Planning for 408 - Possible Solid Flat Tappet cams

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cawcislo

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I've been tearing down a 360 block recently for a future 408 build. I've been trying to put a combo together (see below) First some info on what the car's intended use is and engine/drivetrain combo.

Mostly street use (but not a daily driver) have fun with it, some drag racing a couple times a year, maybe try an autocross event every so often.

Car is a 70 Duster, going to have 3.73 gears (have 3.21's in it now), 4 speed car. Potential Engine combo, Scat rotating assembly (cast crank, forged rods, forged pistons) with compression at aprox 10.5:1, trick flow heads, dual plane air gap intake, dougs headers, 750 holley.

For an off the shelf grind I was looking at the smallest Lunati Voodoo 235/243 @0.50, .525/.546 lift, 110LSA or Hughes second smallest cam 238/242 @0.50, .558/.564 lift 108 LSA, or the smallest Howards cam 238/238 @0.50, .558/.558 lift 108 LSA.

All three look rather similar, I have heard some say custom grind. Staying with a similar duration cam what would a custom grind offer compared to the above (higher lift, more agressive ramp (and do I want that with a solid flat tappet cam)?

Should I be looking for more lift (and can you do that without increasing duration) or will that just compromise street use for the car? The trick flows can handle up to .650 lift, should I be trying to take advantage of that capability?

I'm not after every last HP, but I would like a solid performing combination.
 
cawcislo said:
Can I run 91 pump gas on 11:1? Why a custom cam? What advantages do I gain with a custom?
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Yes.

Because what makes you think someone ground a cam for the shelf that's matched to your combination.

You'll gain many things. You can run more compression, you'll end up with a cam that fits what you are doing and that means driveability. Most guys fawn over driveability like a high school prom queen.
 
A custom cam will also get you what you want.
Picking from a catalog by "smallest to biggest" only guarantees you'll wonder "what if" for years to come.
Talk to an expert and they'll steer you into what fits your goals with more accuracy.

I have a similar combo. Full weight stock dart with a 408, 4 spd, 3.91s and TFS heads. I'm running a hydraulic cam though, 251/257 @.050 (295/307 adv) on a 110 with 1.6 rockers for about .590 measured lift.
It's strong, it will fry the tires from a roll in 1st through 3rd from 2k rpm, but I should have gone custom. I've got other changes to make first and then I probably will next year.

The split duration and wide lsa are doing me no favors. The TFS heads are good, but still too small for 400+ cubes and so trying to squeeze revs with the split and wider lsa is just dumb because the flow isn't there, I still only idle with 8" of vac and it stops pulling (butt dyno) just over 6k.

If I'd talked to an expert, I wouldn't have had to figure this out by reading this forum trying to understand my new engine's behavior... So save yourself the grief and go custom.
 
Custom cam does not automatically give you the better result. Somebody who really knows his stuff has to decide the timing events.

I´ve tested 3 different cams so far in my 408, no solid flat tappets but hydraulic rollers from 110 to 113 LSA, one was a custom cam. No dyno but strip results....and i´m convinced now that there´s some gain with more overlap due to tighter LSA, will get another custom grind to prove my theory. Of course i could be wrong ;-)

My opinion: the mentioned hughes or howards would be a strong runner (especially autocross), don´t think there´s much benefit from split duration since the TF´s exhaust ports are pretty good. For drag only the duration could be increased of course.

Michael
 
360duster said:
Custom cam does not automatically give you the better result. Somebody who really knows his stuff has to decide the timing events.
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It should if the grinder is given all the relevant information and the grinder is knowledgeable. Calling a big outfit likely won't yield great results.

110 is still wide, even with tfs heads on a stroker. Short rod makes it tougher for the head to keep up even if it flows well.
 
the wider you go the more compression you need
and vice versa
pick the rev range you want
then your powerband
then work from there
most everyone here has autos
4 speeds are different
especially if street driven
work from .006 not .050
what the cam picker is going to do is pick your valve events
but you have to know sorta what works because, as seen in another recent thread, the cam pickers can be way off
 
Wyrmrider said:
the wider you go the more compression you need
and vice versa
pick the rev range you want
then your powerband
then work from there
most everyone here has autos
4 speeds are different
especially if street driven
work from .006 not .050
what the cam picker is going to do is pick your valve events
but you have to know sorta what works because, as seen in another recent thread, the cam pickers can be way off
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Not always. I'm on a 105 at 11:1 and that's where it ended up.

BUT...I didn't want to compromise. And I'm confident I can tune. And I planned for it.

As a general rule what you posted is correct. If you are buying a custom cam, you should be able to get what you want. The biggest issue I've found is guys call a cam company (any cam company) and act sheepish or unsure of what they have and want, the cam guys go into default mode and start compromising cam timing.

Do your research before you call them, and know what you want. And don't bend on it.
 
yes but you know what you are doing
when running a stock class we had to spread the LCA to help Piston to Valve then try and keep the compression up with the piston rules
I was just suggesting not building a engine first and then picking the cam
Pick usage
cam to match
build motor
 
If you don’t know what your doing with cams and your engine, then I would to all up a cam company.
The Hughes and Howard cams are nice street grinds for an off the shelf cam. They would work fine in the 408. Not great, but fine enough. I’d run the Howard cam with 1.6 rockers.

Yes! Take advantage of the head flow!
 
Phreakish said:
The split duration and wide lsa are doing me no favors. The TFS heads are good, but still too small for 400+ cubes and so trying to squeeze revs with the split and wider lsa is just dumb because the flow isn't there, I still only idle with 8" of vac and it stops pulling (butt dyno) just over 6k.
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wonder if the hydro lifter is dictating your rpm capability, not the wide LSA and the heads.
if i had heads with a good flowing exhaust port, i'd run a singl epattern cam with wider LSA.
 
cookietruck said:
wonder if the hydro lifter is dictating your rpm capability, not the wide LSA and the heads.
if i had heads with a good flowing exhaust port, i'd run a singl epattern cam with wider LSA.
Click to expand...

I'm sure it has some to do with it, but smaller displacement engines run hydro lifters to 6500+ on the regular so that's where that comes from. I could be entirely wrong, it's just a working theory.

I agree on the cam though, I wanted a single pattern with ~.625 lift and 250~255 @.050, but couldn't find anything readily available (I had some time constraints) so went with the closest I could find. I figured I'd rather have too much ex duration than not enough lift or intake duration, though I would have really liked to have found something on a 106-108 LSA. Oh well, timing cover gaskets are cheap ;)
 
talk to a few custom cam gurus. do the math to average the numbers they swear by for you. I am very happy with the old comp cams 306S in at 107, 11.5:1
 
did you notice the hughes and howard are more than just similar? post 1
the intakes are the same lobe
and as said you do not need a low flow stock manifold long exhaust
phreak? what short rod
chevie owners drive short rods
 
Got a reply from jones cams. Hers what they recommended. 244/252 duration at 0.50, .547/.546 lift 110 Lsa which looks to be one or 1.5 steps upfrom the cams I listed in post #1. I’m sure their lobe profiles may be different than the off the shelf cams I could get. Thoughts?
 
cawcislo said:
Got a reply from jones cams. Hers what they recommended. 244/252 duration at 0.50, .547/.546 lift 110 Lsa which looks to be one or 1.5 steps upfrom the cams I listed in post #1. I’m sure their lobe profiles may be different than the off the shelf cams I could get. Thoughts?
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I can't think of a single reason to split the duration like that, and then end up at a 110 LSA.

They (cam grinders) do that so they can get the RPM the customer wants, but not get the power. That cam will give up mid range power like mad for some small gains at peak power (maybe) and some gains after peak (probably) while giving up power in the middle.

There is an exellent tech article in the March 2020 Hot Rod where Billy Godbold (Comp cams) explains this much more clearly that I can, and also covers "centering" the overlap triangle.

So with the above grind, the grinder either added exhaust duration (most likely) or reduced intake duration (or some of both) to try and get a smooth idle, and maybe pick up some vacuum at idle.

If that's what you want, then that's a good grind. If you don't want to give up a bunch of mid range power, and don't care if over rev power is down, then I'd ask for something else.
 
cawcislo said:
Got a reply from jones cams. Hers what they recommended. 244/252 duration at 0.50, .547/.546 lift 110 Lsa which looks to be one or 1.5 steps upfrom the cams I listed in post #1. I’m sure their lobe profiles may be different than the off the shelf cams I could get. Thoughts?
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I assume you filled out Jones’s street cam request vs the race version? Your proposed engine build is similar in specs to what I’m doing, but you’re at 10.5cr vs. my 10.25, your using a dual plane, I’ll be using a single. Same heads, headers, carb...Using their race request (I did add that it will be used on street occasionally) I got two different single pattern recommendations from Jones (260@.050”/.600”ish/110lsa, then a 252@.050”/.564”/110lsa and then a single pattern from Howard’s. I had a good idea on what I wanted and ordered my own spec’d single pattern from Bullet (better selection of lobes for my preferences) Have you asked Jones why the split pattern? And why the other specs? I’m sure he would explain it best and then there’s your answer.
 
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I’m a cam newbie. I don’t want to give up low/midrange for upper rpm power. This isn’t going to be a race car. More interested in greater street fun with some drag racing (not looking for low ET’s). I’d be happy with high 11’s on the strip. How much/ how little duration would I need with this combo?
 
High to mid 11’s starts to require a cam size a lot of people do not appreciate on the street. Even with the addd arm of a stroker. Though that does help a good bit on street driving and take off on the track. We are also missing some information. The cars weight is one of them.
Above you said 4spd manual and 3.73’s. What size tire?

For 11’s, I think your lacking a little gear. But see how it goes first. I myself would be looking at a cam (mechanical at the min. Though the use of any kind of roller tappet wouldn’t change the duration @.050 any...) of 252 @ .050 with as much lift as I could get.
cawcislo said:
Can I run 91 pump gas on 11:1?
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I personally don’t know but it may be possible. You need to hear from a been there done that guy. If the info doesn’t come around, then a half point less or more should do fine. I’d rather be light on compression and be able to use the ignition system at its maximum than the reverse.

Why a custom cam?
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Most of the time when your calling up a cam manufacturer, they should and mostly do have a greater understanding of how it will work in your application. The more information they have the better the decision they can make.

In the end, the cam should be superior over a shelf cam.

What advantages do I gain with a custom?
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As mentioned above....

The advantages should be what ever you target the build/car for. If your looking to get more, mileage, HP for that top end charge, torque off the corners on a oval, this is what you’ll gain in. A off the shelf cam for the general “Hot Rodding” purposes are ground on a 110 which is fine for most cases but could be better for several reasons and some of which mean nothing. An example would be, I want a nasty idle chop and still get 24 mpg’s. This is where those cams like the (small) Hughes cams come in.

In a custom grind, it should be a more effective and a better dialed in cam for one things and one thing only, that would be for you and what your looking for.
 
cawcislo said:
I’m a cam newbie. I don’t want to give up low/midrange for upper rpm power. This isn’t going to be a race car. More interested in greater street fun with some drag racing (not looking for low ET’s). I’d be happy with high 11’s on the strip. How much/ how little duration would I need with this combo?
Click to expand...


Duration is RPM/displacement/head flow related.

If you want to keep the RPM at say 5500, it won't take much more that 245 or so at .050 but the issue becomes getting enough lift with that duration. You'll need 1.6 rockers most likely.

If you buy a cam with a fairly modern lobe, you don't give up much in driveability IF you can tune and IF you planned for it. I've said it before, but I run 11.08:1 with iron heads on pump gas with full timing (36 total) and my cam is 281/281 255/255 .620/.620 in a 105 in at 105. It will idle at 750 if I let it, but I keep it at about 1k to keep the lifters spinning and keep oil on the lobes.

It doesn't rattle, it doesn't chug at low RPM. My wife drives it.

But, you have to plan for it AND tune for it. If you can't do both, then go a different route and do what PRH said.
 
yellow rose said:
Duration is RPM/displacement/head flow related.

If you want to keep the RPM at say 5500, it won't take much more that 245 or so at .050 but the issue becomes getting enough lift with that duration. You'll need 1.6 rockers most likely.

If you buy a cam with a fairly modern lobe, you don't give up much in driveability IF you can tune and IF you planned for it. I've said it before, but I run 11.08:1 with iron heads on pump gas with full timing (36 total) and my cam is 281/281 255/255 .620/.620 in a 105 in at 105. It will idle at 750 if I let it, but I keep it at about 1k to keep the lifters spinning and keep oil on the lobes.

It doesn't rattle, it doesn't chug at low RPM. My wife drives it.

But, you have to plan for it AND tune for it. If you can't do both, then go a different route and do what PRH said.
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At what octane? 93 or 91?
 
If you care more about autocross than drag race, then bigger is going to not work well. Re-read post #8 several times. Once you talk under 12 ET's, then folks naturally think what will work best for drag racing...and the emphasis on low RPM torque heads out the window. Note the comment in post #17 about not giving up mid-range power... that info is correct but is not autocross-focused talk.

Once you fall off the main mid-to-high RPM torque band of the cam, where the exhaust draw-through is going full tilt, then you lose the torque building effect of that exhaust draw-through and you can only depend on cylinder pressures for your low-to-mid RPM torque. Too big of a cam duration hurts that, and too much overlap makes the lower RPM torque drop off even faster. With a 4 speed car in autocross, road race, or rally, that becomes even more critical; you don't have the torque converter as a way to 'adjust' around that; bogging off of corners starts to happen and you can only address that with more gears and/or close ratio gear boxes.

So IMHO this is kinda at a point where you need to choose the engine/car use emphasis. Great drag racer or a great autocrosser? I am seeing a lot of awesome drag racing info.

If for autocross and therefore not sacrificing low-to-mid RPM, my first instinct is that this going a bit too far the wrong way IMHO. I am only guessing at the advertised number that the Jones cam has... did they give you that number?

What RPM range did you spec for this cam with Jones? How did you characterize the application? The stroker inherently will be more limited at the high end of the RPM range, and too big a cam and narrow LSA will make the torque fall off too quickly at the low end of the RPM range and you end up with a limited RPM band that does not work with the gearing.

BTW, my racing background is rally.... BTDT that with too limited an RPM range... it sucks. There is a lot I don't know but that part I DO know LOL
 
The car Will be mostly for fun on the street, so it has to have torque and not be a dog until high rpms. For max rpms I put 6200 for cam specs for that cam from jones cams. Should I be Revving this 408 higher? No advertised duration from jones cams. I did request a street cam from them and not a race cam. This is not a single purpose drag car. Car weight 3000 lbs.
 
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