Stock 1968 400 rebuild ... Cam suggestions ? - Pontiac GTO Forum
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post #1 of 7 (permalink) Old 11-04-2017, 05:11 PM Thread Starter
 
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Stock 1968 400 rebuild ... Cam suggestions ?

Rebuilding my tired stock 1968 400 motor ... Keeping it stock except for a pair of RA3 exhaust mainfolds and Cam ... Car is a street cruiser with 2:90 highway gears and a rebuilt His and Hers automatic transmission with a shift kit ... AC, Power Steering, Power Disc Brakes ... Looking for a MODERN version of the "068" or the Ram Air III "744" cam ... Right now I'm leaning towards the (068) cam ... Any recommendations ?

Future Updates: Going to convert to EFI next year
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post #2 of 7 (permalink) Old 11-04-2017, 11:19 PM
 
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Originally Posted by flunkie View Post
Rebuilding my tired stock 1968 400 motor ... Keeping it stock except for a pair of RA3 exhaust mainfolds and Cam ... Car is a street cruiser with 2:90 highway gears and a rebuilt His and Hers automatic transmission with a shift kit ... AC, Power Steering, Power Disc Brakes ... Looking for a MODERN version of the "068" or the Ram Air III "744" cam ... Right now I'm leaning towards the (068) cam ... Any recommendations ?

Future Updates: Going to convert to EFI next year
Nice looking car.

First off, do you plan on keeping the 10.5-to-1 compression or lower it? Your cam choice can depend on compression. Do you plan on running race gas or do you want to run on pump gas?

The 068 cam is probably one of the best all around for a street engine. If you want to bump up power, then there are other options, but you may sacrifice some streetability and of course gas mileage. With a more radical cam you could get away with the 2.90 gearing, but probably want to go with higher stall converter.
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post #3 of 7 (permalink) Old 11-05-2017, 12:57 AM Thread Starter
 
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Nice looking car.

First off, do you plan on keeping the 10.5-to-1 compression or lower it? Your cam choice can depend on compression. Do you plan on running race gas or do you want to run on pump gas?

The 068 cam is probably one of the best all around for a street engine. If you want to bump up power, then there are other options, but you may sacrifice some streetability and of course gas mileage. With a more radical cam you could get away with the 2.90 gearing, but probably want to go with higher stall converter.

Thanks !

I am just doing a stock rebuild of my tired 400 ... I am not changing the compression ... car is a street cruiser, I will be using pump gas ... 2:93 gears, 17 inch tires, Rebuilt Auto Trans with shift kit, AC, Power Steering, Power Disc Brakes ... I already had RA3 Exhaust mainfolds on the car ... Besides using new Forged Rods and Pistons I wanted to upgrade the cam ... Is there a mordern version of the 068 with Better lobe profiles for increased performance without a loss in drivability ... or RA3 744 or something inbetween ?

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post #4 of 7 (permalink) Old 11-05-2017, 12:13 PM
 
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A cam choice has to match not only your engine build, but your drivetrain. If you read a few of the aftermarket cam manufacturers notes on the compression range, converter stall, and rear gear ratios suggested, then you can get an idea of where you want to go.

However, you can put any cam you want in your engine respective of what the cam grinder suggests. What you may find is that when you get into bigger cams is that the power band moves up the RPM scale, you give up lower end torque so the bottom end RPM suffers, and get upper end horsepower gains. This is why the cam grinders suggest higher stall converters and more gearing so your engine will jump right up to an RPM in which the cam is designed to "come on." So a cam designed for a 2,500 - 6,000 RPM range will give up power below 2,500 RPM's and add the stiff gearing of 2.90 gears and you may get a slug on take-off. Add a 2,500 RPM stall converter, and you at least get the engine up into the bottom power band of the cam and can pull the 2.90 gears better.

The 744 cam is more radical then the 068, but it was used for 4-speed application where you can get your engine up into the higher RPM's by slipping or dropping the clutch. The rear gearing on such a car would have most likely been 3.55's and better.

BUT, I am of the thinking bigger is better, so I might go with the 744
I would probably go with a set of Rhoads lifters to get back some low end power/torque, better idle & vacuum. Expect gas mileage to go down if gas mileage is of any consideration.

Apparently the Summit 2801 cam is similar to the 068 with a little more lift and if you wanted to go more, the 2802 seems to be the next recommendation.

Found this on the web:

"I ran all 3 of the Summit brand cams, 2800-2801-2802 in Pontiac 400 and 455 engines. The 2800 is way too small and runs out of breath too soon. the 2802 is bigger and lopey but lacks torque- and actually the 2801 would smoke either one of them. The 2801 in a 455 was a real tire burner and ripped your head off but ran out of breath at 5200 rpm as if it had a rev limiter on it- this was with unported D-port big valve 2.11/1.77 heads.
If I had to choose for a 400 it would be a 2801, but truth be told the 2801 is not a "clone" of a Pontiac cam, the duration seat to seat, and at .050" is changed, it's a more modern cam design, and also seems to have a tighter powerband- because mild stock GM Pontiac cams typically had a very wide power band, even the mild ones would rev high and keep pulling.
I'd run a stock 068 instead of a Summit 2801 to be honest. If I went to aftermarket it would be a Comp 268. The 2801 was a good cam but was kind of generic compared to the other 2.
Keep in mind the McKellar was a brilliant engineer and those cam specs came about after many days, months, years, hours on the dyno testing engines. He knew his schitt, and he was so good that there isn't much you can do to improve over his cams, even with modern technology- for a street driven Pontiac.

Now race is another story, the newer race cams whip the old stuff.

On the RA IV cam, John DeLorean thought it was a "piece of junk" (quote his words) because it killed torque below 3000 rpm- but it was basically a WOT drag racing cam developed for the 421 Super Duty with very low gears, and high rpm, and was first a solid cam #10, before they made it a hydraulic cam IV. So that tells you what the IV cam was really made for, drag racing with low gears and high 5000-6000 rpm peak."

Another suggestion would be to email any of the Pontiac engine builders on the internet and fill out their cam spec card and go with what they recommend.
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post #5 of 7 (permalink) Old 11-05-2017, 02:42 PM Thread Starter
 
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[QUOTE=PontiacJim;823458

Found this on the web:

"I ran all 3 of the Summit brand cams, 2800-2801-2802 in Pontiac 400 and 455 engines. The 2800 is way too small and runs out of breath too soon. the 2802 is bigger and lopey but lacks torque- and actually the 2801 would smoke either one of them. The 2801 in a 455 was a real tire burner and ripped your head off but ran out of breath at 5200 rpm as if it had a rev limiter on it- this was with unported D-port big valve 2.11/1.77 heads.
If I had to choose for a 400 it would be a 2801, but truth be told the 2801 is not a "clone" of a Pontiac cam, the duration seat to seat, and at .050" is changed, it's a more modern cam design, and also seems to have a tighter powerband- because mild stock GM Pontiac cams typically had a very wide power band, even the mild ones would rev high and keep pulling.
I'd run a stock 068 instead of a Summit 2801 to be honest. If I went to aftermarket it would be a Comp 268. The 2801 was a good cam but was kind of generic compared to the other 2.
Keep in mind the McKellar was a brilliant engineer and those cam specs came about after many days, months, years, hours on the dyno testing engines. He knew his schitt, and he was so good that there isn't much you can do to improve over his cams, even with modern technology- for a street driven Pontiac.

[/QUOTE]

Thank You ... Found the above very helpful ... Sounds like the stock 068 is the way to go for my mostly stock build and drive train with 2:93 gears and 17 inch tires !
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post #6 of 7 (permalink) Old 11-06-2017, 03:56 PM Thread Starter
 
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Going with the 9779068 cam

Classical Pontiac Camshaft Reference
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post #7 of 7 (permalink) Old 11-06-2017, 07:02 PM
 
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Originally Posted by flunkie View Post
Going with the 9779068 cam

Classical Pontiac Camshaft Reference

If this is your choice, I assume the Melling SPC-7 is the cheapest 068 clone. There are other brands. But I've read that they're all exactly the same cam, made by the same company, probably CMC. These are almost twice the price of the Summit 2801.

https://www.autozone.com/internal-en...amshaft/107135

https://www.oreillyauto.com/detail/m...s/spc7/4441260

https://www.ebay.com/itm/Melling-SPC...xXZuha&vxp=mtr

https://www.ebay.com/itm/New-Hydraul...oAAOSww9xZODlz

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

Last edited by bigD; 11-06-2017 at 07:14 PM.
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