many people who use the FIRST intake here, but anyone concur that a CC 503 (CS XR276HR-12) would be a good choice with 1.6 rockers? Keep in mind that I'm about a mile above sea level.

someone972

iTrader: (2)

So I've been trying to get my head wrapped around this whole dynamic compression ratio thing. I tried using some online calculators and it looks like at 5280 ft with 66 degrees ABDC on the cam, I get in the 6.39 DCR range when using 9.4 SCR. Obviously less than ideal, so I bumped SCR to 10.5 and I get 7.23 which is workable, and 8.29 at sea level. Would I be able to run 91 octane at sea level assuming 10.5 SCR? Could someone verify if my calculations are sound or bogus?

cardo0

I'd have to say your making to many guesses. If u pull the head then u can measure the piston vol/compression accurately with liquid.

As far as matching parts try reading a David Vizard how to book for the sbc.

Good luck.

someone972

iTrader: (2)

Unfortunately I don't have the luxury of pulling the head right now. Would certainly be helpful if I could. At the very least I should be able to do the DCR calculations to know what SCR I need to be running without actually knowing the actual SCR, or at least get close. More of what I'm interested in is if I'm going to have to change out pistons or other components, so a ballpack compressions ratio should be fine for now.

I'll look up this David Vizard, had not heard of him before.

cardo0

Well if u cant pull the head for some reason then what u can do is a compression test before pulling the cam. Once u know what the cranking pressure is u can make a judgement to increase or decrease cranking press with the new cam. U can identify or even measure the old once its out. U want cranking pressue below 210psi on pump gas. I expect your stock cranking press to be somewhere less than 150psi. Remember to hold/fix the carbs throttle blades open for this. And it should be done on a hot engine but no-one ever gets their hands on the plugs with hot exh manifolds.

IMHO removing or swapping the heads is easier than a cam swap but thats up to u.

For selecting a cam the larger the full duration the lower the cranking pressure. Also the smaller the LSA the lower the vacuum should be. But as u shorten the cam full duration number the tighter u can make the LSA with the same vac and it becomes somewhat punchy.

But using a long runner FIRST intake and great flowing heads gives u more options for a cam. The long intake runners will make up for short comings in lower compression. And a longer duration cam with a wider LSA starts to make sense. So i say measure your compression now and pull the cam to see what u have now for a comparison. Without some information like that i cant say which way to go for a cam right now and would just be guessing.

Hope this helps.