What seems to be the problem?
We use the Comp hyd roller lifters to 7000 rpm in BBC`s.
Spring pressure from 90-160 lbs seat and up around 380 lbs open.

 

It looks like they pump up at all kinds of low rpm holding valves open. I loosened them to 10 thou lash and idle vacuum went from 16" to 19.5". With preload (3/4 turn), cruising at 1800 rpm it misses badly. I had some previous threads about this that detail the things I've tried to fix it. I basically replaced everything except cam/lifters.

When it misses I can stop at a light and when I pull away it runs much better. Looks like the lower oil pressure at idle lets them bleed down again. As soon as rpm goes above 1500 it starts blubbering/missing.

 

Well, you know I've been playing with this for awhile. But I'm looking more in the .680 lift range and using more aggressive flat tappets than what you've listed.

That solid is giving up a good bit of lift as compared to the hyd, but we would need to look at the lobes to see some more data. I think you could get a more aggressive flat tappet that would do all you want without being as crazy as stuff I would use.

Do you have one of the Lunati catalogs from when we were at Holley? They have quite a few lobe listings that will give you the @.200 stuff to give some better ideas to compare hyd roller against flat tappet.

I hate to admit it, but since you don't usually like to rev as high as some of us and we are dealing in cams in the 220-235* range, I don't think you will gain much at all. The tighter LSA will definitely add some power with lobes that small, so I wouldn't be afraid of that at all. Vacuum should still be decent enough with 230ish lobes.

Do your hyd lifters have a removable link bar? Could we use the retrofit-hyd roller small block ones that we got from Donny for Nicks pickup? I can't remember if his had removable bar, but if they did, the lifter body should be the same.


We could throw some solid rollers on it to test the issue for a little while. Just set them real tight and see what happens.


JIM

JIM

 

Hey Jim.

My springs only do 600 lift and I don't feel like replacing them so that eliminates most any solid roller. So you think power between the cams would be about the same with the flattappet maybe having a slightly worse idle? If so, that is OK. My current cam idles like a stocker with no lope at all so I don't mind going 1/2 step wilder.

I looked at lunati but they have no solid flattappet voodoo's as far as I can see. Only the older stuff that seemed to have low lift. Unless I missed a page. The lunati website sucks.

My lifters don't have the removable bar, unfortunately.

So you have solid rollers just laying around? I don't know if they would tell us much at this point... I mean, running the hydraulics with 10 thou lash made it run much better so I'd guess that about what the solids would do too, right?

I'm still baffled by this whole thing. The engine is spotless inside. It has been fed a steady diet of Mobil 1 and there is not a speck of dirt in the motor. I can't figure out why the lifters are doing what it seems they are doing.

Could the cam lobes be ground wrong and pump up the lifters? I'm thinking maybe a quick dip in the ramp that the valve can't follow even at low rpm that pumps the lifter up? I'm reaching here, I know. But the whole thing is just so weird.

 

Take a look at the Lunati 402A3Lun:

Advertised Duration IN/EX: 276/284
Duration @.050 IN/EX: 243/251
Gross Valve Lift IN/EX: .586"/.600"
Lobe Sep Angle / Intake Ctr Line: 110/104
Valve Lash IN/EX: .026"/.030"
RPM Range: 2500-6800

This would abe a good start for your car. You could go with 112 LSA to help out with street manners if you would like.

 

In my world that's a "race-only" cam. Just ask Jim, I'm a wimp.

Besides my wimpiness, I'm running 3.08's with a 0.68 overdrive. Don't think that cam would agree with the gearing?

 

How could that be a race only cam? Look at the seat to seat duration. Pretty small for a 454. It would be fine with your 5 speed.

 

The vacuum probably went up at .010 lash because the cam became a lot shorter. Your duration shortened. I doubt it was the lifters. Try it at .000 lash if you want to mesh with that.

I'm working on Voodoo solid flats right now. Should have dyno results by PRI.

Other than taking out a lobe, I've seen nice power results from solid flats.

I've never had any problems with hyd rollers either though. Odd

 

Doug: But can it really go up almost 4" with only 10 thou lash? I just don't know what else it can be. 3 sooty plugs, 1 fuel fouled plug and 4 normal plugs. Borescope shows the fuel fouled cylinder to be spotless. No carbon at all. The normal cylinders have some carbon as expected. All ignition and fuel parts replaced/tested multiple times. What's left?

BTE, cranking compression is normal so valves are sealing.

 

BTW, Doug: Let me know if you need any real-world testing done on one of those voodoo cams!

 

Wildman...that's actually right in the area I was looking at. The 402A3 looks to be using the UF9/UF8 lobe combination. The @.200 #'s are .153/.162. with 276/284 adv duration. That's an easily streetable flat tappet.

I used the old Crane 134761 for years in my 427 on the street and loved it. Never any valvetrain issues even on crosscountry trips. It was overall about the best flat tappet I had in it and using GM iron oval ports, about 9.8 compression, single plane intake, 750 Holley. I ran 4.10 gears and it consistently ran 11.60-11.80's@ 116-118 mph depending on weather. It's a 256/266 and 290/300 adv on a 110. I'm sure it's a little more than you want, but it really wasn't that bad of a cam. But the Lunati above I would expect to beat it hands down on driveabilty and make at least similar power.

Don't forget to subtract the lash for the lift numbers. Your springs can handle .560/.580 or so at the valve right?

For reference the old LS-6/L72 cams were in the 242* range. Lunati and Comp both make "improved" versions of that cam that seem to work well. There was dyno buildup on a "matching numbers" type 427/425 motor in the magazines a few months ago. They built it with a little less compression, stock iron rectangular ports, GM hi rise etc and made like 455HP@ well under 6000 rpm using cast iron manifolds and the Comp enhanced version. I can see if I can find the test.

Of course they later tested GM/Edelbrock rectangular ports with hyd roller and single plane intake. Broke a little over 500hp. Then they used Comp 288R street solid roller and small AFR heads and made 596 or so HP. Sucker was strong!

JIM

 

Zwede, remember reading your cam specs prior - it was custom ground by Comp? Regarding hyd roller cams, I have found that higher seat pressures but lower overall rated springs work the best. IE - seat pressure of 150# with a rate of 350# will net 350# open on a .575 lobe. Perfect for a hyd roller. If I had to guess, your seat pressures may have dropped. With a 340# rate spring, you can push seat pressure to 155# and still stay in the 350-360 open range. I was running a 395 rate spring in the 402 with a hyd roller, set at 125#. The new 460CI runs a 345# rate spring set at 150# seat to yield 357 open at .600 lift. The 460CI shows no sign of valve float at any RPM, the 402 motor was a bit tempermental at 125#. You could even drop to a 330# spring at set it at 160# seat.

Make sure you "do" run preload. Hyd rollers need to be loaded all the time to work correct. Preload and seat pressure.

 

Jim, my springs can handle the 402A3Lun no problem. hmmm... now you got me thinking... Works on the street, eh? Tempting...

Grn69chv: That's right where my spring pressures are now. 155/370. I had the heads redone a few months ago and the shop measured and shimmed each spring. I'm fairly confident the springs are not the problem.

 

Markus..for reference, that little cam in Donny's 327 and Joe's '61 is a Crower circle track cam. It's a pretty aggressive lobe little sucker with 238/244@.050 and 268/274* adv all on a 107 LSA!! But you see how they idle with very slight lope, have run for years with no issues and will turn 7000+ rpm anytime you want to. No way that cam couldn't handle 3.08's and O/D with an extra 100+ cubes and EFI. Joe's using 3.08's but no O/D. Donny has 3.36's.

Now throw in duration in the mid 240's, spread LSA out some to maybe 112 at the most and you will have a handful that still drives decent. Do some overlap calculations and compare it to some of these known examples. The fact that the Crower is a relatively small cam is what leaned us toward the tight LSA which you would expect to cause problems. But on that small of a cam it needs to be that tight to make any power.

I also used that Comp 288r 244/244 .623/.6232 on a 110 LSA solid street roller in my 427. Nice lope, would lug down to 1000 rpm in high gear with 3.36's, peaked Hp at 5850, only dropped 6 RWHP at 7000 rpm, idled with 14" of vacuum etc. Sweet street cam.

I have a pretty good idea of where you want to be manners wise. The above Lunati would be on the edge, but I bet manners aren't any worse than most hyd rollers that actually run well. Spread it to 112 and it would be fine.

JIM

 

How about this:

402A2LUN:

* Advertised Duration IN/EX: 272/282
* Duration @.050 IN/EX: 238/248
* Gross Valve Lift IN/EX: .550"/.570"
* Lobe Sep Angle / Intake Ctr Line: 112/106
* Valve Lash IN/EX: .020"/.022"
* RPM Range: 2400-6800

I'm barely over 9:1 compression so wondering if the A3 will be OK with such low CR?

 

That would definitely work for you. However, the A3 would be just fine at less than the .5 compression recommended. I have a 402A6Lun in my SBC and it calls for 10:1 compression, but I am at 9.6:1, and it really runs good, great throttle response, etc. I went with it on the advice of Harold.

I have a 402A7Lun in the wings for my 496 build.

 

The seat to seat timing will have a lot to do with the manners. I mean look at the old 268H Comp or the 276Powermax Crane's. Those are very mild cams overall. The Comp is on a 110 LSA and the Crane is on a 112.

If you do this, I'd go for the EDM style flat tappet lifters with the oiling hole.

Then of course we have the whole break in issue. Isky etc like to see 250#'s or less open pressure for breakin. That means some outer springs only or LOTS of EOS and some good luck!!

Don't you have beehive single springs on it now?

JIM

 

Yeah, I got the single springs. Will the cam be toast if I try breaking it in on those?

 

Well, it's in the same lobe family. That 4*@.050 gives up 7*@.200.

You are getting a more aggressive cam I think overall, but usually you need to go out there some to make the solids outperform the hyd's due to the way they measure. Not sure you've jumped that much really.

But the 402A2 WILL run well. Looking through the Crower catalog..I don't see anything that looks better than the Lunati's. Was hoping to see Donny's cam in a BBC version. Don't see anything in Isky that jumps out at me either. Just checked Engle...close,,,but these others look better.


JIM

 

Well...maybe Doug can tell us..but these days I'd worry. I went through the hassle when I stuck the flat tappet in mine to just use the outers. Do you have your old springs and retainers still? I have a set of springs you can use, but the retainers are on my motor!!


Also check on the P-55 cam core. It's tougher and Comp makes some nice lifters with hardened faces.

JIM

 

As stated, you can put a set of solids on your existing cam.
It will eliminate any question as to pump up.
I set them at .000 cold when going that route, works pretty good that way .

 

Zwede, when I was looking at solid rollers I think Crower had some that were under .600 lift. After seeing what that old Comp 288 did for Jim, maybe a small solid roller would be the ticket.

Bill

 

Zwede, assume you have the stock dual springs then. Have the same heads on my 460CI (off ZZ502 motor) with the GMPP dual springs. I used the Comp 854's with the matching Comp retrofit pushrods and a set of Crane Energizer rockers. I could see maybe one lifter failing, but a whole set doesn't usually happen. By chance, did you use sealant on the rocker stud threads, these do not have sealant out of the box. Also, depending on deck ht. and head gasket, the rocker is very close to hitting the guideplates. The retrofit pushrods do work ans I get a good contact pattern, but could have went longer on the pushrods.

 

I checked for clearance between the pushrods and the head, but not the guideplates. I'll check it tomorrow morning. Thanks for the tip.

Yes, I used sealant on the rocker studs. I noticed 2 on each head go into the intake port on the edelbrocks.

 

Also check for interference between the rocker nut and the rocker at both ends of travel (valves open and closed). Here's what I have learned - depending on the cam base circle you can be very close to contact (mostly occurs at valve closed). Unlike with a real high lift cam (for a roller .650 & up) you will still get a good contact pattern across the valve. Most likely there is still some practical detail yet uncovered.