My friend is starting a budget 400 sbc buildup. His rough plan is:
- stock bottom end with flattops
- stock castings
- older Edelbrock dual plane
- Q-Jet
- 1 1/2" shorty headers
- 3.42 gears
- TH350 with stock or mild stall
- slicks

We have a slight difference of opinions when it comes to camshaft selection.
He is considering one of:
Comp 292H - 244/244 .501"/.501" 110*
Comp 286H - 236/236 .490"/.490" 110*

I think he'd be better off to go with something like:
Comp XE268 - 224/230 .477/.480 110*

I have two reasons for my suggestion. Most stock heads don't flow that well on the exhaust side. I think a split pattern cam would be more effecient. Also, I don't want to see him use a cam that is too big for the rest of the setup. With mostly stock components, he isn't going to have flow to support high rpms and he doesn't want to rev above 5500 regardless of peak power. My feeling is that if he uses too big of a cam he is going to shift his power band up where he isn't going to be able to make use of it. I would rather see him use a cam that allows peak power to be made at 5500 or less. This would allow him to make more low rpm torque which will actually be usefull. I think that the car would run better and likely be faster with a smaller cam. What do you guys think?

 

- stock bottom end with flattops: Thats fine for the mild rebuild. Make sure he uses ARP rod bolts.

- stock castings: what is meant by this? heads? if so, touch them up a bit

- older Edelbrock dual plane: whats the intake? shouldnt be a problem, though.

- Q-Jet: considering as most flow upwards of 750cfm and have HUGE secondaries; with proper tuning it should suffice.

- 1 1/2" shorty headers: those are too small. at LEAST 1 5/8" maybe even 1 3/4".

- 3.42 gears: should work
- TH350 with stock or mild stall: no problems

- slicks: this setup BARELY justifies slicks. its a waste of money. the cam selections are small ones. theres nothing overly aggressive that sticks out to me that justifies slicks. omit them and get good street tires.

Camshafts: remember, cams that may appear "big" in a 350 arent so big in a 400. For this setup, id look for a cam with a power range of maybe high teens,(like 1800) or so to mid 5000's (55-5800). the 268 is on the small side for a 350, let alone a 400. However, you are correct about the dual pattern grinds. They are ground that way to compensate for poorly flowing exhaust ports. The 274h is a pretty nice cam in a 350. Should be fairly at home in a very mild 400. You can always advance/retard the cam in order to fine tune the powerband. (4° shifts the powerband about 200 rpm either way; advance=down, retard=up)

 

I agree with Stekman for the most part...

For the cam, remember that the power comes from the heads...so if you are using stock castings, don't expect much flow. The cam simply determines the powerband of the engine, so select a cam that will enhance low end torque. Basically look at the powerband of a cam (from the manufacturer) and remember that they are based on a 350. So deduct about 500 rpm from each side to see how it would act in a 400.

The 268XE cam would be my choice and at LEAST 1 5/8" headers...

HTH,

 

i have a solid cam from crane cams. 280-288 duration and 518-536 lift. i think your friend should save up his money and build the motor the way he really wants to. the 400 sbc is a motor with alot of potential. i think if he builds it the ways you said above he is going to be disapionted if he ever dynos the car or brings it to the track.

here is a link from when i was looking at cams for my 400sb. hope this helps you.

https://www.thirdgen.org/techbb2/sho...+picking+a+cam

 

Why not suggest he send an email or call up Comp or Crane, or wherever he wants to get his cam from?

1.5" headers seem excessively small for a 400, too IMO.

BTW... where did he get this 400 from? I might be looking for something to build this summer.

 

Because if you call a cam company 3 seperate times, you will get 3 seperate answers...I know.

Also, if you read my post, I told him how to research which cam will work...the powerband thing really is the key.

Roller cams are more efficient but cost a lot more to upgrade to.

 

Thanks for the responses guys. I think he is going to go with stock heads for now because he wants the car on the road and aftermarket heads aren't really an option for him. The reason that he was going to use the 1 1/2" headers is because I am giving them to him for cheap with a y-pipe and they are a better alternative than stock manifolds. The engine is going in an 85 Camaro (base model). Basically, I see this being only slightly better than a stock 400. Even with more compression, a little bigger cam, and slightly better intake/exhaust, it'll maybe make 200 rwhp and be approaching 270-300 rwtq.

Thanks for the tip. I knew that a 400 will be able to handle more cam on the same setup, but wasn't sure what a good rule of thumb would be.

Adam: he picked up this engine for $300 CDN out of the Sask Auto Trader.

 

The free headers and y-pipe is understandable...and so is the budget...so don't go nuts on the cam...I would suggest something like the Performer cam for the 400 (not RPM)...

Good luck on it...

 

Do not go with any old style cams like edelbrock.. They plain suck and are much improved upon today.

 

Anytime I post a response where I don't spell it out...it comes back to haunt me.

Did you actually LOOK UP the specs for the cam I referenced? Use those as a start to maximize the torque of the engine...since it will run out of breath with the stock heads anyway...

Since you probably won't look up the specs anyway...they are approximately 214 @ .500 on the intake and 224 @ .500 on the exhaust with lift around .442 LSA of 112 degrees.

I would find a cam with more lift...depending on how the stock heads are setup...but that cam should drop in using stock components.

 

If you are referencing the Performer series cam for the 400 V8, its:

288°/288° Adv. duration
214°/214° @ .050"
.442/.442 lift with 1.5 rockers
112° LSA

I think what ME Leigh was getting at with these cams is the ramp rate. the lobes open/close the valves at a ridiculously slow rate compared to more modern cams ground by Comp or Crane. The slower ramp rates mean that the valve is at the higher, more usefull lift range for a shorter period of time. This makes the effective area "under the curve" very tiny.

Do not consider the edelbrock cams. Dont compare cams to them. Xtreme Energy or the Powermax (i like the Xtreme Energy grinds personally)