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1978 olds cutlass supreme sbc406 th400 3.73
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Discussion Starter · #1 · (Edited)
Does anyone have a program or just a ballpark what this setup may be around. I see some people post data points on here. I’m including a few cams from what I’ve gathered from calling around.
i have a 406sbc
78 olds cutlass supreme 3500lbs
rpm intake
Afr 195 heads (1034)
10:5-11:1 compression
Scat rotating assembly 9000 crank/ forged rods 6” pistons 4.155” icon dish -15.2cc
3.73 gears
Th400 10” 2400-2600 stall
26.3” tires
I haven’t bought a carb yet but I’m looking at holley 750hp. If I need to go a tad bigger I will.
I’m keeping it a hyd flat tappet
Crower 00221s 00224s 00226s
Had a Howard’s part number but I can’t find that
Comp cam 12-246-20 or if I can make the 12-254-20work. I have a 2400-2600 stall. The 254 calls for a 3300 stall which I’m assuming is to big.
Sorry if I’m asking to much here. Obviously this is a shot in the dark and I’m really new in here. Thanks Mike
 

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That bigger cam will play nicer with 11to1 comp, and your AFR heads.
From the lots I have learned, and the little bit I know, the 750 should be fine.
I am only (barely) familiar with roller profiles, and I think flat tappets are a little different. But if that was a roller, I have one very similar in a 406 with less head and mine runs like a scalded dog and pushes my heavy ass truck every good.
You didn't mention what car this is going in, but my 4000 pound truck goes 12s. So you have the potential for a stout setup.
Maybe someone can refresh me on the different characteristics of a flat tappet and roller cam specs...
 

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That converter precludes really long duration or tight LSA cams for that matter. This is a place where you want to keep the intake duration at or under about 224 degrees at .050 with an LSA 110 degrees or larger. You can trade into more lift without penalty on the converter.

The two issues with converter stall and cam duration and LSA is long duration and or tight LSA drives a high idle which is a pain to brake on the street. From a racing standpoint the bigger the cam duration and the tighter the LSA the further up the RPM range is the torque and power peaks. The looser the converter the more able you are to rev the engine up into where the torque and power peaks are. So if the primary need is to go fast and to that end you need a very long duration cam with a tight LSA then here you are on a stall speed mismatch.

My S15 runs an LT4HOT cam in a 350 with a 2800 rpm stall converter with a 700R4 on the street it’s a good match to a 3.08 axle and 25.7 inch tire. The low gear of the 700R4 gives a hard launch with high gearing for the interstate. I run an 800CFM Edelbrock AVS-I jetted one jet size rich from their delivered configuration as I’m using 10.7 to 1 compression with a coolant modified LT1 head, so the slightly extra rich mixture is just a CYA for 91 octane E10. This engine on a crankshaft dyno pulled 435 ft pounds at 3600 and 412 hp at 5600 using a modified 454 TBI way back in an earlier configuration. Driving it as a daily driver it got better mileage and according to my butt dyno more mid range torque than it does with the carb but it has a better top end with the carb which I gather is a function of 130 more CFM of the carb. The carb dropped average mileage by 3mpg compared to the TBI. I should note the engine runs D dish pistons, compared to an earlier run with factory circular dish pistons this improved the torque curve by 10 to 20 ft lbs depending on RPM with 20 occurring at lower RPM of 2600 RPM and it changed to a fatter and longer curve while the maximum torque is 435 at 3600 the torque curve hits 400 at 2600 and falls back to 400 till 5100. Needless to say I’m a big advocate for either D or stepped dish pistons or flat tops against the factory type round dish piston. This is a great dyno test that shows the better combustion characteristics of maximizing the area of tight piston to the squish/quench step of the head. This with an LT 1 head that even when ported as mine are is not the best flowing of head’s.

Bogie
 

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Sorry. I forgot about that. 24-2600 10” stall
What brand?

There is a HUGE difference in performance depending on who made it. Some are good, some are just junk right out-of-the-box.

Seems a shame to put a hydro flat cam in such a nice group of parts....

As far as cam choice....list the specs, so we don't have to chase around the internet looking up your part numbers just to know what you are looking at.....
 

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1978 olds cutlass supreme sbc406 th400 3.73
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Discussion Starter · #7 ·
Sorry Eric. I posted this at like 3am and just wasn’t thinking about putting the cam info down. At the time I thought it be easy to search it but now I feel like a bit of a D for making people look. Any way I paid for the Crower camshaft recommendation. They gave me 3 cams 00211s and 00244s and 00266s. The Comp Cam recommendation is the 12-246-20. I’m including pictures below. I did also get roller cam and retrofit rocker recommendations too. But Personally I can’t pull the trigger on the retro fit rollers. I would seriously be pissed if I was one of those people receiving bad parts. I’ve never used them in any of my engines. It’s like a mental block or something. I’m not worried at all about installing. I’m worried about failure. I wouldn’t have a problem spending the extra grand on any reputable brand I can buy. It all comes back to me overthinking everything. Also the fact that it seems I may have to wait until July possibly going with anything but Howards. Flat taps are two-three weeks out. The roller lifters/cam I was looking at was from Isky, Johnson, and Howards. I don’t have a lot of people around here to bounce ideas off of. That’s why I joined here. I basically have two old timers I talk too. They are completely opposite one doesn’t like spending any money and the other would spend 10k. The engine machine shop guys are totally opposite too. I just try learning things from everyone and do something in the middle. Pics coming next.
 

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The 00244 if street manners are more important than strip times.
The 00226 if you're more race oriented.

Howards likely has something close to either one if Crower delivery date is too far off for you.
 

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1978 olds cutlass supreme sbc406 th400 3.73
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Discussion Starter · #11 ·
The 00244 if street manners are more important than strip times.
The 00226 if you're more race oriented.

Howards likely has something close to either one if Crower delivery date is too far off for you.
So am I a Moron for not using a retro roller setup? I do believe that most people in the forums complaing are probably a minority. Is there anyway to test the lifters before installing?
 

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Eric , was it you that told me Howards had a no fail guarantee on flat tappet cams ?
They have a line called "Max Certified", they are guaranteed even if you screw up the install somehow they will replace it.
Five year, no-fault warrantee.
Cost is higher, of course, than the regular hydraulic flat tappet line.

I agree with Johnsongrass, with the caveat you have to mind your details of the install.
For me, it is moly paste rubbed into both lifter bottoms and cam lobes, really worked in like rubbing out a paint job, then cam in block with all lifters installed but no timing chain.

(The red liquid crap some cam companies send in a little squeeze pouch as "cam install lube" is crap for the job and I refuse to use it for cams)

Rotate the cam and make sure all the lifters are rotating roughly the same amount in their bores, swap slow turners with fast turners to get them all about the same, any that remain slow turners or don't really turn at all replace them right then....don't fire it up and hope for the best.
The rest is normal stuff....no burrs in lifter bores, not too much spring pressure, prime the oil system, make sure engine is set-up to fire immediately with minimal cranking.
 

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I install flat tappet cams with Isky Rev Lube lovingly rubbed into the lobes and lifter bases. For performance SBC engines and those for my own personal street or competition use I instsll a roller cam thrust button on flat tappet cams. Last SBC F/T cam I lost was in 1994. At the shop there were enough cam replacements people either did themselves or from other shops brought in to have my attention. In the big scheme of things I don’t know the frequency against the totals out there but it’s a messy enough repair and replace process that I cover the contingencies as well as I can. I also look at the factory conversion to roller cams starting mid 1980’s and or the rendering of flat tappets still in use up to the mid 90’s to incredibly mild with hardly any lift as a signal from the factories that they were worrying about flat tappet cam&lifter life as a warrantee issue. The factories don’t sweat technical details that they can’t make money from so when they sweat a truly functional detail the customer doesn’t know, think or care about then you as a hobbies trodden should pay attention. What the OEMs sweat is mostly touch and feel goodies from air conditioning, stereos of some sort, flat screen entertainment centers in the dash, leather seats the stuff they make money from to the average purchaser which is in the tens of millions every year and the reverse of that what has the potential to cost them warrantee money in the necessary but customer overlooked mechanical details. Hotrodders and performance enthusiasts on the showroom floor are in a small minority that the factories entertain off to the side probably mostly because the majority of customers think that the engineering in these slops over into the grocery getters they are going to buy, so in a way selling a few performance models is really part of an advertising campaign just like winning a NASCAR race on Sunday bleeds into showroom traffic on Monday. The average person has no idea of the engineering disconnect between what they saw racing at Daytona and what is sitting on the showroom floor. So I go back to if the OEM’ in mass changed from flat to roller tappet cams that in reality time and lift no different from the flat tappet that preceded them, you can figure somethings up that affects part life span and thus warrantee cost and perceived product quality. That’s not to say you can’t make a flat tappet work the factory has to solve their problem in the context of rate production, they are not going to pay somebody to smear Isky Rev Lube on cam lobes while break-in is on the purchaser.

So if you pay attention to what you are doing from greasing up the cam at installation and doing a careful break-in and following up with a hot rod oil high in phosphates and zinc Extreme Pressure (EP) additive you should by OK; if you’re a sloppy assembler then not-so-much.

Bogie



Bogie
 
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