Lobe separation
 

Is there a magic number for lobe separation to prevent reversion?

110 degrees has been thrown out ther before.

Does overall lift, flow or cubic inches influence this number?

Re: Lobe separation
 

Lobe sepration plays an effect on it however the major player is duration the amount of time the valve is off seat the intake centerline is at 104-108 it is best in smaller cams to drop the lobe cente to 114 and the intake center line to the before mentiond 110 but size of exhaust and type play a large effect the duration at @50should be under 224 for stock manafolds 234-240 for stuff like powerflow and under 254 for tube type headers, also restrickting the amount of water in the exh helps , like late introduction in the exh when possiable.the cause is the overlap the time both valves are open keeping this time shortist will help prevent most of this

Re: Lobe separation
 

How about for a big cubic inch displacement, very high flowing heads and tublular headers?

Re: Lobe separation
 

Specifically;

605 inches, 9.2:1 compression, 450cfm/345cfm flow at .7". Stellings headers with small .125" hole at the very end of tailpipe to make it "wet"

I can see the water getting sucked up the tailpipe at idle but not at 1500 rpm on up. It does get into the oil.

solid tappet roller Cam specs:


Duration at .050 270 intake 280 exhaust
gross vlavle lift .722 intake and exhaust
lobe separation 110 degrees
seat duration at .020 304 intake 314 exhaust

What changes can keep power up as high as possible but cut the reversion to zero?

Re: Lobe separation
 

If its a Ford it will suck. :D :D :evilb:

Re: Lobe separation
 

They are all just air pumps :D:D

Any input on changing the cam specs?

Re: Lobe separation
 

What is the application ? Kennywould ran more cam in a 564 with CMI headers and had no problems.

Re: Lobe separation
 

What do the heads flow at .300" lift? Specifically the exhaust? What is the inside diameter of the primary tubes on the headers? What is the max rpm? Carb or EFI?

Re: Lobe separation
 

Richard Cranium 572 Great name!!! Welcome to the board. May we call you dick head?

Re: Lobe separation
 

Are you actually seeing water residue or signs of water on your plugs? If you are looking at the outlet of your tailpipes and seeing variable pulses, which may include some minor reversion I doubt you have a problem. Your description on your headers would leave me to believe you should be OK with just about any cam you choose. Only my .02!

Craig

Re: Lobe separation
 

Intake at .300 244.7 cfm
Exhaust @ .300 202.3 cfm

Primary tubes are 2.25 ID

Carb 1250 dominators Max rpm 6250

Swept down headers to exit under the swim platform on a 32 Fountain.

Wette Vette, Yes I am seeing the pulsing you are dscribing but the boat sits very very low in the water. Although the pipes do not go under water, The swim platform is literally sitting on the water creating a pocket of air underneath. If a wave comes up while idling, the motors will suck up water like vacuum poluting the oil.

Seems when fountain removed the bottom material to create the step, it allows the boat to sit 4 inches lower in the water than a non-step 32, The same amount of the step height.

Re: Lobe separation
 

Spread the lobes to 112.Less overlap,reversion, and idle quality will improve.

Re: Lobe separation
 

You need to install flappers if your pipes are that low. That applies even with stock power. I ran a 276/284 dur @ .050" solid roller cam in my Baja. The headers had the water injected about 6" from the end of the tailpipe and the tailpipe came through the hull about 4" below the water. Never had an ounce of reversion. If you aren't seeing water residue on your plugs or milky oil after running your motor you aren't getting reversion. Get some flappers!!

Craig

Re: Lobe separation
 

If you remember seventh grade biology, cranium is skull or head. Richard or dick........Lighten up

Re: Lobe separation
 

Can I ask a question not about lobe sep angle on this post what is the operating temp of the engine with this problem ? I just had a problem with a customers engine and found something I had never seen before and might be able to help find the solution. Feel free to give me a call and I might be able to help Sincerely Laz Mesa

Re: Lobe separation
 

Most would understand the ;) even if it's not there. You are a newbie as well,,lighten up, it was obviously chosen as a funny name,right?

Re: Lobe separation
 

2112, I'm glad to see your heads flow good numbers at .300" lift, alot of head porters get the high lift numbers and don't get the lower lift. Always keep in mind the valve is at .300" twice ;)

As for cam specs for the RPM band you are using, because the exhaust ports are so good, I don't think you need the extra exhaust duration. I would do a single pattern camshaft at ~.750" gross lift and 268 @.050" on a 114 LC. I would also use the 18726543 firing order for better idle quality too. This combination will help reduce pumping losses in your engine. Another plus is you will probably pick up horsepower as well :D