Thoughts on the stock 402?

[CG]

So been reading through the threads tonight and was surprised to read a few thoughts on the 402's in our trucks that were less then stellar heh.

For the most part I'm not really a performance guy when it comes to our trucks. Seems to me with maybe an upgrade to HEI and a good tune the 402 should be a perfectly acceptable engine. Am I way off?

[bhemingson]

A 402 is basically a 0.030 over 396 and was I think 310 or 320 horsepower pre-1972 re-rating to net hp. What's not to like? Good power band and plenty of torque.

Easiest and cheapest big block to build. I am currently doing a Mopar and a nailhead in other projects - parts are double on the Mopar and triple on the nailhead.

[Getter-Done]

Originally Posted by CG

So been reading through the threads tonight and was surprised to read a few thoughts on the 402's in our trucks that were less then stellar heh.

For the most part I'm not really a performance guy when it comes to our trucks. Seems to me with maybe an upgrade to HEI and a good tune the 402 should be a perfectly acceptable engine. Am I way off?

Those 402's are Strong.
I almost lost a drag race 30 years ago
because

[kwmech]

If you are just putting around with a now and then romp on the pedal, then the 402 is ok. Any real performance then pick up 50+ more cubes and build that for the same cost. When I pulled the 396 out of my 68 and built a 454 for it the difference was night and day

[CG]

I had a 454 in my last K20 and it was pretty stout engine even though it had a lot of miles on it. Livrat built it and he did a really great job.

I have a low mile 402/400 combo and was thinking that it would be a great engine with minor upgrades ... Not going in to the internals at all. I was surprised that some didn't think much of the engine.

[Red71gmc]

I have one in a 72 that I bought and want to keep it as the power plant when I fix the truck. It runs well but certainly not real robust in its stock performance. I will be researching ways to get it's performance up.

[weq92f]

.
I'm real happy with the 402/396. In 1970 truck stock trim they weren't much to get excited about, but it doesn't take much to wake them up: intake, headers, cam and some proper tuning.

In my case, I wen't crazy with the roller setup! but that's not necessary.

-klb

[Coley]

I really love my '72 and it is a very well optioned, clean, solid Highlander.
However, if there is one thing I could have changed in the option group....it would have been to have had the big block 402 in it in lieu of the current 350.
That would make the truck darn near perfect in my opinion.

....gotta love that extra torque.

All good
Coley

[dtkarst]

Not an expert on motors and such but I would imagine you can make a 402 perform very well like all the rest of the big blocks if you wanted to.

[67 chevelle]

396/402 is a hell of an engine , the truck version came with a wimpy cam , everything else about it , including the great heads that they came with is great , much better engine than a junk 220 horse 454 with peanut port heads , put an rv cam in there , 260 or 268 , and it will really wake up , your rear tires will hate it

[68Gold/white]

Originally Posted by 67 chevelle

396/402 is a hell of an engine , the truck version came with a wimpy cam , everything else about it , including the great heads that they came with is great , much better engine than a junk 220 horse 454 with peanut port heads , put an rv cam in there , 260 or 268 , and it will really wake up , your rear tires will hate it

Amen on the stock cam!!! The stock cam in my 396 had the groove cut in the rear journal. I thought that cam was only used in 65 and 66 engines, because their different oiling setup...not so... That cam was used after 66 for at least a couple of years (according to my engine builder, who's experience is second to none...)
Any way that stock cam was used in likely every stock low performance big block made from 65 till likely 68 or 69...it's performance was very lackluster. Any good aftermarket cam would make it seem VERY weak in comparison.

a 260 or 268 High Energy cam would make a world of difference, however I do not favor the XE cams...

[COOP3726]

I have been dealing with big block chevy engines just about all of my life until the LS engines came out. One thing to consider is this; if you are going to build it to run it hard. You need to run 6 quarts of oil in it, because the big blocks had the high volume oil pumps in them and the pump would keep all of the oil up in the top of the motor. Performance wise would be to put you a 454 450HP cam and lifters in it with a good Quadrajet carburetor. JMO. The 402's are good engines.

[69Tom]

I just bought a 72 402 for my 70. Looking to do some upgrades as well. Has good compression so was just thinking a new cam and lifters. Any brand recommended? What's preferred, the 260 or 268?

Was thinking about this: https://www.jegs.com/i/COMP-Cams/249...791+4294829790

[68Gold/white]

Originally Posted by 69Tom

I just bought a 72 402 for my 70. Looking to do some upgrades as well. Has good compression so was just thinking a new cam and lifters. Any brand recommended? What's preferred, the 260 or 268?

Was thinking about this: https://www.jegs.com/i/COMP-Cams/249...791+4294829790

Do you know what the compression ratio is on your 402? What heads?

My 68 396 was a high compression engine. I couldn't put much timing in it because of such. I used some octane booster in it a couple of times, that helped. Whenever I get it back together, I plan to go with different heads to lower somp ratio, some...

I know that the Competition Cams 268H High energy cam (NOT the XE version) should work. There's many modern cams on the market these days, some are good, some ARE not. BUT your true compression ratio needs to be known before buying a cam...Hylift Johnson lifters are THE best. You will have to buy them direct. They are a little more expensive, but are by far the best quailty, American Made!!!

[COOP3726]

Look at the Comp camshaft 11-106-3 or the GM #3904362. The GM camshaft is the one I always ran, because I worked at a auto parts supply house for 13 years and I got them with a discount. The Comp cam should be just as good. A lot of people do not like this type of camshaft because it is a solid lift cam. I used what we called back in my days was poly locks, rocker lockers. (Rocker stud nuts with set screw inside of the nuts.) You should pick up a good 50-75 hp from the cam swap and using a 750 CFM quadrajet carb with headers.

[69Tom]

Originally Posted by 68Gold/white

Do you know what the compression ratio is on your 402? What heads?

It's a completely stock 72 402, so I believe it was 8.5:1 that year.

[69Tom]

Originally Posted by COOP3726

Look at the Comp camshaft 11-106-3 or the GM #3904362. The GM camshaft is the one I always ran, because I worked at a auto parts supply house for 13 years and I got them with a discount. The Comp cam should be just as good. A lot of people do not like this type of camshaft because it is a solid lift cam. I used what we called back in my days was poly locks, rocker lockers. (Rocker stud nuts with set screw inside of the nuts.) You should pick up a good 50-75 hp from the cam swap and using a 750 CFM quadrajet carb with headers.

If purchasing either of those cams, should I replace the lifters and/or rockers?

[COOP3726]

Yes, anytime you replace a camshaft you need to replace the lifters unless it is a roller cam.

[rcazwillis]

Put a new timing chain and gears. I have had 2 different 402s timing chains fail.

[CG]

So far all ive read is that its potentially a good engine. None of you seem to like it in stock form.

[67 chevelle]

great engine in stock form 310 hp and 400 foot pounds , but with a cam upgrade it is crazy good , might as well go thru it , new gaskets , timming chain [a must ] and springs to match the cam , and you have a monster

[CG]

Originally Posted by 67 chevelle

great engine in stock form 310 hp and 400 foot pounds , but with a cam upgrade it is crazy good , might as well go thru it , new gaskets , timming chain [a must ] and springs to match the cam , and you have a monster

I saw a "but" in there haha!

[71CHEVYSHORTBED402]

My 402 was rebuilt in 1993 with rebuilt heads off a 396 HP (i.e. Corvette). Word is 10/1 compression instead of 8.5/1. High RPM cam and an HEI. Somewhere around 350-375 HP.

40K miles and many decades later it runs like a top. At least it did, I put it in hibernation 2 years ago. Didn't use any oil despite some leaks, but then I didn't drive it much. Oil is always clear.

Stock gears, a 402 is unimpressive off the line. But gives a nice chirp when it shifts into 2nd. Great response all the way around, Highway is very impressive. One of the cool things about these BBC is they gain speed going uphill without more acceleration. At least that's been the case with my SWB "sport truck". My other 402 is tired, its pulling a C20.

Only downside about old BBC is they're on the downhill slide after 60K. Maybe with today's synthetics and an HEI they'll go longer. 100K its time to think rebuild, but that's true for a SBC as well. That and gas miles is 8-12ish.

Great engine IMO. They look great, what's not to like............This isn't my truck, but it's somewhat the goal.

[engineer_gregh]

I built my 402 with the following specs; bored .30 over, Comp Cams 268H cam, lifter, springs and retainers in 1966 Impala 396 heads with a 3 angle valve job, double roller timing chain, performer intake and Edelbrock 750 carb. Runs like a raped ape!

[COOP3726]

In my day the word "BIG BLOCK" meant power. So go ahead and have a little power. (FUN) I keep saying in my day. I am 64 years old and I still love power from these old rides. I have had a few super rides in my life since I was 18 years old. Oh, the stories I can tell. I know this is a tread about the 402 big block, but the big block is the thing of the past in my book now. The big blocks where the power from the past, but the LS engines are far more powerful and better engines than I have ever known in the past. There are so much power from just stock engines than most build engines from the past. LS engines are the way to go now!!!!!! Performance and fuel efficient. JMO again.
I have now restored a 1985 Silverado with all of the new commodities from the new rides added. I'm also about to start on a 1972 with a 5.3 LS engine and transmission. Happy motoring.