[TransAmRIP]

I'm in the process of having my engine bored 30 over and would like some help chosen a new cam. Nothing extreme just a little above stock. I have a 400 4 Speed with 6x-8 heads. I will keep the stock heads, intake manifold, carb. etc...I would like to have a nice little rumble. I know with these heads I'm limited on what I can run cam wise. I'm not cam savvy when it comes to internals.

Strictly street driven.
Any suggestion would be appreciated.
Bub

[pontibeast]

What is the rear gear ratio? That will help some of the more experienced guys help you out.

[Cliff R]

6X-8 heads are 101cc or very close to it. That means under 8 to 1 compression unless you whack the heads a bit, zero deck, thin head gasket and two valve relief pistons.

Still no problem making decent power with one of those engines. The best cam we've found for them is the Crower 60240. It spec's out at 270/276, 210/221 @ .050" on a 112 LSA. It's low lift so no special springs or installed heights required, they are fine with stock springs.

It will have a bit of "attitude" at idle speed, about 12" vacuum at 750rpm's, and strong power from right off idle to near 5000rpm's.

I ran this exact same combo years ago in my Ventura, it ran 13.78 at 101mph with 2.73 gears and a stock converter. Netted near around 16-18mpg's on the highway, and very user friendly for "normal" driving.......Cliff

[TransAmRIP]

Originally Posted by pontibeast

What is the rear gear ratio? That will help some of the more experienced guys help you out.

3.08

[STEELCITYFIREBIRD]

The factory 4 speed should have a pretty low first gear, that will greatly help to get the car rolling, a big plus for your deal!

[TransAmRIP]

Originally Posted by STEELCITYFIREBIRD

The factory 4 speed should have a pretty low first gear, that will greatly help to get the car rolling, a big plus for your deal!

any cam recommendations??

[STEELCITYFIREBIRD]

Nope

Cliff just gave you a tried and tested recipe, free, don't skip any ingredients!!

If your putting a good bit of $ into the heads and thin gaskets(~$200 pair), might try to find some smaller chamber castings to start with.... the recipe will likely change.

Don't buy pistons till you know for sure what your putting on for the top end!

I don't have nearly enough real world,hands on, proven Pontiac build combination experience to make a responsible, educated cam recommendation, sorry.

I do have some real small chamber head cores, but I am way to far away for them to be cost effective for you.

[pastry_chef]

http://www.claysmithcams.com/h-6474-...ppet-camshaft/

Hyd Flat
Advertised Duration : 264 Intake / 274 Exhaust
Duration at .050 : 214 in 224 ex

For some 'rumble' order the cam on a 108 LSA.

[ponyakr]

Just curious--Aren't the smaller Voodoo cams designed for low compression engines, like this, in order to increase cyl pressure ?

Or have they been proven not to work ?

Or, are most of you non-professional Pontiac engine builders now scared to post your opinions, for fear of negative comments from the pros ?

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

[footjoy]

Would the Summit cams 2801 or 2800 work in this application?

[pastry_chef]

Lunati Voodoo's are fine lobes.
Perhaps the OP wants a bit more rumble than that shelf cam.
https://www.youtube.com/watch?v=eVTlTFTuS18

Both Summit's have too much seat timing. 2800 too small @ .050

[Will]

Originally Posted by ponyakr

Just curious--Aren't the smaller Voodoo cams designed for low compression engines, like this, in order to increase cyl pressure ?

Or have they been proven not to work ?

Or, are most of you non-professional Pontiac engine builders now scared to post your opinions, for fear of negative comments from the pros ?

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

You tryin' to start an argument?

*In general* a small-ish cam on a narrow lobe separation will boost cylinder pressure in the lower RPMs. But even more important than the lobe separation in terms of building cylinder pressure is the intake closing point. Typically for the same duration the cam on the narrow LSA will have an earlier intake valve closing point which helps boost cylinder pressure.

Take two cams with identical intake and exhaust lobes, grind one on a 106 LSA and the other on a 112 LSA and then install them both on the same intake centerline and your cranking compression should be the same.

The LSA mainly affects overlap which affects how the engine will idle and how well it "breathes" in the mid- and upper-rpm ranges, in conjunction with other factors like intake and exhaust tract configuration/flow.

It's a fascinatingly complicated subject which is why there are so many opinions. My opinion is that it's highly combination specific. There are times when a narrow LSA will get the results you want, and there are times when a wider LSA would be the better choice. Intake and exhaust tract configuration as well as gearing, transmission/stall, and what you *want* the engine to behave like all are at play. But I'm no pro, I just do this stuff for a hobby.

Originally Posted by footjoy

Would the Summit cams 2801 or 2800 work in this application?

Yes. Without looking up the specs I believe the 2801 is closest to the specs of that Crower cam that Cliff recommended, which looks like a good choice to me.

[pastry_chef]

Originally Posted by Will

Take two cams with identical intake and exhaust lobes, grind one on a 106 LSA and the other on a 112 LSA and then install them both on the same intake centerline and your cranking compression should be the same.

I disagree.

Originally Posted by UDHarold

The intake valve closing point mainly tells where the intake valve closes.
Get your favorite cam grinder to grind 2 cams with the identical profiles, but with TWO different LSAs, say 106 and 108, or 110 and 112.
Install one cam in the engine, then dyno it.
Install the other cam on the IDENTICAL intake centerline, so that opening and CLOSING points are the same for both cams.
The cams will have different cranking compressions, different power curves. This is not to say one is better than the other, only different.
What effects the REAL dynamic compression is HOW MUCH air and gas is in the cylinder when the intake valve closes, not at what degree ABDC the valve closes.
The different exhaust opening points affect the amount of back pressure, ie, reversion, that is present when the intake valve opens BTDC. The amount of reversion affects the rate of cylinder filling on the intake stroke, and the amount of air and gas in the cylinder when the intake valve closes. This is what gives you the actual Dynamic Compression. The operative word is DYNAMIC.
Other cam designers may differ in opinion.

UDHarold

[Squidward]

OK... So we have Cliff with a real world Crower cam suggestion with real world results. We have Pastry Chef with a suggestion.

I use the Voodoo 702 cam in my 350. I love it, but that is a significantly different animal from the OP's 400.

I use the Voodoo 703 cam in my 400, but that engine has only been broken in, and the car is far from ready for any real world road reports. It also has compression in the 9's, so not apples-apples.

I have used the XE262 in a 6x-8 headed 400. It was a fun ride, but I had engine problems a few hundred miles after the build. I can't put a "worked great for me" stamp on it with 100% confidence. It was simply much better than the crap I had instead of being the ideal combo. Way back in the day, I was totally satisfied with an 066-cammed, 4x-headed 400. Not so much any more.

The XE262 seemed to be the "go-to" cam for low compression 400's on many forums out there years ago. But I am guessing that has changed since I never see it recommended in the last 5 years or so. There has to be a pile of low-compression 400 guys out there with good results, tho.

Anyone have more proven recipes?

[Squidward]

Originally Posted by footjoy

Would the Summit cams 2801 or 2800 work in this application?

I've used the 2800 cam in an 8-1 #47-headed 350 with total satisfaction, except for when the speed bug hit. I always imagined a 400 would like it, and might do more with that cam.

[Will]

Originally Posted by pastry_chef

I disagree.

Interesting. I would not have thought that at cranking speeds with small cams the reversion factor would come into play in a significant way, at least not without the engine running.

Sure would like to see someone actually do this and test it. Be curious to see how much of a difference it really makes.

[pastry_chef]

Originally Posted by Will

Interesting. I would not have thought that at cranking speeds with small cams the reversion factor would come into play in a significant way, at least not without the engine running.

At cranking its not reversion but less restriction.

[gtofreek]

I can't even remember the last time I built a low compressioned 400, so I can't give any real world suggestions like Cliff did. Sounds like he had one running pretty good.

All I can say is if i was building an engine like this, and it was just a cruiser, I would probably do something like this.
http://www.lunatipower.com/Product.aspx?id=1774&gid=287

Never been disappointed with a voodoo cam.

[HoneyHush]

https://www.lunatipower.com/Media/Im...r-Series_1.jpg

We put this cam in a throw together engine once. Stock 73 400 with 70 #15 heads. Stock intake with q jet, headers, 3" torque tech exhaust with flowmasters, 4.10 gears, and a Summit 2500 stall. 3800lb car on literally bald street radials pedaling to get off the line ran 13.20 @ 104. With sticky tires it would've ran well into the 12's as the 60' was in the 1.70s.

Not saying to run this cam but suggesting that your 400 can use some cam even though its low compression.

[HoneyHush]

cription

Hydraulic Flat Tappet Cam. Good for Pro Street. Needs 2500-3000 RPM stall converter, headers, 9:1 com- pression, 3.73 gearing. Rough idle.
Advertised Duration (Int/Exh): 285/285
Duration @ .050 (Int/Exh): 235/235
Gross Valve Lift (Int/Exh): .507/.507
LSA/ICL: 108
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 2000-6000
Includes: Cam & Lifters (#71951PR-16)
Part Number: 10510302LK
Previous Part Number: 07702LK
Jobber Price: $208.63