Thread: I'm Sure You're Tired of Answering Q's on this Subject,...

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but I have decided what all of the other parts I am going to use, so I must ask the dreaded question, what cam should I use? I will make it easy on you and give you all of the information you need to know:

Ok, so I've decided on the bottom end of my block, now it's time for the cam. I'll be running a zero decked 350 with 9.5:1 compression and vortec (as the come from GM because I can't afford head work, I may clean up casting flash in the ports and even out combustion chambers) heads with 1.5 ratio rockers. This is a truck motor, so it needs to have oodles of low end torque and be able to run California 91 octane. I would like to run 89, and I think with the right level of tuning I will be able to, but I am going to be realistic and say 91. I was originally thinking something with not much more lift than stock and not much more duration, but after hearing about Rhodes lifters and Crane's version which I have forgotten the name, I think I'll give them a try. They bleed off pressure below 3500 rpm to, in effect, shorten the duration of a cam. Using these lifters, what is the biggest cam I'll be able to run and still pull enough vacuum to run my power brakes and still get decent gas milage (my other goal of having this engine is to get better fuel economy than stock, hence the higher compression ratio). I don't want to run much more than 1200 or 1500 rpm stall, and I don't mind a lopey idle. I hope this is enough information. Cruising rpm is going to be around 3000 rpm plus or minus a few hundred.

I think this should be enough information to make a cam selection.

So, I did some of my own research and the comp cams xe262h-10 is looking good. On a 9.25:1 engine it produces 17.5" hg at 800 rpm and makes 415lbs of torque at 3700 rpm. When I'm cruising, I'll have 400 lbs of torque available just by stomping the gas pedal, that kind of has me worried. Maybe I should get a turbo 400 instead of rebuilding my turbo 350?

I would give information but, I do not know much about the best cam for a truck. I'm in fact in need of guidence in the same way because I want to run a high compression engine ( maby 10:1 ) on a 350 blazer motor and do not know a good cheap truck cam that will have a good low end torq. By cheap I do not mean one that spins out or breaks but, one that is cheap but still holds it's stability. I don't care about havin to run pump gas, I can get octane booster.

GMC, I usually defer to the experts on cam selection. The best method I have found is to fill out completely and accurately one of the cam reccomendation forms that all the manufacturers have and look at their choices. I sometimes send the same information to two companies, and compare their choices. Once you have all the cam specs they reccomend, you can shop for the best price and availability. Just a thought.

I always call Schnieder cams tell em what I'm using it for and all the specifics,5 to 7 days later ups shows up.....

In an article in Hot Rod they built almost the same motor that you are. It included a stock short block, comp cams xtreme energy 268H, L31 heads, stock groved rockers, stock springs, edelbrock performer intake, Q- jet . They ran headers,and flowmasters with 3"pipe. After they tuned the carb and tweaked the timing it was pushing 375.8 hp@5700 and 395lb-ft at 4,300. From all the resarch that I have done the split patter seems to work best with the vortec. I am builiding the same motor, but I plan on sacrificing a little power for mileage and go with the 262 also, because my truck is my primary transportation. I am going to run a 400. If you run a 350 I would have it built well. Stock one might handle the power, but I don't want to be the one to find out. I bet some of you are wondering if that is to much cam for stock springs? In this test they made 55 pulls 10 of them were up to 5,900. So I guess they hold up. I would probably upgrade if I were going to run the 268.

I think I am going to get one of these 3 cams.

I like the HP and torque of this 262 grind., but I don't like the vacuum. It makes 17.5 inches at idle, and I think that is very marginal.

These 2 cams make the same torque as the first, make 20hp less, and have an extra 1-2" hg at idle. 250 grind, or the 256 grind. Their torque curves aren't as broad or as flat as the first cam and they make only marginally more torque at the lower end of the dyno curve.

If I get the 262, I'll probably need about 2000-2200 rpm stall. I could get away with 1500 with the other cams. I'll ask the guy here who built the 310whp, 600ftlb 468 El Camino that gets 28mpg.

Are you serious about this elcamino guy or this a joke that I missed out on. If you are I would like to see a link to some specs on that.

Normal vortec heads tollerate a .475 lift, GM has a new set that apparenltly just came out that is cut for a .550 lift. They cost $110 more, each, so I'll stick with the .475. Comp makes the XE cam for hydraulic flat tappet lifters, so I'm sure it works fine with flat tappet lifters. I'll ask Comp what they have to say, I'd like to use one of those cams because they make so much torque. For the detonation issues, I may be able to get an MSD ping control dial for free, so I can dial out timing while I'm driving if I start detonating.

For Dirk: This car is a tall deck 468 with stock iron heads. 10.5-1 compression, custom intake manifold, comp XE roller cam, crank trigger ignition, and Accel fuel injection. There is also a 5-speed overdrive transmission and a 2.73 or 2.39 rear end, I'm not sure. The motor has had the crap tuned out of it. The ports are not much larger than stock, but have a certain diameter and shape to get a flow of 2500 feet per minute at cruising rpm, maybe a little higher. The length and area of the intake manifold runners was also matched to the rpm range. Despite the low gears, the car has so much torque, it launches like it has 4.10's. It has only 310whp, though. Around town, I'm sure the car gets awful fuel milage because it has a huge engine, but once it gets on the freeway it cruises at 80 at 1800 rpm, so you can see where good milage comes from. The car will be for sale, as soon as this guy gets his GTO ready to bring up here, it gets 30mpg.