I have a 383 that produces over 350 ft/lb at the wheels from 2200RPM with a peak of 392. My HP maxes out at 350RWHP right about the time it crosses the torque curve and then it drops off. It's really lacking in the top end HP area. I'd like some more top end HP and I'm willing to sacrifice a little low end torque. A cam swap is not monetarily feasable at the moment.

I had 1 5/8 primary pipe shorties which may have been choking me in the upper RPM's. I'm installing 1 3/4 primary long tubes and upgrading to 1.6 rockers. my current cam is hyd/roller, 224/224 .525/.525@.050 110LSA. I'm changing my rockers to 1.6 which will boost the lift to .560. Heads are ported vortecs with 2.02/1.60 valves. RPM air gap manifold.

I'm not sure if the increased lift from the rockers and bigger exhaust will do the trick. I have the intake and valve train removed now and it would be easier to access the timing chain and cam now, rather than after I get everything back together.

So I was wondering if advancing or retarding the timing of the cam would gain me a more top end HP. I think I need to retard it but I'm not sure. Would it make enough difference to make it worthwhile?

And if so, which keyway do I need to use then?


Thanks
Hodge

 

Retarding the cam would raise the RPMs of the powerband.

I think I'd try the headers first.

 

The most important event in cam timing is:
the timing of the closing of the intake valve.
...later closing, power band moves up in rpm.
.
if you retard the cam, the rpm powerband will move up.
Check for, exhaust valve to piston, clearance.
.
as for nombers, you might want to start with
4 degrees 'crank' retard on the camshaft.
Check with the instructions that came with
the cam sprockets, you are using. for details.

 

That's exactly what I'm looking for.

I'd hate to have to drain everything and remove the intake again just to retard the cam. It's all apart now so it would be a lot less work now, rather than waiting for results from the headers. I'm really undecided about it right now.

All I'd have to do to get the heads off now is remove the head bolts so I was thinking of getting them flow tested to see what they really can do. I might find out that the heads are holding me back.

Do you guys have any idea how much the max HP RPM's would go up if it was retarded 4* assuming that all other things were left unchanged?
obviously it'll go up a little with the changes I have made but if nothing else where changed what could someone expect from just retarding 4*?

Thanks everyone

 

Whats the ICA of the cam right now (when installed straight up) ??

Though its true advancing/retarding moves the power band round, sometimes the right combo can really make the motor come alive.

I ended up going with a 230/245 .533/.540 113 LSA 112 ICA
for my supercharged application. (custom grind). If the intercooler works, the motor has the potential to make upwards of 600hp.

-- Joe

 

What does the intake have to do with retarding the cam? What kind of motor are you working on?

If it's a small block Chevy, 4° of cam timing shift, = about 250 RPM of peak HP shift. Miniscule.

 

Retarding the cam changes the ICA, obviously. I'm curious where he is right now vs where he wants to be.

Every motor is different, but 4degrees of ica change can be 1hp, no hp, a minor rpm shift, or 50hp..


Now, how did you get the degree character to come up?

-- Joe

 

Not sure where the ICA is. We didn't get that technical when we installed the cam. we just got TDC on #1 and instralled it straight up according to the timing marks on the sprockets. But I think I got the info I was looking for with RB83L69 comment of 250 RPM's

250 or even as much as 350 RPM's isn't worth the hassle to me. I'll just keep shifting a little lower. I'm planning on a new cam before summer is over anyway. One that is better suited to my motor.

I guess I'll see what the incresed lift and larger exhaust gets me.

Thanks guys

Hodge

 

Yeah, that's really just a rule of thumb, YRMV.

It's a fine-tuning thing. In reality, most timing chains out there today, have more slack than that; so, go figure. The cam timing adjusted itself that much or more between install and now. Maybe yours already has too. Especially if you used a relatively cheap "roller" timing chain (the ones less than $30 or so). Those are worse about getting slack, than stock Link-Belt style ones.

 

Intake centerline angle.


I'm guessing with the 110lsa, your prolly like 106ica ..


You might wanna enter your timing events into desktop dyno, and play around and see how it changes the slope.

-- Joe

 

OBTW .... the ° is alt-0176. ½ is alt-0189. ¿ is alt-0191. é is alt-0233. ¡ (one of my personal favorites: lets me type the name of a certain grain popular in Asia, that the board censors) is available. There's an astounding variety of characters you can get to that way, that aren't on the keyboard.

 

Retard cam? I had a retard cam once. It said "Crane" on it, and was one of those old "Z-28" .447/.447 single grinds. It was maybe good for pulling boats, but didn't even make a good prybar.

Oh. You meant valve timing.

BTW - If you're using the standard ASCII character set, you can also get it by [ALT]248. That's the old fashioned way.

¿Any questions, señor?

 

Man. the marvals of a GUI.. I spend too long in a vt100 terminal .

-- Joe

 

id rather bolt on headers and other bolt ons than redegree a cam assuming you have a degree wheel and a 2 piece cover you still have to unbolt your accessories and take out you rad and other things to get the cam out or pull of the front bumper. if i was gonna do all that id just buy a new cam and rockers if you dont want.5 or.6 you can go up to .7 need new pushrods and springs. that will give you more lift and more hp