74vetteman

I have a 406, with AFR 210 heads, Weiand 7530 singleplane intake, 750 speed demon dbl pumper, SRP flat top pistons, 6 inch rods, 3.75 stroke crank. I am currently running a Crane hydraulic roller 284 (222in and 230 ex @.050) with 1.6 rockers. Valve springs are 1.550 dia. with 1.860@150lbs closed, and and 1.300@375lbs open. Coil bind is 1.100. Compression is 10.45:1. My transmission is a m-20 4 speed, and have a 3:73 rear end with 26.5 tall tires. Car weighs 3550 with 1/2 tank and driver.

My best 1/4 time is 12.85@112 in 5500DA at a 3600 ft track. I would like to better these times yet keep the car streetable (and yes, I am looking into drag radials).

To me, my choices are:
Change out 1.6 roller rockers to 1.7 to take advantage of my heads flow above .500. This would be the easiest option. Would I need to change valve springs to handle the increased ramp speeds? How much hp would this change make? Downsides?

Or,

Change to a different cam. Can anyone recommend a cam for my combo? The mild cam I am currently running made 476hp and 494 tq on the dyno. It seems to run out of breath at 6000 rpm. How much more power could I make and still be streetable? At what rpms?

Thanks!!

MoMo

Yes, I'll bet it's running out of breath. For that many cubic inches, that's an AWFULLY mild cam. Although, I'll bet it's a real nice street cam.
I see your delimma. You want to have some rpm's so you can do better at the track but yet still have a cam that's street-friendly and will pass emissions.

If you can go with a hydraulic roller, pricewise, that might be the largest gains you'll see. If not, then I'd increase duration to something over 230 degrees @ 0.05" on the intake side. As far as exhaust, that depends on how good your exhaust system is. If you have a very free flowing exhaust, then perhaps you might try a symmetrical grind, which Chevy's respond well to. However, if your exhaust is slightly restrictive and your heads are unmodified, then I'd suggest a dual pattern grind.

Even 230 degrees is mild for a 406. Stay a little bit conservative though to pass emissions. If you want, e-mail me and I'll work with you on Dyno2000 to help find an appropriate cam.

If you don't mind the "roughly" monthly ritual of adjusting your valve lash, a solid flat tappet cam is the next best thing to a hydraulic roller, but at hydraulic flat tappet prices. Not sure if you need that though, rpm-wise, but your torque would improve over a hydraulic.

If money's an issue, there are lots of really good hydraulic cams out there.
I run a cam about your size on my 355 tuned port in the IROC, and even that is a bit limited on top. Great torque, but even when it had a 750 Holley on it, it would run out of breath at 5500. With 406 cubic inches, that's really a mild cam.

74vetteman

Momo, thanks for the reply!

The cam I am running is a hydraulic roller. With my 1.6 rockers, I am getting around .560" lift. I could go another .100 lift with my heads (rated to around .670 lift). I have no emissions to meet. My exhaust is 3" dual mandrel bent with an x pipe (kind of planning for the future :blueangel: ).

74vetteman

No one has any suggestions? Please guys, don't leave me at the mercy of the tech's at the cam companies (I've noticed a lot of attitude).

Thanks Momo for the offer to run some cams on desktop dyno. If I get some suggestions, I will email you.

Juliet

I've been playing on the Dyno program with 406 combos (havn't built and run yet) with AFR 220 and 227 race heads and solid rollers with short duration (280 to 290 total, around 240 @.050) with lots of lift (.600 to .630) look good (the high lift keeps the 2500 RPM torque up). Will have to research how to keep the springs alive (probably use oil cooled springs approach as that works well on the big boat motors I've checked). I'm looking for a "play only" car, so am not to constrained like a daily driver (I'd guess 3000 miles or less a year)


-Greg (from Julie's computer)

74vetteman

My car is definately not a daily driver. I will probably put less than 1200 miles on this year. Ever since my son was born (he's now 3), I find myself driving mostly by myself. There is no room for three of us!

The cam you are suggesting is in the range of duration and lift that I am looking for. I realize that short duration and high lift will wear out springs quicker, but what sort of life can one expect? What sort of spring is required?

Thanks,

Marc


[Modified by 74vetteman, 10:11 PM 8/16/2002]

HeaderDesign.com

I've done some in-depth calcs for the AFR210s. You could pick up about 100HP if you used a solid cam with something like 252I/248E duration, with the exhaust lobe being slower opening than the intake. You would shift near 6750RPM.

If you just change rocker ratios, try the 1.7's on the intake only. Then you could try 1.5's and 1.7's on the exhaust after you have established your baseline. You might be surprised at the results, though they won't be nearly as drastic as a cam change.

GregP

Going by my fiends running BBC boat motors with .700+ lit rollers (my boat's motors aren't that radical), replacing spirngs and solid roller lifters every 25 hours seems to keep failures to a minimum. Boat motors run at 4000+ RPM almost the entire time, so I'd think that 50 hours for a street play-car should be a good goal to work with. The oil cooled springs (using special valve covers) are a must at the high RPM duty cycle of the boat motors, probably more in the catagory of extra insurance for a street car.

-Greg

427Hotrod

Sorry I didn't respond earlier.. must have missed this one....

Well, most everyone knows I'm a solid anything believer. I just don't see the value in messing with a hyd. for a nasty little toy like this. 50,000 miles a year? Sure, but not for this stuff.

I with the rest... way too small of a cam, but you knew that already. Looking at your combo, you will be hitting the traps in the 6000+ range if we make the power. With your, cubes and good heads, I would think something in the 245-250*@.050 range would be Ok. A 245* street type roller will probably peak HP around 6100 or so. Even that would be reasonably mild. With a little more gear I'd sneak up to 252-255 maybe, but that's getting serious. For something on the street that runs capped up, I usually select a dual pattern with a little more on exhaust. Full exhaust changes the picture a lot. It doesn't always make the most power, but usually hangs in there a little longer. Plus if you ever add nitrous it's great. I pick the intake duration and closing point to get my rpm range and to maximize my cylinder pressure. Then I play with the exhaust to get overlap I need.

You can go about this several ways. If you can stand the tight LSA of a 105-108 cam along with some overlap, you can make fantastic power. But street manners won't be that great. You will probably go out to a 110-112 LSA to get manners. If ground right, that will have the small duration intake lobe "appear" bigger to the motor with it's delayed closing. You can then think about advance or retard during installation.

I would look for something in the .600-.630 lift range. I would also do it without the 1.7 rockers. Planning it with the 1.6's allows you to run a slightly milder lobe to help life, but sometimes 1.7's on a small block can get into some weird harmonics. Better not to go there if you don't have to.

The cam I put together for my 540 was selected to mimic the manners and rpm ranges my old 427 had. I really liked it. I used a very aggressive intake lobe (faster than a Comp Xtreme roller) but a relatively "soft" exhaust lobe. No need to pound the valvetrain if not necessary. I picked duration based on the cubes and looked at intake closing points to get the valve open the most during the most productive part of the stroke. You gotta do some math to figure where the piston actually is in the cylinder at each point of the valve event. Gotta acount for rod length, stroke, piston speed and then look at your actual head flow to see what is the most important point to shoot for. I'm a little dense, so it took lots of notebook paper to draw little graphs so I could get it "visually" in my head.

Once I had intake plotted out, I worke don ex. Not as crazy there, the piston does the work, but you can start figuring out overlap and use the exhaust points to really set it. Too much blows it right out the pipes. Too little and you choke it at high rpm.

Then play with LSA to get manners. I counted on a 112 LSA to help with vacuum, even though I knew I might give up power.

When it was all done I ended up with a TQ peak at 4600 rpm (4200 capped up) and a HP peak at 6100. It holds 9.5" of vacuum and drives very smoothly on the street.

Now that I have a year or so running on it, I think I could go a little more intake duration, but there goes those manners. At this point I'm going to work on airflow in the intake and heads to extend my rpm range further.

Don't worry about springs. They last a long time these days. Just don't restrict the oil to the top.


Hopefully all this helps a little.


Jim

74vetteman

Thanks 427Hotrod!!

So basically you are suggesting a solid roller, 245-250degrees @ .050 intake, dual pattern lobes, little bit more duration on exhaust (255?@.050), .600-.630 lift with 1.6 rr's, and a 110-112 LSA for streetability.

I shall check my cam catalogues!!

gkull

Custom grind solids are the only way you can get what you need. Match your cam to your bottom end design. Your three inch exhaust IMO should have a spit duration of 6 or less degrees. Your springs are to light for a solid roller with 240+ degrees. At 15K miles my springs were still within a few pounds of when installed. I'd try a 244-46 and 250 .625-650 lift and i'm a fan of the 112 lsa. on anything under 11-1 C/R

sinistervette

I've got a 406 that I built for stock car racing. I'm thinking about putting it in my vette(85 manual trans, play toy). I've got 11.8-1 comp., Highly modified tfs twisted wedge heads, angle milled-2.08I/1.60E valves/223cc Int. runners, brodix hv1000 intake man., holley 850dp modified,now flowing 930cfm,cola crank, 6" rods, custom ground crower .636I(1.5 rockers),.661E(1.6 rockers) lift, 274I/286E dur @ .050, solid roller. Dyno'd 614.7hp@7200rpm 530.8 tq@6100rpm. This combo makes 500+ hp and 500+ tq from 2900rpm all the way to 7200! I'd definiately go with .600+ lift, and270+ dur @ .050 and SOLID! I've run this engines for 3 seasons, and have only had to adjust lash 2 times per year! You also need to look into a real carb! Sorry, Ive been building/modifying carbs for many years, and not impressed with holley's factory work. You've got a good start, but if you want to feed your 406 above 6500 rpm, you need to consider either an 850 main body or at the very least, an 850 base plate on your carb. I started with a 750 main body, annular discharge boosters that I stepped, 850 base plate, it flowed 815cfm. The best hp on the dyno with this carb was 548.3@6600 rpm. tq was 528.0 @4800rpm. The only change made was the carb. The smaller carb did produce as much and at times more tq, but hp as well as rpm range was down. How much work is done to your intake manifold? There could be some huge airflow/hp there also! Just some food for thought! :seeya

Lt1er

Sinister Vette - I was just trying to picture how that would run on the street. I ask some friends with circle track cars and my drag racing 415 ci and none of them had that much duration. They all had bigger lifts the drag racer is running .740/.780

Just to make sure. I went to the Comp cams web pages and your cam is hotter by 12 degrees both intake and exhaust over their hottest 3/8 - 5/8 mile circle track cam designed for 400+ ci motors and has an operational range of 4500-7500. Which really means that it run well from 6000 -8500 using 18 degree heads.

I don't doubt that your using such a radical cam. I just can't imagine that it's very functional.

MoMo

I have to agree. Sinister, your set up is awesome to face life a quarter mile at a time. A combo that can't go wrong, when it's ***** to the wall and max rpm all the way down the track.

But to drive it on the street, your cam would be getting away from the streetability factor. I can't imagine putt putting to work in rush hour traffic with a cam that barely idles and zero vacuum.
I think what is going to be needed for this guy is to do some playing around with Dyno2000.

So e-mail me. Let's work on a few combos.

427Hotrod

Yes...pretty much.

I'm glad that some folks are jumping in here with first hand experience and particular grinds. That is by far the best way to do it.

In real general terms I'm thinking the high 240's/low 250's on duration, and as GKULL said, for yours I'd stay in the 4-6* additional ex. duration. The 112 LSA will make it more driveable and smoother. It's a good way to run a larger duration cam and still get reasonable manners. But before you make a blanket decision on LSA, you really have to look at cam characteristics.

Lobes with very similar lift and duration numbers have vastly different rates of opening. Look at the cam cards on the sites and plot notice the intake opening and closing points to start. If you can get complete plots you're way ahead.

I like a 110-112 on the street. It just makes things smoother. If I was racing all the time and only had to concern myself with gear banging at WFO, I'd tighten it up some and/or run much more duration. But there's that compromise thing again.

I think anything under .650 actual valve lift will live pretty well on the street in a roller application. Your heads are probably pretty much done in the .600 range, so a .620 or so would get you .600 at the valve.

And upon re-read of my note, I might have mislead you. GKULL is right again. I didn't mean to imply YOUR CURRENT springs would be OK. Thye are way too light for thse cams. What I meant was that spring quality has improved drastically in the last few years and a good spring will live a long time without much worry at these levels.
Keep trying to get folks to give you specific details of their imprssions of their cams in the real world. That can give you a lot of insight, but be very careful of how different combinations react to a specific cam.


Jim

sinistervette

This 406 was used(I'm married with children so had to "retire"!) in a dirt late model that I mostly ran on 3/8 mile tracks here in Mi. We have "dirt" tracks, clay is almost non existant, and so is traction. I tend to run higher rpm/lower gearing than all of my competitors, they always said to run a higher gear to make it harder to spin the tires. That is true to an extent, but with the tracks as slick as they were, you still had tire spin. When I tried to run the higher gears, I still ran the same rpm, and actually had somewhat slower lap times(only a couple 1/10's) but still slower. I came to the conclusion that I was actually spinning my tires faster and longer than when I had the lower gearing. I also noticed a huge change in restarts. That higher gear made me restart at a much lower rpm, and the 406 did not like that! I had taken the car to oakshade speedway in Ohio, a 3/8 CLAY track, and had a tough time with this set up. It definiately likes to run higher rpm and not be bogged down. We dino tested this motor quite alot, my sponsor was a engine shop with the dino, and actually had a .630/.630-.242/.242@.050 cam in it, it made close to the same hp/tq, but a little lower in rpm. The thing I didn't like was how fast the power fell off after 7000 rpm. I don't remember exactly what it was, but I think it lost about 30-40hp from 7000 rpm to 7500! The cam in it now peaks at 7200 but only lost 11.3 hp at 8000! That is the reason that I'm running it. If I need a little extra time on the throttle, I don't have to worry about it falling off. I'm not sure why the other cam acted like it did. As far as putting this into my vette, if I do it will not be a daily driver! I'd only use it on special occasions(we have a few ricers and 2 supercharged mustangs in town) to pick on the so called "fast street cars"! The guys with the mustangs claim to have not been beaten by a "naturally aspirated" with no nitros chevy. I know for sure, the slower one run a best et of 10.96 in street trim. I'm sure that if I go with my 406, I've still got a couple of liberty "slick shifted" B/W super t-10's to use for trans, and can find a 4.88/5.13 gear that They are going to be suprised! My major concern is ruining the vette rear. I'm not sure how much abuse it will take, and even if I can get the gearing I want. The other idea is to put the 406 into a 79/85 mustang, and beat them with thier own body style. Then they can't say that I've got this or I've got that, all they could say is.......CHEVYS RUN! I first off am going to try and understand the "EFI/ECM/TPI" stuff, and try to get the vette into the mid/low 11's with either the 350 L-98 or maybe a mild tpi 377. I'd like to do like scorp and see just what I can get out of the L-98. If I do, I'd like to do it with only modifying the stock L-98 parts. The only thing that I'd change would be the tpi stuff. I know this probably don't make sense, but I've never made much sense :lol: :lol: :lol: ! I just like being different! I know that I could buy alum heads, roller cams, nitros, etc. but I like trying to do things different, because most people don't think it can be done. :cheers:

gkull

Well i went different and it runs nice. 240/248 112 600+ lift 195# closed springs and a rev kit so the lifters ar seeing 225# K-motion .700 max lift.

For a max drag racer it's hard to say. i was just thinking about what we had in a 8.90 dragster 355ci

Some days I wish I had a better high end charge. Instead of being on the down slope after 6500 to 7000. My goal was different than yours. I just want a certified 200+ mph street car

mountainmotor

Well here is another opinion.

He is intake limited and the heads will allow for a single pattern cam. But because of the Corvette exhaust I would use the Howards solid lifter flat tappet # 112311 286-292- 250-256 @.050 .525-.537 lift with 1.5 rockers so aproximately 555-567 lift with the 1.6's. It is a 110 LCA cam with 2 degrees of advance in it then set the springs down to 125 seat. It will run from 2600 to past 7 grand with this cam with max power guessing at 6400-6700 rpm. A $140.00 bill gets this done. I would expect a HUGE improvement for the money spent


[Modified by mountainmotor, 7:10 AM 8/23/2002]

74vetteman

Thanks for all the replies!

However, these answers are giving me more questions. Mountain motor, you are suggesting a cam similar to what Rod Davis (Headersbydesign) gave. What do you mean by intake limited? I thought the Weiand was similar in flow to an Edelbrock Victor Jr., but with a little better bottom end. Is there a better manifold that will fit under my stock hood (I have maybe an inch to spare)?

I guess what I am saying is I'm prepared to replace what is necessary to make the best overall package (besides heads, my 1 3/4 Hooker headers, and rotating assembly). Intake, carb, valvetrain, and cam can be changed if needed.
It seems that everyone is recommending a solid of some sort. Is a solid roller lifter cam going to make significantly more power with my setup vs a flat solid tappet, or is the difference negligable for the extra money spent? Why not go for more lift with around the same 250ish duration. Say somewhere in the .630+ range, or would that kill valvesprings?

Again, I appreciate all the advice and insight!!

gkull

The 7530 is a nice manifold use a 1/2 inch wood open (one hole) thermal spacer. It requires very little work to port match up to FelPro intake gasket size 1206 heads. Which your AFR's are.

Solid roller with the same cam timing is worth probably 30-40 hp in a sub 240 degree motor and Solid flats generally can't be made to exceed 250 degrees with lifts above .550

Stingray Racing her on the forum is running a consistant 11.70 car with a 383 solid roller 246/246 and sub .600 lifts and I think 110 lsa