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Discussion Starter · #1 ·
Hi all, I have a 68 396, block casting # 3916323 with heads casting #3917215. It was a virgin block when I bought it with some minor cylinder wear. Bored .030 over to a 402 Std. Heads had no porting done, just new valves, seats and guides. I could not find forged pistons that were anywhere near affordable, so I bought Keith Black Hypereutectic pistons with Moly rings. Had them installed on the stock (non-forged) reconditioned rods. The crank is nodular iron. It cleaned up .010/.010 rods and mains. So, the big question, with the flat top KB pistons and the 101 cc closed chamber heads, what kind of horsepower can I expect with a decent cam, like a Lunati 60203, an Edelbrock Performer intake and 650 (or so) CFM carb? It is going in my 68 Chevelle (being resto'd). Currently, I don't have a new cam, intake or carb for it. Any suggestions??? Thanks in advance.
 

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Discussion Starter · #2 ·
Anyone? Come on guys, a little help please...I am a newby to big blocks, engine rebuilding, classic car restoration and the works. Since buying the engine and having the machine work done, I have heard the,"why didn't you buy a 454 core and rebuild it instead" line a hundred times already. Moot point now. I am already a couple grand into this build. I just want to get it done and in the car. I am not "wanting 500 HP" like others I have read about with their 396 engines. I just want a strong engine that sounds great and will romp when I step on the pedal. That is what big blocks are supposed to do, right?
 

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I would guess 350 to 375HP, but would depend on if you are using headers. You would need to do some pocket porting of the heads and use headers if you want 400 to 425HP.

I've been looking for KB flat top hypers but all I can find are KB160 that have a 17cc dome. What is the part number for the pistons you are using? I have 1966 heads (702s) that have 96 to 98 cc chambers and the 17cc domes give me more compression than I want with a mild cam. I would like a 5 cc dome or less. I have been considering buying forged pistons and milling the domes, but I would rather have a hypereutectic piston.
 

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Well since no one else has responded I will toss some things out for you. First you may want to go with a 750 carb rather than the 650 due to teh displacement. 650s usually work better on a 350ci sbc (my experience). As far as the combination, It sounds good to me but without knowing compression ratio its hard to get a complete picture. I will assume about 9.5:1. I would keep at most a 3:31 gear but 3:55 would be better in my opinion, and a 26-28 inch tire. if you have highway gears (3:08 or lower numericaly) then definately run the shorter tire, or a smaller cam so you have enough low end to get moving. What trans are you using? I am guessing Th400? if so it will eat ups some power vs a TH350 but maybe a 2000 - 2500RPM torque converter wont hurt. I think your combination will make ~ 350 hp and a nice torque curve up to about 5500 RPM. Just keep in mind teh whole combination of; Engine operating RPM (based on cam and compression and intended usage) Torque converter, axle ratio and tire size, make sure they will work together.

This is all based on my limited knowledge but others will chime in, just give them some time.
 

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Discussion Starter · #5 ·
As a matter of fact, I think they are KB160 pistons. So, I guess I was wrong about them being "flattop". At the time I bought them, they were the ONLY piston available in 4.125" from Summit. I could have bought a set of forged pistons from another store, but the price was almost a grand. I don't know what gear ration I have at the moment. It is the original 10-bolt non-posi rearend that came in my 68 Chevelle. I have a Muncie 4-speed. From the numbers I have looked up, it appears to be either an M-20 or M-21. I know that isn't a lot of help as both transmissions are slightly different. I think it is an M-21 from the date (1965) with a newer input shaft (no rings). In any case, I will be having the muncie gone through before putting it back in the car. I am debating whether to have the rearend regeared with a posi added or buy a 12-bolt posi unit ready to go. I am not looking to race my car. Just want it to hold up with the increase in h.p.
 

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Alan, you may not have but about 9.5 CR or less with the flattops and 101cc heads.

If it were mine, I would chose a Lunati 60202 hyd flat tappet cam with that low CR and, even though headers will always help any engine's performance, you could still use the stock manifolds with that cam and still have a peppy street car with that 4 speed trans.

3:31 rear gears will be good also along with a 750 cfm Qjet carb (especially from Sean Murphy Induction (SMI). Power levels should be about 350 - 360 hp and 430 tq, but if you have the heads mildly ported and use headers, expect higher numbers.

Charles
 

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I used to run a 396 and it wasnt a bad little motor. As mentioned, you are a couple grand into this motor, so the whole 454 thing is long since out the window.

Also, as previously mentioned, the 650 is too small (although I know someone is going to say it isnt).

Personally I would never build a 396, but if I found one at a heavy discount, Id have no problem playing with it. If youve never had a big block before, and its the most cubes youve ever had, then it will be a very satisfying experience....it may be the smallest short deck big block, but its still 400 cubes.

As a frame of reference, I currently have a bone stock LS4 Corvette with 3:36 gears. While I speculate it probably makes more torque than my old 396 did, my 396 DEFINITELY made more horsepower, but then again the 396 was not stock.

750 carb, small tube headers, appropriate choice of torque converter, and you will have fun.
 

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you could have bought the Speed pro 2240 in a .030 for about $40 each which is around $320. They have about the same dome and come in a 4.124 bore. My buddy runs these in his 396 and they are good cheap pistons. The KBs are fine and you have them so don`t worry about it.

Depending on your deck height and gasket thickness you could be anywhere from 10.25-9.25:1 compression. Your 215 heads list a 101cc chamber but can vary.

I like the Comp 280 magnum, seen it work out great many times even though its considered old school. My friend pretty much has your exact engine with the 280 magnum and with a 2800 stall and 3.73`s its a very fun ride. The 60203 is suppost to be a good cam too. The performer is ok but definatly step up to a 750cfm carb like a Holley 3310 or 770 Street Avenger. with some headers and a good carb Id say your in the 400hp range with 400-430ftlbs of torque. It will be a nice street engine for sure.
 

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Discussion Starter · #9 ·
Thanks guys, all of you. I appreciate the advice. Now I have some good info. to mull over. I am feeling better about my choices I've made now. It really sucks to spend $2K and then find out there are lots of better alternatives out there. So, from now on, I am consulting you guys BEFORE I spend. I agree the 60203 Lunati is a little much with my present setup. I will spend some time researching the 60202 and the 280 Magnum. I think I will probably go with the Performer RPM and Holley 750 for fuel and air delivery. Again, thank you to all of you for giving me much needed information. I appreciate it. Guaranteed, I will be staying in this loop!
 

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Go to the search box in the perfomance section and type in 280 magnum and then 60203. You will find alot of info on both cams. I know 2 guys who used the 280 magnum in similar engines, a 396 and a 427, and they both run really good. They are both basicaly stock engines with 9.5-10:1 compression, closed chamber oval port heads and the 280 cam. The 427 ran super strong but it was in a pro street 55 chevy truck with 4.11`s, 4spd and a tunnel ram but that thing would spin those 18.5" wide mickeys at 35mph with a 3500rpm dump. the 396 is built almost the same as yours and in a 66 chevelle and probably really close to how yours will be set up. It has a ton of low end power and pulls strong all the way up till he shifts. I know he is really happy with it.

Everyone says, "build a 454" but I think the little motors can run good too. Everyone told me to build a 350 or 383 when I built my old 327 but I didnt listen and it ended up running low 12`s, faster than the guys that were telling me to build a 350 or 383 were running at the time.
 
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