Over cammed 402

[Whamp48]

I have a 402 bbc in '72 Cheyenne Super. I've had it running a few times, but it never seems to run very well. I'm thinking whoever put it together was thinking more about power than usability. Do any of you guys know what cam, lifter, valve springs, carb and intake combo will work best for an everyday driver? I don't mind a little upgrade to maybe 350hp, but I don't want something that has to idle way high and has a tough time making enough vacuum to be usable. Thanks in advance for any suggestions......Warren Hampton

[engineer_gregh]

I'm running a Comp Cams High Energy 268H kit in my 71 402 and I'm happy with it. You might like the 260H kit if you want a smooth idle. I would suggest calling Comp Cams tech support line and discussing it before buying either.

[Whamp48]

Thank you, Greg.

[geezer#99]

possibly not the cam!
Could be the tune.
What carb, what distributor, what intake, what exhaust?
A little tuning could save you a chunk of money.

[Whamp48]

Thanks, Geezer.....I really hate to do anything to this engine. The truck itself has been a nightmare, with just about everything that's possible to be wrong being wrong. I put a new distributor, rebuilt quadrajet from National, one rocker was broken. Ran better, but still don't suit me. It's supposed to be newly overhauled, and appears to be. I'm the third owner since it was all partially put together. I've been suspicious of the cam since I've had it. The fellow I got it from told me it has a "big" cam, but I don't know the specs. So the only solution I can see is removing the cam and replacing it with one that will be suitable for a driver. Then if the heads have double or triple springs, they'll have to be replaced with springs that will work with the cam I get. I'm leaning toward the Comp 260H or 268H Greg suggested. I don't want a racer, just a good usable, driveable truck. Whew, don't I run on???

[geezer#99]

Sell that lumpy cam 402 and get a mild 454.
You’ll be money and time ahead.

[webfoot]

What is the initial timing set at, with the vac advance unplugged?

[68Gold/white]

Originally Posted by geezer#99

possibly not the cam!
Could be the tune.
What carb, what distributor, what intake, what exhaust?
A little tuning could save you a chunk of money.

Way too many unknowns here. Don't know what cam, if cam was degree'd, what heads, chamber volume of heads.
An off the shelf carb generally does not help...has to be calibrated to exact engine it is on...

General rule of thumb is to start with distributor. Has it been worked on???
If you have the funds, I know a guy in Tennessee that can dial in your distributor...if it is worth fixing...he IS good!!!

The 268H or 260H (NOT the XE cams!!!)are very good choices to change to, compression ratio needs to be known first......but not knowing what you have, I would do other things first...

[Whamp48]

Originally Posted by geezer#99

Sell that lumpy cam 402 and get a mild 454.
You’ll be money and time ahead.

Keeping the 402 because that's what come in it.

[Whamp48]

Yep, put in new distributor. Maybe after I get this thing to go to town and back, some fine tuning might be worth thinking about.

[geezer#99]

Originally Posted by Whamp48

Keeping the 402 because that's what come in it.

Likely the best way to go.
Do a compression test.
The numbers should reveal some good (or bad) info.

[Minkota]

I have seen many engines set to a high idle to overcome the fact that they did not install a Converter with the correct Stall. Do you know what converter is installed in your setup?

[Ziegelsteinfaust]

Originally Posted by Minkota

I have seen many engines set to a high idle to overcome the fact that they did not install a Converter with the correct Stall. Do you know what converter is installed in your setup?

Among the other things mentioned a torque converter designed for towing can be the culprit in poor idle or having to have it idle high to overcome fluid drag. Also the low stall or towing converter will make the truck slam in to gear when you shift from park to reverse for instance.

You need to do a full evaluation on your set up.

[Whamp48]

Yeah, I'll have to rip in to her. Take the cam out and take it to the machine shop. They're engine builders, too, so they can tell what it is. The heads are clean and have new looking rockers, so I'll have to look at them. I was told thwy had bigger valves. I just wanted to know from someone who knows what a good mild cam number was, and Greg gave me that. Thanks guys....I'll just have to get going on a job I was hoping wouldn't be necessary.

[Minkota]

Most aftermarket cams typically have the part number stamped into the end of the cam, you will be able to see it once you remove the top timing gear.

[Whamp48]

Thank you sir. I'm almost sure I'll find a cam that is not suitable for how I want the truck to run, but we'll see.

[webfoot]

So no clue on the timing then?

[Ironangel]

I second the Comp Cams 268H, ran great in mine for years...

[Whamp48]

Originally Posted by webfoot

So no clue on the timing then?

Other than turning the distributor to where it works best, no, I can't give you any technical answers on timing, degrees, etc. I'm going to tear into this thing next weekend and instal a mild cam and whatever valve springs go with it if mine are not suitable and I'm pretty sure I'll end up with what I want, a good running vehicle. Thank you for your interest.

[engineer_gregh]

I set my 402 exactly like this video even though the video is for a 350 not a big block. Its a good starting point. I hope it helps you.

https://www.youtube.com/watch?v=e-k2fdTZP7o

[geezer#99]

If you’re going to tear into, you mights we’ll pop a head off to see what pistons are in it.
If you have high compression (over 10 to 1) and install a mild cam you won’t achieve your goal. You’ll have a underpowered dawg that runs out of breath at 4000 rpm because you can’t put any timing in it.
Not much more to pop a head off.
You’ll need the drivers side off anyway to put #1 at tdc to be sure your timing tab/balancer are accurate.

[Whamp48]

Yeah, I'm thinking it'll have heavy springs, so I may have to replace them also. Easier to do with them off. How fast would you be going at 4000 rpm? 80?? I don't want to go that fast aboit 99% of the time. The 260H is a mild cam, but Comp says it has low end torque. We'll see.

[geezer#99]

Take some pics of the pistons when you tear it down.

[Whamp48]

OK, will do. Y'all have a good rest of the night. Nap time for me.

[davepl]

Take a look at the cam specs for the 396/350, and then look for a modern cam somewhat similar. That's what I'd do!