So Im thinking about rebuilding my stroker motor again(it ate a cam and needs the rotating assembly rebalanced) and want some advice on cam choice. I could just throw a replacement cam of the same one I had, but might as well see what you guys think.
Engine specs are a 70's block already been punched out 60 over and clearanced for the stroker crank, forged eagle 3.75" stroke crank, 6" eagle h beam rods, forged flat top srp pistons, block hasnt been decked as far as I know, but Im not 100% on that one. Heads are 096 casting iron vortecs un ported, stock valves, but heads have been machined to handle .500" of lift. And i currently have 1.6 ratio roller rockers on pressed in studs (i plan on putting in screw in studs eventually)
http://www.summitracing.com/parts/CCA-12-242-2/ thats the cam i was using until it ate a lobe.

 

I forgot to add, Im also running an rpm air gap and holley 650cfm.

 

Are you going to stick with those 3.42 gears?
What's your compression ratio?
Mostly street, occasional strip?

With mild gears like that and a CR of 10.5 or less, I'd be inclined to stick with that same cam for driveability.
If you're 11.0 CR or above and plan to really rev it to wring out all the hp you can, then step up at least to the XE 230/236/110.

 

street DD, with maybe a track pass or two. 3.42s are staying unless i swap in a 12bolt or a 9" and IIRC compression is under 10.5

 

high compression on iron heads just doesnt sound like a street DD to me. Did it run well before with that small cam? I wouldnt hesitate to put in the larger 230/236 atleast or even something a touch larger than that with that compression ratio. Tight LSA, 108-110.

Or convert to hyd roller to avoid eating cam lobes again. Need special oils to handle flat tappets these days...shelf oils dont do the trick anymore.

 

i looked up the CR from srp for thos pistons. according to srps site, with my 64cc chambers, i should have a cCRof 11.1. and it ran great before it wiped a cam lobe (other than the vibrating from the poor balance job)

 

of course the 11.1 CR is based on a zero deck.

 

ive been tossing around the idea of converting it to a roller cam, but it doesnt have the bosses for the lifter spider, and conversion lifters are expensive. unless you know of a different way of converting to a roller cam for less than the $400 for just the lifters, im all ears. and ive considered switching to a roller block, but ive already invested the money in all the machine work on this block and dont really wanna spend that money again on preping another block.

 

yeah you'd have to run the link bar lifters. They can be pricey....but in the long run its not a bad investment for reliability and smooth operation.

I'm surprised 11 to 1 with tht 268 cam worked ok with iron heads. 93 pump gas? I bet it didnt take alot of timing?

 

it got up and went when i mashed the go pedal.....timing was set about 12* initial with about 30 over all. it probably helped a lil since i had the 1.6 rockers instead of the 1.5. and i did run it on 93 oct.

 

Orr89, I'm concluding that he hasn't verfied a zero deck, which is what he stated the SRP calculator assumed.

 

i could spin the tires all the way through first and half way though second on dry payment with normal street tires from a dead stop and a 3g rev and clutch dump

 

yea, im pretty sure its not zero decked, and i was using a .043" compressed thickness gasket, so compression was under 11.1

 

Yeah, with the pistons in the hole alittle and .043" gasket your looking 10.3-10.4 to 1 or so. Still abit high IMO for that cam. I'd run the next step up and enjoy the new found power. Quench is abit high then if the piston is .025" in the hole with a .043" gasket. I'd run around .028" to even it all out but if its working for now then keep it.

 

If you're rebuilding the engine anyway, I'd deck it for about .010" in the hole and run an .026-.029 gasket like Orr said. Those Vortec heads love that tight quench and not much ignition advance. It would like at least that 230/236 cam then.

 

alright, so battle plan is deck the block and run a thinner gasket with http://www.summitracing.com/parts/CCA-CL12-246-3/. should i keep the 1.6 rockers or down size to 1.5?

 

I'd run the 1.6 rockers. maximize the flow area around .500" lift for most airflow thru the vortecs.

 

got it, you have an est HP with this set up?

 

As you're aware, cam timing and compression ratio go hand in hand.
Determine EXACTLY what kind of static compression raio you have now and what you may have once you deck the block. Since you have the ability to nail down your SCR you can choose a cam that is ideally suited and will maximize your potential with an optimum dynamic compression ratio.
It's doubtful that your current SCR is 11:1. Using a short duration cam such as the one you listed would build a lot of cylinder pressure and undoubtedly have detonation problems.
Have you ever done a compression test? Some reasonable assumptions can be made with that bit of info.
The suggestions so far have you on the right track. Keep the quench near .040", add some cam timing but be sure it suits the SCR or you'll have a slug on your hands. Keep the 1.6 ratio rockers. Vortecs tend to run out of steam past .500"-.550" lift but the more time you spend in the low lift area the better for making power with those heads.

FYI: Using the values listed and a zero deck height, SCR comes in at 11:1 (give or take). With the stock piston below deck value of .025" (which can vary in an engine from cylinder to cylinder by .010" !!) the SCR comes in at 10.4:1.
My experience with my Vortec headed 350 is that 10:1 is near the limit for the street and that's with a cam that has 276 degrees of intake timing.
:

 

with the block decked to put the piston .01 in the hole and a mls gasket with a compressed thickness of .03 i get a CR of 11.24:1

i cant find any thinner gaskets that dont require an oring in the quick search i did...

 

64 cc heads
piston .010" below decks
Piston with 6 cc valve relief (standard relief volume but assumed)
.030" thick gasket with 4.100" diameter (standard dimension)
4.060 x 3.75
SCR 11.12:1
That's pretty close to your calculation.

Victor Reinz makes a .025" gasket. I have a part number somewhere.

 

according to srp, i have a 5cc valve relief

 

i guess it helps if i leave out the bore in my search, the head gasket i found had a diameter of 4.06 exactly.

 

OK. That puts your value closer to what my calulator cranked out.
Even with the stock piston below deck value of .025", you have a boat load of static compression. I would have liked to know what the compression pressure was on that engine before it ate the cam.
For the record, my 350 wiped out a handful of lobes too. That's when I made the switch to a retro roller.
Keeping that kind of SCR gives you a little room in the cam timing department. Just remember, if you increase the intake duration and keep the SCR the same, you will actually lose some cranking pressure and possibly a corresponding amount of low end torque. The upside is that your 388 already has plenty of torque from what you describe.

 

you know, the thing did blow out a head gasket shortly after i assembled it. i though it was just the cheap over the counter gasket i used....

 

Cranking pressure of minimum 180 psi for a worst case street build. 200 psi is more on the mark. 220 psi for a racing engine.
My Vortec 350 with the old flat tappet cam (VERY similar in specs to yours) made 205 psi during a compression test. I had to watch engine temps and use 94 octane rpemium but had no signs of detonation. Calculated SCR was 9.85-10.1:1 depending on the cylinder that was measured. I run a XR276HR cam now with the same SCR and cranking pressure is down somewhat to 185-190 psi.
Victo Reinz head gasket:
http://www.cnc-motorsports.com/produ...D=20108&CtgID=

 

alright, so i found a good clevite head gasket with a 4.125" diameter and a compressed thickness of .26" so thatll give me a SCR of 11.35:1. if i go with that set up, do you suggest a different cam with more intake duration, or the same cam with some cam timing? or so you suggest using the thicker gasket to bring down the SCR?

 

also with the roller conversion, do i just need the tie bar lifters and any roller cam, or do i need a retrofit cam too?

 

First thing I would do is determine what your piston height is. We're just speculating at this point and guessing here could result in a disapointment down the road.
That said, if you DO end up with an SCR of 11.25:1 with the Vortecs, I would be looking for a larger cam. Decide where you would like to develop peak power (below 6000..past 6000 rpm) and work out your cam specs from there. Keep in mind your lift limits (you'll definitely want to do something with the pressed in studs) and work the duration numbers to suit your rpm target.
If you haven't read this article, I highly recommend it. There's also a DCR calculator you can download. From there you'll have the tools to calulate what would work well and what wouldn't. Try Comps cam selecting software too. It's free and there is a lot you can learn about possible cam choices.
Retro roller would mean: cam, lifters, push rods and some means to control "cam walk". Usually done with a cast timing cover and a thrust button. I highly recommend the roller if it's in the budget. Retro fit roller cams and the OEM rollers have slightly different configurations. I don't believe they're interchangable.

http://www.empirenet.com/pkelley2/DynamicCR.html

 

well im deff looking to keep power lower in the rpm band since this will be a 99% street driven vehicle. and since im going to have to have the rotating assembly rebalanced, i might as well take the block and have it decked to be sure where the piston is in the hole. and have the heads drilled and tapped for screw in studs. possibly even bigger valves.

 

You don't have to have the block decked to determine the piston height. That can be done anytime the heads are off. Getting the optimum quench value is never a bad thing but the Vortecs are a very efficient head and as such suffer less than the old OEM castings when the quench values get a little on the large side.
Screw in studs for sure however you may want to rethink the bigger valve thing. Unless the shop is EXPERIENCED with the Vortec casting, it's easy to make things WORSE by going to a larger valve. There's over 450 hp potential out of the stock castings and that's with a little 350.
Perhaps saving some cash by avoiding the decking and the valve job will leave some to finance the roller upgrade. THAT would be money well spent.

 

looks like i can get a set of howards retro roller lifters on ebay new for $300, plus cost of cam. thats about twice the price of the flat tappet replacement but i think im gonna go with it anyway. now the question is do a need a retro fit cam, or will any roller cam work?

 

This may answer your question.
https://www.thirdgen.org/forums/tech...ry-roller.html

 

alright, so we got the battle plan with the stroker figured out.....

i picked up a nearly complete from a 97 1500 truck for next to nothing. it had spun a rod bearing, but other wise its in great shape. it was just missing heads and intake.

ill be rebuilding it as pretty much a stock rebuild to throw in my truck. it was from the 4wd version of the 1500, which from my research was rated at 255hp and 330ftlbs.

ill be toping it off with a set of stock vortecs. should i keep the stock truck cam, or would it be worth it to upgrade? the truck its going in is a 86 silverado 4x4 with 700r4. wont see a lot of towing but will be used occasionally. and of course more low end torque is always better.
not gonna see a whole lot of time at speeds over 80, or high in the rpm band. what would be a good cam for this?