Does anyone now what the deal is with hydraulic rollers in the Gen 6 BBC? Crane says extended travel lifters are needed for cams over .570" lift. What I am curious about is why GM uses the stock 7.4 vortec lifter in the zz572 with a .631" lift cam?
I am building a 540 stroker on the short deck two-piece main version of the block the zz572 uses. Are the lifter bores closer to the cam in the bowtie blocks? Crane sells their version of the stock lifter for $250ish the Crane extended travel lifters are $500ish.

Any clues?
Thanks

 

I doubt the two piece rear main bowtie block is machined for the factory hyd roller lifters with spider. Maybe but I doubt it. You'll have to use aftermarket hyd roller lifters which will as a bonus allow more than .57". I'm running .585" lift on my Gen VI with factory rollers, but there is not much more room than that.

 

Currently I'm running the comp cams xr294hr cam with factory roller lifters and spider in a gen VI block. I have a set of 900-16 rollers from comp on the way. Mine are way to weak to handle the pressures of the beehive springs I just installed from comp as well. I am running 1.78:1 roller rockers as well so my lift is .565/.585. The next step up is the xr300hr which will still work with the factory setup as far as my measurements go. That would leave you with .586/.607 with the 1.78 rockers. This is about the limit of the hyd rollers from the factory. The lifter won't fall out of the dog bones while riding the base circle and it won't push up on the dog bone at max lift. It will get really close but it won't hit unless it ramps off at the top.

The comp cams replacement lifters are around 220 from summit, I don't know how well they will fit yet or what lift they can take as mine are still waiting to be shipped.

Good luck.

 

We just got in 10 "Bowtie" BB's #25534362-2 pc. rear seal based on the late casting (Gen-V-VI). You probably can use the 1 pc. seal also #25534363. The blocks are identically cast except for the rear main cap and the alloy seal retainer they install. This would eliminate producing 2 different blocks . The problem we've found is you need +.300" lifters to clear the bores when the lifter is down on the base circle. I have done one with machining (lowering) the lifter bores. It worked fine with the shorter retro's. It appears they have provided the mounting for the factory hyd. roller setup. We have already delivered 2 finished engines on this platform (+.300"), but we have been using Comp Cams retro's. We feel we can get the RPM's higher if we can "lighten" the lifter ***'y. We will be doing a fair amount of testing in the next few weeks. We absolutely need .700"+ lift at the valve to get over the 750HP range. On all the dyno testing we can't get the RPM's in the 7000 range (on BB's only). They float at 6550. On most 540's we do it's OK, because we can still send 'em out the door with 740+HP at 6300. I'll keep you posted on our results. We will get to the 800HP range on the hyd. roller platform eventually, we think. Thanks, Gary in N.Y.
PS All the engines we've delivered have no higher than 9.75:1 C.R. and with aluminum heads have been tested and will run on 89 Octane. Also, the "good" ones are producing over 700Ft.Lbs. torque. The heavier lifters require at the minimum a set of "Titanium" retainers. We've spoken many times to "James" at Comp Cams about this particular platform and now with the Pro-Topline heads coming out of Comp we will be in closer touch. The first one out the door made 706 Ft.Lbs. with these heads. A .630" lift on a decent 540 platform is absolutely useless at the point we're at now, we would probably "give-away" some 30/40 horses. This is merely a "guesstimate" as we never tested for loss.

 

Good info here. Doesn't someone make solid rollers for the taller lifter bores of the Gen VI motor, though I guess your aim is to use a more streetable hyd roller. Have heard others claim the taller lifter bore also has advantages in more lifter stabilitity, though I guess that is relevent for more extreme cams?

How much spring tension do you run on these cams and do the lifters ever bleed down?

Do you have any sort of hydrarev kit?

How much duration are you running on these 540's

 

Springs are run around 160# closed, 380# open (@.700" lift), no lifter bleed-down at all, totally maintenance-free. The cams are in the neighborhood of 250/260 @ .050 duration, with .720" lift and on 114L/S. The motors make in the neighborhood of 750HP and 700+ Ft.Lbs. torque @ 6200 and 4600 respectively. The heads are a critical item, must maintain smaller cc's (320/330) through the intakes and a minimum of 375CFM-intakes and 275CFM exhaust. This is all with a 9.75 C.R. and able to run on 89/91 octane. We do a number of these units. I'll make one recommendation here however, I wont use G.M.'s "base" 502 BB, as it's really a flimsy block and you can't safely go past the 4.500" bore. On a final note, Comp for sure has +.300" lifters (both solid and hydro-retro) and I assume other mfr's. do likewise. We are partial to Comp due to their involvment in the overall racing picture. When my phone rings for parts, it's usually Comp's parts. Thanks, Gary in N.Y.
PS On 540 solid roller, slightly higher C.R.'s (still under 11:1), and the same heads with us porting them we are well past 800 HP at slightly higher RPM's. The heads we strictly use on our own "out-the-door" assemblies are part #124-19000-320. Comp Cams owns the foundry and has already produced HP numbers in some ads using this line. We've been using them for years. We do use other brands also, such as Brodix, and have had excellent results also. What really impressed us with the "Topline' heads was the fact there was no porting to speak of, we could spend a total of about 2 hours on them, and they were ready to run and the 750HP produced, falls in this range. The heads flowed 375/275 from the box AND on the 4.500 fixture. The RPM's are limited to 6550, so far, due to the lifter weight, as I've said before, but these strokers don't make power there anyway. They peak around 6300. We used Comp's parts in our SB (N/A-468 C.I.) that made 736 HP and 650Ft.Lbs. on Pump-Gas (tested on 93). We had posted those numbers back somewhere in April of 2005 on the Camaro website.

 

That 375 cfm, what lift is that at?

 

The heads were checked on the 4.500" fixture and flowed 375CFM @ .700" intake and 275CFM exhaust at same checkpoint. What impressed us originally with these heads was the fact as I said before we could have them ready to install in a few hours. From our standpoint this is excellent in the fact that we can make well over 725+ H.P. with not a lot of time invested and keep the head porting costs lower (you'd probably spend only about 300.00 on what we did). The flow numbers are also with a 320cc/330cc intake runner, if you go bigger on the runner volume, you will go down on the torque you achieve. We just did a pair of iron "Pro-Toplines" with the same CFM but using 360cc runners. The torque dropped to 660+ Ft.Lbs. as opposed to 700+ Ft. Lbs. with the smaller runners. They both used identical short blocks and C.R.'s of around 9.75:1. Thanks, Gary in N.Y.
PS Comp Cams is the owner of the "Pro-Topline" foundry now. One more item we just learned the factory Hydraulic Roller lifters are just slightly heavier than the retro's. We'll be doing more testing in this area in the days ahead.