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Discussion Starter #1
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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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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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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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-stock-valve-springs-400-455-389-350-428-GTO-Firebird/282243069072?_trkparms=aid=222007&algo=SIM.MBE&ao=2&asc=45729&meid=4af4e06f9e0c432a9c2a94e8fb9fc42f&pid=100005&rk=1&rkt=6&sd=282579700457&_trksid=p2047675.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-PERFORMANCE-valve-springs-400-455-389-350-428-GTO-Firebird-/282579700457?hash=item41cb100ae9:g:hvgAAOSwB4NW0LgK&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-Hydraulic-Lifters-Oldsmobile-Pontiac-260-307-350-389-400-403-421-425-428-455-/282591309766?hash=item41cbc12fc6:g:JDoAAOSww9xZODlz&vxp=mtr

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

https://www.summitracing.com/parts/cro-66056x3-16?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-crower&gclid=Cj0KCQjwierMBRCHARIsAHl9i4Fr_DS6lEDOEDbruOQrR02qyGgVbQcv2a0PxWsvlaYSpYKrM5wuNIMaAlNKEALw_wcB
 

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Discussion Starter #6
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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"...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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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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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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"...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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"...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..."

I think it would be very interesting to know all the exact specs of your custom, and the exact shipped price. There are lots of shelf cams which are less than $100. And, since there are lots of Pontiac shelf cams, from very mild to wild, it would be interesting to see how much your custom differs from the available shelf cams.

So, if you don't mind, your info might be helpful to some here.


"...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"..."

A custom would allow you to stick with the low lift, but increase duration, and get the LSA you want. An extreme example of this is the NHRA Stock Elimunator cam. NHRA sets a maximum valve lift, when using factory original ratio rockers. But, all other cam specs are legal. So, the cam grinders, especially CC & Bullet, grind these low lift cams with mild to radical lobe specs, depending on app. So, there are quite a few Pontiac Stockers running high to mid 10's, using cams with no more than .425 lift.

Here's some Bullet lobes that are available.

http://www.bulletcams.com/Masters/Hlobes.htm

Just as an example: Here are 2 of the Bullet lobes, a smaller one for the intake, & larger one for the exhaust, which might make a decent low lift cam for a low comp engine.

H268/272B 268 adv 214 @ .050 .2720 Lobe Lift x 1.5 Rocker = .408 Valve Lift

H277/273 277 adv 224 @ .050 .2730 Lobe Lift x 1.5 Rocker = .409.5 Valve Lift

That cam would have aprox 10° more exhaust duration, which many Pontiac engine builders recommend for unported iron heads. It would have just under .410 lift, which might work with press-in studs. And, with the lower adv duration, should help increase cyl pressure in a low comp engine. Then you could get the LSA you want. Most say a 112 will have a smoother idle & more vac. Opinions differ on the best LSA. The steep ramp CC XE series cams have a 110° LSA. But the similar small Voodoo cams have a 112° LSA. Some prefer CC, others prefer Voodoo. Anyhow, because of the higher lift & steep ramps, these cams may not work with press-in studs.

This lobe has .411 valve lift. Don't know if there would be any noticeable difference in this and the .409.5 lift lobe. Probably not.

H277/274 277 adv 224 @ .050 .2740 Lobe Lift x 1.5 Rocker = .411 Valve Lift

I don't have a clue what one of these Bullet customs would cost. Anybody have a total shipped price on a Pontiac HFT custom, of any brand ?
 

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It's important to remember that everything has to work together and it's very easy to get into a situation where you have to change more than just the camshaft. If you go with a cam that has more lift, for example, you very soon get to a point where you need taller springs to allow for the increased valve travel. That also usually means machining the spring seats in the heads. If you go with more overlap (this is what causes the lopey rumpity rump that you say you're after) then going 'too far' will also kill idle vacuum which will also hurt braking effectiveness with power brakes. The more you increase duration, the more you'll be shifting the power band towards the higher rpm ranges which will be accompanied by a corresponding loss in low rpm torque (not that Pontiac people have to worry as much about this as the bowtie brigade does). More aggressive opening and closing ramps, and more lift, means you need stronger springs to keep the valves under control.

Picking the right cam is serious business and it's easy to go down the wrong path. First things first. Be POSITIVE you know exactly which engine you have (lots of sites you can Google up to learn how to read the codes and find out), and also your transmission type, rear gear ratio, vehicle weight, etc, before you start.

Then I'd recommend calling up a vendor and discussing with them what you want with all that information available. Lately, I've spent a lot of time talking with the folks at Bullet cams and so far, I like them a lot. They've been willing to take time with me and hash things out, and I've never felt like they were rushing me.

Bear
 

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Lunati had priced the cams we were discussing at $140......,, the custom grindwas $190 ......shipping was $10-15 got Lunati lifters as well.

Lot's of off the shelf stuff for $99,.. so you don't have to get a custom grind. I wanted all low end, torque not horsepower and in the lower power band for a street cAr.,,, I like high velocity moving thu carb and valves for snappy and responsive throttle....do not want any high end above 5 thousand RPM don't race and never go there......

Too much lope is just as the guys describe, inefficiency at low RPM traded for high efficiency at HIgh RPM's, I get a nice exhaust note off the exhaust system and a solid idle as well with strong Vacumn and perfect timing curve, and AFR...

Cam is 108 Center line, at .050 231 intake, 239 exhaust.....adv 277 intake 285 exhaust, lobe sep is 112,.. 1.5 rockers, 9.1 compression

will be on a cast Iron all around 400, .030 over stroked to 460.....

Smooth and nice in the low end.....
 

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Ps the lift is .449 intake and exhaust,....

plan to put it in the engine and trans in car next week, so we will see how it does....
 

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Spot on Big D,....you know your cams and all engine building stuff

I was down at Butler this afternoon, they supplied cut the short block and supplied most everything including rotating assembly......the Butler/Schumann oil pump is quite cool....

All their stuff is first class they are stocked to the rafters and just great people who love pontiacs,....

I always compare prices and They are real competitive...

Their machine work is second to none, they zero decked the block, and do all the little extra things. They race prep it.

The gang on here, you, Pontiac Jim, Pinion head, Goat Roper, GEeteeohguy, really know that engine building stuff,...

I am not an engine builder so I love reading it, buy my friend is is an excellent Pontiac builder built this stroker in my garage,..and with him and Butler behind it..I am looking forward to firing it up next week....

David Butler told me it should have 550 ft lbs of torque.....:nerd::nerd:
 

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Been too busy today to get on here. After another page of responses, no one has touched on the fact a std bore, never decked '400 "99" headed engine is going to have less than 8-1 compression ratio, & the stock "99" casting heads have poor low lift flow numbers. Just don't get the putting a rowdier cam in such an engine, or even spending the $$$ to put guides & a good valve job in a pair of "99"s... Need to dig out my Pete McCarthy book, but isn't an 066 cam what would have come stock in a '71 400 2bbl?

Any reason not to watch for a good deal on some barely used .030 -.035 milled 5C-4's or 6X-4's? Both have much better low lift flow numbers, already have hardened ex seats, screw in studs, & would provide better performance with several of the cams mentioned.
 

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PH:" but isn't an 066 cam what would have come stock in a '71 400 2bbl?"

Read my post above, it is the "555" cam that is shown for that 1971 engine which is a little tamer.
 

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PH:" but isn't an 066 cam what would have come stock in a '71 400 2bbl?"

Read my post above, it is the "555" cam that is shown for that 1971 engine which is a little tamer.
Both smsll factory cams are extremely tame, we are still speaking of a very low compression 400 engine which "might" put out 200-220 net hp. Low lift head flow is what is holding this engine back, my point is adding either of the above cams is not going to amt to much gains.
 

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"...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?..."


If I understand what the OP said, he is not interested in any big power gains. He just wants a noticeable idle sound, and low end torque and power.

Probably don't need to make power past 4000-4500 rpm.

That would be easy, except for the press-in studs. I'd consider a screw-in stud conversion or changing heads "extensive modification".

I realize that there have been lots of guys who have somehow got by with fairly large cams, with press-in studs. BUT, some studs have been pulled by small cams. So, increasing cam size and/or valve spring pressure COULD possibly pull a stud. Therefore, the safest decent cam might be the 066, or maybe the 068 at the very biggest, of the shelf cams. Some might not like an 068 in a low comp engine. But, they were used in the low compression 455HO engines.

If the adv duration of the 068 is a little too much for the low CR 400, some Rhoads lifters should fix that, if the OP don't mind the Rhoads lifter "tick". This would make the 068 more of a steep ramp cam, at very low rpm, giving it a little more vac and very low rpm torque, plus more power at 4000 rpm than the 066.

The only other possibility I see, for a very low lift cam, is a custom, as mentioned. The 744 clones have low lift & provide a nice lumpy idle. But, with 301/313 adv duration, some say these require stronger springs, which will put more pressure on the studs. Also, without Rhoads lifters, this cam may not make enuff vac for power brakes, and won't have the off idle torque of the 068. BUT, IF the 744 would not pull a stud, I'd choose it and Rhoads lifters, over the 068. It won't have as much low end, but will have a lumpier idle & more power from 4000-5000rpm.

Again, without the stud problem, I'd recommend the Voodoo 256, to build cylinder pressure. But, I don't know if that cam would pull a stud or not. ???

I've used the 068 & 744. But the engines had 10:1 CR or more. So, I can't say from experience how they would act in a low comp engine.
 
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