Guest zfan Posted October 27, 2001 Share Posted October 27, 2001 Ive got a 1971 240 Z with a 350 sbc, 700r4 vette tranny, r200 3.54. All said and done the car seems very under powered for whats in it. Ive got a lower compression stock 350 short block, edlebrock rpm heads, airgap manifold and 750 carb. Cam is a hydraulic 234/244. 488/510 cam with 112 lobe seperation, 1.50 roller rockers. 1 5/8 sanderson shorties with dual 2 1/4" exhaust with spintech mufflers. Wheels are 235/60x15. Car seems under powered. Ive not run the quarter as on first try the old r180 went out but guessing from previous cars i have owned it will probably turn high 13's to low 14's. Edlebrock claims with their rpm set up it puts out 420 to 430 hp. This is knowwhere close. If the compression is too low could it have that adverse an effect? Also running all msd ignition with 36 degrees total advance. Do not know compession ratio for sure but can run 87 octane and at wide open there is no ping. Car seems to have no real pull/tork, tire will spin some especially first to second shift with 700r4. Any guesses or ideas, hints would be appreciate as Im seriously looking at a new built short block possibly a 383. Im looking for high 11's to low 12's. Doesnt seem to un reasonable to me! Thanks zfan...Mike Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted October 27, 2001 Share Posted October 27, 2001 Get it to a dyno or if yo umust use a G-Tech. I thought mine was really doing well with the old buttometer - 300RWHP I've got the RPM setup too on a 383 with decent compression and was shooting for 450flywheel HP. I suspect my secondaries, do you run vacuum secondaries too? If so, are you SURE they're opening? Compression can make a big difference, you need to figure out what it is too. A compression test might give you a clue but I'm not sure how accurate that is. Good luck, and keep us posted! Quote Link to comment Share on other sites More sharing options...
pparaska Posted October 27, 2001 Share Posted October 27, 2001 With that cam, you'll need 10:1 or more to have any dynamic cylinder pressure. I think that's the problem. Thinner head gasket might solve SOME of this. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 27, 2001 Share Posted October 27, 2001 According to Edelbrock, the 430hp figure was generated using flat top pistons, and 1.75 inch long tube headers. Compression was right at 9.5-1 using 70cc chamber (Edelbrock RPM) heads. This simply isn't enough compression to develop adequate low end torque numbers. I know, I tried this combination almost to the part number. The car ran high 13's and low 14's and never seemed to run consistently. The cure was to build more compression. As a point of reference, the OEM 350hp 350 cam is a 224/224, 488/488, 114 degree profile using 11-1 pistons. Your cam is ten degrees warmer than this, which means for the compression you are running, you have TOO MUCH cam. I combined this exact same cam with flat tops, RPM manifold, and 155 cc intake cast iron 2.020/1.600 valves with a 64 cc chamber. I match ported the intake to the heads to 1.280 x 2.090 and added a 3300 stall 9.5 inch converter (turbo 350). The car ran a shocking 12.26 at 114 mph! I expanded on this combination in the current engine in the car as follows: same cam, flat tops with 56 CC heads = 11.3-1 and 180 cc intake volume. I added long tube headers and an open plenum(Wiand Team G) manifold. The first pass off the trailer ran 11.34 at 119 MPH. Almost a full second from 10 cc improvement in intake volume, and 2.3 points of compression. Addition of a enclosed fresh air filter system, underdrive damper pulley, electric water pump and alternator field cutout took the car to the 11.0's Addition of a lower first gear (3.05) 700R4 with a 3500 rpm lockup converter took the car into the high ten's. Don't give up on the induction system and 350 platform. Once you get the combination which works well together you would be surprised at how little carb is takes to make the car run. In an attempt to please the NHRA boys, (no cage or jacket) I tried to slow the car down by removing the secondary throttle linkage. Full out it ran an 11.78. With just one inch of pedal travel (one half primary opening) it ran 11.87. So put a set of raised dome pistons in your existing setup and secure a taller stall converter. I think you would be mildly surprised at what just these two things would do for overall performance. Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted October 27, 2001 Share Posted October 27, 2001 "So put a set of raised dome pistons in your existing setup and secure a taller stall converter. I think you would be mildly surprised at what just these two things would do for overall performance." Just a suggestion, I'd put a more normal cam in their first....might be great for you. Something with lobe sep/lift/duration to suit your comp. ratio. My stump puller 325hp cammed 327 was wild and yet it was a 'mild' motor, would squall all through 1st and light up 2-3 etc. Cam changes are relatively easy and can be done in an afternoon if you want. Cheap and simple/lo cost test before spending much bigger bucks and time. Just an option. We're not all knocking on 10's like Kim and his Z army plus trailered Z's (that's a green with envy comment Kim . PS have you been thru a dyno session with A/F data logged, what's your full timing curve look like? Quote Link to comment Share on other sites More sharing options...
z ya Posted October 27, 2001 Share Posted October 27, 2001 z fan, wich spintechs did you get? The sportman street or prostreet? How do you like the sound? I just picked up some 6x4x12 prostreets for my z project.Please tell me they sound bad ass! Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 27, 2001 Share Posted October 27, 2001 you could always git your heads shaved 10 thousends and run stock gaskets it works beleve me tryed and tested.. also might wana try a bigger carb just TRY it might just fall on its face but if you shave them and you have a nice size cam it just might run better with a 800 BUT IT MIGHT NOT dont hold me to this some times it dus some times it just falls on its face depends on brand carb intake and so forth Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted October 27, 2001 Share Posted October 27, 2001 Thanks for the imput. to answer a few questions, yes the carb is a vacuum assisted edlebrock 750 part number 1407 I think. The 700r4 is equipped with a 2600 hole shot converter(brand new) . The engine doent burn or blow oil which leads to believe low compression(8-9-1 range. The spintechs are 2 1/2" x8 x 16 I believe low profile for underside of car cant find paperwork for them. They sound alot like flowmasters, maybe not as loud as two chambers? I like the sound myself. Maybe less cam/roller setup is the answer but have given the idea of 10.5 to 1 forged short block. Regarding carb, without load secondaries dont open so how do you tell? Should of bought a Holley! Thanks Mike Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 28, 2001 Share Posted October 28, 2001 The 2600 rpm stall is still quite low as converters go. Have you ever power braked the motor and noted the stall RPM? How high can you "flash" the converter to? Having lots of available horsepower and getting to it are two different things. The B&M 2400 is an 11 inch converter. I had a similar stall 11 inch GER converter which produced 2.0+ sixty foot times. I changed to a 9.5 inch 3300 stall GER and the sixty foot times dropped into the 1.70+ range. The problem is that most converters which retain the lockup feature, have relatively low stall numbers. Grafting a 9 inch converter onto the full size stock 700R4 lockup converter works like a charm. 3300 rpm stall AND a clutch which can take the 450 lbs.+ torque which even 350's can develop. Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted October 29, 2001 Share Posted October 29, 2001 Got a few answers yesterday. Secondaries do open under load bad thing is ran a compression check and best read pulled was 125 lbs, obviously not good at all. Good news is a friend knows a reputable shop that has a built 383 long block that a customer backed out on and they will let it go for 2200. it has eagle crank and rods with forged pistons. Im going to call them today. zfan..Mike Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted October 30, 2001 Share Posted October 30, 2001 I agree that your problem is the low comp. pistons; the 383 should be an excellant solution. You'ld easily spend the $2200 on machining & proper building of your 350 if done correctly. Find out the actual spec's on the 383 & let us know (curious as a cat I am I am Sam I am). Kevin, (Yea,Still an Inliner) Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted October 30, 2001 Share Posted October 30, 2001 zfan let us know what cylinder heads,intake and true compression ratio you wind up with on that 383 and the max valve lift that your heads/springs can handle and we can give you a good idea as to the best cam to use. [ October 29, 2001: Message edited by: grumpyvette ] Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted November 1, 2001 Share Posted November 1, 2001 Well I was too late for the 383 , it was already gone. Called engine builders looking for a 350 that a customer backed out on. Sometimes you can get a good deal. I found a 350 four bolt, bored 3 over with eagle crank,rods,arp rod bolt,hyper 10.5 to 1's for 1100 with no cam. Bought the motor and am going full roller cam. Im having heads looked at, springs need replacing, for roller cam, roller lifters,treated push rods and 1.6 roller rockers and engine completly assembled and tuned Im looking at 2100. out the door. This was by far the best deal of them all. What do you all think? zfan...Mike Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 2, 2001 Share Posted November 2, 2001 If you have a choice of cams at this point, why not simply buy a bigger cam and stick to 1.52 rockers? I have never liked the rocker tip to valve stem contact of 1.6 rockers. Getting the valve geometry correct is a must, and adjustable push rods designs leave me cold. My best efforts to get 1.6 rockers right the first time resulted in valve guide wear which was way premature. (less than 3000 miles) The attendant decreased fulcrum leverage at the rocker, combined with roller cam compatible springs can sorely test even 7/16" rocker studs. We think that it was rocker stud flex (should have bought a stud girdle) caused the uneven wear patterns on the valve stems. I cured the problem with a cam and rocker change and had no other problems in the last six years with the top end of the motor. IMO, dyno results I have seen comparing 1.5 and 1.6 rockers just didn't build enough additional HP to justify the other problems which can accompany the longer rocker. Quote Link to comment Share on other sites More sharing options...
pparaska Posted November 2, 2001 Share Posted November 2, 2001 Sweet cam selection - if I was doing a hyd roller, that'd be the one! (for the 10.5:1 you're building for) I agree with Kim - no need for 1.6's if the cam can get enough lift for the duration used. A roller opens up the possibilities greatly for more duration with mild to a bit high lift - and 1.5's make sense - unless you need more lift than even a roller without going to more duration. BTW, I seriously doubt you'll call your 350 underpowered with that compression increase and that cam! [ November 02, 2001: Message edited by: pparaska ] Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 3, 2001 Share Posted November 3, 2001 Your going to love that cam. The midrange really pulls well. I think you might find some idling problems unless you free up the torque converter a bit. Below 1000 rpm this cam doesn't produce a whole bunch of HP. To get to the bottom end of your torque curve quickly, you will need at least a 3300 stall converter. The problem has been in the past that most lockups aren't being offered with that high of a stall and a full size clutch. The grafted HI TECH converter gives the best of all worlds. Full size clutch, 3300 stall and under $400.00 I adjusted my 700R4 governor to shift at 5800 and 6200 on a full bore shift. This cam runs dry right at 6200 and with a set of 3.54's your second and third gear should exhibit a pull duration to die for. Second/third will shift right at 600 ft and peak right at 1320 ft. at anywhere from 120 to 130 mph N/A. (Even a small NOx setup will take you well into the low to mid tens!) Enjoy. Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted November 3, 2001 Share Posted November 3, 2001 I just spoke to engine builder and we have decided to go with the comp. cams extreme energy roller cam xr288 hr-10. We are using 1.5 roller rockers after all but spring in Rpm heads will need to get changed out. The cam is listed at .50 to be 236/242..520/540. also using new push rods. I think at 10.5 to 1 compression I should be good to go for now. Next week it should be in the car and then its time to go the dyno shop. Thanks for the imput guys. zfan..Mike Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted November 4, 2001 Share Posted November 4, 2001 Well Guys thanks for all the imput and help. Had to laugh friday engine builder said short block in it was probably 8.25 to 1 at best. Had dished four valve relief and was in the hole20 to 30 thousandthes. Dooh!! no wonder it was under performing. The guy at the shop was actually impressed with the cars performance with the low comp. motor,I let him drive it!! Maybe now he'll want a v8Z!! zfan..Mike Quote Link to comment Share on other sites More sharing options...
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