Thread: Need 402 help

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Hello, I am new here and figure after reading numerous threads someone might be able to help me out. I am building a 402 for bracket racing. This is my first bbc build, im a die hard sbc guy but the price was right. I aquired a freshly rebuilt engine carb to pan, but its a stock rebuild. The heads are 241 w/ stock valves and a fresh valve job. The short block is stock w new rings and bearings, it wasnt decked.

My plan so far is to use the shortblock the way it is.
comp cams magnum 292
victor jr o w/ worked 750 holley

I have a set of good 820 castings that im port / polishing and going to have 2.19-1.88 valves installed. Is angle milling an option to raise compression. Will this set up make decent power.

Are the 241 heads an option w/ the stock valves?

I know there is more info needed but not quite sure what is relevant.

Thanks,
John

"bbc newbie"

The 402 can be a formidable player. I have one the came factory in my 72 monte carlo. I rebuilt it a year ago and it runs well. I wanted to maintain the factory appearance with the cast intake and snorkle air cleaner and cast manifolds. I went .030 over, KB hypereutectic pistons w/ .180 domes ( stock domes) arp rod bolts, Heads are casting 292, they are the same or similar to the 840's you have. I pocket ported them and cleaned up the runners and bowls. I installed stainless valves 2.06 int and went to the larger 1.88 on the exhaust. This helps scavenging, so i am told.113cc chambers yields 8.8 to 1 compression. Cam is awesome. Crane 272 powermax. 216/228 .515/.510 112 lsa. Small cam but big car.. Has mild lobe sound. Cast iron intake w/ 750 rochester done by jet performance. When I raced it last year, I ran it twice and both times spun the tires through 1st and part of second. 1st run- 14.81 second run 14.38. I did run the car with headers but quite honestly, with the manifolds on now, I don't notice any difference. I'm confident that if I could hook, I would easily be in the 13's. Not bad for a 8.8 to 1 compression mild street engine in a 3900 lb car.

I f you want to use that short block, at least change the oil pump and measure the pickup distance. I would also go with new rod bolts but that involves dissassembly. Take the 840's and cc them. Hopefully they are 113. if they are and you have the stock cast pistons, you're looking at around 8.5 compression. Although a bit expensive, go with a small hyd roller as this will really wake this motor up. Howards has a few good candidates and they are sold at competition products. The 245 and 255 part numbers are great choices. You could probably get by with the 255- it is 230 at .050 and I don't know the lift off hand.
You should really talk to the grand pu bah of chevy build ups. He is Pat Mccarthy and he is on this forum frequently. He says 402's are great eng if you run a small roller. It really wakes them up. Also he says that larger intake valves may not make a difference.

Sorry 820 heads not 840. Also TRW makes a forged piston for the 4.155 bore. It has a .360 dome but it could bring you to around the 10.25 comp mark and you will probably need more cam to bleed it off. I'm told with 119cc heads it brings you to around the 9.5 mark. Don't know the part number.

If you would like to install that 292 in a low compression eng, give the car lots of converter and gear. the 292 is 244 duration at .050. Beware, BBC are known to wipe flat tappet cams. I have had good luck but historically, I have only installed small cams. Save the cash and go with a hyd roller around the late 220's- to early 230's at .050....you won't be disappointed.

The 241 heads are also similar to the 292 casting in they have the extra shrouding around the exhaust valve. IMO, 781 or 049 castings are the desireable ones and they are easy to find. Both of the castings that you have will work out well with minor work. You should probably talk to Pat.