denny411 Posted January 30, 2002 Share Posted January 30, 2002 Heres my dilema; I`m building two engines. One is a 383 sbc w/11:1 weisco pistons 5.7 eagle rods,dart sportsmanII heads w/200cc runners and 64cc chambers 2.02 int 1.65 exh (will be flow benched)w/1.5 ratio crane full roller rocker arms, comp roller cam w/ .631 int .631 exh, dur@.050 268, lobe separation 109 degrees-----or w/ 1.6 harland sharp roller rockers the gross lift would go up to .673 all else stays the same.The question is...Would the extra lift from the 1.6 help at all or would it be overkill. The other engine is a 355 sbc w/ 11:1 weisco`s 6 in.summit stagr II rods, dartII heads w/200cc runners /64cc chambers 2.02`s and1.60`s, will also be ported the cam is Comp cams 305H-10 .525 int/.525 exh Dur,is 253@ .050 lobe separation is 110 degrees. Which engine would benfit the most from the added lift of the 1.6 ratio rocker arms Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted January 30, 2002 Share Posted January 30, 2002 in most cases extra lift over .600 or so does not add much if any hp on a small block because the amount of extra flow in the port above .600 lift is minimal,my first thought would be to use them on the 355 to gain flow on both lobes but after playing with several sbcs lately with different rocker arm ratios I would say try the 1.6 rockers on both engines intake valves only and the 1.5 rockers on the exhaust valves , Im betting that will gain you the best results. the intake lobes on most sbc engines have less duration and can use the extra flow that lift can give, while the exhaust has a longer durration and is easier to get the flow anyway because its under pressure. Quote Link to comment Share on other sites More sharing options...
denny411 Posted January 30, 2002 Author Share Posted January 30, 2002 what kind of horsepower/torque should I expect from these engines? does anyone have recomendations on carb/intake combinations for these engines? I`ve got a victor jr for one of them. Thanks in advance Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted January 30, 2002 Share Posted January 30, 2002 the type intake and carb depends somewhat on the cars weight and gearing but the cams you have chosen are made for use with higher rear gear ratios (4.11 and higher)and single plane intakes like the vic jr you have chosen,btw with the rockers used as I suggested the 383 will be close to 470hp/450 tq and the 355 will be close to 445hp/440 tq Quote Link to comment Share on other sites More sharing options...
denny411 Posted January 30, 2002 Author Share Posted January 30, 2002 Thanks for the input,I`m gonna have to rethink my cam choices.These engines are being assembled mostly w/ parts that I have gotten from people who never finished their projects or just needed the money.Specifically, the cams were not chosen according to my plans for either of the engines.I guess I`ll need to do some more research to find cams that will maximize torque and horsepower alike,for both engines.---------THE SEARCH GOES ON Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted January 30, 2002 Share Posted January 30, 2002 with those cylinder heads those cams come close to the max you can get, its not the cam choice holding your hp numbers back below 500 its the CYLINDER HEADS, heres the heads you need to kick the hp above 500hp, http://www.dartheads.com/sbpro227.htm Quote Link to comment Share on other sites More sharing options...
denny411 Posted January 30, 2002 Author Share Posted January 30, 2002 What do you think I could expect from the 383 if I used the pro 1 heads and the 1;6 rockers on both valves(or would you still suggest the 1;6 int/1;5 exh)? I talked to a guy about a year ago in indiana that builds circle track engines,He stated that on his flow bench he had been able to flow dartII`s out to produce 525 hp from a 355 w/11;1 comp .670 total lift.I can`t recall duration or lobe separation.At that time he said that was the best you could get from those heads and that any lift over .670 was wasted.I had planned on having this guy do my head/dyno work. He has two engine dyno`s and one chassis dyno.Do these numbers sound reasonable or do you think this guy was exagerating to get some business? What kind of $$$ will I have in the Pro1`s? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted January 30, 2002 Share Posted January 30, 2002 Also you should think about piston to valve clearances. You said you have 11 - 1 with the 64cc heads on the 383, With over .600 lift you will most likely have to fly cut the tops of the pistons (domed pistons probably) because you may not have enough distance between the valve and top of piston at max lift. Also you should check the springs out on the 383, thats a good size roller for a SBC and will require heavier springs than what probably came on those heads, along with checking to see if you have proper clearance(and not coil bind) at max lift. I agree with grumpyvette, the heads would be the limiting factor, instead of the cams. Quote Link to comment Share on other sites More sharing options...
denny411 Posted January 30, 2002 Author Share Posted January 30, 2002 springs are 280#@ seat/580# open.O-yeah I was planning on checking piston to valve clearance,I have a close friend who trashed his 460 after 5 runs.valve hit a piston and thats all she wrote The valve head broke off and went through the cylynder wall. he ended up trashing one head,the block and two pistons.(he was running a .690 lift roller cam) Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted January 30, 2002 Share Posted January 30, 2002 heres a quick and reasonably accurate way to judge heads as to the airflow necessary to get to a certain hp level, .257 x flow x #cylinders= MAX PROBABLE HP so looking at those heads you have lets say they flow 260cfm at your valve lift just for some numbers to plug in! .257 x 260 x 8=534 potential max hp now they are not saying the heads get you that hp ,they are saying that those heads block you from getting more than that hp level unless ported to flow more fuel/air mix and thats a flow number with the carb and intake atached so you better figure on looseing at least 10% minimum from the head flow figures, so that means you need heads that flow 275-310 cfm to get solidly above the 525hp level in a small block chevy with an average intake/ carb combo! Quote Link to comment Share on other sites More sharing options...
biohzrd Posted January 30, 2002 Share Posted January 30, 2002 boy grumpy you sure know some stuff thats a pretty nice formula. thanks for the help Quote Link to comment Share on other sites More sharing options...
denny411 Posted January 30, 2002 Author Share Posted January 30, 2002 Thanks grummpy ,Back to the drawing board.I`m looking to get 500+hp and similar torque from the 355,and as close to 600hp/torque as possible from the 383.I know it won`t be cheap or easy, but I`ve got plenty of time for the 383.the 355 will go into the 77z that I have now, and I`ll save the 383 for a 240 project down the road(max hp/wgt ratio) Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted January 30, 2002 Share Posted January 30, 2002 that 500hp and 600ft lbs you are looking for are at or even above the limits that a non-supercharged, non-nitrious small block is capable of ECONOMICALLY GETTING TOO AND MAINTAINING LONG TERM! my advise would be to build a big block 540 rat motor(FOR WHICH GETTING THOSE NUMBERS ARE EASY) or use a supercharger on the small block engine. Quote Link to comment Share on other sites More sharing options...
denny411 Posted January 31, 2002 Author Share Posted January 31, 2002 I suppose I could tame down the engines themselves and make up the difference w/ nitrous.A big block would be nice but the fabrication of the body would be extensive. I really didn`t wan`t to get that involved in body modifications.if I tone down the 383 to around 550hp that would be a little more reliable.I already have the block w/steel caps-main studs- Je rods-weisco pistons-head studs and a 4340 steel crank.That should be a solid foundation I just need a great set of heads and I should be in the ballpark. The 355 is a zz3 4 bolt main block w/ a Gm performance steel crank w/ one piece rear main seal.w/ weisco pistons and summit 6.00 stage II rods.In my opinion another stout foundation.I guess anyway you look at it any thing over 450hp is still kickin a$$ in a 240 or 280.Thanks much for the input Quote Link to comment Share on other sites More sharing options...
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