Cam Selection with Vortec Heads

[Guest gbvol54]

I've finished tearing down my junk yard 350 (out of a '72 pickup, 4 bolt main, 993 heads, original compresssion was 8.5) Bottom end looks good, original bore with no scoring, taper measures out fine. My thought is to do a simple hot tank/cam bearings and hone, and stay with the original bore and pistons. The heads are more in question. I hate to sink dollars in a rebuild of average heads so I'm considering going to Vortec heads and a matching Performer intake manifold. I've read that the max lift these heads can take is .450 and that really limits cam selection, so my question is (finally), am I better off with the Vortec and a 'small' cam or with rebuilt large chamber heads and a more aggressive cam. I know the Vortecs can be modified to accept more lift but the price or the stock ones are already pushing my budget and aluminum ones are out of the question (for now).

 

Desired end result is a daily driver with 300-350 hp in my 73 Z. Couple more questions: (1)Is it possible to get in this range with a Quadrajet carb (budget reasons), (2) are the exaust ports on the Vortec compatible with Flowtech Block Hugger headers?

 

Sorry about the length.

[Guest kc6wfs]

Sallee Chey board has a lot of great info on Cams and the Vortec heads.

I have a stock 1999 Vortec crate motor and I'm going to put GM's HOT cam in there.

You will need to change springs,keepers ect.

I don't have the specs on the cam but it's over .525 and 280 duration.

 

Tom Sallee says it will give my motor another 125 hp with the cam alone!!

The Hot Cam kit is around $550.00

Here is the link to the GM message board.

http://www.sallee-chevrolet.com/Discus/board.html

Hope this helps.

Dave

[Tim240z]

I bought the factory upgraded valve train with my Vortecs. It adds about $200 to the total price on the pair, but is well worth it. I believe(??) it allows up to .600 lift cam. For a cam recommendation from GrumpyVette (THE guru) check out the post "Desktop Dyno Revisited" from about a month or so ago.

Tim

[Guest gbvol54]

I've checked the sites Grumpy listed along with a few others. All build up with Vortec heads must have had the upgraded springs ect. since they used cams with lift in excess of the max .450.

 

My question is really whether the stock Vortec heads with a cam lift under .450 will make 300-350 HP with 9.5 CR, RPM Performer intake, Quadrajet carb and block hugger headers. Since I can't seem to find standard Vortec heads in any of the dyno lists I'm guessing they are not a good option unless modified.

 

Correct?

[Guest Thurem]

The modifications you need to have performed on the vortec heads are: 1. cut down the valveguides to accept more lift (should only cost 2 to 4 $ a piece) 2. replace springs with comp cams 981 springs..

It don't get much easier than that.

Thure

[Tim240z]

Gary,

GM sells a crate engine with Vortecs that makes 330 HP.That's with a cam lift of .435"/ .460" lift. I am assuming that is the STD valve spring heads. So with 9:1 compression that motor claims 330 HP @ 5000RPM and 380 ft/lbs torque at 3800 RPM.

I think that with the STD Vortec valvetrain, 350 HP is probably not out of the question, but if you haven't bought the heads yet, get the upgraded ones. They are good to .525' lift.

Hope this helps,

Tim

[DavyZ]

Gary, although I'm not as well versed in engine building, from everything I've read, your combo should produce about 300 hp with the right cam, still being under the specific amount of lift you desire. I would call Comp Cams and Crane Cams--talk to them and see what the most aggressive cam is that you can put in there w/o going with too much lift. Also, they may be able to get you a true custom grind just for you without charging you any extra--something to think about.

 

Davy

[Guest gbvol54]

Thanks guys. Good point reguarding a phone call to the cam builders.

[pparaska]

Comp Cams and others make "lift rule" cams that have fast ramps, a good amount of duration, and low lift to be able to run in certain racing classes. Many times these cams have a LSA of 106. I'd think a custom cam with the lobes that these cams use on a wider LSA might be the ticket here?

[Guest willie 1983]

WHAT IS THE BEST SIZE CAM FOR STOCK VORTEC HEADS WITH USING A STALL?

[grumpyvette]

the standard vortecs are significantly better heads,than many cast iron heads like the early fuelies,but theres TWO destinctly differant port sizes in vortec heads, the standard 173cc and the newer 206cc , the larger ports support ALOT MORE HP, THE LARGE PORT VORTEC HEAD VERSION, can easily support 550-600 hp while the standard vortecs max out in stock config at nearer too 430-450hp

 

http://www.sdparts.com/product/25534431/SBChevroletCompleteLargePortVortecBowTieCylinderHead.aspx

 

Large-Port Vortec Cylinder Head Flow after mild mods, the stock large port heads are limited to a .530 lift, unless modified but easily raise the max potential rpm range by several thousand rpm

INTAKE EXHAUST

Lift Volume Lift Volume

0.200 128.6 0.200 100.8

0.300 188.4 0.300 138.6

0.400 234.8 0.400 154.4

0.500 257.2 0.500 152.5

0.600 263.2 0.600 163.8

0.700 269.1 0.700 167.0

 

standard stock smaqll port vortecs max at about 230cfm, but cost less, the cylinder head flow will restrict power and rpm levels to some extent, as they are designed for low and mid rpm tq.

 

http://www.sdparts.com/product/12558060/CastIronL31VortecSBChevroletCylinderHeadsAssembled.aspx

 

both types of vortecs can be modified with better springs and machined to work with better/higher lifts

be aware youll need self aligning rockers and center bolt valve covers and a vortec specific intake

 

http://www.sdparts.com/product/SD8060A2/VortecSBChevroletCylinderHeadwValveSpringUpgrade.aspx

 

 

naturally if your going to be installing better/longer/larger valves ,pushrod guides, better valve seals,and doing some port/bowl work and adding better springs, like beehives and titanium retainers, too get a head that will work with .650- lifts you buy bare heads and save some expences since youll discard the stock valves and springs, retainers etc. anyway

 

http://www.sdparts.com/product/25534371/SBChevroletBareLargePortVortecBowTieCylinderHead.aspx

 

 

 

http://www.2quicknovas.com/vortecheads.html

 

http://www.kendrick-auto.com/vortec_cs_gm_head.htm

[Pyro]

With no stall and 9.5:1 cr. I would use a simple Edelbrock performer cam with a performer intake and a q-jet.

 

The cam has 204/214 duration with 0.420"/0.442" lift. Should make about 325hp with a set of vortec heads. Set total mechanical advance timing at 35 degrees.

 

More exhaust duration really helps out the vortec head. I would also spend a little time cleaning of the sharp edges under the exhaust valves. Pull out the exhaust valves and smooth the transition between the port and the valve seat. Could be worth another 10 or 15hp.

 

Q-jets are great carbs as long as they are in good shape and not rebuilt by autozone. Cliff's performance carb shop is a good place to send your carb.

 

 

With a stock converter I would not go over 208 degrees on the intake and use another 10 degrees for vortec heads (poor flowing exhaust ports).

[Pyro]

check out this site.

http://www.ryanscarpage.50megs.com/combos1.html

 

combo 77.

 

crane 260 cam is another good choice. 204/216, 0.427"/0.454". made 323hp at 5000 and 390 ftlbs at 3500 with a 355, 9:1 cr, and dart sr heads.

 

There is a perfromer cam test with edelbrock heads on this site, 8.5:1 cr 350, shorty headers, q jet, made 310hp. But 9.5:1 cr will add about 5% more hp (325hp).

[Guest willie 1983]

thx 4 the info but what if i add a small stall 2300 etc