Cam knowlege plz.

[Kawtoom]

Hey guys,

I just inherited a 400 small block and I'm going to freshen it up, shove a nasty cam in it and stick it in my 69 longhorn. (the 396 was plucked out long before I got the truck and the current 283 isn't doing so hot)

The purpose of the engine build will be to make a fun Street and stoplight racer. Just a fun head Turner. And next summer I'll put 5-8psi on it through a single turbo, nothing crazy.

Here is what I can give you about the engine, I don't pick it up until the 29th so I don't have a casting number yet. But I do know it's a 2 bolt, pre 1986, "junkyard purchased" 400.

I plan on doing ARP Rod, main, and headstud bolts, boring it to a 406 and balancing the bottom end. I will be using stock re-finished crank, rods, and (possibly) pistons (all are probably iron) with a single plane torker 2 intake and a 625 cfm carb. it will have 2.5" exhaust and a 2500-3200 stall.

It currently has a turbo 400 and stock 14 bolt rear end with at least 373 gears, maybe even up to 410s. (3200 rpm in 3rd gear at 65mph)

My question is, what's the most aggressive cam that will not be useless or over the top? I want it to clack and lope as if it's struggling to stay running, but without high compression, and stock heads, I don't know what my limits are.

I like the sound of the lunati voodoo 286-292 but my cam knowledge is limited, and I don't know how to calculate the ideal lift/duration. What are your suggestions and most importantly, WHY?

[70blackfish]

you want to make power its all in the heads...install a big cam and do nothing else, you will have a pig.
its all about the right combo....

[bigmac73]

Originally Posted by 70blackfish

you want to make power its all in the heads...install a big cam and do nothing else, you will have a pig.
its all about the right combo....

I have to agree, in this case i would get a top end combo like what trick flow or edelbrock has to offer for SBC, and build the lower end to match the set up

[hugger6933]

Ok, first I know it is hard when getting and starting a new project but try and calm down a take a breath. Now you said pre 86 yes the 400 were only made till the late 70's so yes it is way pre 86. now keeping in mind that the 400 is a smog era motor and most of them were considered boat anchors [wait guy put away the torches and pitch forks] before the mid 80's when guys decided they could be made to do some wild stuff. Now the heads are gonna be the smaller valve thinner wall castings that don't have tons of hope if your wanting to make some crazy power. the intake is wrong as well you can do better with a newer designed Edelbrock dual plane RPM Air Gap, with a carb closer to the 750 or at least the 650 than the 625. Keep in mind that the motor is 56 cubic inches larger than the 350 that most people use to figure when they talk about intakes and cams and such. So a cam that may be just right for a 350 is gonna be a little on the smaller side for a 406. Another thing to keep in mind here is NOT to go to big on the cam because the camshaft will bleed off compression if too large and you will be wasting effort to make compression by different pistons and better heads and maybe even a turbo to have it bled off by over camming it. I had a motor in my street car chevelle. It ran like 8.20 in the 1/8 mile at a weight of 3860 with me in it and it sounded like a pro mod if you were listening and not looking. I put in a SMALLER cam and went back and ran a 7.76. The heavy car had a power glide and would still pull the wheels and go 1.40 short time[60ft]. So with that said I would have you look into a dual pattern cam of course like that of comps Extreme energy, I have had great luck with those. Also their dual energy cams they make a 275 that ran like Ape poop in another thing I had and still made real good vac for brakes[S-10]. Think on these things for a while also try to keep your stall lower than your cruise rpm or your trans will overheat kinda quickly and any time you put in a stall you need a cooler. Jim

[hugger6933]

You asked for it. If you need more let me know. Jim

[mmiddle]

That Lunati cam for a 400 is about right, however, I'm not a turbo guy so others need to chime in here that have knowledge of Turbo-friendly cams.

All little 400's where 2 bolt mains and cast cranks and 2 barrel carbs.

I would be a little hesitant to force induct stock heads and cast pistons with stock rings. Sounds like you are just begging to trash a piston.

[WIDESIDE72]

Originally Posted by mmiddle

That Lunati cam for a 400 is about right, however, I'm not a turbo guy so others need to chime in here that have knowledge of Turbo-friendly cams.

All little 400's where 2 bolt mains and cast cranks and 2 barrel carbs.

I would be a little hesitant to force induct stock heads and cast pistons with stock rings. Sounds like you are just begging to trash a piston.

Not all 400's were 2 bolt main, but that is irrelevent. 2 bolt mains are good for up to 500 with studs.

What was stated above about a cam being too big in a 350 being just right in a 400 is correct.

I had a 383 in a 79 Malibu a few years back with a Comp Xtreme 4x4 X4262H Hydraulic Flat Tappet Cam
Lift: .462''/.480''
Duration: 262°/270°
Lobe Separation Angle: 111°
RPM Range: 1300-5600

It was a BEAST with great torque!


My advice is to call Comp Cams tech line for advice. Be ready with a lot of info such as compression ratio, converter stall, final drive ratio, tire height, etc.

[mmiddle]

WideSide... are you sure on the 4 bolt 400's? I think I remember reading that all 400's where 2 bolts. never intended for performance like Hugger said.

Hugger... Great post. I always get a little fidgety with questions about cam/heads/stall stuff. I've pulled a lot of cams out because someone got starry-eyed and put a big-ol lumpy cam in.

Kawtoom. Think of your engine as an air pump. Heads and intake are critical along with the exhaust. Stock GM heads are crap without a bunch of work. The double humps are goods with work. The rare single humps only need to be cleaned up to be great. Most of the Aluminum heads are good as well with work.

[hugger6933]

As long as we are gonna talk about heads we need to mention the Vortec heads 96-00[+?] small block. Those heads were the best flowing production heads for the small block ever. They even outflowed the first gen bowties and lots of early aftermarket heads in stock form,and warmed over they are even better. Also we cannot forget to talk about the fact that if we are talking 400 we have to talk about steam holes. They have to be placed in the deck of the head or else overheating will ensue. The vortec will produce about 40 hp and 30 ft lbs over a regular production heads, head that it would replace and that has been proven time in and time out by every rag on the shelf, I guess except for Mustang 5.0 and they don't care. oh and while we are discussing the 2vs.4 debate, I belive there were both 4 bolt mains and 4 bbl carbs to be had possibly in the 4x4 truck. Jim

[Longhorn 70]

if you want to play and dream, Comp Cams also has a CamQuest Online tool that will help you select the right cam range before you call and ask the tech guys.

[trac209]

Hey hugger that's a real impressive 60 foot time for a 7.76 1/8 = to about 12 sec 1/4 mile time. Most cars that run 9-10s have those 60 ft numbers.
And on topic op don't forget that if your going to boost the truck later a turbo cam is way different from one you'd use to make power without boost. I'd call a reputable cam company and tell them exactly what your needs are going to be.

[cdowns]

how many miles are on this motor??

lots of times it is a complete waste of muney tryin to hotrod a himilage engfine without doing the whole thing from the groundup

[CC69Rat]

Yep, the heads are where it's at. Vortecs, 041's, Dart / Brodix if your budget allows. Then Id suggest a 286H 'Enforcer' cam from Cam Dynamics. I think Crane calls it the 282H (?) CD was bought out by Crane. 2800 stall. It would make a nice 'cha chunk' cam lick sound but still streetable. I had one in a 69 Camaro that sounded wicked. The 292H sounds good too and still (IMO) on the high end for the street.

[mmiddle]

Ok, I stand partially corrected anyway...
70-72 400's some were 4 bolt mains. Also some only had the 2 core plugs, but all had the boss for the third. All had an external "bulge" around #1 cyl.

I still can't find any information that leads to a 4bbl carb.

Production dates.... 1970-1980 only.

[Kawtoom]

Ok guys thanks for the many responses. No offense taken on any of them. Let's try and narrow this down.

I will be rebuilding the engine. So fresh bearings, bore, rings, and ARP EVERHTHING. This is a mild build. So I'm trying to avoid buying forged internals and thousand dollar heads. And in doing that, I know my power gains won't be tremendous. But can I expect 350hp without boost and 425 on 8psi? That's seemed reasonable with this setup. (barring the fact that the carb will be too small with boost)

That being said, I wasn't aware that old GM heads aren't great, I'm not very experienced with the 400 yet... So I'll start doing some head flow research. What is a good head to work with? A port job and bigger valves shouldn't break the bank. But heads get spend quick. I do know that the siamese blocks tend to run hot and struggle with overheating, so steam holes, oil cooler and a new radiator will be installed.

As for the turbo, I'm very experienced in this area, but again, not in the carbureted world... That being said, (and this is just an educated guess) I wouldn't think 5-8psi would be too big of a problem as long as detonation is kept at bay. But again, a 406 doesn't have a ton of cylinder wall, and in my experience, cast pistons and cranks are OK if the pressure, timing, and fuel tables are kept reasonable... I shattered the ring lands on a few of my first imports, but that was at 15psi...

Also, I know that I'll get more power out of a "turbo cam" but I can't imagine that a 292 with that kind of lift will be that bad will it? How much overlap will I be looking at?

All in all, I'm just looking to narrow down my search. If that profile is too aggressive, what is more my speed?

[mmiddle]

87 up aluminum GM heads are pretty darn good with some work. Port matching is a must.
The older heads have a major problem with the short-turn radii in the intake ports, even the vaunted Double Humps.

350HP at the crank should be no problem at all and still be mild. Run a well build Q-jet or a 750 vacuum secondary Holley, no matter what.

[BrianG]

Okay, please don't start sending your arrows my way, but a couple of quesitons. Aren't turbo's really most benifficial on a motor that likes to run a lot of rpm's? Is a 400 sbc, really a good rpm motor? I always though of them as a bettter torque motor. (long stroke). That's why many people will use a 400 crank in a 350 block to create a 383. Some benefits from either 'engine' without some of the negatives. IDK, but seems as though the two don't really mix well. Again, I'm sure there's a million opinions about this so be nice. Just asking :-)

[mmiddle]

400's are low RPM engines comparatively speaking, but high torque. To answer your question.... No, turbos are powered by air flow (exhaust). That is why diesels respond so well to them. My Duramax is 402cid (6.6L), max RPM is 3200 at which it defuels. Normal range is 1800-2300 RPMs. Max boost is 27psi, normal boost at 70 mph cruise unloaded and level ground is 3psi.

So no, any engine will work well with a turbo. This is why the Ricer crowd and the Coal-Rollers likes them so much.
Also consider aircraft... 4,5 or even 600cid turning a prop at 1800RPMs redline.