396 / 402 BBC Performance and Converter selection comments wanted.

Discussion in 'High Performance Modifications' started by 73 Rs, Apr 18, 2017.

  1. 73 Rs

    73 Rs New Member

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    Hi,

    1973 camaro 396.
    i am currantly rebuilding my small, big block motor and had some questions on what converter to go with, and if someone have a simular build motor, can say something about hp gestimates?. (i am new to old american cars)

    The car will be CRUSING ONLY, and will never see a track.

    The Block is a 1966, 396 & 030" over, should make a 402.
    Engine block casting number 3855061
    pistons are L2240N 030

    Statick Mesured and calculated comp is 9,6

    the heads are closed chamber and mesured to 104,6cc
    castings 3917215, oval ports.
    They have had some work done to them in the past, and valves where not stock.
    valves in the top now is inlet size 2,250 & exost 1,875

    Cam going in is comp cam XE262H - 10
    rpm range 1300 - 5600
    duration @ 050 = 218 & 224, lsa110,

    intake manifold is new type weiand stelth 8019, dual / single plane hi rise.

    Exost is:
    Long tube headers going to 3" colectors, down to dual 2,5" exostpipes.

    ignition is msd 7-2

    the gearbox is a th400.

    rear gears: i think it is 3,73

    my converter has 1500 writen on it and assum that means 1500stall speed.

    when i put the engine numbers in the comp cams camquest sofware, it recomends a stall speed between 2100 - 3100rpms.

    so my 1st question is:
    is it worth canging my current converter for a 2100rpm stall, and will it have a big inpact on the drivebility of the car?. (remember cruising only)

    Question 2:
    anyone that can say anything about aproxematly hp the Motor develops?.
    when i put the number in the comp cams sofware, camquest, i thought the hp ratings they put out sounded on the optimistic side. (430hp @ 5500rpm & 502ftlb @ 2500rpms)

    Question 3:
    this comp ratio, 9,6 should allow me to run on pump gas without any problems?.
    (95 or 98 octane pump gas)
     

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    Last edited: Apr 18, 2017
  2. 73 Rs

    73 Rs New Member

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    Qusetion 4:
    carburator:
    i am planing to run the motor with fi-tech meanstreet 800.

    and i also have a quickfuel carb as back up. it is 680cfm,
    will the 680 carb be enough for my engine combo?

    (the car had a 850holley when i bought it, with no chocke etc. but it was hard to start the motor with no chocke)
     
  3. fatkid_racing

    fatkid_racing Veteran Member Lifetime Gold Member

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    Hello, and welcome new guy. Your 396 is very close to the one I just finished for my first gen. I feel you're a tad small on the camshaft, and a little big on the inlet manifold. The weiand stealth is quite cavernous internally, it excels at wide open throttle but suffers everywhere else.

    The Comp cam you mentioned is for 67 and later big blocks, the 65-66 models used a unique set of cam bearings and the rear most bearing journal has to be grooved in order for it to oil.

    My combo is a 69 396 block, the same pistons that you're running but mine is 0.040 over. My cam is a custom ground bullet 221/230@.050 .515/.515. I'm also running the semi open 820 casting heads it's a fairly stout cruiser.

    With your pistons and assuming the block isn't decked your piston is 0.025" in the hole with a standard 0.039 thick head gasket will be more in the 9.5:1 range static, 7.4:1 dynamic with 0.064 quench which isn't anywhere near optimum but I'm not sure what kind of petrol y'all have access to either.

    As for your converter, something in the 3,000 RPM will be fine. Make sure you order a quality converter possibly even have one custom built Freak Show performance in Abilene Texas USA will custom build you one for about the same price as ordering a shelf converter from B&M or the like.

    Your 680 CFM carburetor is a bit small in my opinion, but would be great for snappy throttle response and midrange power. The fitech system is great you'll never regret that swap.

    Anyway my entire combo is 396, 0.040" over, L2240N-40, block decked 0.010, 0.020" thick head gaskets for 9.3:1 compression. The cam was mentioned above and produces 8.1:1 dynamic compression. I'm using an old Edelbrock Torker with the twisted carb mounting pad, a quickfuel "brawler" series 750 CFM carb, 2" primary headers with 3.5" collectors. Th400, 3,000 stall and 4.10 gears. It's no race machine but is quite fun on the street. Your build is quite similar to mine and should be a good guideline for you to refereance.
     
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  4. 73 Rs

    73 Rs New Member

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    Hi,

    Thank you for your comments.

    it kind of confirmed my suspitions about the valves. To big and will hurt the low end torq and inlet flow. a bit hard to find others with a 396 and those valves. Those heads might be better on a 427 or 454.
    found a youtube clip saying that max recomended on a 396 was 2,19 and 1,88. it was not the exact same casting number and bowl cc, but i guess it can be comparared to my heads anyways.

    the guy sounded like he knew what he was talking about...

    i dont know how mutch porting has been done behind the my valves. the runners have not been mesured, and the heads has not been flowed. (my engine shop just sayed they locked really nice and clean, no bumps etc from casting)

    Motor is currantly at a shop beeing rebuildt. and it was the engine builder that mesured and gave me the static comp.
    Me to got a little lower comp when i put the numbers trough a online calculator. (but he did measure it) block has not been decked i belive. all the motor numbers are still intact. (but i dont know about the heads) when i compared the pistons to other picktures i found online, it looks like the top of the pistons has been milled for bigger valves. but the job was done in a way that it looked orginal. only when comparing it with a picture of orginal ones you cold tell it had been milled. also when i locked inside the runners it locked wery smoth, but it was hard to see any evidens of porting job. so ither a wery good job, or my heads came like that stock??. i asked questions about it to my engine builder, becouse i coldant get the info on my casting numbers to match up with valve sizes etc. He didant mesure it, but he said the valves needed to be that big to fit those runners.

    we have the choise between 95 & 98 octane fuel over here. so hopfully i will be ok to run on that.
    i had my totalt timing at 36deg before. maybe ill try 38 when i get it back. info i have found so far, suggest that this engines like a lot of timing.? but we have a little higer octane nubers over here so i dont know how that changes it.

    i started out only planing to change the cam in the motor, as i thought the motor was over camed. it had a 292h in it, and wery low manifold vacum. (2,5-3) so i coldandt get the fitech to work. (min 6) i ordered new cam and only planned to change the cam, but when i pulled the engine apart to change cam, i found a lot of small metall pices in the motor and in the oil, so the motor had to come apart.
    (there were a good bit of things in the motor gone wrong. the valve springs had not been proparly shimed, so the inner springs hadent been compressed enogh with the valves closed, and they had been rattling around and broken the shims under the springs, and the pices had gone around in the motor, ruining the main bearings etc.+ alot of other stuff not beeing proparly asembled / matched)

    so i ordered the cam before i took the motor apart and knew the inernals. thats why the cam is a little small. i asumed stock valves.
    The new cam has the oiling groove in the rear journal as recomended. and the engine builder will dobble and triple check the bearing to make shure the oilflow is getting past the rear journal. (i told them to make 100% shure)

    as for inletmainold i also have a choise of a old weiand 7544, hi rise single plain manifold. but i am guessing it will be worse than the stelth for low end? (or maybe better for fi-tech?)

    How much torq and hp do you think you have in your motor?.
    and how mutch do you think my low end torq will suffer from those valves and intake manifold?.
    (hopfoully i will have enogh manifold vacum to run fi-tec)

    i will have to use the parts i got now due to long lead time, and the engine work shop is fully booked this spring. if i where to wait for more parts, it will be a wery long time before i get the engine back. (not wery many in my part of the contry that want to or have equipment to work on this old engines. had to drive 4 hours to find one. next one was a 10 hour drive away)

    will it be ok cruising with a 3000stall?.
    i will have to use the converter i got on it right now, but looking to order a new one after i have tested how the outcome was with this one. i am not 100% shure whats in this one. last time i drove the car, motor didant like running between 800 & 1200 rpm in neutral :) i guess due to wrong cam timing and low vacum...
     
  5. 73 Rs

    73 Rs New Member

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    7,4 dynamic, you said.

    i do not know how to calculatet that. (and that is with my new cam?)
    thats even worse than i thought.
    i did a leakdown test, and a "dynamic comp" test with the starter & plugs out before i pulled the motor.
    i only had 140psi. i assumed it had something to do with cam timing & i also had leaking valves, so i assumed the low dynamic comp was due to valve leaks / cam and wrong timing. but maybe also that low dynamic comp numbers you listed is going to hurt the motor as well... i found from the interweb that i should have had aproxematly between 175 -190psi dynamic, if the comp was ok. but that is depending on cam selection also i guess?

    hmmm, is this motor going to run anywhere near my persheption of what is satisfactory i wounder.....
    or is it going to give me more headaces.....
     
    Last edited: Apr 20, 2017
  6. fatkid_racing

    fatkid_racing Veteran Member Lifetime Gold Member

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    The 7.4:1 dynamic compression was with the new cam. The 9.5-9.6:1 was the static compression I came up with. With that large of a valve with the bore spacing you have the cylinders were probably relieved at the deck surface. All 396's had a minor relief from the factory but I would take an educated guess and say yours was opened up a bit. If the pistons were indeed fly cut for valve clearance that will effect the total volume of the dome and lower compression, but probably not enough to harm anything. Since the engine is already with a builder I'd have him do at least a skim cut on the heads and deck. So you can run a shim type head gasket as you really need the quench area. Don't run the single plane inlet, it's going to make a far from optimum situation worse. With the cam you chose I'm reasonably sure you'll have enough vacuum for the fitech I don't recall what my total vacuum was but I've got enough to get about 3 pumps of the brake pedal at idle.

    You've got a great start to a respectable street combo, and I commend you on conservatially camming. I think you'll be rather pleased with the overall outcome of the build. It's not going to be what we call a "barn stormer" here in Texas but it's not going to be too slow to enjoy.

    As far as your converter if you can stand the lead time and have the money for it I'd really look into having freak show or BTE in the states build you one. I know Michael at freak show quite well and can help you out if needed. Or if you need a bit bigger converter I've got a low mileage but used 2,000-2,500 summit brand converter you can have for free if you want to pay shipping and import duties.

    As for my combo, it hasn't been on the dyno yet. But I conservatively estimate it to be in the 350-375 horse range and 400-425 torque at the flywheel.
     
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  7. 73 Rs

    73 Rs New Member

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    Thanks,

    i will slip freek show a mail.
    i can get a god quality converter over here for around 7-800usd (or a cheep one for about 400)
    i think i will try the one i got on before ordering.... then it dosent mater with lead time.
    crusing with a stall of 3000rpm will be ok?.

    i tryed to call my engine builder, but he was out on a diffrent job for the rest of the week. so i do not know how far he has gotten already. if the motor is asembled or not.

    hopfoully the motor is going to run when they are finnished :)

    i am trying to get the motor to be more of an enjoyable cruiser, that i can take out and drive & have fun.
    the motor was preatty mutch undrivebale as it was. with no vacum for breaks, terrible low end qualitys, etc.
     
  8. 73 Rs

    73 Rs New Member

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    Got 1 pickture of the heads.

    looks like pocket porting?.
     

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  9. fatkid_racing

    fatkid_racing Veteran Member Lifetime Gold Member

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    The bowls don't appear to have had any work done, but in factory form they're pretty good. A good 3k stall converter will act like a standard converter under most driving conditions, but for sure talk to the builder as they can loosen/tighten the converter for your needs.

    I think you'll be quite pleased overall.
     
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  10. 73 Rs

    73 Rs New Member

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    When i put anoter picture of a 215 casting next to mine it appear that my bowl is a little bigger, and has a little more room around the valves. My bowl was mesured to 104, 6cc instead of 100.9cc as the info on these casting numbers should be. Looks like the arc of the bowl around the inlet valve is closer to the spark plug, than other 215 castings i have found picktures of. Also i have 2.25 & 1.88 valves in them. I havent found any other heads with this casting and those valves @ cc. Or maybe my heads came like that orginal?. The milling in the pistons for 2.25 valves was also very hard to see that work had been done. Maybe the motor was like this orginal?. But i have not found any other motors like this online, so i doubt it. Didn look like there had been done anything to the runners vehind the valves.
     

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