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Roller Cam for my 408 SBC

3084 Views 34 Replies 10 Participants Last post by  KAMjenII
Looking to upgrade the failing flat tappet in my 408 SBC to a roller cam. The engine has about ~20-25k miles on it and has been a great engine until the intake gaskets started to delaminate last summer and it started to burn oil. In the ensuing teardown to diagnose I found that the lifters were starting to wear. Not a total failure, but all the lifter faces were concave so I'm thinking only a matter of time.

About the engine: Stock cast crank turned .020, 10.5:1 comp, Eagle 5.7 SIR I beam rods, speed pro hypereutectic pistons, balanced rotating assembly, Performer RPM 60899 64cc heads(the newer 195cc version) and regular Performer RPM intake Lunati Voodoo p/n 10120704 dur @.050" is 233/241 and lift is .505/.526 comp roller tip rockers poly locks, and magnum chrome moly pushrods.

Looking to replace the Voodoo with one of the following Howards cams:
110265-10 233 241 @.050 .530 .545 110 106 or (similar numbers to my current cam)
110275-10 241 247 @.050 .545 .565 110 106 basically one step up from my current cam

Leaning towards going with the bigger cam to spice things up a bit. I'd like to upgrade the heads at some point, but the budget for this winter doesn't include that at this point. Howards says the 110275 makes power to 6400, but I'm thinking that's referring to a 350 so the 408 should make power closer to 6000.

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1979 Chevrolet Malibu 496-TH400-9" (cruiser). 1992 Chevrolet S10 355-700r4-7.625" (daily driver).
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Yes. Convex.

Considering just the engine combination, in my opinion, the smaller off the 2 cams seems like a better fit for the combination right now.

What do you have for a transmission/converter and rear end/gearing?
 

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I am pretty sure they are supposed to be concave, so the lifter rotates in the bore and wears even on the lobe
They are supposed to be Convex, not Concave.
The lifter pictured is well on it's way to failure....cam lobe nose will be similarly worn.

Waylon, I think your assessment of power peak for the #110275-10 is going to be about right, might be as high as 6200 rpm since you've got decent heads
 

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Discussion Starter · #7 ·
you will need to go through the entire engine and clean it. Freshen rings n bearings as requires. Your heads probably need a split.
Post the flow numbers?You did not say if you are using an 850 CFM carb?
Yes will be going through everything shortly as the rest of the engine comes apart.
Head Flow numbers from Edelbrock are below. Mine are 60899.
Not the best flow numbers, but with the old cam, 3:73:1 gears, 2500 converter in 700R4 my 3800lb Malibu(with me in it, I'm a big guy) would run 12.70's @ 107mph. I was eyeing up either AFR or Profiler 210's for this engine, but another project is sucking up the funds.
 

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Discussion Starter · #8 ·
They are supposed to be Convex, not Concave.
The lifter pictured is well on it's way to failure....cam lobe nose will be similarly worn.

Waylon, I think your assessment of power peak for the #110275-10 is going to be about right, might be as high as 6200 rpm since you've got decent heads
[/QUOTE
I can live with 6200 as that's still pretty reasonable. The only thing I'm worried about is my power brakes with the @.050 duration well over 240. My power brakes are fine now except when the engine idles really low like at start up.
 

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Discussion Starter · #9 ·
Yes. Convex.

Considering just the engine combination, in my opinion, the smaller off the 2 cams seems like a better fit for the combination right now.

What do you have for a transmission/converter and rear end/gearing?
700R4 with a 2500rpm stall converter. Seriously considering going to a 3000-3200 rpm converter while the engine is out. 3:73:1 rear end gears. You're probably right about the first cam being better for the combo right now. I street drive the car a lot too an the first cam would for sure be fine with my power brakes and such. I drive the car ~20 miles each way to work in the summer when the weather is good.
 

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Discussion Starter · #11 ·
those cars usually go 12.0s with what you have?
Lets say your combo is 300 lbs over weight thats still 12.3s?
Lets figure out your issues,,,
I'm more worried about picking a good cam right now. Won't be back to the track for 4 or 5 months anyway due to winter. My 'meh' 1/4 mile times are a product of not enough converter(supposed to be 2500rpm stall, but is a 12" unit), mediocre heads, 1 5/8' headers.
 

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The fellas here have 370 ish crate style 350s with 3k converters. You have other issues. We can help you,,,
example of low power cars here a good local 12.0 car is doing it at 100 mph. Leaving hard, hooking, no top end charge.
I know you "need " a camshaft but that is not top of the list. What is your actual CR? The 106º icl can use a little duration
 

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just looked at your head flow numbers. The int/ex ratio is terrible. Its like an FE? You need 10º extra on the exhaust side. I would use split ratios and a moderate cam profile. If you like 106º icl I think 110-112º ecl with 8-10º extra on the exhaust side. If you buy AFRs or profilers later this camshaft will suck
 

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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 I mentioned, I think the smaller of the 2 cams is a good fit. Knowing you need the cam, lifters and pushrods to have it running again, of course you start there. If/when you have the heads off, see if a better valve job is in the budget over the winter. I can't recall seeing a valve job on anything mass produced that left much to be desired. To me, the gain from a good 5 angle valve job is money well spent. Especially if you plan to run the heads for a while and I think you should. As you mentioned, upgrading "at some point" would be a nice luxury in the future. As Moosecountry mentioned there is much to do before that becomes a priority.

You are aware of the need for a different torque converter. You nailed your next step right there.

You have a really nice combination going there. It brings back so many memories for me. I turned 16 in the summer of 1989. For $500 I bought a '79 Malibu earlier that spring (before I turned 16). It was the same color as the one in your thumbnail photo. I didn't have my drivers license yet when I drove it home. My parents required an explanation for that. Here on the eve of 2022, that old car is parked in the garage. It runs, looks and sounds a little different than it did in those days though.
 

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Discussion Starter · #15 ·
just looked at your head flow numbers. The int/ex ratio is terrible. Its like an FE? You need 10º extra on the exhaust side. I would use split ratios and a moderate cam profile. If you like 106º icl I think 110-112º ecl with 8-10º extra on the exhaust side. If you buy AFRs or profilers later this camshaft will suck
Yeah, the exhaust is weak on the Edelbrocks. I originally picked them up several years ago for a 350 used in a pickup truck before I got back into working on engines. I've been soaking up as much knowledge as I cam about head porting and did some mild porting and valve destrouding on a set of 882 heads that went on a 327 for practice. Thinking about cleaning these Edelbrocks up some while I have the time. My calculated compression ratio is 10.7:1.
 

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porting 882s is like mounting a drag shoot on a 14 second bracket car. If anything they get worse. Your door stops will be lighter so the scrap price will go down.
Porting the Edelbrocks can help but without flow bench time you wont know where you are or what camshaft to pick? You can get over 400 hp with those heads,,,
What end results do you want? If its a daily driver live with the lower power output. Work on making the car hook. Converter might take away a tenth or slightly more?
 

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Discussion Starter · #17 ·
I know the 882s are boat anchors. The point of doing the work on them was to get experience doing. Nothing I did was radical or would hurt flow.

For the current combo, I'm just trying to get the most out of what I have while keeping it streetable. For the fun per dollar ratio, I'd go right back with the same Voodoo flat tappet if I knew it would be reliable long term.
 

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Without a flow bench I do not recommend self porting. If the lower power output was agreeable before
then just buy a better suited roller profile for the heads as is? Getting a better suited profile will make more power through entire rpm range.
What headers are you using and what carb/tb system?
 

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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
 

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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
 
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