Thread: BBC 402 looking for advice on head work, cam and stall

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I've got a 1970 396/402
cast# 3969854
date code: A 7 70

With #063 heads dated March 25, 1969 ( C 25 9 ).

The block appears to be 4-bolt based on the fittings machined into the block above the oil filter housing. I'll confirm this soon with a scope through the drain hole. My research suggests if it is a 4-bolt, these heads are wrong. No worries as a 2-bolt should do fine.

Edel. Performer II+ intake
MSD EFI TBI
currently with stock BBC exhaust manifolds into dual 3" pipes, no cats. Will be fitting long tube headers post refresh.
700r
stock converter w/lockup
3.73 posi

3600 pound vehicle

I'm going to remove the heads and have them freshened/worked at a local machine shop ( need some pointers here ), remove and replace the stock cam with a hyd roller unit that will fit with what I'm after with this engine:

o street use mostly
o need vacuum for EFI and brakes
o loads of low-rpm torque
o operating range of 1500 to 5500
o basically a stop light to stop light fighter
o ...and highway cruiser

This motor runs strong with no issues so I'm not worried about the bottom end. I'd like to "wake it up" via the above.

After lots of reading on this site ( through the last 50 pages of posts ) I've decided to just run the 063 closed chamber heads after some useful and appropriate machine work ( need pointers here ) and update the cam to a roller. Likely will need to add some stall too, but I'll wait for the boards opinion on that.

With my goals and hardware in mind, can you guys help me determine the best course of action on my 063 heads ( assume for now they're completely stock ) and give me some options for the cam? Looking to pull as much grunt out of this BB as possible while keeping it streetable.

I have a set of 781s too, but don't think they're in the running without also swapping the pistons, which I don't want to mess with.

thanks much,

-unix

Slight update here and bump...

The heads are off. Looks like the pistons have a very slight pop up dome rather than being completely flat top as I suspected. They also appear to be slightly down in the hole, which is a bit confusing and doesn't help with CR calculations. My best guess based on a bunch of research on these engines was roughly 9.0:1 or 9.5:1 if everything is stock. Since I was expecting flat top pistons with these heads and ended up with slightly domed top, I'm not sure what that does to my estimated CR. Here are the values I used just now for my CR calcs on Engine Compression Ratio (CR) Calculator :

bore 4.125
stroke 3.760
comb. chamb. size: 97cc
piston dome vol. .012
piston deck clearance 0

...which brings me to 9.0 => 9.2 to 1 compression

What do you guys think about that? Does it seem accurate? Any pointers on exactly how I can get that even more accurate?

Still looking for some input here on whether to go with larger valves ( other head mods within reason and reasonable $$ ) and some cam suggestions.

So far, using CamQuest, I'm getting 270h and 280h recommendations with 110LSA and the about .51 lift. These are calling for headers, gears and stall as well.

Thanks,

-unix

Well, I managed to disassemble the top end, finally!

Got quite a surprise when I found slightly domed pistons. They appear very much like the Speed-Pro Forged Pistons L2300NF. Was expecting flat tops. Given
the #063 heads with these pistons, I'm thinking about 9.5:1 compression is pretty close. Using Engine Compression Ratio (CR) Calculator with this data:

bore/stroke : 4.125/3.76
Gasket thickness: .044 -- Not measured just taken from online sites
Comb Chamber : 101cc -- Not measured just taken from various online resources
Piston Dome : 11cc -- conservative here as I don't know for sure what pistons these are.
Deck Clearance : 0 -- ??

...we get compression calculated to 9.3:1


I'm interested in your opinion whether this calculation seems ballpark correct for this engine and whether you all have suggestions for bringing it closer
to reality ( how to measure the cc of the piston dome perhaps or get the deck clearance properly measured for instance ).

Also still in need of machine shop advice and some cam suggestions as well given my intended use and this new data here.

Much appreciated,

-unix

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First thing I would do with those 063 heads is to have hard exhaust valve seats installed and have a good 3-angle valve job performed.
https://www.youtube.com/watch?v=3TdW_rjwB-8
Then I'd cc the chambers....I've seen 063 chambers advertised from 93 to 109 and everywhere in between.
https://www.youtube.com/watch?v=yqAr4DUqEt4&t=29s
In order to choose a camshaft for the motor, you need to know the combustion chamber volume so that you can figure the static compression ratio so that you can choose the proper cam timing. You can't run a race cam in a low compression ratio motor and you can't run a "take grandma to bingo" cam in a high compression ratio motor. This is where most neophyte builders screw the pooch, choosing the wrong cam. And left to his own devices, a beginning engine builder will always use too much cam. It comes from the old hot rodder's axiom, "If some is good, then more is better and too much is just right". Then the builder can't figure out why he is getting beaten, thinking...."Hmmmm, maybe I need more cam".

The camshaft in a motor is not a stand-alone part. It is one part of a complete team of parts that, chosen wisely, will result in a motor that does what the builder wanted in the first place, to be a strong runner that will operate detonation-free on pump gas. The camshaft and the torque converter should be the final two pieces chosen for the build. I will be recommending a Howards retro-fit hydraulic roller camshaft with Howards roller lifters as a kit. Big block Chevies are known to be flat tappet camshaft eaters, so we will not be entertaining that idea.

We will need to know how far the piston crown is down from the block deck with the piston at top dead center, so measure that while the heads are off. Here's a cheap, easy way to do it at home with a steel rule and a set of feeler gauges. Make certain that the piston is at absolute top dead center. Bump the crank with a long-handle ratchet, one way and then the other to make sure you have found the smallest measurement.
http://bbhp.bigboyzheadporting.com/a...tachmentid=202
A photo of the piston crown would be very helpful also.

Your overdrive transmission will be next to useless in this application, so I would be looking around for a good, solid TH400 that maybe you could trade out for.

I'm going to stop right here and wait for you to complete the operations listed above, so that we can then do some calculations and get some insight into what will work best in this motor.

.

Seems my posts here just go nowhere. I've posted twice here with my progress and both times the post just disappears.

I've posted about my estimates on compression ( 9.0:1 to 9.5:1 ) based on 101cc combustion chamber estimate, piston dome at 11cc, 0 deck clearance, .044 gasket thickness ). I expected flat top pistons but found domed ones much like Speed-Pro Forged Pistons L2300NF.

Not understanding why I seem to be unable to post responses to my own thread?

-unix

Unix, that same thing seems to happen to all newbies. The Commandant wants to make sure that you don't screw up the site any more than it already is. Keep posting, post about anything or nothing at all, post poetry, post quotes. The point is that the more you post, the more you will be accepted as a player here. Hang in there, this project should gain considerable interest from the other members here and once we get the playing field squared away, we can have some fun.

And by the way, the word (((ESTIMATE))) does not sit well with me. I want cold, hard facts if I am going to help you achieve the goal that you want to reach.
.

OK, I was thinking that was only if pictures or links were involved. Maybe any punctuation triggers the audit of newbie posts? I'll try to post up a picture or two and see what happens.

-unix

Originally Posted by unixoracle

OK, I was thinking that was only if pictures or links were involved. Maybe any punctuation triggers the audit of newbie posts? I'll try to post up a picture or two and see what happens.
-unix

Great, if you have difficulty, many of the members here are very proficient at posting photos and will help you. I usually don't post any photos, so I don't know how. By the way, my name is Richard.
.

Here you can see the piston design and the 063 chamber. This motor should have about 8k miles on it.

-unix

piston1.jpghead1.jpg

Originally Posted by unixoracle

piston dome at 11cc, 0 deck clearance, .044 gasket thickness ). I expected flat top pistons but found domed ones much like Speed-Pro Forged Pistons L2300NF.

Did the fellow who put the pistons in, bore the block? If so how much?

Install hard seats and cc the chambers and we'll have all the info we need.
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be very careful putting in hard seat in the xhaust valve that is at the end of head-water jacket is extremely thin around that area------

Originally Posted by jerry clayton

be very careful putting in hard seat in the xhaust valve that is at the end of head-water jacket is extremely thin around that area------

Would you chance running pump gas without seats, Jerry ?
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Maybe for a while-those pistons/heads closed chamber---------11to 1 compression, cast iron--------if he uses those heads hes too much compression for pump gas ( plus 93 octane is maybe dollar gallon higher than 87?) That exhaust valve shows very lean condition on at least one cylinder------

He can do seats and rebuild on the heads but will have too much comp for street tune so he ll need to change pistons---------or he can but new alum heads with somewhat larger cc and hard seats, etc and use pistons he has------then later put a 454 / 502/ 572/etc short block using the alum heads he will have already at that point-------

If he has this in a vehicle that needs numbers matching components--------whole nother story

Unixoracle, I will offer you a tip on your posting problems. See in your #1 Post, the word "oil" appears in blue text, and if you hover your mouse over it, it's an active link to the AmsOil site? That's because of the program "VigLink", and it will turn just about every post you make into a link-loaded text string that requires Moderator approval as a newbie, UNLESS you "Opt Out" of VigLink. Check out this, and yes, you'll have to Opt Out every month or so, because it seems to turn itself back on - https://www.viglink.com/opt-out/