As a HP machinist I can tell you made the common mistake of not checking piston to head clearance. A 402 is just a 396 over from factory. anytime you change heads, pistons or head gaskets you should make sure you have .035 piston to head (quench) and dome to head .050. Even more clearance if your running extra piston skirt to cylinder wall, as piston rocks. Every .001 in extra piston to wall needs .003 piston to head. Don't assume anything in engine building, as none of these components aren't exact whether CNC d or otherwise. I've seen CNC d blocks have their decks out over .002 by the supposing experts. Bores can be off significantly also from side to side and front to back depending on how good ones machinery is and how they went about centering boring bar, like did they center the b bar at the top, middle or bottom of bore. Also how bad bore was worn and where it was worn affects these dimensions. At bare minimum you should always check on ever corner. Better yet every bore! Once had a SBC that had never been worked on, have one deck .016 taller than the other. Must have been Friday quiting time! As for the 820 heads they are superior to 049 as the area around the exhaust valve on quench side helps stop the reversion of gases. That is not due to port problem just a chamber problem. 049 can be corrected in that area with a skilled machinist.

Cut the guy some slack. He’s obviously a new engine builder and doesn’t have much experience in blueprinting. Give him some time. He’ll blow a few engines up then start to figure out that everything needs to be checked. Several times. He should go get one of the old school books on how to hot rod a BBC. Books are way better than the internet for getting accurate information.

I used 820’s on my Gen6 build with Speed Pro domed pistons and Mahle markIV to Gen 6 head gaskets. No issues and when I cc’d my 820’s they were right at 124cc’s.

Thanks for sharing this is a old video but a lot of great information on the 781 and 049 making power!!!

@realsteelmotorcars2894

2 жыл бұрын

The end result 820 After a little grinding kzread.info/dash/bejne/iJOo2quIc9THqbg.html

@realsteelmotorcars2894

2 жыл бұрын

End result 049 kzread.info/dash/bejne/pIubsruJk8mcfLg.html I installed the 049 On the 402 because I didn't find a lot of options for dome pistons being as how the block was .040 over = .070 over 396 , 41cc Dome. Anyway in the end it all worked out...

They make special pistons for those heads

I have 820 heads that i am about to use in a build on a 454 that is .30 over. What size engine is that ? Also what size bore on the pistons? Is the engine stroked? Were the 820 heads decked and if so, how much? Finally, what head gasket and part number did you use. Thanks for the info.

@lockdun10

6 жыл бұрын

mark k the 427 kB227 pistons he used are the same dome height as the 454 kb257 they are actually the same piston with different compression heights for stroke so they both stick out the hole same amount. So they are both at standard bore 4.250” and the domes of both are .250 high. I’m building some 820s for my .040 over 454 with kb257s right now as well. They are getting big valves and some port and polish work but my heads surfaces are pretty pitted so they will be milled quite a bit. That being said that lip that is present will need to be worked so that piston clears it. In another video I asked your same question and his response while laking the gasket thickness and milling amount stated that he ended up using them and needed to remove about and 1/8” in material off the lip and now she runs fine.

@realsteelmotorcars2894

5 жыл бұрын

BB Chevy 427, Bore 4.280, Stroke 3.760, Rod Length 6.135, Dome +26cc, Hydraulic Flat Tappet, Advertised Duration 284/284, Lift .519/.519 Fel-Pro Performance Head Gaskets SFL17046 Compressed Thickness (in): 0.039 in.. Bowtie GM Performance 12363406 Big Block Chevy 454/502 Aluminum Intake Manifold edelbrook 1411 carburetor I ended up grinding the area that was touching 1/8'' or so not much at all no noise now .... that said 820 heads are a good choice

I've got a 67 396 .030 over .629/.629 lift and 260/260 duration with 38cc domes and running 820s and have had zero problems...I guess I got lucky. best of luck bro hope you got it figured out by now

@realsteelmotorcars2894

2 жыл бұрын

Good to hear that the 820 heads can handle large dome pistons on a 396 and a .629 camshaft. My 427 has a 26cc domes, 540Camshaft lift . Good street manners. The piston to head contact was due to The larger bore . After the Hassle of grinding the heads I put the brakes on Installing the 820's on the 402 block I was working on with 41cc domes ... it would of been good... Went with 049. Due to the 427 nightmare So tell me about fuel 91 Octane ? Over all any down side ? My 402 was A beast ended up in a 71 Montecarlo . Check out my channel Did a road test on both Builds. Thanks for the info.

@hillbillyeverything4357

2 жыл бұрын

I originally built it for a mud truck but now it's in a 80' C10 2wd I had one test drive and so far seems good but it was only around the block lol. I run 93 octane in mine and seems to like it but I'll update as I get it on the road

I just purchased a set of 049's for $250 for my 402. Taking them to machine shop today. Can you recommend a camshaft? Be running this in my 69 chevelle with Muncie 4 speed.

@realsteelmotorcars2894

5 жыл бұрын

Are you planning on or have you replaced the pistons you are putting heads on that have a larger Quench area 123 cc O.E. pinstons are 17 cc domes so the compression will drop just saying. I would not go with a lift more than .510 with stock springs you buy matching sets and go to .540 lift ... I did the 44 cc dome pistons made by Icon changed the wrist pins 183 gram. press Fit pistons wieght came in less 50 grams but the pins added 30 grams so I was still 20 grams Light But doable next up copper head gasket .080 to keep compression around 9.5 to 1 Out of pocket the build was maybe 1200.00 all done I cleaned up the crank honed cylinder My 402 was just rebuild by last owner so I did not pay for all the ups and extras Anyways point being if you are not going to do it all. the cam if too large a lift My not help .480 for 8.5 to 1 compression good up Grade......

@My1969chevelle

5 жыл бұрын

@@realsteelmotorcars2894 thanks for that information. I still currently have the stock piston but I was told my cylinders are close to being out of spec for those pistons. The engine shop has my block and heads for checking and cleaning. I am going to go with your recommendations on pistons and camshaft, thanks again.

@realsteelmotorcars2894

5 жыл бұрын

@@My1969chevelle good luck with your build keep in mind weight differences in pistons you could weigh old and new pistons with pins if new piston and pins are less your in luck . If they weigh more make sure you get it balanced. or play with pin weight ...do a you tube search for tips to save on balancing crack shaft better to remove weight from crankshaft than ad....check out 427 building 454 block 396 crankshaft by Real Steel

@My1969chevelle

5 жыл бұрын

@@realsteelmotorcars2894 thank you, just recently learning the importance and benefits to piston weights.

@realsteelmotorcars2894

5 жыл бұрын

@@My1969chevelle It's not hard to grasp the concept of balancing rotating assembly less is better . I work at a used car dealer inspection factory as a diagnostic tech. New car technology is close To rocket science. What it is and what it should be is not always right . Got to think about it... Old school real steel is what it is....just nuts and bolts and basic math .

you have open chamber head domed pistons instead of closed chambered domed pistons because the heads are semi closed chamber

@realsteelmotorcars2894

Жыл бұрын

Ya the head are semi close champer . In the end I ran with it, due to the plan for the 049 heads . A little grinding did the trick... I would not do this again for sure but I made it work. I forked out over 5 hundred on pistons with the numbers coming out to 9.7 to 1 comp with 820 heads . If I knew what I know now I would of got different pistons to go with the 049s maybe 37cc dooms . The area that was coming into contact was minimal so I hit it with a die grinder problem solved. I do a lot of Franklin sine builds mix matching. The latest was a 350 block 307 crank Zz4 heads . 200R4 transmission S10 drop spindles and Jeep steering box. In a 64 SS Chevelle. It's a hobby that keeps me busy. By the way check out the Video msd efi on a bbc.road test

Your head to the right is a smog head look at the cc vs the open cc on the right ! That's like wanting to use a open chambered piston on a closed chambered head won't work ! And the smog head is a lower combustion cc , use an open chambered piston w/an opened chambered head ! There are 3 types of BBC heads. ( open , closed and smog ) let me know how this works out ( maniacal s10)

@realsteelmotorcars2894

3 жыл бұрын

Thanks for the info

I would of pulled engine to do inspection an depending on cam I would try swapping heads if not notch pistons with grinder,..😎✌

@realsteelmotorcars2894

3 жыл бұрын

I did go with the 820 , grinding out the area that was hitting and .050 head gaskets. Check out the You tube video.. Atomic msd efi on a BBC road test The montecarlo is now Running the O.E. 402 BBC That block got the 41 cc Dome Pistons and the 049 Heads also a test drive video 396/402 BBC with dome pistons 9.6 to 1 compression

RICHARD JARAMILLO 3 minutes ago BB Chevy 427, Bore 4.280, Stroke 3.760, Rod Length 6.135, Dome +26cc, Hydraulic Flat Tappet, Advertised Duration 284/284, Lift .519/.519 Fel-Pro Performance Head Gaskets SFL17046 Compressed Thickness (in): 0.039 in.. Bowtie GM Performance 12363406 Big Block Chevy 454/502 Aluminum Intake Manifold edelbrook 1411 carb

The best and only two heads I use are 353049 and 366791 and 366781, 3999241 in a pinch

update 820 VS 049 after cleaning up quench area minimally with die grinder. I went with the 820 castings, I put it in a 1967 El camino purrs like a kitten and roars like a tiger

@havebenthere

5 жыл бұрын

The area where the piston was touching is not the quench side. Your still in the chamber area. Also I believe you quoted wrong chamber cc s

820 heads are a good flowing head . Semi open chamber . They were on the 402 and 454 from 70 to 72 . I have a 402 made to 413 with 23 cc dome pistons and no issues . Open chamber heads need open chamber pistons and closed chamber heads need closed chamber pistons.

@calvinblackburn5272

4 жыл бұрын

So which pistons go with a semi open chamber? Open or closed

@billpeet5556

3 жыл бұрын

@@calvinblackburn5272 Never heard of a semi open chamber ? its open or closed .

@skylinefever

2 жыл бұрын

@@billpeet5556 I also don't understand what a semi-open chamber is. For example, the SBC heads in this video are called open chamber, yet I can clearly see a quench area. kzread.info/dash/bejne/oJqlqseBitfdhqQ.html

@noahdunaway

2 жыл бұрын

@@billpeet5556 there are open,semi-open,and closed chamber BBC heads. The closed chamber were the very first design and the semi-open came out in 68. The open came out in 69. I have several sets in my shop but I don’t know how to post pictures.

Ck b4 assembly. Then recheck

You don’t know what quench means! You mean to use the word “combustion chamber”!

Shave it off , if that’s the cause and save the heads for the motor that come out of the car.

Get thicker head gaskets

Run 049s, might be chevys best.

@musclebone7875

3 жыл бұрын

Gm 088 heads

@msh6865

3 жыл бұрын

The #049's and #781's are the best GM iron heads for the street.

@GJ-DT

3 жыл бұрын

@@msh6865they are just really heavy

@noahdunaway

2 жыл бұрын

@@GJ-DT yep 75-80 lbs, I just built a new BBC for my 1978 truck which came new with 781 heads. I ported the 781’s and installed 2.19 in. and 1.88 ex. Right after I bought the truck. I just built a 557 ci. and used Edelbrock performer rpm aluminum, square port, heads.

@noahdunaway

2 жыл бұрын

@@msh6865 the 781 and 049 are virtually identical and are good flowing heads when ported with the larger valves. But they are out of date now days with the reasonable priced aluminum oval ports that are available now. 75-80 lbs is a lot off of the front end.

run the 049's

@realsteelmotorcars2894

5 жыл бұрын

I ended up grinding the area that was touching 1/8'' or so not much at all ...I may end up installing the 049 I can hear a little pinging like maybe comp too high are running lean..

Are you kidding????? You don't know the answer to your own question? Either way, you are going to explode your rods. You are playing Russian Roulette with 2 bullets in the six shooter. That is the answer to your question. Or, you take your heads to a machine shop and have them put clay on top of the pistons and turn the motor over by hand and measure how deep the indentations are and have you pistons flycut around 0.015 where the valves would hit and then they won't ever touch your pistons again. Problem solved. Now you owe me the 402. OK?????

@msh6865

3 жыл бұрын

"Explode your rods"? You're crazy. The pistons will eventually clearance themselves but, aluminum fragments will scar the cylinder walls. The simple solution is to have the pistons cut for relief. Simple really.