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

Tweet

Thank you for the explanation Roger, I had no idea about that. I still think I was born 100 years too late.
.

Originally Posted by rspears

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/

Excellent info to have. I always wondered why those stupid links show up.

Thanks Richard. I'll have to measure the bore to know for sure. Original build info is lost unfortunately. If, as you note Jerry, the compression is too high due to these pistons and the closed chamber 063, wouldn't the 781's do the same as aftermarket $$alum$$ heads for less $$ with their larger chamber and more open design? Maybe I misread your post?

-unix

You might want to sell the 402 and get an LS 6.2 from an Suv/pickup-------
they are cheap and modern

Looks like the block has been cut a bit, see the picture, but best of my ability to read this thing looks like the bore is 4.150, so not stock. More likely it is .030 over and my skill at using the caliper are just lacking.

I've been trying to figure a way to measure the piston dome. No luck so far. Any pointers?

-unix

Originally Posted by unixoracle

I've been trying to figure a way to measure the piston dome. No luck so far. Any pointers? -unix

You will need a cc burette, 100cc, a holding fixture for the burette and a clear plexiglass or lexan plate with a 3/16" hole drilled in it. You will also need a bottle of Isopropyl alcohol from the drug store and a bottle of red, blue or green food coloring from the grocery store, your choice. You will not need 100 cc's for this operation, but if you are going to invest in a burette, get the 100cc unit.

With the short block on an engine stand, loosen the holding bolt on the engine stand and twist the block so that the cylinder you're going to check is almost vertical, but has one side of the bore a little higher than the other. Tighten the bolt. Span the edge of a steel rule across the block at the bore and bring the piston up until the pop-up is just slightly below the edge of the rule. (maybe 0.010" or 0.015"). Now, using the sliding function of your dial caliper, measure how far the flat part of the piston is down in the bore. That would be the crown of the piston that is flat and even with the edge of the piston just above the top ring. Write it down.

Let's say that the crown is 0.135" down from the deck surface of the cylinder block. Now, use Vaseline to seal the edge of the piston to the cylinder wall. Use as little Vaseline as possible. I used to wipe around the bore with a Q-Tip and wipe away the excess with my fingers and a shop rag. You want to make sure that the piston is sealed to the bore or you will have to do all this over again. Now, smear the block deck with Vaseline and place your cc sealing plate onto the block, with the filling hole at the high point of the bore so that air will automatically escape uphill.

Affix your burette and fill with colored alcohol. Pour the void and record your volume.

If the piston were absolutely flat on top, with no valve reliefs or domes, it would take a certain volume of liquid to fill the void atop the piston crown. We will determine that volume mathmatically.
We know that the bore of the block is 4.150" and the depth from the top of the ring land to the deck surface is 0.135. If we multiply 0.7845 times the 4.150 bore times the 4.150 bore times the 0.135 times 16.387, we find that if the piston were flat, the space we are pouring would be 29.9 cc's.

Now, we pour the volume and find that we actually used 14.3 cc's of alcohol to fill the void. If we deduct 14.3 from 29.9, we find that the pop-up is worth 15.6 cc's.

Simple, huh ?
.

Thanks, but... The short block is staying in between the frame rails. It's not coming out.

This is a top end only refresh. Quick and dirty.

Would this be possible you think with the block sitting level?

-unix

Originally Posted by unixoracle

Thanks, but... The short block is staying in between the frame rails. It's not coming out.
This is a top end only refresh. Quick and dirty.
Would this be possible you think with the block sitting level? -unix

I've never done it with motor in frame, but yeah, I suppose you could if you're careful.
.

Piston domes-------

Speed pro #L2383 dome .110 13.9 cc
L 2328 .319 36.6cc

L2300------- were listed for 427 but .140 dome 16.8 cc

If you clean carbon off tops of yur piston probably can read part number maybe

Rule of thumb about piston domes for closed chamber BBC heads------1 cc for about .010 of piston dome height------.100 aprox 10cc-----.150 aprox 15cc etc--------accurate to about 2 or 3 cc

Droppin' off the heads tomorrow so I'll be doing my best to CC the chambers tonight!

The owner of the shop, Wayne, sounded very much as I expected over the phone. I wen't ahead and told him I'd need that 3 angle valve job, hardened seats and "everything else it would take" to get those things put back together with new valves, guides, seals and such. I dribbled on about cleaning up the mating surface and fully assembling the things with the parts from a cam kit that would be purchased in the future. LOL, that might be why he quoted me 6 or 7 hundred! LOL.

-unix

Well shoot. I'm stuck now. Back to second guessing my goals and budget!

I'm going to run away from the 6-7 hundred valve job on the heads. Found another shop that may suit my needs better. Regardless, that first place was kind of a race shop. Probably pay premium for basic machine work there.

Managed to measure #7 chamber at 102cc. That's accurate methinks as the first several attempts were meaningless due to leaks. Until I found a way to remove the gasket material completely, no dice. Razor blades are, apparently, the only way but just removing enough to seal my plate against #7 I managed to scratch up the surface! Don't really want to fk up everything else eh. So, I'm done with that. The machine shop can go further if necessary. Still have to get the deck cleaned somehow though. Wire wheel on a drill anybody? Other suggestions?

Once this thing is alive, it'll probably eat the 700r, although I can probably control the rate of decay with my right foot, for a while. A new 4L80 ( B&M 118001:2400+CNVRTR:500+CNTRLR:600 ) is 3500 plus flex plate, plumbing and shaft work.

The budget is sitting at 100% unused at the moment. I've bought some tools and such but nothing seriously detrimental. Since it's getting time now to commit and spend, I'm waffling and looking around at what might need to be spent after I put this engine back together.

I must have OD, so the th400 is out. Something else I must have is the ability to light 'em up at will from any speed...let's say...below 25MPH. Another must have is good manners under light throttle and stop/go cruising. And finally, the reason for the OD, this thing must roll down the road 80MPH under 3000 RPM, probably more like under 2500.

The question banging around in my head:
Assuming in the near future I'm OK with upgrading the 700r, what then should my immediate goals be for this engine? Just top end? Build the bottom end as well? If so, then why not ditch the 402, go 454 with my 781 heads with new rotating assy ( choose everything outright )?

I'm also considering commissioning the engine build now from a shop but only if the price is right! That way I'd get proper clearance checks ( P/V ), new cam bearings and I'm sure other $hit I can't imagine!

Thoughts?

Thanks,

-unix

You might want to go back and read post #19 from Jerry Clayton.
.

No!!!! Really don't want to swap out everything!

Did see a CL for 2017 EcoTec3 6.2 w/8L90e, 10k miles... hehe No....No.. Nooooo

This thing definitely rocked the freeway before I broke it apart............
The speedometer indicates 10 MPH higher than actual MPH. Verified via GPS.

I would not use a wire wheel to clean the deck. A 3M Roloc surface conditioning disc works well if you are careful with it. Don’t use those on aluminum. A razor blade with a razor blade holder might be the best way. Either way be patient and take your time.