Putting together a new 68` small block rebuild using a hydraulic roller cam. I have an Edelbrock #3711 Performer Intake and the exhaust cross-over is interfering with the Comp Cams #857 Retro-fit Hydraulic Roller Lifters, looks like cylinder #4. Anyone else have this problem? I'm considering modifying cross-over and welding in patch plate, might consider Performer RPM but wanted to retain lower rpm torque and responsiveness/throttle crispness. I want to retain velocity of air/fuel charge at lower rpm. Any experience appreciated,

Patrick

 

I ran into this on two builds. I ground right through the casting of xover to gain clearance. Wasn't a problem as heads were filled so there was no exhaust flow through there. If there is to be flow through there I would grind where necessary & make small little patches as opposed to cutting out a hunk, though either way would work.

IIRC turkey tray gasket or valley shields are a no go. That xover is really deep. No such problems w/ RPM.

 

i can't help but think that for any roller cam application that the performer rpm would be a much better match... that std performer is come up short on the top end.

considering the money involved in setting up a roller cam in an olds i'd be sure i could get all the "good" out of it i could. the more i think about it there is no way i'd run a std performer, you won't lose much if any with the rpm. i'm inclined to think that the agressive nature of the roller cam lobes will offset the larger plenum of the rpm intake at low speeds...

 

Don't assume because he has a roller in it that it will run better in the upper rpm. There are small duration rollers as well.

What are the cam specs?

 

I don't know, but does the 2711 non-egr performer have a lower profile exhaust crossover? Either way, you could take it to a machine shop and have them fill the ends and then clearance the bottom of the crossover.

X2 on the roller cam specs...roller doesn't mean squat, you really gotta know the specs.

 

Yah, specs certainly can come into play, Its a comp grind 3314B Int. and 3315B Ex. meaning .335 and .340 lobe lift. Duration isn't going to play here. The riveted washers that hold the Tie-Bar are coming into contact and modeling clay is telling me by not much, I'm guessing around .100 interference. Too much to clearance with a die-grinder and not break through. I fit iron plugs in head crossovers with 5/16 hole drilled through. Electric choke on Speed Demon but I live in Eastern Wa. and I know I'll drive it in winter. The heads were milled .010 and decked block .029. I milled the manifold port flanges .041 each which calculates a manifold drop to block-center line of some .057.

I am especially interested in BigD's reply about manifold choice. I'm looking at the 7111 Performer RPM. The specs appear to be much more favorable to my present set-up. Just using what I had. Been piecing this build together since 2002, 6 years ago I dropped near $450 for Harland Sharp Rockers, not that the motor required it, but the they should live a long happy life. Sooo, No clearance problems with the 7111 Performer RPM? Stock valley tray work? I still have it.

Patrick

 

i really can't say for sure about the 7111, i'm running a performer at this point in time and i have a Holley street dominator on the shelf which is essentially flat bottomed. your best bet would be to talk to the guys at comp cams and get their opinion as to what is most suitable for your camshaft since it's a custom grind...

 

I had problems before with compcam roller lifters and ended up not using them. Check lunati cams they have a new hydraulic roller lifter that may eliminate your issues.

 

ran into same thing with my 72 cutlass s 350 rebuild using same manifold & same lifters,linkbar was hitting underside of manifold.called comcams talked to their tech he said to flip lifters around so link is facing outward on ones i have problems with . so far so good about 800 miles on engine. BILL

 

And if you wanted to retain the port velocity as you stated in the opening post you should have backed off on the lift.

Jmo

 

Just checking back in - fwiw the one HR I can recall basic specs was .515 or .525 with 202/212 @ .050 which is in the red car. Idles nice, runs well (9:1, small tube Hookers)? We did just swap over to RPM from base Performer & I don't think it gave up anything in low rpm response, seat o the pants feels a boost mid & higher rpm. Car has a 3.08 / 200-4R & will really break em loose on a 2-1 or 3-2 kickdown. Hoping to get some times @ track rental Friday If weather cooperates & we can compare the intakes. I think I'm gonna have to share my drag radials with the kid!

I wish I had figured out flipping the lifters around, coulda saved myself some work. I feel like an idiot on that one if it works!

 

yeah, thats so obvious that i probably never woulda thought of it either... i think you'll be happy with the rpm intake. i've never run one, the performer i'm using now seems good & i really like the holley street dominator...

 

Wow, thanks guys for your help.
I checked to see about flipping around just #4 cylinder lifters, but the head locating pin bosses cast into the block only allow #3 and #6 to be reversed and forgot I had already tried that. Got me excited there. I'm leaning heavily on the RPM manifold idea. $250 and 2 hours on a Saturday with a Bridgeport at work again for fit and another set of intake gaskets for port matching and I'd be in the clear.
Edelbrock guy didn't know what would work or not, his cheat sheet didn't list anything. Comp guy when I pressured him asked around to his fellows and one guy was aware of their lifters interfering with the Performer and said about .040 clearance cut into the intake would solve the problem. Unfortunately I milled the intake with .057 drop already and .100 total would likely break through the casting.
As to the cam and intake recommendations, Comp ground in Int. 224° @ .050, .335 lift, Ex. 230° @ .050, .340 lift, and 110° Lobe Separation. I'm using stock rocker ratio. Light weight custom pistons. OEM cast exh. manifolds and 2-1/2 dual exhaust with free flowing turbos. Convertor built to High Stall Jaguar specs, maybe brake stall of 2100-2300, depending on torque produced. I built a TH400 auto with the usual, dual fed clutches, restricted convertor feed, etc. , 3.08 rear-end in a 3600 lb. 68` Cutlass Supreme Holiday Coupe with my fat self in it.

It's true that lower lift (restriction) causes the back pressure to force its way past the valve at velocity, both intake and exhaust, but I was speaking to the volume of the intake runner and it's influence on intake charge velocity. The valve is acting as a variable restriction on demand. Some of which is required, valve closed, and some we have to live with as the valve events take place. Since I decided to reduce the valve restriction, I'm paying closer attention to runner volume in conjunction with minimal volume increase of intake side of head porting. The exhaust side I opened it more, If I get the exhaust charge out of the way, the intake charge will have the room to move in, if motivated. Did I go too far? The dyno should say. and yah, I'm crossing my fingers, but any advise is welcome. as long as it comes with a smile its greatly appreciated, so thanks again guys.

Patrick

 

Update:
Engine running. Went with RPM intake. I have it idling at 650RPM in gear and gauge reads near 9" vac. No loss of low-end response, although I am not comparing both intakes back-to-back with same cam/comp.ratio. The cam and engine combo I ended up with is absolutely incredible! More than what I expected. Major torque right off from idle and up. It winds up much faster than a stock big block. Traction is now the issue of the day. With 3.08:1 differential and accelerating full throttle in second at 70MPH, shift to 3rd causes much more than just a chirp from both of the posi-fed tires! I need to stay alert when horsing around in my car now. A rev-limiter is next on my list of needs because over-rev is a real concern and I need to avoid valve-float. Rainy day driving is a thing of the past.

Patrick