[ponyakr]

Hello guys so I am getting my hands on a 1977 pontiac 400 for my firebird. I was of putting a new performance camshaft before I install it in the car. I was looking at summit racing but they have so many and I dont know which one would be the best for the engine being stock and all that. I am not expecting much from it I just want it to add a bit more power.
Anyone with any suggestions

Thank you

Everybody seems to have different opinions when it come to cams. You didn't mention what the motor is going into. If it's an auto tranny car, the cheapest decent cam would be the Summit 2801. But if you use this cam, you'll have to use new springs, cause it has more lift than a stock cam. With stock springs, a duplicate of the 068 Pontiac cam is about the biggest thing you can get by with.

Now, if the car is a 4-speed sick, the Summit 2802 will work (with the appropriate springs). The biggest thing I would consider is a RA4 duplicate, such as the Melling SPC-8, and then only with Rhoads RL-9518 lifters to smooth out the low end a bit.

While the motor is out, it would be a good idea to have some taken off the heads to increase compression. If you take .050 off the surface, also have them take .050 off the intake port side so that the intake manifold will still line up correctly. I don't know what your budget is for this project, but one thing leads to another. While they're doing the heads, it's good insurance to buy new stainless steel valves to replace the almost 40 year old ones.

And if you do this, since you'll need new head gaskets, you can buy the .027 thick Cometics, with a 4.160 bore and increase the comp a bit more. All this extra comp will help to "add a bit more power".

Also be sure to use polylocks, and adjust the rockers to no more than 1/4 to 1/2 turn below 0 lash. Some roller tip rockers, like the PRW's will help prevent wear on the valve tips. Well, I won't take this any farther. But you can see how one thing leads to another, and can quickly blow your budget.

If you wanna price any of these items, from somewhere other than Summit, I'll help you find the best prices.

 

[ponyakr]

thank you Ponyakr the engine is going in my 1980 firebird currently i have a 71 pont 350 and i don't like it. I am hoping the 400 will wake up the car a bit. The 400 its going in with a th350 or th400 i have both i just got to decide, i know the th400 is better but if i go that route i have to change the driveshaft or at least the yoke. On the camshefts you were talking about the springs how do i go about and buy the right once could i get them on a camshaft kit??

Most of the high $ cams are available as a kit, with springs. But I'm not aware that any of these cams I mentioned are.

When I get time later tonite, I'll look up several choices and post that info for you.

Unless you run a loose converter ( say at least 2500 rpm stall ), the 2801 Summit is probably the biggest cam you'd be happy with. More later.

 

[ponyakr]

I prefer the XE series cams from Comp Cams but on a budget Summit cams are ok...

I've read that the XE series cams have much steeper ramps than older style cams. That means that they will open the valve faster and close it harder on the seat. This also means that a stronger spring will be required to keep the lifter in contact with the cam lobe. These 2 things combined will put more stress on the valves. So, if you go with this type cam, I'd consider it mandatory that you buy new stainless steel valves.

They are good insurance, even if you are going to use an older style cam with a bit higher lift, requiring stronger springs. Remember, if your valves are original, they are nearly 40 years old and have been thru many heating and cooling cycles. Many people get by with using them, but some don't. A friend of mine tried it and the head popped off one of the old valves and wiped out his motor.

 

[ponyakr]

Thanks alot guys. One more question sorry if its a dumb one. I was told that the engine i am getting is the w72 one which is the last of the 400 built and i guess it was a good performance one. The compression ratio on them its like 8.2:1.0 with what i could find, the summit cam 2801 requires a 9.0:1 or higher ratio i believe. Will this still work or do i have to shave off the heads a bit to raise the compression ratio. I am planning on doing that regardless I just dont know how much it is gonna raise

Yes, you can take enuff off the heads to get to at least 9:1 comp on a 400. Here's a 400 which Len Williams sells, with 6x heads, that he says has 9.25:1 comp.

http://lenwilliamsau...Long_Block.html

And here's just one site that shows some of the Cometic .027 thick head gaskets that will increase the comp a bit more.

http://www.spottsper...0head%20gaskets

I think they are available in a 4.160 bore size which will further raise comp. A .027 thick gasket with a 4.160 bore size will probably have to be special ordered. The cheapest place to buy Cometic gaskets may be to have Summit special order them for you, and have them drop shipped from Cometic. I'm not sure about that. You may be able to buy direct. I'll try to look into that further. But anyhow, a little over 9;1 comp will increase performance but still work with pump gas.

There is a site with a system for approximating your comp ratio with different combos. You just have to plug in your specs, such as chamber volume, bore size, stroke, piston valve relief or dish volume, distance from top of piston to deck, gasket crushed thickness and bore size of the gasket, etc. But you'll hve to know all these specs to use the site. For example: you or someone will have to check the head chamber volume. Cause you don't know for sure whether your heads have been milled before or not. Anyhow, I'll look up that site and post it here.

http://www.wallacera...om/cr_test2.php

 

[ponyakr]

OK, here's some cam prices I found.

The best price I found for an 068 duplicate is a Melling SPC-7 from Auto Zone

http://www.ebay.com/itm/AUTOZONE-SPC-7-Camshaft-/251373486801?_trksid=p2054897.l4276

Of course the Summit 2801 is cheaper and has a bit more lift.

http://www.summitrac...-2801/overview/

http://www.summitracing.com/parts/sum-2802/overview/

http://www.ebay.com/itm/AUTOZONE-SPC-8-Camshaft-/251430113412?_trksid=p2054897.l4275

Summit always has the best price on Rhoads lifters.

http://www.summitrac...ew/make/pontiac

 

[ponyakr]

Now springs can be a bit tricky. I'll start with some that will work with the 068 cam. It has barely over .400 lift, so you can get by with fairly light springs. Somewhere between 90-100lbs is plenty of seat pressure. And somewhere around 250lbs or a bit less of open pressure will be plenty for this cam to turn 5000 rpm safely. It won't make power much past that.

http://www.fastengin...et-1967-79.html

For the XE268 cam, CC recommends 995-16 springs. They should work for the Summit 2801, 2802 and the Melling SPC-8 RA4 grind. I'll show these and others similar.

http://www.summitrac...6/applications/

http://www.ebay.com/...b5ec3#vi-ilComp

I personally like the specs on these Crower springs. They should drop right in, and give plenty of seat and open pressure with stock length valves on the 6x heads.

So, I have to recommend these Crower # 68404-16 springs.

http://www.summitrac...6/applications/

 

[ponyakr]

hey guys the the engine foes have the 6x heads, i found some 66 092 heads but they are from a 421 engine, they have 70cc chambers and 10.75 c.r. I am just worried that they might not fit anyone has any insides on this?? Joe i have the 3.23 in the back you think that will be an issues ??

That's WAY too much comp for pump gas ! And I've read that if you go with early heads you also have to get hardened valve seats installed to work with unleaded gas. I just don't see how you could come out any better or cheaper than going with the 6x or 5c heads, shave 'em and use the thin gaskets too raise your comp. Usable cores are available for $200-$300 most of the time. Less if you look around locally and don't have to pay freight. They came on most all 350's and 400's from around '74 thru '79. So that should make the 6x the most common head around.

 

[ponyakr]

http://books.google.com/books?id=O--NmlNfSYwC&pg=PA73&lpg=PA73&dq=whats+the+most+compression+you+can+run+on+a+pontiac+motor+with+pump+gas&source=bl&ots=AHjusCfce2&sig=nhx1oFDXxRSrp4znVPRMFEE3RBQ&hl=en&sa=X&ei=eRQBU43ZJY37kQfBzYGQCA&ved=0CFUQ6AEwBA#v=onepage&q=whats%20the%20most%20compression%20you%20can%20run%20on%20a%20pontiac%20motor%20with%20pump%20gas&f=false

http://psp.aquacomp.net/topic.asp?TOPIC_ID=1803

http://forums.highperformancepontiac.com/70/9599907/drivetrain-restoration/maximum-safe-compression-ratio-for-premium-pump-ga/

http://transamcountry.com/community/index.php?topic=52770.15;wap2

You can go online and find LOTS of arguments, back and forth about max compression with pump gas. Many insist on certain cams so they can "get by" with more compression. And many will brag about how they have run 11:1 for years without any problems at all. Then there are many engine builders, and people in a position to know who recommend 9.5:1 as the max SAFE comp with today's pump gas. I don't personally know who's right and who's wrong. But as for me, I choose to err on the safe side. Especially with a 455, why push the limit just for a few measly HP. Just stay under 9.5:1, be safe, and enjoy 500 ft lbs of torque on pump gas. Or run over 10:1 with iron heads, but make sure you have EXACTLY the right cam and tune, and do so at your own risk, knowing that many engine building experts recommend 9.5:1 max. I have no problem with those who choose to run high compression. Hey, if that's your bag, "knock ya self out" !

 

[ponyakr]

Can someone tell me what the difference in these two cams would be and what might be better with a 69 400 with KRE heads? I am a little confused about some of the numbers, mostly with Lobe Separation and Intake Centerline as to what they mean and what is better to have. Thanks in advance!

Comp Cam HR
Intake Duration at 050 inch Lift:224
Exhaust Duration at 050 inch Lift:230

Advertised Duration:276 int./282 exh.

Valve Lift with Factory Rocker Arm Ratio:0.502 int./0.510 exh.

Lobe Separation (degrees):110

Intake Centerline: 106

Grind Number:XR276HR-10

Lunatic Voodoo Retro-Fit Hydraulic Roller Cam

Advertised Duration (Int/Exh): 270/278

Duration @ .050 (Int/Exh): 219/227

Gross Valve Lift (Int/Exh): .515/.530

LSA/ICL: 112/106

Valve Lash (Int/Exh): Hyd/Hyd

I'd say go with the smaller cam for a 400, the larger for a 455. The higher LSA of say 112 usually will provide more vacuum at idle, which can help with vacuum power brakes. I won't even attempt to get any farther into cam technology than that. There is certainly plenty of online details about cam technology you can read for many days.

 

[ponyakr]

Thanks Don, but how much vacuum am I really giving up going with 112 LSA vs 110 LSA? If I understood correctly some of the info I read, and I by no means understand all this stuff, but the greater the gap between the LSA and ICL (is that overlap?) means leass vacuum?

No, the LSA is what will affect vacuum. If you'll look at the specs for some racing cams, you'll find that some are 108 or less. This is supposed to increase top end hp, I'm told. If you'll look at some of the LSA'a for factory Pontiac cams, you'll find some of them to be 113 and even higher. They are meant for street operation, low end torque and enuff vac to work the brakes. When I have time I'll try to find a link that explains it all better.