Cam question for '66 GTO with '72 400 - Pontiac GTO Forum
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post #1 of 20 (permalink) Old 08-21-2017, 01:18 PM Thread Starter
 
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Cam question for '66 GTO with '72 400

Hi everyone,

I have been thinking about purchasing a cam for my GTO, but have no idea where to even start. There is so much information out there about intake/exhaust duration and lift, valve springs, lifters, etc. and I am just totally lost. I love the sound of a lumpy/lopey cam, but don't want to go so aggressive that the idle is overly rough, and since this is solely a street cruiser, I would prefer a cam with more low to mid range power/torque over a high RPM screamer. Is this a possibility without other extensive modification?

The engine is out of a '72 Trans Am and other than adding a new Holley 650 carb, headers, and 2.5" exhaust, everything is stock (to my knowledge). It has an auto trans. The engine was in the car when I bought it. I am unsure of compression ratio, gearing, and other important things like that, but it seems like companies like Crower or Comp Cams make hydraulic, flat-tappet cams that will basically fit any Pontiac V8 from 265-455 from the '50s to the '80s...?

What should I be looking for, and do you have any recommendations? I apologize if this is way too broad of a question.

Thanks!
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post #2 of 20 (permalink) Old 08-21-2017, 03:37 PM
 
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On the engine, it actually needs to be fully identified. No 400's were factory installed in '71 or '72 TransAms, instead TransAms built these two model years received true (round port) 455 HO's. To ID what cast iron components your engine is made up of, below is a link to John Wallace's Pontiac site. Poke around on his site for awhile, aquainting yourself with how to ID what heads you have. Besides IDing the cyl heads, the two letter block code, as well as the alphanumeric casting date back by the distributor hole are needed to know what your engine actually is. For cam recommendations, it also doesn't hurt to know what ratio of gearing is in your '66.

Pontiac V8 Cylinder Heads
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post #3 of 20 (permalink) Old 08-21-2017, 04:06 PM
 
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Yeah, as P h said, you need to know what heads are on it. If it does have '71-'79 400 heads, a Voodoo 256 will be very streetable, and will increase cylinder pressure and power. A Voodoo 262 will make more power, at a higher rpm, but will have slightly less low end torque, the idle will not be as smooth.

The 256 might be hard to beat, for what you are wanting, IF you have low compression heads. Some of the low comp heads used from 71-'79 are: 96, 4X, 4C, 46, 5C, & 6X, plus a few others. As said, it's best to get your block casting number, date code, block code, and head numbers.

Voodoo Hydraulic Flat Tappet Cam - Pontiac V8 256/262 - Lunati Power
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post #4 of 20 (permalink) Old 08-21-2017, 08:39 PM
 
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cam

I'm at this same point with a 1972 stock 400. You mention it won't idle smooth. Is it tolerable?
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post #5 of 20 (permalink) Old 08-21-2017, 09:10 PM
 
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That depends on your definition of "tolerable". The 256 will have a fairly smooth idle. But, the 262 will still be what I'd call "tolerable". Lunati describes the 262 idle as "choppy".

http://www.lunatipower.com/Product.aspx?id=1775

The 262 will need, at the very least, some CC 988-16 valve springs. CC recommends these for their similar XE262 cam. For anything bigger, they recommend stronger springs. Many Pontiac guys recommend Crower 68404-16 springs, for the 262 Voodoo. The 988-16 springs should be good enuff for the 256 Voodoo. These springs from Spotts, should work great with the 256.

http://www.ebay.com/itm/Pontiac-V8-s....c100005.m1851

Here are some Spotts springs for higher lift cams, which should work for the 262. They're a little cheaper than the Crower springs.

http://www.ebay.com/itm/VSH3-Pontiac...NW0LgK&vxp=mtr

Just curious. Does your "1972 stock 400" have the 7K3 4-barrel heads ?

The reason I'm asking is because the 7J2 2-barrel heads have press-in rocker arm studs. Sometimes, performance cams can pull out a press-in stud. But, some have got by with it.

You'll need new lifters. Spotts has some nice lookin stock type lifters for $59 shipped.

http://www.ebay.com/itm/New-Hydrauli...xZODlz&vxp=mtr

These Crower Cam Saver lifters splash extra oil on the cam lobes.

https://www.summitracing.com/parts/c...MaAlNKEALw_wcB

Last edited by bigD; 08-21-2017 at 09:54 PM.
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post #6 of 20 (permalink) Old 08-22-2017, 07:47 AM Thread Starter
 
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Thanks for the replies. The code on the heads looks like it could be 99, which is actually a '71 400 according to Wallace Racing... 98cc 1.96/1.66 valve size. Would that be 9:1 compression ratio? Still not sure on the gearing. I looked for an axle code but may have been looking in the wrong spot. Seems like the 256 cam will probably be the way to go.
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post #7 of 20 (permalink) Old 08-22-2017, 09:23 AM
 
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"...98cc 1.96/1.66 valve size. Would that be 9:1 compression ratio?..."


That all depends on the other engine specs. Here's a calculator. You must plug in your actual engine specs to get an accurate CR number.

Compression Ratio Calculator - Wallace Racing

But, 98cc heads on a flat top piston 400, will have closer to 8:1 CR than 9:1.

Those are small valve, press-in stud 2-barrel heads, unless somebody had bigger valves and/or screw-in studs installed.
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post #8 of 20 (permalink) Old 08-22-2017, 09:03 PM
 
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The engine appears to be a 1971 400, 265 HP with 8.2 compression. The limiting factory is the heads with press-in studs and smaller valves.

The lower compression engines respond better to the tighter 110 Lobe Separation Angle (LSA) cams to build a little more cylinder pressure. Many Pontiac factory cams are ground on wider LSA of 113 degrees or so. You can get an aftermarket 110 LSA ground cam, but they go into higher lifts that may be too much for the press-in studs.

However, looking at the factory cams Pontiac produced, the factory "066" cam looks to be a possible fit that will give a little more performance if just the cam change is all you are looking to do. The cam has about a 111 LSA and has more duration on both the intake & exhaust valves, more lift on the intake valve, and more overlap than the "555" cam which should be in your 1971 engine if stock. The "066" cam was used on low 7.6 compression 389 automatic engines in 1966 as well as the 10.5 compression 389's, but was also used in other engines throughout the years.

Using the "066" cam should not require new valve springs as the exhaust lift of .406" is the same as the "555" cam and the intake lift on the "066" is .406" while the "555" is .374". The springs on your heads should be the same, intake & exhaust, so the extra lift from the "066" intake valves should not be a problem, just get matching lifters to go with the cam. Again, the cam supplier should be able to advise you on all this.

This would be a slight improvement in HP/torque over what you have, but you can also email a cam grinder or Pontiac engine builder with your engine specs and ask them to suggest a cam grind for you.
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post #9 of 20 (permalink) Old 08-23-2017, 07:22 AM
 
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This is great advice from the gang,....I just had lunati grind me a custom cam,...you will be surprised how little extra that is from an off the shelf grind,..$40 or $50...

Get all your engine specs together and know your driving desires and call lunati techs, great help and they will set you up with cam and lifters etc,....I am sure crowed, comp etc can as well...

Then it will be set for what you want exactly...
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post #10 of 20 (permalink) Old 08-23-2017, 10:36 AM
 
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"...the factory "066" cam looks to be a possible fit..."


The 066 clone is sold under at least 3 different brand names, probably several more. I assume that all the brand names are exactly the same cam, cast & ground by CMC, and sold to the different vendors.

The Melling part # is SPC-4. The Sealed Power # is CS641. The Enginetech # is ES641 You can search these part numbers on Ebay, to find the best price, at the time of purchase. Here are Ebay listings for the 3 brand names mentioned, but not necessarily the best prices available.

Melling SPC-4 - Stock Engine Camshaft | eBay

ENGINE CAMSHAFT CS-641 2291626 1965-1976 Pontiac 350CI 389CI 400CI 428CI 455CI

Engine Camshaft Enginetech ES641 fits 65-66 Pontiac Catalina 6.4L-V8
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