For those of you that have been following my thread on the First Intake/ SLP runner thread you remember we are thinking the problems with the motor peaking at 5000rpm was a combination bad valves springs and too small of a camshaft. Well I have had the valve springs changed out to the Manly beehives with 150# seat pressure and 340# over the nose. Also changed out the camshaft from a Comp Cams XFI268 to a custom Mike Jones cam with 228/228 at .050" and .576/.576" lift. The advertised duration at .050" is 10 degrees more than the Comp Cam. However overlap is only 3 degrees more seat to seat. 50 degrees of over lap versus 47 degrees. Advertised is 276/276 at .006" lift. I had the car put on a flatbed and taken over to Dyno Don's shop today to clear up a couple of issues which Don did in short order. There were a couple of air leaks that kept the idle quite high. Fixed those, adjusted the timing and adjusted the idle for 800rpm in gear. Well to my amazement the car idles very well and with the previous tune. Hardly any lope to it at all. I was fully expecting some noticable lope. I never dreamed a car with a cam of 228 degrees on the intake could idle that smooth. I drove it home and the road manners are excellant. Did not take the motor over 3500rpm. Reason being that the Manley instructions for the valve springs say not to rev the motor until the springs were brought up to temperature and then allowed to cool all the way down. I wanted to make sure that happened in full. Next test and the big one will be the dyno. I will try to work something out with Kevin but I don't think it is looking good for this month. I might have to sneak over to the other dyno shop for a quick pull to see what is going on with the new combination but no tuning would be available without Kevin.

subscribing.. i cant wait to see it man.

That little overlap is why its idling soo smooth. those are some aggressive ramp rates you have on that cam. I hope it helps break past that 5300-5500 rpm peak you guys have been seeing with those other TPI combos. Either way it will make some good numbers

I know Kevin has something up his sleeve and wants to put his car back on the dyno. Normally we do this on a Saturday and we each have something going on Saturdays this month. I will see what we can work out.

The ramp rates on the cam are pretty good from .006" to .050" with a 48 rating. Then not bad to .200". Mike Jones uses the inverse radius technology. I noticed that Comp Cams does the same on a number of their lobes.

Yeah, if I can just get the motor to peak at a minimum of 5500rpm that should generate quite abit more horsepower. Looking at DynoSim the change in horsepower from 5000 rpm to 5500 rpm is 36. Multiply that by .8 for the drivetrain loss and that becomes 28.8hp to the rear wheels.

Add the 28.8hp to my already 350rwhp and that becomes 378.8rwhp. At this stage of the game I would readily accept that. However that is probably not reality as I'm finding out.

Well Allen, all of your research is definitely based in reality, so I believe your predictions / expectations should be close. Good luck! (although luck has nothing to do with it; as I said, you do a LOT of research!)As a side note, when I read about how often you change cams, it makes swapping from HSR to TPI and back to HSR every two years sound as easy as doing oil changes... -Bill

Hahaha. I don't think I will be changing cams again anytime soon. Like was said my XFI268 probably had more left in it. This Jones cam is very good for a daily driver so I will put the XFI268 cam up for sale.

Allen,

We are all excited to see what your new cam does. When you installed the springs, did you check to see how much space you have left before coil bind at full lift? Do you know what that number was? Thanks.

Hi Zipdrive. The specifications for the Manley beehive valve spring is exactly the same as the Comp 918 springs they replaced except for the spring rate and pressures.

What we did was to confirm on the bench that they were indeed the same dimensionaly. We checked the valve spring pressure at 1.800", 1.200" and where coil bind was. Every thing confirmed what Manley said it was. So I'm around .065" from coil bind.

thats right where you want to be

Let me correct my above statement a little. When I was speaking of the dimensions for the Manley spring I was looking for the fit of the Comp Cams retainers and locators. So the inside dimensions are the same along with the installed heights and coil bind.

However the outside dimension of the Manley beehive springs are a little larger than the Comp 918's. Again that is not an issue as there is plenty of clearance on the head. Also when free standing out of the box side by side the Manleys are taller.

Looks good, can't wait to see the results.

268XFI H13 268 280 @ .006 224 231 @ .050 .520 .515 1.6 RR 113° lsa

Did they make different xfi268's? This is from their catalog.

.

Part number
12-366-4

Grind number
268XFI H13

Flat tappet cam 2000-6000 rpm range

Part Number
12-466-8

Grind Number
268XFI HR13---268 276 @ .006---218 224 @ .050--.570 .565 1.6 RR--113º lsa

reto fit cam 1800- 5800 rpm range

From comp Catalog online.

This is the hydraulic roller tappet. Part number 08-466-8 for the Chevrolet small blocks made after 1987. Also 268XFI-HR13

Do not mean to be so picky. It just seems that the two differant comp cams (Flat and Roller) have the same Grind Number, Different part number, different dur, different lift, and rpm range (200).

So you were running the roller comp cam with the 1.6 rocker?

Those grind numbers in your latest post are different. H and HR.

He was running the one he listed, hydraulic factory roller, 218/224 .570/.565

Yep it was the roller version. NON retrofit, just the OEM style roller cam XFI268

The above posts are correct.

Thanks.

The devil is in the details.

Couple of more thoughts about the camshaft change after driving the car around some. One is how good the car runs with a camshaft change of plus 10 degrees on the intake side and no additional tuning. This is a speed density car and it does not appear to have changed much at all.

Idles just fine and has excellent around town manners. 2nd thing is if I have lost any low end power I have not noticed it. It pulls very well and it will push you right back in the seat. So it looks like the only necessary tunning will be at wide open throttle as soon as we get to the dyno. The car is ready.

Allen,

Just looking at the cam specs, I bet you have not lost anything on the bottom end and the mid-range is fatter than the XFI cam as well. To bad we don't have the duration at 0.200" lift from both to compare. Mr. Jones makes very good stuff. I would be surprised if you lost anything at all below peak torque. The ramp rates are more aggressive on the Jones cam than the XFI. Does the motor rev faster with the new cam?

Thinking out loud, what is the narrowest cross section of the intake runner on your manifold? You are using Pipemax, yes? Have you calculated the max air velocity in the runner? Was it near 260 ft/min ave.? From those numbers, you can get peak hp at X rpms. Some where I have a link for a calculator that does it for you... I will try to find it.

Cheers.

Actually I do have the .200" cam lift measurements. The XFI268 is 143 degrees at .200 lift and the Jones cam is 150 degrees at .200" lift.

The smallest CSA of the intake system excluding the heads is 2.2 square inches. This occurs at the mating surface to the heads on the intake manifold. At the runner entry point it is 2.686 square inches. I do have some taper.

Near as I can tell the CSA at the pushrod pinch point is around 2.05 square inches.

That cam should show some nice gains... it really is keeping the valves open alot longer over the entire lift range of the cam, so alot more air should be getting in. Once tuned i wouldnt be surprised you touch the high 370 low 380whp range

"Once tuned i wouldnt be surprised you touch the high 370 low 380whp range"

If I could do that it would really be nice and I would call that mission accomplished. At 380rwhp that would convert to 475hp at the motor. That might be a bridge to far. It more likely will be somewhere in the 360rwhp range. That is 450hp+ at the motor.

Took it out for another drive today with my scan tool hooked up. Wanted to check for knock and nail it once. Couple of things happened. One is I got only 2 knock counts. That is with 91 octane gasoline. My DCR will have dropped some with the slightly later intake valve closing. So that part was good.

2nd thing that I did not notice until the car started to drift sideways a little was that the rear tires had broke loose right away and stayed that way well through 2nd gear until they caught again. Apparently I was going a little too fast for the transmission to drop down into first gear when I nailed it. Had to let off shortly after the trans shifted to 3rd due to traffic.

From my previous experience trying to hammer it while in 1st gear is a waste of time. It just spins the tires. So my torque appears to still be there in full. From Kevins post the dyno will be Saturday the 22. So in the meantime I will hook up my laptop and do some datalogging.

I hear you..I thought it was the converter stalling when I nailed it mid second gear....nope, wheel spin, and sideways drift...from 320whp (375wtq!!). TPI is fun! -Bill

Bill, I think you and I will be very close on the torque. In fact you may have me by a little. Will find out that Saturday on the dyno.

reason i say 370 ish whp is because your last setup made 350 at only 5000 rpms before you had to have float problems. Your springs were only 100 lb on the seat if i recall right. That is not enough for that XFI lobe. I can see another 15whp another 1000 rpms higher with the old cam, and this new cam is abit bigger.

But yes, 360's whp is STILL very impressive.

How to calulate some useful numbers (excerpts from Speed Talk.com)
T Moss Porting

velocity=(stroke / 360) x rpm x (piston area) [4.03/2 squared x pi]/ (port area)
velocity=(3.48/360) x 5800 x (12.75/2.05)= 349 ft/sec

Written by: David Vizard - Neil Erickson aka Maxflow (Edits by tmoss)
To calculate the limiting port velocity: LPV=(.00353*RPM*S*B2)/CA Where:
S = stroke (in)
B = bore (in)
CA = minimum port cross sectional area in sq./in.’s
RPM = peak power rpm
LPV = limiting port velocity in feet per second
LPV = (.00353 * 5800 * 3.48 * 16.24)/2.05 = 565 ft/sec ~.5 mach

Hope this helps.

Orr89RocZ I agree with your analysis. Just by extending the curve on my dyno graph I should be making around 380rwhp at 5800rpm. You are correct in that the old valve springs were between 95 and 100psi and to light for an XFI lobe. So with good valve springs and bigger camshaft it looks like the motor could make that much power.

Pandin: Thank you for the information. I have bought Pipe Max and it shows that with my 2.05 MCSA I should be around 230fps at the pushrod pinch area at 5800rpm. According to PipeMax that is on the low side of being OK.

Also with PipeMax my lpv is 500.4fps.

It would be nice to know why the differences.

Must be the way they calculate it. I'm also assuming I'm reading PipeMax correctly. I'm new to the program.

They're empirical formulas so they may be using different formulas or factors. Guesswork.

1989GTATransAm,

I am curious how you came to select a Mike Jones cam? Before this thread I had not heard of Mike Jones. I've been to his website and I am now considering one of his cams.

Unlike you, I am only interested in a very moderate performance gain. I am more interested in optimizing torque from 1,000 to 5,000 rpm in my 350 TPI/700R4 from an 89 GTA. I will be calling Jones up for a cam recommendation as soon as I decide what heads I'm going to use.

His name pops up on Speed Talk where a lot of the big name engine builders hang out. He is involved in all types of racing including Indy cars, Nascar, circle track and a host of other events.

He actually grinds his own cams from base cores and has some pretty sophisticated machinery. So he can whip up a cam for what ever you want. One of the reasons I went with Mike Jones was he took the time to work with me on my set up and I have not been disappointed.

I can't say that about some other well known cam guru's.

Thanks! Those are exactly the things I wanted to hear. I don't mind paying for service and quality. As a matter of fact I really enjoy paying for service, quality and a little respect. Hope that I have as good an experience when I contact him about my requirements.

BTW you say it doesn't lope. Would you say it has more of a lope than my LT-4 hot cammed 383 LT-4. I am just trying to get a reference.

As you know the 228/228 cam is a single pattern cam and therefore does not have as much overlap as say a 228/236 cam so it will idle better. For reference my cam has 50 degrees of overlap plus a KevinZ28 tune. So that might give you something to compare to.

yeah 50 degrees is pretty tame overlap wise.

I also havent heard much from mike jones but then again i didnt know many cam grinders. I went with bret bauer and so far i like his work from what i've seen in the LT1 world. I may give mike jones a try if i dont like this cam's power or if i ever do go "bigger" on the cam. I already got 78 degrees overlap and idle tuning is getting me frustrated