cam change what to expect

I misunderstood ... I thought the talk was about electric CRANKCASE vacuum pumps.

results> busiest day at brainerd I have ever seen. the staging lanes were full. the cars were backed up to the pits. some said it might have been due to the muscle car shootout coming that the weekend.
....anyway I manage to get it up to line without overheating. lots of others didn't. it was a chick next to me on a sport bike. we launched side by side. I hit 4500 and it fell on its face, shifted, same thing. next three days I second guessed everything I did. timing, degree wheel. valve springs, fuel pump, fuel lines you name it. of course all the while at work trying to catch up with my garage door customers.
....finally on Friday it occurred to me I never put gas in the tank after my cam break in. go figure. laugh at me not with me! go figure. today I am gonna also check to make sure the pick up isn't un covered during a hard launch. the pussy cam I had never did as long as the stock tank was mostly full. moronski-bob

zbob wrote:results> busiest day at brainerd I have ever seen. the staging lanes were full. the cars were backed up to the pits. some said it might have been due to the muscle car shootout coming that  the weekend.
....anyway I manage to get it up to line without overheating. lots of others didn't. it was a chick next to me on a sport bike. we launched side by side. I hit 4500 and it fell on its face, shifted, same thing. next three days I second guessed everything I did. timing, degree wheel. valve springs, fuel pump, fuel lines you name it. of course all the while at work trying to catch up with my garage door customers.
....finally on Friday it occurred to me I never put gas in the tank after my cam break in. go figure. laugh at me not with me! go figure. today I am gonna also check to make sure the pick up isn't un covered during a hard launch. the pussy cam I had never did as long as the stock tank was mostly full. moronski-bob

Update ?

I missed the street races in Duluth/ superior last sat. same guys will be running at the siren wi airport this sat. three days off to fix the car. lol.
.....got a 8 gall rear sump fuel cell, new -8 hoses. new valve springs. not sure which is the problem but in either case I will be covered. thanks for asking,,,zbob

With a duration split that little between intake and exhaust at a given rpm range it will feel like it hits a wall.

https://www.lunatipower.com/Product.aspx?id=1681&gid=28                                         6                                                                                                                         

supervel45 wrote:https://www.lunatipower.com/Product.aspx?id=1681&gid=28                                         6                                                                                                                         

That has 6 degrees of split, probably help on the Edelbrock heads. Should run good........

75% I/E will require duration at .050" to be the same number on both intake and exhaust. RPM will change this a little.

standard box cam for fords, exhaust biased. Put a 250 shot on it and smile............

kim wrote:standard box cam for fords, exhaust biased.  Put a 250 shot on it and smile............

The Comp Cams Extreme Energy 4x4 270 is very close also to the Voodo. The box stock does seem to have some merit and I sometimes wonder if they can measure and grind them within two degrees. The Comp has a tad more lift and they claim a 111LSA. When the OP gets his car lined out I bet he is happy with his choice.

http://www.jegs.com/i/COMP-Cams/249/34-239-4/10002/-1?parentProductId=#moreDetails Here are the Comp XE270 4X4 specs. you have to scroll down to see them in the link. I think they skipped making it on a 110LSA on the other EX cam lines and bumped to a 272?

I put that 6 in the post Blake for that reason, I think it is the one the OP has.

Problem is, Bob is trying to race his car, not get his Class C motor home to pull his 45' stern drive out the lake. A little more cam, woulda made it a whole different animal.

thanks guys for replies. yes super that is the cam. and kim the rings are plasma moly file fitted for nitrous according to manufactures specs. the pistons are the older two ton speed pros forged. 4 thousand cylinder wall clearance. approx. 5 in hole. the cam should work with in the rpm range that I should be running. 200 shot for third gear would be the ticket.
....the falling flat on its face is the crappy shaped 6 cylinder stock gas tank. I just fitted a 8 gallon cell and will plumb it tommory. I changed the valve springs for maintance.
.....sat is a local airport run, hope to get there. bobn

kim wrote:Problem is, Bob is trying to race his car, not get his Class C motor home to pull his 45' stern drive out the lake.     A little more cam, woulda made it a whole different animal.

I did mention a little more cam on the first page with the Edelbrock RPM cam, but it was more to kill low end torque since he is traction limited. The point I was trying to get across about the box stock deal you brought up, is that a few cam companies make almost identical grinds and they follow an industry pattern it seems. He was also concerned with vacuum for breaks, so you have to draw the line somewhere. I think it was a good compromise for what he wants. I have the CompCams version and hopefully will get to try it soon. I doubt the time slips will show much gain from the old Isky 270 single pattern though as I am not traction limited.

Based the on the stuff that I have cammed in this family of "Air Pumps" with OEM heads it better have 20 degree split at .050" favoring the exhaust if you want it to perform.

For those of you that want to prove this thinking correct. If you have OEM heads with the typical OEM I/E flow ratio and you have a cam with less the 10 degree split and it is a solid flat or solid roller. Make yourself a pass then in the pits crank down on the lash on the exhaust only, tighten it up .010". It will be a new car.

straub, are the edelbrock rpm heads as bad as oem in this respect? thanks for replies, bob.

zbob wrote:straub, are the edelbrock rpm heads as bad as oem in this respect? thanks for replies, bob.

Based on published stock numbers from the catalog around 10 degree split will get someone real close to what he or she needs.


Listen there is not right or wrong on the % of I/E ratio. Some camps want it high some want it low. The important thing is to cam for it.

I have camed these heads a bunch and 6 to a 10 split works good in that duration area . Is it optimum, I don't know, but they made very good power.

I would sure like to see some honest dyno tests on these baby cams, I think we are splitting hairs pretty thin between some of these grinds.

supervel45 wrote:I would sure like to see some honest dyno tests on these baby cams, i think we are splitting hairs pretty thin between some of these grinds.

There are some truck pulling classes with a vacuum rule of 15" at 1000 rpm. The right cam can embarrass field. I know that for a fact.

I was going to mention, I want to see the dyno pull start as low as possiable, like under 2,000 Rpm so we can compare down low numbers. Almost everyone looks at the peak HP when cam shopping.

supervel45 wrote:I was going to mention, I want to see the dyno pull start as low as possiable, like under 2,000 Rpm so we can compare down low numbers. Almost everyone looks at the peak HP when cam shopping.

Won't happen on the dyno stuff. Most dyno shops have water brake units. A water brake dyno below 3500 rpm is not accurate due to the absorber and how it works. Now Ford has a few that will test them but most engine shops don't drop a few million on just a dyno.

I know that's what I was getting at. Also nobody wants to spend the money are time on it and most of the magazines always change something else with the cam swap or slant the test for the biggest advertisers any way. Even ZBOBS numbers won't hold much weight because he is changing other things on his combination besides the cam, like the fuel system for instance, and it will be at a different track on different day, but they will be interesting none the less. I can see him picking up a few tenths in the 1/4 but that's about it.

supervel45 wrote:I was going to mention, I want to see the dyno pull start as low as possiable, like under 2,000 Rpm so we can compare down low numbers. Almost everyone looks at the peak HP when cam shopping.

Most dynos won't hold that low and race engines get to moody down that low. We did EMC on year pulling from 2500 it was a challenge and very interesting.

But to be honest pulling any kind of performance engine, especially a race engine that has a super loose convertor is useless any way, it typically will never be used their so what is their to prove?