[Amc-list] V8 Cylinder Head Questions - 2nd Follow up

[Nick ALFANO <71amx@xxxxxxxxxxxxx>]

Mark,
 
If torque is the main goal, maybe a smaller intake valve on the 360 would help slightly but the smaller exhaust valve is going to hurt more than it helps.  If you can speed up the charge into the cylinder that would help.  Another way to benefit down low if the engine is doggy off the line but picks up hard at a little higher RPM range is to simply advance the cam a few degrees.  This will increase the cylinder pressure giving you more low end power but will take some away from the top end.  If the other components don't match though, you are fighting a battle that is hard to win until you find the part that is hurting your set up.  
 
On the 360 engine with a mild cam, I wouldn't increase either of the valves as the stock size works well for that engine as well as the 390 and 401.  The 360-401 engines respond well to larger intake valves when the cam warrants them.  If a person wanted to spend the money wisely on anything in the heads for a mild engine, clean up the ports a little like matching the intake and exhaust ports to that of the intake and the exhaust manifold and clean out any casting obstruction.   An HEI or MSD Ready To Run distributor is also a good add for power and fuel mileage over a stock unit.  An X pipe in the exhaust is also going to help in low end torque helping scavenge exhaust gas better.  
 
You are correct about the adds out there for increasing power.  Most seem to go after just peak HP increases or Torque increases at an RPM that is not really helping the average driver.  The best ones out there work with the computer to change the mapping in the lower RPM range for torque and fuel consumption and then again at WOT to gain HP in the upper RPM range.  A little harder to do with a non-computer controlled engines with a carb.  
 
If you want the best of both worlds so to speak, a hydraulic roller cam is the way to go.  The aggressive ramp speeds and lobe design really allows you to have good power throughout the RPM range by broadening the power band and is less prone to hurting one end or the other (as long as you stay within reason for duration).  
 
 
Nick,
 
 
Alfano Performance
4849-76 st.
Kenosha, WI. 53142
262-308-1302
262-942-8271 after 6pm central and weekends 
 
 
So, what your realy saying here is that greg realy needs to look at what rpm he is operating the jeep in and how he drives it before decidng if the 304 heads need to be messed with.
  I agree that depending on the driver many street driven 4X4's see rpms up to the 6,000 rpm range, but in theses days of gas at $3.25 a gallon for 87 octane, well my 4x4 gets driven gently, so it may well prove that Greg drives his likewise. My 04 with a 4.7 in it that likes to rev nice a cleanly still only sees 4500rpm on a rare occasion. I'd probably not be too bothered by a natural rev limt in the form of small valves. Specially if the torgue was there below that.
  I know I have looked at many dyno runs shown in many mags, [yeah, i know, mags not real life]. I often notice that torque drops off in the lower rpms on many of the mods the mags claim give horsepower improvements. Yeha the numbers go up, but a lot of the time they don't go has high as hey startd off till they are getting up to the 4,000+ rpm, range. 
  How does the AMC V-8 respond to larger valves compard to stock? let alone 304 heads?
I'm realy curious as in that case of the Ford engine when my brother dropped the small valved heads on it. Well, it was VERY torquey, course we did not do any dyno time, so how it would have been with actual 351 heads on it i do not know.

--
Mark Price
Morgantown, WV
1969 AMC Rambler, 4.0L, EFI, T-5
2004 Grand Cherokee Laredo, 4.7L, Quadratrc II
" Chronic Pain Hurts"
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
_______________________________________________
Amc-list mailing list
Amc-list@xxxxxxxxxxxx
http://www.amc-list.com/mailman/listinfo/amc-list