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Discussion Starter · #21 ·
What is the valve train? High lift cams need a better that average supporting cast that includes for flat tappet cams the use of hard face lifters, sturdy pushrods, 7/16th studs with for aluminum head’s must have a 3/4 inch long bottom thread to grab as much of the head threads as possible when they project into the port the length is correct, probably even 7/16th studs need a girdle. Getting into these high lift flat tappet cams with fast lobes using a roller can thrust bumper is a damn good idea it greatly relieves the lifter interface from having to also manage the thrust moments that high lifts and high spring pressures engender. This thrust problem is also enhanced by running roller or gear driven timing sets. These remove a flex absorption point that a link belt style timing chain provides at the cost of a short life but the crankshaft has its vibratory modes as does the cam unlike a turbine which at least in theory has a smooth rotation the piston engine is introducing discontinuous rotation moments on the crankshaft and does a similar thing on the camshaft albeit for differing reasons but the result is a shaky motion on both shafts that meet at the timing set. If the timing set pretty rigid as dictated by the need to keep the timing in a tight circle of error probability but the downside is a whole lot of shaking goin-on between these shafts. This tends to tear up lifters and lobes pretty fast. This might grab you where you’re not expecting it but street driving is much more severe than racing in this regard because at lower RPM the forces are present over longer time periods. But transferring this to high levels of competition builds over the years you see top top end competition builders try to deal with this by the use of thrust buttons on flat tappet cams often using silent link chain drives with frequent replacement or belt drives and the really radical flat tappet guys go to Chrysler (.904) or Ford larger (.875) diameter lifters which wear better than the Chevy .842 and a matching contour cam lobe. Another thing is keeping track of the lifter bore diameter and clearance. The lifter bore wears in an egg shape and clearance between lifter and bore should be .0015 to .0021 inch. The question here is how many guys actually measure these things? The lifter’s motion is much more complicated that just up and down abs round and round in its bore, there are substantial lateral loads that push the lifter pretty hard against its bore wall in a motion that would like to bind it across to bore diameter.

So the message I’m trying to put through is on the Chevy and GM engines in particular that use the .842 dia lifter are subject to motions that want to restrict vertical motion, that the lifter has a lot to do in order to maintain lateral thrust control of the vibrating and rotating cam. The Chevrolet in particular snd GM in general is one of few if not the only company that doesn’t use a thrust plate on flat tappet engines. And Chevrolet SBC’s in particular suffer abnormal cam and lifter wear some of that can be directed at the smallish root diameter of the cam as well, but that rather than an excuse is another reason to beef up the thrust control efforts on these engines even with flat tappets. Now there’s a thought for the aftermarket to make a flat tappet cam for Gen1 roller blocks using the thrust plate and the OEM roller cam timing set. This would be pretty simple mod to standard flat tappet blanks by just machining the thrust step on the nose and drilling the roller timing set bolt holes.

Bogie
The roller cam thrust button on a flat tappet is something I haven't heard of before. It certainly couldn't hurt. Also, I've heard talk of "hard faced" flat tappet lifters but never seen any specified as such. I've wondered if the lifters I've seen with a different material around the foot of lifter were "hard faced". If I knew they would make a difference and which ones to buy, I might just stay with the flat tappet for simplicity and to not sink more into this particular engine. I've been using the Lunati "micro trol" lifters because they had the snap ring retaining the plunger and I've had issues with the cheap wire ring style lifters coming apart. The remainder of the current valve train on the engine consists of the the valves and springs, etc that came with the Performer RPM heads. Rocker arm studs are the stock 3/8" ers that Edelbrock installed along with the Edelbrock guide plates. Comp Magnum pushrods and Comp roller tip cast rockers(I know, not ideal).

I realize a bunch of that will have to change for the roller. I planned on the appropriate springs(I have the tool to check installed height now) along with Scorpian roller rockers and the appropriate length pushrods, cam button, better timing cover, etc.
 

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Discussion Starter · #22 ·
great info Bogie but maybe a bit complicated? Because you are good at explaining maybe explain to Waylon how long duration on the exhaust side can while helping improve hp especially as a crutch to bad exhaust ports can also cause a loss of bottom end torque. (should not be as big a deal on his 408)
Thanks for a great post Bogie
I understand that these Edelbrocks need more crutch on the exhaust side than even other SBC heads do. The cams I'm looking and my current cam at all have split duration and lift. This engine was built 5 yrs ago and I've learned a lot since then. The 383 I built for my Dad's El Camino last year got 195cc AFR's. I upgraded the rocker studs to 7/16" and it got a Howards hydraulic roller single pattern cam since the AFR's have a good intake to exhaust ratio. 237 @ .050 duration and .560 lift with 110 LSA and 106 ICL. That engine pulls extremely hard. I really don't have any complaints about my current combo on the 408 either. If it hadn't started sucking oil through the intake gasket I never would have known the cam was on its way to failure so I guess I lucked out?
 

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1979 Chevrolet Malibu 496-TH400-9" (cruiser). 1992 Chevrolet S10 355-700r4-7.625" (daily driver).
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As usual, you're getting great information. Bogie, Moosecountry and most of the folks on here know a lot more than I do, but I try to give what information I think I know nonetheless.

Like Moosecountry said, home porting can get a relatively novice guy (like you or I) into trouble if we aren't careful. If you go ahead with a better valve job, a bowl blend and taking any edges off of the short turns shouldn't be enough to get you into trouble. Even though aluminum clogs up sandpaper rolls pretty quickly, I would use them to get the job done. You shouldn't have to remove too much material and the sandpaper rolls help to avoid taking too much away too quickly.

As Bogie mentioned not enough people pay attention to measuring things. The lifter bores (and bores in the cam tunnel) seem to get overlooked. The thrust button or thrust plate is a must for me as well. Even on flat tappets. Along with helping with wear on the cam and lifters, I think it helps out the timing chain stretching.

If you don't have a degree wheel, that's also a must. As Moosecountry alluded to, getting the cam where it needs be is critical. Just making sure the cam is what it's supposed to be is important too.

At the projected power level you have here, what do you know about the transmission? If it's not a "built" unit already, there are some pretty budget friendly upgrades to be made there that do not require the transmission to be fully disassembled or even removed from the car.

If you're running the factory rear end there are things to consider too.
 

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I agree on home porting best being confined to cleaning up the valve pocket. This is 80% of the problem on older heads. Starting at the L31Vortec and certainly most but not all aftermarket head’s you will notice that the guide sail is already much improved to old factory head’s. So there isn’t so much to be gained on modern heads in this area beyond clean up. A caution is not to make the pocket wall a straight bore to the seat i.d. Here a little throating approaching the seat will aid the transition across the seat. An issue with flows is a thing called vena-contracta. This works in both directions of a flow across a change in area. Essentially without guidance a flow crossing an abrupt edge naturally contracts reducing flow area, dropping pressure in the remaining flow and accelerating it. The take away here is less area, lower molecular density (weight) at a higher velocity. Power is the result of the weights of reactants less fuel and air is less reactants is less power.

Port matching doesn’t net a lot unless you have the intake your going to use snd a flow bench and are prepared to chop at both to do a better job of controlling where the flows are in the manifold passage and matching the head port to receive that flow. This is tricky to do and the resultant cutting can look pretty ugly and counter intuitive, i.e. forget having 4 identical intake ports to a V8 head.

Back cutting the valves is very effective at improving low through mid lift flow and is pretty harmless to flows above .4 inch. Larger valves most aid high lift flow starting at .4 and going up. One piece valves that do not have the big old time weld between head and stem flow much better than the old welded two piece valves. Reduced stem diameter approaching the valve head is better still but you need to bring more money to up the material quality as this feature reduces the structural area carrying loads and transmitting heat into the stem so such valves are more subject to failure without improving the material properties.

Much is written about how lousy the SBC exhaust port is, not that there isn’t room for improvement but I really wonder if the authors of such articles ever tried to get port flow up on a Ford Cleveland head to something reasonably close to the intake, that takes more than a die grinder. For any street vehicle with an exhaust system that doesn’t get you pulled over or drums your brain to mush in 5 miles really can use the extra open exhaust valve time afforded by a split duration cam.

Bogie
 

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Discussion Starter · #25 ·
@BogiesAnnex1 Great info. Less is more with home porting. Have been doing my research and know not to go too far, but a guy's got to dig in and try some of this stuff to get good at it. I might wind up having a valve job done, will decide when I'm done.

Any specific cam buttons you'd recommend or at least what to look for?

Which hydraulic flat tappet hard faced lifters have you had luck with?
The GM Performance look like they have the hard face, but have the chintzy wire retainer instead of a circlip:
The Comp Magnums claim made in USA, seem to have the hardened face and have a circlip retaining the plunger:
 

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1979 Chevrolet Malibu 496-TH400-9" (cruiser). 1992 Chevrolet S10 355-700r4-7.625" (daily driver).
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If you're thinking hydraulic flat tappet set up, contact this guy.


He will likely recommend getting the cam ground on a P55 core. It's a premium cast harder core. He will set you up with the recommended lifters to match. His quality control is spot on. Mike is a cam designer with proprietary lobe profiles. With the amount of information you have on this build, he will spec a camshaft for your application that will be ideal. I'm sure he will recommend the proper oil to use for break in and what to use after that.

Google search Mike Jones Cams and let the reviews speak for themselves. In my opinion, money well spent. It's what I would do and an inquiry on your part can't hurt to look into.
 

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This is basic stuff, but it never hurts to ask:

How did you break-in the cam, and what kind of oil did you use during break-in and since then?

Wth the current cam's .505"/.526" valve lift, do the springs have another .050" safety margin until coil bind, and is there similar retainer to seal clearance?

Are you running 1.5 or 1.6 rocker arms?
 

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Discussion Starter · #28 ·
Cam was broken in properly with plenty of the prescribed Lunait cam lube and break in oil. Edelbrock says the springs are good to .575 max lift and I'm using 1.5 rockers. If you look at the first pic I posted, you can see that the lifters are showing mild wear after 25k hard miles. The only place where I could have done things differently would be to use lighter springs for break in. The springs I'm using only have a damper and are not double springs so I just used them. Maybe it accelerated wear? I'm wondering if the wear is more due to the VooDoo cams 43 degrees of hydraulic intensity and just won't ever live a really long life. If trying to get by with a flat tappet and trying to get a lot of miles out if it I should probably pic a cam with lazier ramps, but that's no fun!
 

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Did anyone else see that his build is using 5.7 rods in a 400 sbc. I would be very concerned about cam lobe to rod bolt interference. The factory SBC 400 rods are shorter and use shorter rod bolts for block rail and cam lobe clearance. using 5.7 rods is a concern. Even in stock 400 shortblock with cam upgrade a small base circle cam is frequently used to clear the rod bolt interference.
 

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Discussion Starter · #30 ·
Did anyone else see that his build is using 5.7 rods in a 400 sbc. I would be very concerned about cam lobe to rod bolt interference. The factory SBC 400 rods are shorter and use shorter rod bolts for block rail and cam lobe clearance. using 5.7 rods is a concern. Even in stock 400 shortblock with cam upgrade a small base circle cam is frequently used to clear the rod bolt interference.
Yep, rod to cam clearance was checked! The Eagle SIR rods I used don't have the best rod clearance, there are better out there but they work. Scat makes some nice stroker rods with lots of clearance.
 

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Hey, how is the car and engine going? The scat stroker rod is a good rod. i would go 6". Try a Mike Jones Cam Designs hydraulic roller. Pick a cam one smaller size than you think you need and you are on your way. Try one of their EHR designs and use their roller lifters. Careful here, you may think you can get away with another lifter. You can't. You must use their roller lifter with the high lift design and engineering and metallurgy that they use. These cams are the best street hyd. roller i have ever seen or heard of for a SBC.
 

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Discussion Starter · #33 ·
Hey, how is the car and engine going? The scat stroker rod is a good rod. i would go 6". Try a Mike Jones Cam Designs hydraulic roller. Pick a cam one smaller size than you think you need and you are on your way. Try one of their EHR designs and use their roller lifters. Careful here, you may think you can get away with another lifter. You can't. You must use their roller lifter with the high lift design and engineering and metallurgy that they use. These cams are the best street hyd. roller i have ever seen or heard of for a SBC.
I wound up freshening the engine up, new bearings and rings. Changed things up and went with the new version of the Dart SHP 200cc heads with 72cc chambers for 9.5:1 so I can run it on 87 octane since I drive the car a lot. Those 5.7 rods are still doing fine. I would go with something different if I did it again, but they work in this combo. I chose a Howards retro roller cam, 233 in and 241 ex @.050 roller cam on a 110. Runs really strong. Best pass in a 3900lb car last summer was 12.01 @ 113 with consistent 12.10's.....on 87 octane.
 
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