The MAXIMUM lift you should use, is no more than .460 on the intake and the exhaust with stock vortec heads.
As to having the stock heads "Bench flowed" to decide what cam to use; that's BS for the "average" street driven vehicle. Flow figures are available for most heads (from the manufacturer and/or the after-market manufacturer). The figures that they can provide are sufficient to select a cam with. Unless you have done some major head modifications and are building an "All out" racer or an experimental vehicle having the heads Flow tested is a waste of money and time.
I saw the answer you are referring to that suggested that. I'm sure the person that posted had the best intentions in mind, but they really didn't know what they were talking about. See the above paragraph. Unfortunately, misinformation is rather common on Message Boards. Read the answers you get from your questions. Verify the info if you are able. Then proceed with caution if you are entering new territory.
Apparently some don't understand the process of casting. We refer to core shift all the time and how it varies from head batch to batch. Flow numbers can be off significantly from "posted flow numbers".
Frisco is correct, most street cars don't need custom camshafts, but for someone who wants optimum performance it is the only way to go.
Flow testing is but another way to optimize performance. So lets see, choose 3 cams, none really do what I want so I have wasted $450, or flow test heads $75, and get 1 camshaft. Hmm, think I'll save some money.
As far as misinformation, your right. . .there are plenty of guys that have read the BS that is published and spew it like the gospel. Those of us in the trenches. . .laugh. . .and go on.
Last note. As for the camshaft, for something that is suppose to be so easy to figure out. .. we sure do get alot of people worrying about which one is best.
Last note. As for the camshaft, for something that is suppose to be so easy to figure out. .. we sure do get alot of people worrying about which one is best.
I can not agree with you more. Everyone (well almost) want the "Top Fueler" sound, but also want to do it with low compression, good bottom end, 3.08-1 gears (for mileage and low RPM freeway cruising), and on and on.
Which cam to run is best answered by the Cam Manufacturers IF they are given the intended use of the vehicle and the complete specs on the engine/driveline combo. The same is true with regards to which torque converter to use.
However, since the questions are posted here; hopefully, one or more folks that post here will have already experienced what works for them and post an answer that points in the correct direction.
Have you had the machine work done on the heads to allow bigger springs and therefore a cam above .460 lift? If so, go with the XE274H and a 2200-2400 stall. I had a 355 with Vortec heads and the XE268H cam and It ran really well, but from what I have seen motors with the 274H do, If I had it to do over again, I would use that cam. The average flow limit of a set of Vortec heads is around .500 lift. Until there they flow very well. After that they drop off. If you keep your cam around .500 lift, you will be happy.
A very nice, CHEAP camshaft that works well with the vortec heads is available from www.speedwaymotors.com It is intended for circle track but if you are running a manual or around 2500 to 3000 stall this cam rocks and talks!!:thumbup:
HYDRAULIC CAMSHAFT 3000 to 6500 rpm range
Duration advertised= I 284 E 290
at .050= I 228 E 234
Lift with 1.5 rockers= I .480 E .494
Lobe Centerline= 106 degree
Part #915-110591
You will have to machine the guides to clear that much lift! But, this cam is EXCELLENT for the vortec heads!! With more duration and lift on the exhaust side it really helps out where the vortecs need it!! And the 106 degree centerline makes this girl really gurgle at an idle!! Be aware though that this cam may be tough to use with vacuum assisted items, like power brakes. (add a vacuum canister)
That was exactly what I was aiming for something in the .480-.500 lift range. you mentioned opening up the exhaust side a little more, and that's the conclusion i'd come to also.
basically i think i might have a little too much stall for the XE268H. Probably either the 274H or a magnum 270 is what I will go with.
as for buying three cams and testing each, then having wasted $450? isnt' that what ebay's for?
The stock torque converter is fine with the XE268H cam. The other cams you listed will need more stall.
You haven't said what your intended use is, but I'd go with the Magnum 270H or even a Magnum 280H. (That's what I am running and it pulls very strong compared to the XE268H I had before. I also have AFR 190cc aluminum heads)
The 3.55 rear gears will work well for street and freeway use. 3.73 would work better, but you probably wouldn't like the RPM's at 70 MPH. Around 3200 depending on rear tire diameter.
I would recommend going with a dual pattern cam. Unless you have a set of heads that flow really well on the exhaust side, a dual pattern cam will make more hp. If you had a set of AFR heads or any other aftermarket head that had porting, I would say single pattern, but with vortecs less than excellent exhaust flow, I would go dual pattern.
That, more than any other answer I have gotten after repeated phrasings of the same question, is exactly what I was looking for. If I upgrade heads at some point, then yeah, I'm gonna upgrade the cam to match. For now, with the vortechs, the XE274H is the best option for me.
Be very carefull of your static compression ratio with that cam. It will build up a lot cylinder pressure so anything more than 9.25:1 or so may cause detonation. Comp Cams admits to their Extreme Energy cams as being more aggresive in the ramps and timing than they expected.
He is right about the extreem energy cams. Comp told me the same thing. I however ran 9.8:1 in my 355 with the xe268h and never had any problem with it. I think I was able to to this because my quench area was set to .052. The closer you can get to .040 the better. If your quench is geater than .060, the fuel will not atomize properly, and even with less compression from having a bigger head gasket, the motor will sometimes preingite.
Well I'd addressed my concerns about static/dynamic compression in this setup earlier, but got conflicting answers. It seemed I was always either giving too little or too much information for determining what setup would work. And then I was told that the dynamic compression calculator I was using didn't work right.
With 12cc dishes or valve reliefs on my pistons (depending on piston selection) and the large duration of both the XE274 and the Magnum 270H or 280H, I'm going to bleed off enough of that cylinder pressure to stay in the range for pump gas.
I'm confident that my setup is going to work, and if it doesn't... well he11, then I guess I'll just have to try another camshaft, won't I? I'll take my time setting the timing right, and select a proper configuration for my carburetor, and as long as I haven't made any serious mistakes, I'll avoid detonation.
Just my .02 but the Summit #1107 cam which is the copy of the Performer RPM cam (.488/.510 w/234/244 @.050) is a very good power producing cam for the Vortec head design and at a meager $79.95 for both cam and lifters its a cheap HP componet... And yes I have ran this combo in a 4500lb truck w/355 flatop and ran a nice 13.62 @98mph and drove it to work every day...
Bull... I went with the good stuff which to me for that app was the K-motion K-7500 springs w/10 degree locks and retainers... These springs are supposed to be good for up to .610 lift (Hyd. stick) and are 1.250 diameter (stock) so no spring pocket work had to be done... Also I used a 2800-3000 stall that was actualy for a BBC for that range but did around 2500-2600 behind the SBC which also matched very well with the Vortec Eliminator mainfold that I used... One other thing I went with a Holley 650 DP and found it to be best for ET times (tried from 600-825cfm)... Again bigger is not always better...
Also for those interested the sound this cam combo makes gets alot of attention besides the good performance and price...
TCI Saturday Night Special. Advertised stall is 1900-2200 RPM. My truck weighs 2660 lbs. and with 28" diameter tires I am getting the stall at the lower end of the advertised numbers. Works very well. I am thinking about going a little higher stall though.
I've got a TCI Breakaway that I am considering trying out. It has a little more advertised stall.
I'd prefer to just get a Coan 2600-2800 stall. That's what they suggested I use when I contacted them.
Having done the 268 and 274 cams you will need more stall and quite possibly more gear. The 274 cam will be a slug out of the hole with 2500 stall and the 3.55 gears. The 268 would be a better choice if you do not want to increase stall and gearing
I am currently running a muscle car blueprint cam for a 350 hp 327 on my 350 with Vortec heads and it works like a champ. It;s 222/444 on both sides.
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