Heres my problem. At 5700 rpm the engine straight lines at 5700. No hp gain or loss. This is on a chassie dyno.Engine will rev past 6500, but no more than 302hp at 5700. Have spent 6hrs on dyno setting up the basic's. Here is the related info. 92 roller block,with SCAT 347 stroker kit. All forged internals. Main girdle,10 1/2 final compression.202/160 valves. 210 runners.Stud girdles. 750 HP carb.Custom grind Cam,249/254@50,593lift,108CL.Installed straight up as per verbal communication with cam manufacturer. Cam card says required spring pressures are 200 at the seat,and 600 open.Comp Cams 838-16 roller lifters,comp 1632-16 rocker arms. My heads have 220,630.Good to 650 lift.Valve lash was 26 hot. After multiple pulls, carb adjustments(jetting) air/fuel ratio is 12.5 from 3000 to 6500. AFTER more long distant communication with Cam manufacturer,and his suggested changes this engine still won't produce more than 302 at 5700. Still a straight line after5700. No drop or gain in HP or Torque after 5700. any suggestions as why the HP and torque are this low.302HP and 292tq.. at 5600. Built C4 with 4800 TCI convertor. 462 spooled rear. thks to any1 for info RON
darren I,m running a MSD 6al, Msd dizzy, Msd coil. Have checked out coil, and the 7000 chip. all OK Total timing is 33. This is where the most HP and Torque was on the Dyno
YA thanks Derek. Me and other friends can,t figure it out either. There is no cheap parts in this motor.
First off.. I would be questioning the validity of that dyno. A quick backroads quarter mile test should easily verify.. or debunk.. the numbers you've been given. also.. you don't mention what intake you have on there.. but even an airgap shouyld give you better than that. and .026 hot seems like a bit too much clearance.. but the cam mfgr should know what you need there. PS.. also consider that too loose of a converter can surely cause similar issues as well.
Thks for your reply. After 6hrs of consultation with cam manufacturer, giving them all info about car, tranny and engine, and hopefully wanting to have 400 hp at the wheels(gotta have a goal), they decided on the cam specs. When that wasnt acheived, I spent more time long distance talking and they suggested to drop the lash to 20, which i did and several other changes which made no difference.Parker funnel intake. The dyno was a Mustang dyno operated by a man with 10 yrs experience with dyno tuning. De silva racing(mustang store).
That combo should obviously be peaking much higher than that. 400+ at the wheels isn't unrealistic either. And based on that.. I would be looking at the converter for its potential role in soaking up the engines upper power band on you.
I would also suggest looking at the converter. If I remember right your only allowed like 9% slippage ( engine rpm vs mph ) I once had this problem on my car mine was slipping 12%. A new converter gained me 6 tenths and 4 mph in the 1/4. Also what fuel are you running? Higher octane than you need will slow you down.
well I didnt think convertor would take away 75hp and100tq.I could put in my 3800 convertor and try that, but the season is just finishing up here. only 1 more weekend for racing. I run 94 octane pump gas.No racing fuel for me. Thats why only 10 1/2CR. gas pump friendly.Several knowlegdeable ford racers are saying Cam might be the problem. My 4800 converter on a trans brake, leaving at 3500, generated a 11:60@ 114.8 mph.That was in my mav,weighing in at 3050 with driver.Foot brakings best was 12:30s Don,t know what is goin on. How do you test a converter for slippage?.Converter flashes at 4500 on the dyno.
I personally think the cam is falling short. I would expect you to have at least .630+ lift and more like 264+@.050. I am assuming you are running solid rollers, so if a change in valve lash gave you nothing.......................again it comes down to the cam. Did you use a degree wheel or just take the cam guy's word fpr straight up....................never take anyones word......always double check yourself................... Also, I'd be checking with the guy that built your converter. My rule of thumb has always been the stall should be around 700rpm below your peak torque...............the other thing is to run the Funnel Web I think your CR and duration/lift is just not enough, the intake should really come alive at just under 5000rpm, if it were me I'd try a AirGap................................IMHO
Ron to check your slippage you need to know your engine rpm and mph as you cross the 1/4 mile mark. The mph you can get from your timeslip. Rpm you'll need to watch for as accurately as possible. Does your dyno sheet have that info? Next you figure out what your engine should be turning at your given mph as if it had a manual transmission as in no slippage which involves mph,gear ratio, and tire diameter. The best thing about figuring slippage is it doesn't cost anything. The last time I figured mine I googled dyno math and found the formula. If slippage is within limits I'd look at cam and or intake as mentioned.
Thks to you. I was hoping you would say something.Yes they are mech roller lifters.Yes my engine builder put the cam in using a degree wheel. The converter is a TCI 4800 that flashes at 4500 on the dyno.Well my cam manufacturer was told I was using the parker intake, along with the 750 Holley. Using or trying for 10.5 CR(final). Am thinking of Comp Cams 35-772-8 cam as a replacement if cam manufacturer wont warrantee cam.Its NOT doin what they said it would do. Again thks for your knowledable comments. Ron
Why I,m thinking of the Comp Cam 35-772-8 is a friend runs this cam in his stroked motor with excellent results. Same weight car only its a top loader not a C4.
You are welcome Ron. One thing to keep in mind is the cam is probably the single most important and also the most difficult thing to get right..............and it is actually the "Brain" of the motor. I'm not saying that cam manufactures are.......how should I say.............maybe out of touch with certain engine combo's when it comes to stroker small block Fords........................but............................ Now with that said, the cam is one of the easier things to change on the motor so I'd look at something a little more aggressive that will fit the profile of the intake/heads/CR. I would also talk with your engine builder......if he is experienced with building street or strip motors.........he should have some input.........maybe. Before you go out and buy/get another cam I'd call a number of the cam manfacturers and give them your specs............then evaluate what each one has said.......and there is also having one built to your specs, I am sure there are a number of us here that could help........just a suggestion. As was suggested, you can check slippage, but you are going to have to run it on the strip. I would suggest doing this anyway just to get a feel of where you are and if you need to shift around 6300rpm so be it. Remember that if you were getting peak HP at 5700rpm you really want to take the motor to just a little over 6000rpm because you want to stay at the peak HP...........................................................................IMHO
