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post #1 of 5 (permalink) Old 05-14-2013, 02:13 PM Thread Starter
 
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Cam selection Questions

I have a stock 350 from a 71, #94 heads hearing some conflicting info on these being 8.2:1 or 8.8:1. Leaning towards 8.2:1 or even 8:1 quite frankly. I think they're 96cc but the info on the net seems to be of varying accuracy (for instance I found a site for instance that said these have screw in studs.)

I currently have a fully stock 3/8 press in stud valvetrain. I know this will make a difference, trying to keep downtime minimal as well as expense but am not going to argue with working smarter instead of harder.

That all out of the way, I'm looking to keep head gaskets in tact. REALLY not wanting to do a set of heads for this engine right now. Really not looking for all out power, just a bit more oomph and more drive time. If I do that I'm looking for a set heads that have chambers in the 10-20cc smaller vicinity.

Other relevant stuff is a 3 spd, 3.23 rear axle. Stone stock exhaust that will get tossed for duals in the 2-2.25" range with an intermediate (X/H) pipe. Headers are an option as well, but I've heard the manifolds are pretty decent. If i get headers I'm doing long tubes though.

My candidates as it stands are 2 Howards cams. 410931-11 is a [email protected]/.450 lift cam with a 107CL/111LSA on the stock base circle. This means I should theoretically be able to use the stock valvetrain with it. The second cam is similar except it is 213/223 duration instead and a 108CL/112 LSA. Howards recommended the single pattern cam, they said for increased torque. I am looking for a max RPM of the low-mid 5000s. With a SBC this would be a safe combo on press in rockers, how does it make out on a Pontiac?

The springs I was wanting to use have an install height of 1.75, and would be at 270 with the valve open and 135 with it closed. Does this sound about right for this cam? Howards also offers another smaller diameter, shorter spring. Would I need this one for my heads without cutting the spring pockets? I know that the early heads are a good bit different than the later ones, including having valves closer together.

Opinions?

ED:forgot to mention, Qjet and probably an iron intake as well for it unless I can find a Performer/HO/SD intake.
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post #2 of 5 (permalink) Old 05-15-2013, 08:45 AM
 
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I'm building a 72 Lemans with a 350, cast iron intake, q-jet. My heads (7H1, 91cc's) give me about 7.6:1 compression. I bought a Summit 2800 cam 204/214, .421/.444, 112 lsa. The car isn't on the road yet so I can't tell you how it performs. But if your heads are 96cc's, your compression will be lower than mine. I don't think either one of our motors will make any power at or above 5000 rpm's. But in a street car, do you need to rev that high anyway?
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post #3 of 5 (permalink) Old 05-15-2013, 09:59 AM Thread Starter
 
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Yeah was sort of afraid of the compression side. 8:1 seems sort of optimistic :/ Really sounds like I want to find some 1960s heads in a way. Or turbo this thing.
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post #4 of 5 (permalink) Old 05-15-2013, 08:53 PM
 
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1971 #94 heads are listed as having 8.0 compression using the factory #555 cam. However, in the Firebird bodies it is listed as 8.2 compression. The 555 cam is: Int. duration 269, Ex. duration 277, Int lift .374, Ex lift .406. For comparison, Pontiac had a really hot 330 HP 350 HO in 1969 which had a Q-jet, 10.5 compression, used #48 heads, and 067 cam (Int duration 273, Ex duration 289, Int lift .406, Ex lift .406). I suggest a factory LSA which was typically 113 for a broader power band. The 110 LSA will pull, but power can drop off fast. In my 400 w/7K3 heads, I used a 110 LSA cam, hydraulic lifters and at about 5600 RPM you can feel it drop off flat and anything more is just a waste as there is no more power, period. My next cam will be on a 112 LSA and I prefer solid lifters. Had a 1967 Firebird in 1978 with a 350 CI that supposedly had some head work, had a Q-jet, duals, and 3 sp manual. No problem dropping the clutch and smoking tires, chirping tires on a 2nd to 3rd shift, and I spun it to 6000 RPM - a lot. But that's me. Here is a tip from Jim Hand's book, page 39, "The cams with relatively early or advanced intake lobe centers will make the lower compression engines act as if the compression were higher, resulting in crisper low and midrange throttle response. That, in turn, can allow longer duration cams to be used without sacrificing the expected street driving capabilities." So cam timing is a big consideration along with lift and duration. Hope this helps.
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post #5 of 5 (permalink) Old 05-15-2013, 10:05 PM
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Mr Roboto,

The key questions for you to answer are, what are your goals for the car and what kind of budget do you have to get there? It won't take too long throwing money at a 350 until you will have spent more than it would have cost you to build a stroked 400.

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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

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