do nailheads need special cams.

this subject was started on putting new engine together thread with dual quadism. this is what i think so far with cams now. but it always changing as i try new combos. would like to here all opinions to learn more. i think there is a big difference in torque between a 401 and 425. have to be care full going to big on a 401 for bottom end with a 2-speed and like 308 gears. if you want to rev past 5200 rpms with a fast ramp cam you need to go with solid lifters. on LSA tighter is better 108-110 but it will affect idle. am sure on intake and exhaust spread they will be some disagreement. my first 425 i ran a 12 degree spread and it worked great, but the intake was not that big to start with. you start having big duration cams with lots of exhaust spread you will hurt low end. i went only 5 degree spread on solid lifter on my 446 and has plenty of top end. the 401 = 410 cubes i just did has 6 degree spread and will pull to 5900 with power, bottom end is a hair soft but its on 111 LSA on a 108 centerline with 308 gears. to do it over i would put it on 109 LSA with a 105 centerline. then if you running stock or ported heads and if your running headers all effect what cam. does a nailhead need a special cam ? you tell me. i know i need special needs a short bus for messing with cars. lol

 

Every engine family can benefit from different cam profiles to be optimized.
Imagine the R&D costs.
Would the casual hobbyist notice or be able to offer more than an opinion?
Without any tech info...look at every non chevy engine and how the enthusiasts complain about the generic chevy grinds that leave much to be desired.
Also keep in mind that any skilled builder having strong background with induction systems can easily work around limitations such as idle problems or stretch the powerband around beyond what hobbyists seem to find.
The heads and how they relate to the cylinder determine how to feed the cylinder.
The cam's physical dimensions determine many aspects of final grind.
(As an example, Cadillac 500 has a long, thin, poorly unsupported broomstick of a cam that offers obstacles when it comes to spring pressure, the severity of the lobe profile and the fact that the heads are restrictive compared to the cylinder's needs)
Think about how a serious Engine Masters entry might purchase 5 custom cams knowing the one they use might still be less than perfect...
Many catalog cams to the mainstream market are grinds intended for how engines were built 50 years ago, with aftermarket parts and build scenarios available back then.
Even stuff from 15-20 years ago intended for builds of the time period blow those old ones away, being that builds changed.
Now introduce a niche platform...

 

f85 what do you thing that adding 2 degree advance on a cam. would you even notice the difference ? or not worth the bother.

 

Tough to say
Are you asking me to feel any guilt for the amount of time you'll put into your car to possibly see .05 at the track?(sarcasm)
That's a lot of work for what at best? (the never ending journey for 10hp at a time...)
The gain from trapped compression is minimal, the gain from overlap timing and VE increase would depend on a few things, like headers for one.
If you are using that strategy then the cam would be much tighter anyways...
The wide LSA will help it hang on near and past peak hp better whereas the tighter LSA is intended to be stronger as soon as the cam wakes up until it runs into a wall, but these are just generalizations without very specific info.
The magic of the bumpstick always depends on the EXACT conditions of the top end.
A large part of the developmental strategy and success of top level engines such as Prostock and Nascar was to increase header efficiency and overlap effect, then increase the induction side of things.

 

lol i wont hold you to anything. this wasnt an all out built. i wanted it as close to stock acting as i could. wanted it quiet no headers stock mufflers and only 2.25 pipes. stock idle as much as possible thats why on a 111 LSA. didnt expect it to pull so hard on the top, i would have went one size smaller cam. will be glad to trade 400 rpms top end for a little stronger from a dead stop. dont get me wrong this built is way way better then stock

 

The heads really control the behavior, IME.
Heads flowing better via evening out velocities in the port and more cfm via faster flow really tame a wild cam from an unported, choked up example.
Powerband wakes up a few hundred sooner, hangs on longer, higher manifold vacuum, drives better.
Basically you can live with a bit wilder cam and it hides things somewhat.
It pulls as hard as it does because the flow is there. The door doesn't have to be open as long if more air flies past.
Every engine out there will benefit from a sharp head and cam guy.
It erases much of the niche specifics.

 

yes the heads were ported with a solid lifter cam.

 

I might have chatted with your head porter a time or two...impressive results.

 

What was/is your 0.050" duration for the 401 with 3.08 gears? Getting ready to put a 0.030" 401 together this fall and the cam is one of the last things I need.

 

my solid is 224-230. need to minus about 5 degree duration to compare a solid to a hyd cam. same cam in a hyd would be 219-225. what gears you going run. ?

 

Ok thanks, I'm not sure what the gear ratio is. I'm doing this project for my father in laws buddy. He has a super nice 62 Wildcat with 40k original miles. We're build another engine so he can save the original and show off his dual quads on the new one. I'd imagine the gear ratio is 2.5x or so but I will ask.

Thanks for the cam info!

 

I'm going to disagree and play devils advocate here. This experience comes from the LS world, but still valid nonetheless. Typically high flowing heads move the entire power band up. They don't have the port velocity to support as much low end torque, but have the port flow to support high RPM horsepower. A big cam with heads that flow an astronomical amount of air ends up leading to a combo that doesn't wake up until 3k rpms, but will easily rev past 7k rpms. I've driven and tuned combos like this - definitely a challenge. There is certainly a balance that needs to be maintained.

My theory is this; the Nailhead needs a split profile grind (more exhaust duration and lift), on a tighter LSA (~108*), advanced a few degrees. The split profile helps with the asthmatic exhaust flow, the tight LSA increases overlap which will promote increased cylinder filling at higher RPMs (again compensating for lack of flow), and advancing the cam will gain some of the low end lost from the tight LSA. That's just my opinion though...

 

Hi Andy , glad to see your still around here. I think I have read a few things in the past that says the more rpm you run the more of a need to have better exh. Flow. I don't know where that really starts to matter but I would think at least above 6000. Nailheads exh. Sucks. But on a street nailhead if they are ported they are not to bad. I wonder how that thumper would work with ported heads. How does that thumper pull up top with that big split. As for as making a head to big it has no low end I do know that the set of head joe ran a 12.38 with was a Mcsa of 2.0 straight through which I wasn't sure how it was going to work off a flow bench and on a car. It worked good but as this thread is asking, Joe picked a really good cam. Only 5 degree split though. He says it pulls real good up top. And with a nailhead we are only talking 5500 to 5800 or so. AI have read before that bad breathing heads can be helped by a 107 or 108 lsa. I have a head that is flowing really good low and middle and hits 246 at 500 and 257 at 700 with a straight 2.00 Mcsa. Not a lot but not bad for a nailhead. I wonder if a thumper would like this or would a cam made for the heads be better. Then you have to ask do you want street TQ with some good top end or just a top end screaming cam. That might make the cams totally defferent .... I love these cam threads. Lots of quistions on my part sorry I am on my phone

 

Hey nice to hear from you. yes the hyd cam in my old 425 nail, had a 12* split 218 -230 on a 110 LSA with 2* built in, and ran great. trying to get best of all worlds, go fast with stock exhaust, 308 gears and its hard to do. a tight LSA should give more bottom end not top ?. its been so long your baby you had must be big by now ?

 

CFM (high flowing heads) and Cross Sectional Area of heads are not exclusively tied together.
Bob's heads are a good example of the port CSA not being drastically enlarged and having huge cfm increases, aka velocity and port efficiency being the contributors to the CFM gain.
I've worked with many engine families that the heads are barely enlarged and may still see a 80-100 CFM increase.
Other large cube GM's were comparably choked, using architecture and top ends designed for much smaller engines (Olds and Pontiac come to mind). It's really tough to kill torque on those, even with big cam and ported heads.
Also really tough to drastically increase port CSA.
Try to find many published torque curves or dyno sheets showing where the cam actually wakes up, if it can even hold it at low rpm.

Peak torque follows when the Minimum CSA reaches a certain port velocity, which does not hold to rigid CFM figures. More cam duration doesn't drastically change peak torque upwards past the port limiting speed, the head is still the choke. It does lose more bottom end though.
Small duration cams that swell the curve below peak torque on a more capable top end still see torque hang on as it goes up.
Flat torque curves deceptively hide things with dips and tuning reversions, obfuscating what rpm peak torque might be, but nonetheless...it begins dropping when the induction system begins to choke out.
The example of the stock LS is explained by it being choked with short cam duration (delta P) keeping it responsive and the cylinder pressure curve coinciding with that cam's events in a lower rpm range, along with a long branch induction system intended to boost VE at a low rpm. Torque still hangs on a long ways upwards.
Obviously that changes when duration increases. The bottom drops quicker.
Find CSA and velocity #'s coinciding with your findings and I'll revise my opinion.
High overlap cams are generally only soft below the cams operating range if chosen correctly.
They are usually stronger through the entire powerband, as soon as it 'comes on' with the penalty of dropping off fast after peak hp.
This might be defeated if the exhaust doesn't jive well with the specs to coincide with the scavenging strategy.
The compression increase from closing the cam a couple degrees sooner is less of a gain than the benefit of the overlap pulling on the intake tract sooner in the cycle to enhance VE (cylinder fill).
If you are truly seeing exactly as you describe then you would likely benefit from a sharp induction guy, to help match the induction to the cam.
I've believed the benefit to be from early blowdown and overlap enhancing VE.

Most of the available cams for these are going to run 'pretty good' anyways.
Trading a few hp around the rpm curve, for the most part.
I don't think too many being used were really optimized for max effort heads.
They do have a fairly fast profile that helps the restricted stock top end.
*How would a Thumpr or any really high overlap cam do?
Depends on what the header scavenge strategy is.
None? Random? Then it's just a guess.
Nascar and Pro stock went that direction for gains. There's always a restriction somewhere...

 

More specifically.... Is more than the usual exhaust duration beneficial in a Nailhead?
For example, Comp has straight pattern cams, the High Energy series, with equal intake/exhaust durations such as the 270H with duration of 224 degrees on intake and exhaust.
The Xtreme series adds 6 degrees to the exhaust for 224/236 duration.
And doing a custom grind by using the exhaust lobe from the next larger cam can result in 224/236 duration.
All have 110* lobe separation. Overlap ranges from 50 to 60*. For comparison, all have the same ramp rate of 3.0.

Comparing these on Dyno 2003 software shows the extra exhaust duration gives a significant higher rpm increase without much of a loss in the low end. They will even make more power than a straight 280H 230/230 cam that has more intake duration.

Do these results sound realistic? And would the 224/236 give a similar performance increase both on a car with stock ex manifolds and one with headers?

My goal is the replace the 244/244-108 Isky cam in my blue 66. The custom 224/236-110 will supposedly make more power up to 5250 rpm and add about 40 ft lbs torque to the low end!
Thanks for input.

 

Hey Bob, yep still around, just been super busy! Thumpr pulls pretty good up top. I usually shift ~5000rpms. Shifting higher never helped in the 1/4mi, didn't really decrease either though.

Hey Joe, the baby is now 2! Time flies! A tighter LSA will typically have less low end, with a "peakier" curve.

I don't have time for a long response, but can agree with a lot of your comments. My point was that the statement was very generic. Just because you slap better flowing heads on something doesn't mean a big cam will suddenly act different. As I'm sure we can both agree, lots of variables at play

 

Walt, I'd tend to think the grind from Comp would perform better. I've played around with both the 2000 and 2003 version quite a bit. What I've found, when comparing to actual builds where flow numbers are available, is that the trends are very close. One could argue if it can produce accurate trends, that comparative analysis in the program should be a good indication of real world results. Again, just my opinion.

 

Walt can you explain ramp rate of 3.0. how does one do that ?

 

Not trying to argue...
Absolutely it will.
Do a few more A to B to A swaps or get involved with making heads or other aftermarket induction parts and you'll see things differently.
The behavior of any cam is completely dependent on the relationship the cylinder, it's geometry, size and how that relates to the induction system and it's characteristics.
It's easily demonstrated.

Good flowing heads can easily change when the cam wakes up by 1000 rpm or extend the powerband by the same, just like a 100 ci increase would have a dramatic effect on the cam's range.
Peak tq and hp rpms will still change according to the port's CSA and max velocity relating to the cylinder.
It would be impossible to progress the discussion without that basic understanding of engines.
Some basic formulas demonstrating this could be found in the Harold Bettes airflow book.
I recommend reading that as a starting point in understanding these concepts.
I would suggest mastering these concepts if one was to consider making a living using their flow bench

Relating to the nailhead and temporarily suspending the massive misinformation about CFM #'s ...it would be extremely difficult to have too much CSA or velocity slowed due to huge CSA increases.
You would exceed the port walls and be in the water.