Thread: trying to learn something here

Tweet

why do i need more compression to run a bigger cam? im trying to understand.
if i have a 350 with a magnum 280 that runs good what happens if i put the same cam in a 305? of course the 305 would have less hp,but would it run right? or would there not be enough compression because the valves would be opening further?

Originally Posted by S19243H

why do i need more compression to run a bigger cam? im trying to understand.
if i have a 350 with a magnum 280 that runs good what happens if i put the same cam in a 305? of course the 305 would have less hp,but would it run right? or would there not be enough compression because the valves would be opening further?

The larger cam will not increase your compression it will actually tend to blow more of it out the exhaust.
To understand all this do a google search for dynamic compression and static compression.

what are you using the 305 for? a race car or?????

no im just comparingsay a 3800 lb car to a 2000lb car. does the wait of the car have anything to do with how big a cam i can use. i have a 305 out of a 86 z28 it has a 268 extreme energy and ran pretty good .now i have a 23 t that weighs 1600lbs can i run a 274 or one of those new thupr cams in it because the car weighs so much less?

Smaller engines "see" a cam as being bigger (more radical) than larger engines.

Putting the cam that performed weell in a 350 into the 305 MIGHT make it idle rougher and more tempramental.

Weight of the vehicle, like everything else, has a bearing on how certain parts respond.

Originally Posted by S19243H

no im just comparingsay a 3800 lb car to a 2000lb car. does the wait of the car have anything to do with how big a cam i can use. i have a 305 out of a 86 z28 it has a 268 extreme energy and ran pretty good .now i have a 23 t that weighs 1600lbs can i run a 274 or one of those new thupr cams in it because the car weighs so much less?

It will take more tq. to get the heavier car to move off the line as the lighter car at the same rate.
The larger cam makes torque also but farther up the rpm scale.
In other words the larger cam will want to rev. higher so you will need more gear and more stall for everything to work together.

That XE268H is about the biggest camshaft you can run in a street 305 with less then 10.1 C/R . And your light car . That 1986 Z-28 305 has #601 or #416 heads with only 1.84 intake valves . And the intake ports have the EPA bumps in the top corrners . I have a set of the #601 heads in the Basement . They need hours of porting . Do the porting to the heads . Leave the XE268X cam in it . Even the XE262H would have been big enough .

Originally Posted by S19243H

why do i need more compression to run a bigger cam? im trying to understand.
if i have a 350 with a magnum 280 that runs good what happens if i put the same cam in a 305? of course the 305 would have less hp,but would it run right? or would there not be enough compression because the valves would be opening further?

The later than stock intake valve closing event bleeds off pressure.

Do a little reading on dynamic compression ratios.