Max lift stock 452 + cam for smog '77 400

Metalmarty

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Hi All,

I've got some basic questions I can't really find the answers to.
Not a lot of people use the 400 engines, and almost every post I can find about this engine is people saying "up the compression". I agree, the late 400 engines have shitty low compression. But it's what I have and I don't have the money to play with higher compression ratios. And these engines can still be a lot of fun.

And remember, I'm from the country where people drive 60ci cars with not a lot of horsepower. :lol:

To answer the first to be asked questions:
I've send multiple Cam manufacturers a message, but I want to hear some experiences.
This is a cheap/budget build.
No I'm not taking the heads off to up the compression.
No I'm not replacing the heads. :)

I've got a '77 Chrysler 400 engine for in my '68 Newport.
(original 383 too expensive to fix at the moment).
I'm thinking of swapping the camshaft before the engine goes in.
Not looking for a lot of power, just for a bit more than stock.
I'm just not sure if it's worth it with this engine.

Thumpr/Whiplash cams are always advised for low compression engines, but I don't think I can get away with one. I have power brakes and I'm planning to keep them!

Some specs:
- stock 1977 400 engine
- 135-150PSI on all holes
- edelbrock DP4B intake with rebuild edelbrock 1406 600CFM carb
- New electronic ignition system (distributor, coil, leads, box etc)
- Hedman 78070 short headers
- Dual 2.5" exhaust
- 2300-2400RPM stall converter
- 3.23 rear gear
- Power brakes

Is it at all worth it to swap out the stock cam in this engine?

It has 452 heads on it. What is the max lift (on average) on these heads?
Can you always get away with .480-.500 lift or it that already cutting it close?

Sorry for another cam thread. I'm really looking for experiences. :)
 

413

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Just drive it like it is. Leave the cam alone, or use the cam from your 1968 383.
 

CBODY67

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If you look at available camshafts, almost everything with the .475"+ lifts also have very long durations and long overlaps, too. Not good for anything like a low compression engine. So that limits your choices immediately. To keep enough idle vacuum for power brakes, it'll probably need a 114 degree "centerline" (which is close to the stock cam's number).

Aim for "asymetrical lobe configuration" cams, which open the valve quicker and close them slower, and usually have "more area under the lift curve" than normal-lobe cams do. End result, more airflow into the cylinder without the higher lifts and/or longer durations. Comp Cams started them in the later '70s and Lunati has some grinds like that now. Lunati has a "factory performance" cam which replaces the 440/375 (also 383/335) cam, which one member has in a '68 383 4bbl, stock heads and pistons, that he claims works very well. But his factory motor is rated at 10.0CR. Check that one out. DO upgrade to a roller timing chain, for long-term "insurance" in that area.

The easiest way to increase the compression ratio, without new pistons, on the 8.2CR moitors is to put the earlier,, pre-906 casting heads on the motor. Smaller chambers than the 906 and later 452. Simple bolt-on, same gaskets for the intake and such.

Enjoy!
CBODY67
 
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badvs3vil

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I'm rebuilding the exact same engine for a 73 Newport with 452 heads. I went with a Hughes engine whiplash cam.
 

Metalmarty

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I'm rebuilding the exact same engine for a 73 Newport with 452 heads. I went with a Hughes engine whiplash cam.

Do you have power brakes?
Is that doable with a whiplash cam?

I'm thinking of the hughes whiplash. But it seem to have mixed reviews with power brakes.
 

fury fan

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From my extensive reading of anecdotal internet info on 383 cams swaps, here are 4 cams that were recommended frequently and with near-zero complaints. (I have not used any of these)

Summit 6400 or 6401 - this is an old grind but still satisfies a lot of folks, apparently
Lunati 60301 or 60302 - this is a 'more area under the curve' cam that makes it perform better than its specs would suggest.

Comp, Crane, and others never had specific cams get as much frequent mention as the 6400, 6401, or 60302.
Or some folks mentioned those brands while other folks complained about them.

The 400 should do a little better than a 383 due to 17 more cid.

Here are some threads from a guy that has done some systematic dyno parts swapping with some low-compression engines. He has disproved the old adage that high-compression is mandatory to make decent power, he demonstrates that airflow trumps CR. As you have 135-150 psi on all cylinders, you have enough pressure to somewhat be in his ballpark. Several caveats, though: he doesn't mention it specifically, but he's blueprinting these engines nicely and likely putting extreme quality into the 'stock' rebuild. Bore prep and ring sealing are paramount. You won't have this with a used factory engine. Also, as he starts building more power, his power curve RPM starts higher - he doesn't show the bottom #s being smaller (which is unavoidable as the cams get larger) and this should be considered due to C-body usage.
So I would follow after his lower-hp configurations to assure your satisfaction.

The slug 400 on the dyno.
Dyno a 7.5:1 400? Sure, why not?
Dyno testing a stock(?) 1972 440
 
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