GregP

I'm trying to decide between two candidate solid roller cams for Project No Flight. It's time to order the new cam, gaskets, and get the motor reassembled so I can get it into the car (and out from under my feet), so this is the last chance to change my mind about cam selection.

The motor is a 408 SB, internal balance, 11.3:1 CR, with AFR 220 CNC ported heads and will run my EFI Hilborn 8-stack injection. I have a full race prep 200-4R trans and 3500 stall LU converter and 4.86:1 rear gears. Car "should" weigh about 2500# when done, but I havn't had it on a scale.

The two cams I've been looking at are Crane solid rollers. Both have 630/630 lift. One has 4 degrees less duration, 248/256 vs 252/260, but with tighter 106* lobe centers, the other has 110* lobe centers. On the desktop dyno they both show about 575HP and over 400 ft-lb torque from 2800 RPM up, not enough difference to make a decision given a reasonable "fuzz band" on their accuracy.

Here are the two spec cards.


http://www.cranecams.com/index.php?s...41&lvl=2&prt=5

http://www.cranecams.com/index.php?s...11&lvl=2&prt=5

What whould you expect in the trade between lobe centers and duration? Comments??

-Greg

SG4206

Greg -
Assuming this is a street car ;a 110 lobe separation will be much more drivable on the street.

If this is a drag race car ; I think I would go with more camshaft and utilize the heads ......how hard do you want to twist this?

GregP

It's going to be mostly a wild street toy with an ocassional run at the Vette only drags. It has 6" H beam cap screw rods and SRP forged "nitrous series" pistons, but I'll probably use about 6300 RPM limit with the long stroke.

-Greg

gkull

It's good to see that your back and making progress!

IMO - you have to missmatches with those cams. You said that you ran some simulations. Where did they produce peak HP? The two possible problems I see is low static compression and your 6300 rpm red line is probably where these cams are really starting to work.

After lots of simulations and a 7000 rpm redline on my 427 ci small block I went with a 242/248 110 SR. I'm just trying for 600 hp. Cams in the 250 intake range were 40-50 hp higher, but started needing 7500 rpm to make use of the power band. You really want to be 1000 -1200 rpm past peak hp at your intended redline

GregP

I've looked for shorter duration solid rollers, but can't find any that don't also really drop the lift, most are down to about .540, which seems too low to work well with the heads. I agree that at 6000 the sims are showing just at peak HP, peak torque is around 4500.

With the current cam the motor was dyno'd by the builder at 600HP, I'll really be plenty happy with anything over 500.

-Greg

gkull

Greg - I have run two different Crane billet case iron sleeved small base circle SR cams.

Just go to the Crane web site and download the Master listing PDF. Go to page 16 and 17. It's easy to make your own cam from the list of existing lobes

Like for an intake i took the TR series 242 @.050 and it's .580 lift on the intake with 1.5's I have 1.65 crower RR's it gives .638 gross lift minus .020 lash

Exhaust lobe R-248@.050 with .630 lift with 1.5's. .672 lift with 1.6's That combo might work with your 408

Then all you have to tell them is grind it straight up (without ground in advance) and what lobe centers you want. They will make it 104 - 116 what ever you want.

Just run your simulations with the valve event degree numbers and very the LC and feed in + & - advance and retards and see what you like.

I have valve even number equal to 4 degrees retarded so my power band is moved up in rpm for even my relatively low duration numbers. With a multi keyway timing set I could always change it if I wanted to.

SG4206

Yes , camshafts affect rpm range ; but I believe the heads will have more impact.
I think your sim is very low on operating band rpm. Can you get hold of the dyno sheet from the builder?

GregP

The original engine ran different heads, cam and intake, I'm basically taking it for the short block.

AFR has dyno results for some 406 combos using the 210R head (really about the same flow, but the 220R intake ports match my Hilborn port size). They run about 575 HP and also use smaller cams.

I did some playing at lunch, tried a Herbert CCH7 profile, 242/246 .567/.585 @ 112, which the sim seems to like as it got the port velocity up with the shorter duration. I may have been actually hurting myself by trying to stay with the bigger .630 lift profiles. Guess I'll look at what some lower/shorter lift profiles might do, they should also be easier on the valve springs.

-Greg

gkull

I get acceptable spring life with my extreeme ramp profiles and over .600 lift with a 7500 rpm red line. My last set of .700 max lift 195# closed 540# open had only degraded about 20-25#. This last set of springs I went with 175# closed .740 max lift and opened up the oil restricted top end from .065 to .110 so heat would be even less.

My circle track racer friends run simular springs to 8000 rpm twice a lap. So they should run great in my mild application.

SmokedTires

Here's my custom ground Comp Cam. The part number is 12-000-9 which is the mechanical roller blank and the grind numbers are CS 4875S/4876S SR112+4. The lobe separation angle is 112 degrees. This cam has 4 degrees ground into it to improve the lower rpm torque so when it's installed at 108 degrees it will essentially be straight up at 112 degrees. The lift is intake .616"/ exhaust .622" with 1.6 rocker arm ratio. Duration @ .050 is Int. 248 & Exh. 254 . The cam timing events @ .050 are 16 52 63 11.

This cam works great in my 388sbc (4.125bore/3.625stroke) with AFR210, 6" rod 11:1 compression street motor. Standard shift transmission. The idle is great and the street manners are really smooth and predictably. The power goes up very nicely as the rpms rise

GregP

Thanks. After playing with some more grinds and re-reviewing the AFR dyno data I decided to stay on the milder side and ordered a Crane 118131. It's 242/250 .580/.600 with 106* centerline and 1.5 rockers (I have 1.5's already).

It's close to the Lunati in the AFR dyno test (I've always used Crane before so decided to stay with them) which dyno'd at 570 HP with 210 heads and 10:1CR. The sim with 220 heads, 11:1CR, and the 8-stack injection shows 590@6000. I don't expect the sim to be 100%, but it looks like 570-600 should be possible and plenty for some fun. Also, I'd probably run out of fuel flow with my 36# injectors if it got over 600.

-Greg

gkull

The off the shelf Crane cams have mild ramps compared to the custom circle track lobes - It's the one on the left that has oil on it. Your springs will be happier!

Crane probably offers a .930 inch diameter small base circle if you call and ask. I've always had good luck calling them.

Smoked tires your cam should be a good one!

big632

I would bet your car if a vette is closer to 2900+ lbs,something you might want to ck for sure.

GregP

George - I don't think the current cam is a small base, I didn't think I would need it with the 3.75 stroke??

big632 - I don't know for sure, but am thinking it will be close to the Gran Sports which are about 2500, as there isn't that much Corvette left on mine.

-Greg

gkull

Greg it really just depends on the rods. The cam on the left is .930 the right is 1.030. You just have to look at how much difference the off side of the lobe is compared to the central diameter.

You need to post pictures again of all the nice custom fabrication you did on that beast.

SmokedTires

It's been awhile since I've seen your project pics

GregP

Just click the signature link, the updates from when I blew it apart to paint the chassis and the start of "FINAL"!!!!! assembly are in the August 2004 and later pages.

Thanks - Greg

gkull

I just looked over all the home page pictures. I think that you need to rethink the motor rpm! That thing is pure race car and needs a sticker that says "NO WIMPS!"

I've always wanted to place my battery behind the passenger rear wheel to help balance out the car. I'm going to have to do it.

GregP

Gee, I thought I was being really subtle

Thanks - Greg