Cam for 8.2:1 350P - Pontiac GTO Forum
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post #1 of 9 (permalink) Old 08-13-2014, 03:12 PM Thread Starter
 
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Cam for 8.2:1 350P

Hi, guys.

I need help picking a camshaft for my 74 GTO. I rebuilt this engine in 1999 using a chevy machine shop. I picked a cam that is way too big for a 350. It's been a turd ever since. I've managed to put about 3000 miles on it since then. Please help me pick a good street cam for my 350. Street only, no race.

Here's some info on the engine 350P +.030, forged pistons, stock rods, balanced, heads are original #46 96cc milled .080 (chevy shop); they are maybe 80cc ish now. I can't remember. So maybe 8.0-8.4:1. 1.52 roller tips, headers, q-jet, HEI 3.08 posi, Saginaw 4 speed, power brakes.

The current cam is clevite K1270 230/230 480/480 way too big for the 350. It finally comes alive a little above 3000-3500.

I kept the original 46 heads because it's a numbers matching car. The chevy experts who helped me in 1999 bowl ported the heads and helped with cam choice.

I've had this car since high school. Always a pooch, I got bad advice from the SBC shop that helped freshen it up in 99. The engine was first built in maybe 1988, I still have the cam from that build it's close to the Summit 2801 and was probably too big for it then, causing the Turd drivability from day one. I'm debating on just trying that cam again now with the higher compression and mild port work.

Now I want to fix it and drive it. 3000 miles in 15 years is neglect.

Another forum recommended the Crower 60240, will this cam make up for the low 8.2 compression? I read good things about the XE series on low compression Pontiacs. This will be just street driven cruiser. I'd like to be able to do a burnout leaving dairy queen.

I'm leaning towards the XE256H to build some compression and give it good low end.

Any other cam recommendations for this combo? Thoughts on XE262H?
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post #2 of 9 (permalink) Old 08-14-2014, 05:20 AM Thread Starter
 
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I found my cam card from my first rebuild back in the late 80's it specs out the same as a current Summit 2801. The old cam is a general kinetics P1H-272-P 214/224 442 465 on 112. I think this is still too big for my little Pontiac 350. Any recommendations?
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post #3 of 9 (permalink) Old 08-14-2014, 05:23 AM
 
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I'm using a Lunati Voodoo 901 in my 9.0 compression, mildly ported 326, it pulls strong from off-idle thru mid-range, but the power starts to fall off at about 4,700 rpm. Great for street driving if you ask me, and works with my M20 and 3.08 gear. Idle a little bumpy at 900 rpm. Dyno simulator says my setup makes 310 hp, 360 ft-lbs, I think that's a little optimistic, but not far off. The Voodoo line is similar to the Extreme series, I think, short adv. duration compared to the 0.050" duration so you get good breathing with a fast-closing intake valve.
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post #4 of 9 (permalink) Old 08-14-2014, 09:16 AM
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Is your car a stick or an auto? What rear end? Have a friend who installed an XE cam in a low compression 389 and the thing flat out hauls the freight. I think with the smaller 350, you are thinking in the right direction. Weather it's a xe256 or xe262 depends on the trans and rear end ratio, to some degree, thought. Cams act 'bigger' in smaller engines and 'smaller' in bigger engines.
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post #5 of 9 (permalink) Old 08-14-2014, 09:44 AM Thread Starter
 
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74 GTO, Saginaw 4 speed (not sure which one), 3.08 POSI, 225/70R15

Thanks for the advice. I'm leaning towards the XE256H, maybe the summit 2800, or crower 60240. I have about 8.2-8.4:1 compression on a +0.30 350, 46 heads with light bowl work. Q-jet with headers.

Dean
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post #6 of 9 (permalink) Old 08-14-2014, 11:58 AM
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I think the XE256H would be a good choice. But by all means, do as much 'homework' as you can to make the best decision.
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post #7 of 9 (permalink) Old 08-14-2014, 06:54 PM
 
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Don't know if this helps, but you might use this as a base line. Here is the factory cam specs for a 1968 Pontiac 350CI, 9.2comp; [email protected], 355 [email protected] It is known as the "254" cam.

2 bbl, 3/4-speed, 3.08/3.23 gears.

Intake Opens 22BTC
Closes 67ABC
Duration 269
Exhaust Opens 72BBC
Closes 25ATC
Duration 277
Valve Overlap 47degrees
Valve Lift .412

Now the base 8.6 Compression 265HP 400CI 2bbl (regular gas)engine uses the same camshaft as the 350CI above.

The HO 350 4 bbl, 10.5 comp, [email protected], [email protected] shows 3.36 gearing for 3/4-speed, and 3.23 for automatic.

The cam used is the "066" cam in the automatics and the "067" for manual transmissions. Also used in the 400CI engines. But, you can see it took advantage of the higher compression and Q-jet carb.

Pontiac factory cams are typically ground on a 113-116 LSA. The Competition Cams XE cams are ground on a 110LSA which seem to work very well with lower compression engines -very snappy and pull strong, just a geeteeohguy mentioned. Had one in my low compression 1972 400CI and it pulled great -I was happy with it all considering. The only draw back is that when it hits maximum RPM, the power drops off noticeably and any more revs of the engine is a waste of time. My cam seemed to drop off about 5600RPM's. I could wind it more, but no real power. I think you might be pleased with one of these grinds -but just my opinion.

I would talk with Competition Cams on an XE grind for your 350CI. A Pontiac cam is different than a Chevy cam, you don't want the same duration on the intake and exhaust. You need more duration on the exhaust to help with the poorer flow characteristics of the exhaust side. Remember, the more duration you have, the higher into the RPM band the engine will need to go to use the cam. Just have to decide what you want your car to do as no cam does it all.
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post #8 of 9 (permalink) Old 08-15-2014, 08:36 AM Thread Starter
 
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Thanks everyone. I ordered a xe256h last night. It'll take a few weeks to find the time to slip it in. I really think it will wake up the engine. I like the lope of the 230/230 can I have now. But its way too much for my little 350.
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post #9 of 9 (permalink) Old 08-15-2014, 05:00 PM
 
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Originally Posted by Dean Benson View Post
Thanks everyone. I ordered a xe256h last night. It'll take a few weeks to find the time to slip it in. I really think it will wake up the engine. I like the lope of the 230/230 can I have now. But its way too much for my little 350.
Good deal. I think you will like it. Let us know what you think of the cam. We don't get too many low compression Pontiac 350CI engine questions and it would add greatly to the forum archives.
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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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