Posted By: Ian
comp vs cam - 10/02/11 11:06 AM
what are your guys theorys on comp vs cam, 408 with big heads flow 350 cfm/230 700 lift with 11.5 comp what cam vs the comp i have seen cams very from 250 to 280 @050 
comp vs cam
Posted By: viperblue72
Re: comp vs cam - 10/02/11 06:36 PM
Are you saying what size cam for 11.5 compression? How much rpm do you plan to spin it? Stall speed? Car weight?
Posted By: emarine01
Re: comp vs cam - 10/02/11 08:15 PM
Hey Ian 
It does come down to a point of how high you want to turn , weight & gearing, We droped down from 280@.050 to 260, lost around 1000 rpm but we made up for it with gear & tire & have picked up speed with less ware & tear, remember We mud race so its all about instant wheel speed on shift recovery, 
It does come down to a point of how high you want to turn , weight & gearing, We droped down from 280@.050 to 260, lost around 1000 rpm but we made up for it with gear & tire & have picked up speed with less ware & tear, remember We mud race so its all about instant wheel speed on shift recovery,
Posted By: Ian
Re: comp vs cam - 10/03/11 04:08 AM
hi craig got the engine torn down and givin it a freshin up i have that 270/277 roller 700/650 lift or would it go better with a smaller 260/266 cam with the same lift car weight 3550 and 4500 stall and 1.76 glide my max rpm will be 7200 4.1 gears 28 /9 tyres which cam
Posted By: Cab_Burge
Re: comp vs cam - 10/03/11 05:42 AM
I would try the smaller one 
I have a comp Cams custom ground solid roller cam in my 518 C.I. pum gas motor that is very close to yours. Mine is 260 @ .050 on the intake with .420 lobe lift, 1.65 rockers on both sides and 266 @.050 on the exhaust with .409 lobe lift. The motor pulls real hard to above 7800 RPM according to the VDO Extreme playback tach in the car 
The last time that motor was on a engine dyno it made peak HP at 7300 and 7400 RPM 
Good luck 
I have a comp Cams custom ground solid roller cam in my 518 C.I. pum gas motor that is very close to yours. Mine is 260 @ .050 on the intake with .420 lobe lift, 1.65 rockers on both sides and 266 @.050 on the exhaust with .409 lobe lift. The motor pulls real hard to above 7800 RPM according to the VDO Extreme playback tach in the car The last time that motor was on a engine dyno it made peak HP at 7300 and 7400 RPM Good luck
Posted By: Ian
Re: comp vs cam - 10/03/11 06:53 AM
Quote:
I would try the smaller one
thanks mate i have never had a roller before , the cam in it was ft 259/265 109 l/c 600 lift ,all my seats on the indy heads were oval my head man here said they were the worst he has seen lol should have listed to ryan on there valve jobs lol
Posted By: emarine01
Re: comp vs cam - 10/03/11 01:27 PM
260 vs 270 .... the 11.5 should support either cam, Our 414 W5 doesn't flow as much air as your heads, the 260 duration .680 lift cam we run now makes the best power @ 6600 to 7000 then falls off hard, It maxes out @ 7200 & we shift @ 6800, What was your power band with the old cam?
Posted By: Ian
Re: comp vs cam - 10/03/11 04:37 PM
went flat 6700 rpm ,comp woz 11.3 i have milled heads and taken 4 cc out of them , i will be flowing them in 2 days see if valve job makes any changes thanks ian
Posted By: emarine01
Re: comp vs cam - 10/03/11 08:04 PM
Cab may have the right answer for ya, My engine is intake manifold restricted < small port M1 > so I really don't know where the top of the 260 cam should be, We hit the vert hard @ 5500, rips right to 6800, truck noses over @7k and has nothing left @7200
Posted By: Ian
Re: comp vs cam - 10/04/11 02:58 AM
cab ,how big are your heads that cam is pulling well up high above 7 k the heads must increase rpm up top thanks
Posted By: Cab_Burge
Re: comp vs cam - 10/04/11 04:53 AM
Quote:I have had several different sets of heads and different intake systems on it, it would not pull good in high gear above 6200 RPM with the CNC ported Eddy RPM and stock type low deck six pak intake and carbs. It pulled real hard in 1st and 2nd to above 7300 RPM but not in high gear
cab ,how big are your heads that cam is pulling well up high above 7 k the heads must increase rpm up top thanks
I switch the heads and intake to a set of Indy SR heads with the M.W. size intake ports with a Indy 400-3 modified by Bob George Racing and I have used several different 1050 Holley Doniators on it as well as a Indy 400-2 intake abd 850 Holley D.P. 
It pulls real hard now in 3rd gear with the Indy 400-3 and 1050 carb I shift it between 7200 RPM to 7600 RPM in 1st gear and around 7000 RPM in 2nd egar and it crosses the finish line at or real close to 7000 RPM, depending on where I shift it out of 2nd gear It will cross the finish line in the 1/4 mile at a higher RPM if I short shift 1st or 2nd gear I was pleasently suprised on how much better the motor runs with the bigger heads 
Big C.I. motors need big heads I guess 
Posted By: 440Jim
Re: comp vs cam - 10/04/11 04:04 PM
Quote:I was thinking 266 to let the head flow do the work not more cam. The 11.5 CR really limits the duration I would use. The 260 sounds a little small, but since the lobes are more agressive than the 270 (same lift), I would start with the smaller cam. Better to under cam than over cam, IMO.
hi craig got the engine torn down and givin it a freshin up i have that 270/277 roller 700/650 lift or would it go better with a smaller 260/266 cam with the same lift
Posted By: Ian
Re: comp vs cam - 10/04/11 05:45 PM
Quote:thanks i will try to get comp 11.9 if i can i will give it a final cc after increasing valve releaf and i will give it a sniff of gas at times.Quote:I was thinking 266 to let the head flow do the work not more cam. The 11.5 CR really limits the duration I would use. The 260 sounds a little small, but since the lobes are more agressive than the 270 (same lift), I would start with the smaller cam. Better to under cam than over cam, IMO.
hi craig got the engine torn down and givin it a freshin up i have that 270/277 roller 700/650 lift or would it go better with a smaller 260/266 cam with the same lift
Posted By: Cab_Burge
Re: comp vs cam - 10/04/11 05:48 PM
I forgot to mention that the change of heads also increased the comp. ratio from 10.29 to 1 to 10.82 to 1, not much increase, but some
Posted By: emarine01
Re: comp vs cam - 10/04/11 07:27 PM
Ian, what center are the cams cut on... 108...106? When we swapped to the smaller cam I installed it 106 on 106... with the large cam it was installed +4 107 on 103.
Posted By: Ian
Re: comp vs cam - 10/05/11 04:19 AM
thanks guys, the cam is 108 l/c and run it at 102-4 should pull harder on conveter and better mid range with more cld pressure,i may be wrong