As the title says. Doing a 305 build with 601 heads, 1.6 roller rockers, etc. I've got a set of chromoly pushrods, 7.9", but they don't seem to be long enough. Rocker geometry seems way too low and the lock-nuts don't even go down far enough on the studs to take up all the slack, and that's before I've even installed the guide plates. Genuinely wondering if I'm doing something wrong here, as far as I'm aware there shouldn't be any major differences between the 601s and the stock 614s in terms of rocker geometry.

 

601 heads took the same push rods as any other SBC when they were put on motors originally.

7.9" sounds kinda long to me. 7.8" is stock. Butt who knows; "sounds" isn't authoritative, after all that's why we measure.

When you "solidified" a lifter and used your adjustable push rod to attain the narrowest possible sweep of the rockers on the valve stem tips with your checking springs, what length did that require?

 

Alright, so let's pretend I knew either of those tools existed before today. While I have those on order, here's a picture of how the rocker sits with no pressure on it - it's occurred to me that the locking screw ships upside-down inside the adjuster nut, and that might be why it doesn't screw down far enough to reach the pivot ball. It looks a lot less weird right now than it did this morning at 2 am.

 

Couple of things:

Those push rods look WWWWWAAAAAAAAAYYYYYY long to me. There's a popular oversimplification about it that says the rocker should be "level" at half-lift: that is, the top of the push rod and the contact point of the tip on the valve stem, should be at the same "height" above the pivot. I don't think it's that simple but it's a good "first approximation" or "smell test" at least. Looks to me like you have about .150" or more too much push rod for that, depending on how much lift the cam gives.

Also looks like the shop didn't cut the top of the stud bosses down enough (if at all) for that type of studs, let alone guide plates. Looks more like they intended it to be used with studs without the hex. Probably also intended therefore to NOT use guide plates, but rather, "self-aligning" rockers. Which those don't look to be.



Here's kinda what it should look like. Note how much lower the top of the stud boss is cut down on my head, compared to yours. Looks like at least 1/8" difference, maybe as much as ¼". Note also, how much farther the rockers are tipped back. I should point out though, if memory serves me right, when I built these heads I had to put those washers under the studs that you can see there, because the studs went so far into the casting through the water jacket there, that they smashed into the top of the intake ports. I didn't feel like cutting the studs off to fit. Your ports may not be as big as these so there might be more room in there, but that's a good example of the kind of thing you can run into building a non-stock motor. And notice also, the sealer on the stud threads (looks black in the photo); they all go right directly into water.

 

You're nowhere near close enough and you need much SHORTER pushrods. Look where the roller tip of the rocker is positioned - it's almost off of the outer edge of the valve stem tip. And, like you said, the guide plates are not even in place yet. Here is mine - this is what you are shooting for.

Zero valve lift - base circle of cam lobe.


Max lift.


Mine with the checking tool.



And this is what you are trying to achieve.

 

Thanks for all the help, guys. The heads did come with guide plates installed, but they were too wide and wouldn't let the pushrods move. I'll try the stock pushrods and see if it's any better, when I get the tools in to adjust the lock nuts. Adjustable guide plates will also be on order.

 

I think you should use self-aligning rockers, not guide plates. Your setup doesn't look like it's meant to include them.

Work WITH what you've got, not FORCE whatever YOU THINK you want, onto it.

 

Yeah, sure, why not. Anything else important I should know before I make another decision that'll cost me $300 six months down the road?

 

Alright, small problem - I can't find self-aligning roller rockers for a Gen 1 SBC. Everything I've found is meant to be used on LT1 engines.

Edit: It looks like the stock rockers weren't self aligning. Hell, I can't even buy rockers for a gen 1 SBC that are. Everything I'm seeing is meant for centerbolt valve cover engines.

 

#601 heads have a slot in the casting to guide the push rod (like a guideplate does) If guideplates are added the slot has to be drilled out. Its one or the other nit both.. If the valves are longer than stock eg +.100" or +.150" longer then pushrod needs to be longer.
If rocker stud boss is not machined to correct height for screwin studs + guideplates the push rod will be too short also...... Looks like a mess. Someone got too carried away on a low budget head.. I just drill and pin the stock studs and shorten the guide boss for seals and lift and use .550" stock dia 1.26" perf springs. Thats all these heads deserve..

 

Verify those are chevy rockers not Ford 1.6 rockers
Different geometry.
Verify your valve lengths.
Rocker geometry and sweep is checked using s solid lifter..
If the integral pushrod guide SLOT is still intact in the heads the guideplates can be removed. May improve geometry. (If the valves are stock length.
Be sure to put sealer on the rocker stud threads..
Check guide boss (seal) to retainer lift clearance too.

If small base circle cam the push rods will need to be longer than stock..

If 1.6 rockers are used the integral pushrod guide SLOT in the head must be made longer towsrds the rocker stud to clear the pushrod. Assuming it is not drilled out now for guide plates. Its slot or guide plates not both...

 

601 heads, like virtually all 86-back ones, originally came with the narrow slots in the heads that guide the push rods.

If there was any intent to use guide plates, the holes would have been drilled out. It's an extremely common "performance" upgrade.

There are 3 systems that can be used to control the rockers and keep them on the valves: the narrow slots, guide plates, or self-aligning rockers. One AND ONLY ONE of these must be in effect at any time. If none are, then the rockers can fall off of the valve stem tips or otherwise misalign. If more than one is present, they usually "fight" each other, and cause something to bind, and parts destruction is then inevitable.

Post a photo looking down from above at the holes where the push rods come through the heads. That will tell right away what options you have available.

Self-aligning rockers started in 87. That was at the same time that they went to the center-bolt valve covers. They were used in all Gen 1 SBCs from 87 - 2000, and all of the LT1 variants in the 90s. It's possible to use them on ANY heads though, if the narrow slots are drilled out, to allow the push rod to follow the path that the rocker wants it to follow, rather than being the thing that forces the rocker to follow a particular path as it moves.

 

Okay. NOW I have some sort of an idea of what went wrong here. And it's important to note that I received these heads with guide plates and screw-in studs already installed. The only modifications I've made were beehive LS6 springs and retainers to get more valve lift.


It seems pretty obvious to me that these slots were never drilled out (the pushrods move side-to-side by maybe 1/16th of an inch at most) and that's why I was having so many issues with the pushrods binding up on the guide plates. And yes, I know about the sealant on the studs - I already have a tube for the head bolts. The valves are just stock 350 valves so the height should be the same between them and what came on the heads originally.

Overall what I'm getting from this is that I can use non-self-aligning rockers without guide plates installed.

 

Nope, not drilled out.

Gotta do 1 of 2 things: ditch the guide plates, or drill em.

Gotta use the 86-back style rockers if you leave the slots. Can't safely use self-aligning ones; they'll do the same thing as the guide plates. Namely, "fight" the slots. SOME SA rockers have enough slop in the locating feature, which after all doesn't have to be all that precise, that the slots will force the rockers into a range acceptable to the rockers, but you can't count on that.

Looking at what you've got there, I'd say, just ditch the guide plate idea and move on, to measuring for the correct length push rods. No idea why somebody would have "sold" you an incompatible setup like that, other than, to just take more of your money.

350 and 305 valves are the same thing except for the diameter of the head. Same height (4.911").

What cam ended up in this thing? Is it a roller?

 

It's a Lunati Barebones 280/290. Regular hydraulic lifter cam. I'll get some 1.6 roller rockers on order.

 

Not much of a cam. Just yerbasic copy of yerbasic generic copied copy of yerbasic copied generic copy of a copy of a generic cam. Won't win any races, but sometimes that's not the be-all end-all I guess. Some people are willing to settle for that. Sorry you spent too much; coulda got the same thing, and been just as obsolete, with this. https://www.summitracing.com/parts/sum-1103 Same cam, just acoupla different ratings methods.

You'll have to drill the holes for 1.6s.

Consider carefully. If you want to keep the worms in the can, don't get greedy.

 

Or he can elongate the double-D slots with a Louis tool.

 

It's going to be a street car, just wanted some more horsepower and the option to give it more later, if I wanted. Hard to get much more rowdy without changing the torque converter out and/or obliterating the poor old 700R4. And frankly, this build, despite all of the expensive mistakes I've made, has still been much cheaper than any slant six build.

For drilling out the guide slots; Am I just drilling 'out,' or am I slightly widening but mostly making the slot longer towards the outside of the engine so that the pushrod has more room to travel? I'd assume the latter.

 

Got any links for a good quality one? The only one I can find in production is the Proform one, which appears to be a terrible quality tool all around.

 

To lengthen the slot towards the stud for 1.6 rockers
I never use that tool.
I use a 5/16" rat tail file. Cut the end off . Put in a electric drill. The rat tail file files the slot longer, easily.

Longer not wider.

Wasted money on wrong cam and 1.6's.
More power and torque with a 108 lsa cam and stock rockers.
The 1.6's are only needed on the intake side.
Use 1.5 on the exhaust side.

 

Christ, sorry I didn't consult everyone in the universe before buying parts. In my experience, whenever I've asked for specifics, people tend to go 'HURR DURR MY BUILD YOU NO TOUCH.' I just went with a cam that looked like it'd be fine for a street car and sounded nice.

 

That cam will work best the higher the compression is.
Get it as close to 10.5:1 as you can. Anything at, over 10:1 is good... Gasket selection helps.
Heads need to be generously ported.
They are modest but get better with full porting.

 

Comp used to make a Louis tool. Was a pretty decent piece, considering what it's being asked to do. Still, it would only do a few sets of heads, before the side load on the drill bit wore it out. Don't know if they still do or not, what with the looming obsolescence of all things SBC these days.

A 5/16" chainsaw file works well, as said. A bit more time-consuming, and not as "precise", but gets the job done well enough.

Note that the way the push rod comes through the slot, it's not perpendicular, even though that's the way the factory slot is made (or for that matter, the way the Louis tool holds the bit while drilling it); and when it has to "lean in" toward the stud more because of the increased rocker ratio (shorter arm on the push rod end), it's even less perpendicular. The end of the hole in the rocker gallery needs elongated more than the end closer to the deck. The lower end of the hole barely needs any elongation, usually; while the upper end usually needs more than 1/16". It is CRITICAL that the push rod NEVER touch the end of the hole AT ALL: if it does, the end will get DESTROYED in its seat in the rocker. There's no danger of hitting water or any other malfunction if you go "too far" to the extent that you'd be likely to with a file, so don't be afraid to make it ALOT longer.

There's no "harm" in the higher ratio on the exhausts, as long as your springs and whatnot can withstand the higher lift. I think you won't like that cam very much though; especially with a stock converter and typical terrible stock gears, it'll have a pretty soggy "leave".

The little plastic tool is what I was referring to as the oversimplification. I wouldn't consider it authoritative, if for no other reason than the variation from one brand or model of rocker to another. It does make a good enough "smell test", in that if you use one, and it comes somewhat close to your correctly done precision measurements (where you find the length that produces the minimum sweep of the rocker tip across the valve when using the "solidified" lifter, adjustable push rod, and checking springs), you have some degree of assurance that you measured properly.

 

What cam should I be using, then?

 

In 2021 I would not use a flat-tappet cam AT ALL; it would be a roller. Unfortunately that can be $$$$ if your block doesn't have the factory setup for it. Let's hope you don't encounter the misfortune that goes with flat-tappet cams in 2021. Cleaning it up, and THEN getting a roller system, would be more like $$$$$$$ instead of merely $$$$. Kinda sucks all the fun out of the hobby. But let's not go down that rabbit hole, it's non-productive at this point.

We can all talk about "10.5:1 compression" and all that, as much as we want; but at this point, that ship has already set sail. Your compression is what it is, whatever that might be; you no longer have control over it; it's too late to worry about it. It is what it is. My best guess at it, is a shade under 10:1; not bad, but ... a shade under 10:1. I would NOT use steel-shim head gaskets to "crutch" it higher: EVERY SINGLE ENGINE I have ever torn down that has had those in it, which runs in the hundreds I think, has had a failure in at least one place. Not "more than usual"; not "lots"; not "most"; EVERY with a capital V. Usually between the 2 center cylinders on one side but sometimes somewhere else. Professionals who properly prepare a block and set of heads BEFORE ASSEMBLY can get them to seal, no question of that; OTOH, a "rebuilder" short block with NO prep, and a random set of stock heads, put together by an inexperienced assembler, is a recipe for problems. The thinnest gaskets I would even consider using are the old GM "Victorcore" ones that were about .028", if they're even still available. Otherwise, It would be FelPro PT7733-whatever they're up to these days. Once again, putting a motor together and having it fail, is MUCH worse than leaving acoupla tenths of a point of compression on the table. In fact, I think 10:1 is already too high for a beginner with real-world pump gas, a block with no quench, and a street cam. It would be a recipe for a spark-knocking untuneable monstrosity. Great for an experienced builder to run at the track; not so much for the situation at hand. There are sometimes other considerations besides just squeezing the last available HP out of a motor on the dyno.

Be that as it may, among off-the-shelf cams, I would use a Comp XE262 in your situation.

XE262 specs: 218°/224° @ .050", 262°/270° @ .006", .462"/.469" lift, 110° LSA; lobes are asymmetrical (faster opening than closing)
10121010: 214°/224° @ .050", 280°/290° @ .006", .443"/.465" lift, 112 LSA; lobes are symmetrical (same opening and closing rates)

Cam specs often look like black magic to most people. But they're really not all that hard to understand.

Intake duration @ .050", more than any one other spec, determines the operating RPM range the cam will favor.

Exhaust duration @ ,050" in relation to the intake duration should be chosen according to intake, head, and exhaust flows; the worse the whole exhaust system is, starting with the head port, the more benefit will be derived from a longer duration exh lobe. The lift is irrelevant; it's only higher than the int in these 2 particular cams because they're both part of a "series" of cams, in which the same lobes are used ont he int & exh, in the next step. So for example if you look at the next cam in the Comp XE line, the 268's int lobe is the same as the 262's exh lobe; just like the 258's exh lobe is the same as the 262's int lobe. For the old early 70s generic "Stage 1" cam that you have, the whole series is built the same way.

The .006" duration tells you when the valve starts to leave the seat. At lifts below .050", little or no meaningful flow occurs; it's really just a "leak". On the other hand, consider an "ideal" cam: it would snap the valves open to full lift instantaneously at the exact point in the engine cycle that you want for whatever RPM range you are trying to favor, and snap them back closed instantaneously when no further flow was desired. Obviously this is impossible in the real world; for one thing, the closer a cam gets to doing that, the more it just beats parts to death, makes noise, and so forth. That "ramp" between .006" and .050", especially on the closing side, is needed for parts life. But it extracts a penalty in engine performance, esp on the int side, by allowing compression to "leak" out of the cyl and back into the intake tract, diluting the air/fuel mixture in the intake, which is precisely what causes most of the "big cam" behavior you'd want to avoid: poor low speed torque, poor gas mileage at low RPMs, "lope", and so forth. That one spec, more than any other, is what's wrong with the half-century-old design, in 2021.

The duration #s are given in crank degrees. Keep in mind, this is a 4-stroke engine; the crank turns 2 revolutions for each engine cycle; each cyl has an intake, compression, power, and exhaust stroke, in each engine cycle; each one is one-half of a crank revolution, i.e. 180°. For an engine that's never supposed to turn very fast, let's say one of those old oil-field 1-cyl motors they used to use that ran at about 100 RPM, having the valves open about 180° works fine. But for one that runs at a higher RPM, at some point, the inertia of the air becomes a factor; it takes time to get it moving, once the valve opens; so it has to open longer. The higher the RPM you want the engine to run at, the longer the valves have to be open, esp the intake.

Lobe separation is the # of degrees of cam rotation between the peak of the int lobe (which is the event that all others are measured off of) and the peak of the exh lobe. Since the int peak is the reference, a greater LSA means the exh valve opens earlier. What this does is to begin releasing the pressure in the cyl sooner, specifically, before the piston reaches BDC in the power stroke; effectively, it throws away low-RPM power, by ENDING the part of the power stroke that accomplishes useful work. OTOH it also means that the cyl will "blow down" more fully before the int opens at the end of the exh stroke and beginning of the int, therefore there will be less reversion into the intake tract and consequently less "big cam" misbehavior, the cyls will fill better with fresh mixture, and there will be less "overlap" where the valves are open at the same time because the exh not only opens sooner but also closes sooner. Idle quality will be better, gas mileage at cruising will be better, idle vacuum will be higher, tuning will be easier. Factory cams use this technique to the extreme, because it also lowers emissions, most especially raw HC getting into the exhaust stream by way of both valves being open at the same time. A narrower LSA will give higher torque because the energy in the combusted mixture is more fully extracted, rougher idle (more "lope"), more "peaky" power curves (torque and HP peaks are closer together in RPMs), and otherwise is more "performance" oriented.

This is why the cam you picked is inferior, in 2021. It was all the rage when those came out, in about 1971 or so; thoroughly obsolete today, but CHEEEEP, because the design is in the public domain and doesn't have to be paid for anymore.

Capische?

 

I have never had a .015" gasket fail ever..
If a head gasket is going to fail, it will fail.
overheating detonation etc. The thicknesd has nothing to do with it.. The mating surfaces are either flat enough or they are not..
The comp 12-310-4 is a nice choice. 212-218- 108 lsa 104/112 .444" nice with your 1.6 rr. too.
The comp 110 lsa EX cams are nice and can be tweeked a hair for effect by installing on 104/116 centers or custom ordered on 108 lsa too. (104/112)

Use correct oil.. and or add some Moly additive
I like Moly Slip E oil supplement .It works.
I like these lol 108 lsa cams on 305's and 350's that have 305 ho heads (ported) and 10-10.5:1 cr.
Yes the .015" head gasket allows you to get there on a ft piston 305...
Your cam is ok but thesee 108 lsa cams will be a hair better overall. Your cam is not bad if the cr is right.
you get that thru gasket selection.
Use champion RV8c plugs or equal like AC42T. .035 gap..
Install gasket clean and dry on clean dry surfaces.
The flatness of the head is the more critical than the block deck.

Cc the chamber on your modded #601 heads so you can get the cr correct.

 

If you have not ported these heads keep your power expectations modest.. They are kinda lame in stock as cast form but get much better with full home porting... Most 305 cid high perf buildups go wrong because the head flow is lame (stock as cast ports) and or the compression ratio was not set right.. It matters... I like blocking the twin center exhaust egr ports on these heads.. Reduces center ex port heat stress and stops center ex port cross talk so your headers can function. You can do this using thick gauge catering type hd aluminum foil balled up and jammed into the center exhaust ports. Block each port passage and the center passage. (3 big wads of aluminum foil each head) .

 

Any progress on the rocker geometry?
Did you check VG seal to retainer clearance?

 

DON'T use steel-shim gaskets.

I have NEVER torn down an engine equipped with them, where they hadn't failed in at least one place. EVERY SINGLE ONE had signs of leakage. Not sure which letter of "every" I need to explain more fully. Let me know if any of them are not clear. When I was just starting out in this hobby, that's what I was told too: "use the thinnest gaskets you can, for compression". After I think it was the 3rd time I tore down my 1st motor (a 283) for blown head gaskets, I quit listening to that. That was right about the time FelPro came out with PermaTorque gaskets; mid-late 70s or thereabouts. Before that all there was, was Victorcore, which worked well enough, but took like 3 days to clean off of the castings whenever they came back apart.

The first motor top-end I ever tore down and put back together was a 389 in a 59 Pontiac. You'll never guess the reason... so I'll let you in on the secret. It was because the factory gaskets were steel-shim, and one was blown. Turned out the other was blown too, just hadn't failed all the way through yet.

While it's probably possible for an experienced builder to put together a motor using steel-shims and get a success, THIS is not a situation where that is likely to apply. For someone assembling their first motor, with no tools, it's best not to try to push the envelope that way. Especially not since it puts you into territory where even if it works you can't buy fuel for it anyway.

Another kind of situation that this one represents, is the difference between "what I'd do" or even "what I usually do" and "what makes sense for YOU to do". Those can be 2 very different things. Just because some one or another of us can achieve success in some way, doesn't automatically mean that it's A Good Idea for anyone else.

DON'T use steel-shim gaskets.

If you already have the cam, then that airplane has already pushed back from the gate, too. Obviously you do: wouldn't hardly be possible to put in push rods and take pictures of valve train geometry without one. Not much point now in talking about which one you should get right now. Maybe next time, you can use some of the info here, to make a more informed choice.

Best thing to do now is to assemble what you've got in the most RELIABLE manner possible. IMO "reliable" is worth AHELLUVALOT MORE than 5 HP or whatever. Right now, you need to be worried about lengthening the slot in the heads so the push rod doesn't hit it, since that can turn your brand new motor into GARBAGE. Be aware that it will come closest to hitting at full lift. That's the point at which you need to check them. Grind em out, put in your checking springs, assemble one cyl, run the engine through one full cycle, see how much clearance you have at full lift. Then do the other 14 to the same length. Check them CAREFULLY during your mock-up assembly test, before you button the whole thing up. Leaving the heads unported might leave acoupla HP on the table but doesn't carry the risk of DESTRUCTION like some other things do. Don't turn from the path by getting distracted by the shiny things laying off to the side.

Reliability, freedom from risk, and best chance of NO FAILURES should be your goal. You're already tempting fate just by using a flat-tappet cam; try not to pile any more risk onto that by doing things like ... steel-shim head gaskets.

 

Try a stock sbc rocker arm.. How is the geometry.
The thinner .015" head gasket will also make yhe push rod effectivly longer by the difference in hg thickness...

 

Okay, to answer a few things; I have the HO motor, with the 601 heads and the composite gasket I'm using, I'm getting an estimated compression ratio of just over 10.6:1. Who knows what it'll actually be, but the engine's in decent shape so I might get somewhere close to that. I don't have the geometry checking tool in yet, and I won't have a solid lifter until next paycheck as I have once again run myself out of money.

The valve-guide-to-retainer seal is well over half an inch by a rough measurement, like I said I've got the LS6 Beehive springs and modified retainers on.

Theoretically, I could get the steel shim gaskets to work, if I wanted to spend eight hours cleaning off each side of the block. Like everything else, I'm doing it wrong - I'm scraping the old gasket material off with a flat razor. No, I'm not scoring the deck, I can still see the factory machining marks on the mating surface. However, the multitude of warnings to not install them on anything but an extremely smooth surface led to me using PT gaskets because, frankly, I don't like tearing motors apart more than once unless it's absolutely necessary.

And yeah, the cam's in the block, but the front cover isn't even on the engine. If it's not a great cam I may as well swap it out while I've got the chance.

And one thing everyone seems to be forgetting; This is not a high-horsepower build. This is a fun (but drivable) street build. I'm shooting for 250-280hp. This is going to have a stock converter and 3:1 rear gears at most. If I really wanted to give the 134,000 mile 700R4 a viking send-off, I'd stick a larger motor in.

I'm also unsure of what's so wrong with flat-tappet cams given that they were used in damn near every engine right up to the early nineties (actually, my LS400 has solid cam buckets, so even then) but no, I'm not willing to throw another five figures at a 305 just for a roller cam.

 

Nothing is wrong with flat tappet cams.
The problem is the off the shelf motor oil HAS CHANGED. They stripped most all of ghe Zinc out of it.
So you either have to now use a special oil with still has generous zinc in it. or add a zinc additive to your oil.. I use MolySlip E oil Supplement in Shell Rotela T 15w-40 oil... The MolySlip E has both Moly and some zinc in it... It works.
I believe that Liqui Moly is a similar product. but never tried that brand.
Google both.
Don't expect a ball of fire with a stock converter and 3:10 gears . Hot rodded cammed 305's like rpm
(3500 stall- 4.10) When the th700r4 gives up replace with a Th350...


This 1 Litre bottle is good for 5 oil changes.

 

Don't get so snippy.. People sre trying to help you..

 

http://www.wheelspin.net/calc/calc2.html
Here is a website java calc you can use to
Calculate Compression Ratio instead of
your BS.. Garbage in garbage out.

 

^^^ This ^^^

Flat tappets (lifters) aren't "flat". They are concave, with a radius of about 60". Hard to see by eye, but if you put the "flat" of 2 of them together, it's more apparent.

Cams for flat tappets aren't "flat" either. They're slightly slanted, with the rearward edge of the lobes just slightly taller than the front. That does 2 things: forces the cam rearwards as it spins, and makes the very outer edge of the lobe ONLY run against the tappets. The lifters therefore ALSO spin in the block.

Problem with modern oil is, it's too "slick" for this whole system to work. Instead of the lifter spinning, it wants to sit still (it's easier for it to just sit there), and the cam just slide under it. It doesn't take long of this before the cam/lifter interface WIPES OUT. When that happens, the whole motor gets filled with metal chips. Death. This is what it looks like, ganked from On All Cylinders.

There are additives, such as the zinc/phosphorus organic compound ZDDP https://en.wikipedia.org/wiki/Zinc_dithiophosphate, that adhere to surfaces like those and build up on them under extreme point-applied pressure, and add a little bit of "stickiness" to them while also providing a form of lubrication for them. People say "zinc" but that's not the "active ingredient" really; it's the phosphorus. The Zinc just "delivers" it. However, zinc in general is a heavy metal, and poisonous to living things in amounts greater than traces; and it poisons catalytic converters. For those reasons it's being phased out of oil. Very little oil that you can buy today contains this additive to support the antique cam type, that hasn't been used since 1995 or so, at the latest.

So, no matter the relative merits of flat tappets versus roller ones, flat ones are going (or arguably, have already gone) the way of the dodo.

It's 2021. Things we've "always done" don't always work anymore. Not that the things themselves are different, necessarily; just, the world has moved on and left them behind.

Compression ratios of over 10:1 with iron heads running on pump gas with a carburetor are also in that class of things. I don't think you'll have that much, since I'd be willing to bet you didn't take deck clearance into your calculations; but regardless, it'll be REAL HIGH even without the failure-inevitable obsolete gasket type, to the point you'll have trouble with pump gasoline. Never mind that for the time being though; just, don't poke the bear in your parts choices, and concentrate on doing things that will WORK rather than tempting fate.

 

Incidentally, if your heads are already bolted down, and you still need to clearance the push rod slots, you can tape a sheet of paper or plastic or something across the lifter valley, to catch the debris. Just be REAL careful taking that back out.

 

I've got one bolted down already, yeah. Plan is to stick an oil-soaked shop rag anywhere around the hole, and I've got a shop vac to get rid of any shavings that manage to make it out. At the very least, with the cam and lifters in (for the moment) it's a lot more difficult for any shavings to get somewhere dangerous.

I think I might widen the slots a bit and just use the guide plates I've already got, seems like those would be a lot better for the pushrod than it rubbing on the jagged edge of whatever crappy hole I manage to file out. And I did already know about the oil - I was running 10-40 Delo in it plus zinc additive before I took it apart, and I'll be running the same plus some added break-in goodies afterwards.

If you want a good CR calculation I'll need two things: the volume of the valve cutouts in the flat-top pistons, and a calculator that works. Because as soon as I enter a dish volume on the one F-BIRD sent me, it breaks. CR without that calculation (set to zero) is about 10.4:1. Deck clearance is roughly .030.

 

Is anyone old enough to remember spraying the steel shim head gaskets with ALUMINUM (not silver) paint? It works.

And here is a long forgotten single pattern FT camshaft with the specs that you are calling out. I am using one.
It's an ISKY 264 Mega hydraulic:
Grind No./Type: 264-MEGA HYDRAULIC FT**
Application: Tremendous torque & good mid-range power.
9-10.5:1 compr., good idle, stock converter.
3.23-3.70 axle ratio. Up to 625 CFM Carb.
RPM-Range: 2000-5800
Valve Lift Int/Ext: .450/.450 (1.5), .480/.480 (1.6)
Valve Lash Hot Int/Ext: .000/.000
ADV Duration Int/Ext: 264/264
.050 Duration Int/Ext: 214/214
Lobe Center: 108 108° LSA /108° ICL = straight up

IVO is 24.0 ° BTDC (- indicates ATDC)
IVC is 60.0 ° ABDC
EVO is 60.0 ° BBDC
EVC is 24.0 ° ATDC (- indicates BTDC)
Overlap is 48 °

.050” Valve Events – IN Opens 1 ATDC IN Closes 35 ABDC
EX Opens 35 BBDC EX Closes 1 BTDC

 

It's not the cams that have changed - it's the oil. When the industry went to roller cams, the oil companies took the zinc and phosphorus out of the motor oils. Z & P are the high pressure additives needed for a flat tappet setup to survive. That's why you need to use an additive if running a flat tappet in these times.

This is a very controversial subject, so I am keeping this short on purpose.

 

And use strong magnets to "grab" the filings.

 

Do not spray anything on a shim head gasket.
clean and dry.

 

The biggest problem with FT cams these days, is a lack of a quality lifter. 99.925708 percent of lifters available these days are soft cheap Chinese garbage. Coupled with cheap cast cam cores, and it won't matter what oil you put in the thing, it's pre- destined for failure. You can pay now, or you can pay 3x later to redo the whole engine again.. you can get a cam like an L98 or LT1 reasonably, and spend the money for decent lifters.

 

You don't need to "widen" the slots; you need to LENGTHEN them while leaving their width as-is (5/16") to fit somewhat tight to the push rod.

The higher rocker ratio is accomplished by making the length between the pivot and the push rod seat shorter than lower-ratio rockers. This means the push rod is closer to the stud at all times. That, plus the fact that higher lift means the rocker's arc will swing farther, moves the push rod so far that it hits the END of the slot toward the stud.

Don't use guide plates with the slots still slots. If you use guide plates, the slots have to NOT ONLY be lengthened toward the stud, BUT ALSO widened to accommodate the guide plate moving the push rod to where IT wants it to be, instead of letting the slot handle that. ONE AND ONLY ONE system for guiding the rocker must be in effect at a time. The slots MUST BE drilled out to use guide plates. ALOT. Don't bother.

 

I didn't want to read all the replies but what length are your studs and it kinda looks like the stud bosses weren't cut down much. They make several diff length threaded 7/16 studs. Sry if someone already mentioned it, as I said didn't feel like reading all the replies.

 

The more I look at that picture above, it looks like those rockers are wrong for a SBC engine.

 

I've used those same comp cam roller tip rockers, they blued the ball pivot area. Looks high to me, shorter pushrod would move the roller back on the valve tip BUT he ran out of threads is my guess. I'd measure the rocker stud and compare to ARP specs for their sbc stud.

 

A few things here: Basically what happened is the company I bought the heads from advertised them as 'performance' heads but didn't really know how to properly prepare them. I didn't quite run out of threads in the above pic, the rockers just shipped with the adjuster screws upside-down inside them and those bottomed out of the studs. The studs are, as mentioned, too high up because aforementioned company didn't cut the stud bosses down AT ALL.

I did end up buying some Comp 1.6 full roller rockers as the cheap Summit ones shown above didn't really sit right with me. The rollers felt really crappy and loose.

I'll probably have to get different studs to make this work as it seems there's quite a lot of dead area on the current ones (apparently the company that made them assumed a machine shop would know what they were doing) and that really limits how much I can adjust them.

 

Yah those rockers suck, but they were the first set of rockers I bought over 20yrs ago and used many diff full roller since, still got em someplace LOL. I had some sim 305 heads that came on a car I bought that the studs were cut unevenly down. When I tore it down to mod n fit stuff, I found some of the full roller alum rockers were hitting on the stud hex/base enough to remove material, quick fix was lash caps and longer pushrod. If they are off you could have another shop cut them down and tap deeper if needed. They make a tool you can buy BUT a shop will get them even a lot easier than diy. I actually just bought that tool for a future video and have a fix for uneven boss height BUT don't wanna say until I make the video, so PM if you really wanna know.

edit: Summit brand is often another well know co or generic china, if you ask sometimes they tell you or you can just look on ebay and see if the same thing is generic n cheaper.

 

Alright, I've checked the geometry, and I get perfect rocker geometry... right when the rocker hits the flare at the base of the stud. Obviously this isn't going to work, so I'll need to either get new studs, or cut the bosses down, or both. I'm leaning towards different studs as that seems easier. Something like this, as it looks like they have significantly more clearance compared to the ones I'm using (though I'm not sure of the downsides to these and I'd have to toque them down with vise grips).

 

I'll assume you mean shoulder/hex-less studs. I planned to double nut the ones that I got for some vortec heads and use the new OJ loctite. Gonna need to seal the threads up FYI exhaust goes into coolant on my vortec & 305 heads and intakes into the int runner, gotta seal both.