I,am building a fake 65 396,with a 66 two bolt block ,oval port heads,can I use the vette rectangle intake,I have a standard block,and flat top Pistons,no head work yet,so I need suggestions on cam ,valves,carb ect,thanks,
I would get a 270 duration cam, 650 Holley DP, and set of headers. This combo has always been very streetable for me.
The cam selection kind of depends on the rest of the car...what does it have for a transmission, rearend gears, what will you use it for, etc? The rectangular port intake on oval port heads looks like won't work, but some guys who've tried it say it works fine. I never tried. Also, which oval port heads do you have? are they open or closed chamber? Probably won't get much compression if they're open chamber, with a little 396 with flat top pistons. 396 low performance pistons usually have about a 3/16" dome.
I built 15y ago 396 using these parts; 2 bolt block. Big ovalport heads 290, victor oval port intake. L88 old hot rod cam (427). 12:1 nos trw orig to gm pistons nos stuff. Orig rods with l19 bolts. 700 db holley. Msd 7al2. I used 140lbs springload, crane rollers+ girdles. 455hp in dyno. 8.9sec in quartermile (old vintage altered short wheelbase). High compression and L88 cam = never forget that sound !!! Rock n roll.
Square port on oval port will work , But I think there was three sizes ( Oval port) use race gasket Performance will depend on combination.
Evidently not too many old BBC drag racers on here. The rectangle port intake on an oval port head used to be common on the Super/Stock drag cars of the seventies. Works fine. Just use rect port intake gaskets. I have a couple of street racer customers that presently use this setup on aftermkt oval port heads.
The port overlap kills power. You can use an intake with smaller ports than the heads and it won't hurt power too much. Larger intake ports and small head absolutely kills power. Proved in on the dyno. Any motor, not just BBC. Think about it, the intake air is hitting a wall on the edges of head. This is why port matching helps power. Get the correct intake.
I have a '66 396/375 with the medium rise factory intake. Cam is a solid lifter L88, carb is a Holley spread bore. Heads match the intake and are from a 454. I ran this in a Nova stock car and it pulled strong on a short track.
I know it works well with N2O Not a desired mix of parts, always best to match ports up as said above. Cam? I have to line up behind squirrel and others for more info. I'm a fan of the BBC, best HP/$$ ratio in the game. a 396 can be a fun engine given it's bore limitations, but let me throw this out there, find a 2 bolt 454 block, use the rods and crank from the 396, get a set of 4.251 bore pistons (can't be too hard on the wallet) and poof! Instant bragging rights because you'll have one of the legendary displacements in the BBC MK IV family, the mighty 427. Even if you end up .030 or .060 over it's a misdemeanor not to continue calling it a 427. Power? Hang on, even with oval ports. Looks? Well, all BBCs are pretty sexy in traditional dress. Price? Have you priced Mopar or Ford big block stuff lately? Makes a BBC just short of a criminal persuit! At the end of it all it's a Chevy as well. Transmission options abound, swap meets are nearly littered with good parts, drag racers almost always have a stash of stuff they've cast off long ago chasing the "flavor of the month" in speed parts. Just sayin, carry on...
There are two L-88 cams, the early one has a lot more low end torque and works great in a 396, however it is a solid lifter design. Had one in a 402 with torker intake, small chamber oval heads and 650 DP
I had an L-88 cam, I pulled out of an otherwise stock 325 hp 396 decades ago...I sold the cam a few years ago on ebay, to pay for other big block goodies. It's a good cam if you have the big heads, some compression, a lot of gear, and a 4 speed. The last one I built is a 427, although it's .040 over so it's really a 435. But it still deserves the big number on the fender.... But back to the budget 396 build. How much money do you have? how fast do you want to go?
Speaking of port mis-matches, in the vintage motorcycle world the BSA Gold Star of late '50s/early '60s is noted for it's pronounced step at the carb/port junction (the carb being larger than the port), discovered by accident to offer a noticeable power improvement. From the memoirs of BSA racing dept. honcho Roland Pike: "One of the strangest occurrences to do with carburettors was when one day Reg Wilkes sent an apprentice from the test shop into our main shop for a 1 3/32 GP carburettor and he misread the size and gave Reg: a 1 3/16th carburettor and they immediately got quite a jump in power. They reported this to me and I went to the shop and the test was repeated and there was no doubt it was quite a gain in power. I suggested to Reg to open the port to match, immediately we lost what we had gained plus a bit more, so we made a thin sleeve and pressed it in and the power was back. We repeated this on other engines always with the same results. A number of private owners of DBD Gold Star noticed the carb being bigger than the port and opened up the port thinking to gain power, but not having a dyno were not aware of the results."
I've never seen or heard of a flat top, 396, BBC piston; maybe a blower motor piston? Even the Lo-Perf 396's, with cast pistons, used a domed piston. Who makes the piston you're thinking of using? The engine will have a very low CR if they really are flat top pistons. It was't until the 454 came around that a BBC had flat top pistons (or the tall deck, truck 366 and truck 427 tall deck). As far as the rectangle port intake going on oval port heads (and vise versa), it will "work", but not be ideal. Trade your rectangle port intake for one that does match your heads intake ports. I am Butch/56sedandeliver
My 56,454 block 427 crank oval port Yorker 2 396,375hp carb 400 turbo 23 bolt nova rear mild stall cruises at3,00 rps at 60 mph.
My heads a closed oval 66 396 chevelle , block standard bore 2 bolt , forged crank ,flat top pistons no heads 386206,oval block 355961,crank 6223
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