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Discussion Starter · #1 ·
71 Chevy C10 Fleetside. 3.73 gears. Turbo 350, stock converter. 350 Chevy, bored .60. headers, Edelbrock Performer RPM intake, Holley 670 Street Avenger Carb.,
RHS heads, 2.020” Intake/1.600” Exhaust.

Rebuilt the motor, new cam, heads etc. ended up wiping the cam. Heads, springs etc. are “relatively new”

Ordered a new Comp cam.
Operating Range:1800-5800 RPM
Duration Advertised:270° Intake / 270° Exhaust
Duration @ .050'' Lift:224° Intake / 224° Exhaust
Valve Lift w/1.5 Rockers:.470'' Intake / .470'' Exhaust
Lobe Separation Angle:110°
Got the kit with springs. Springs are smaller diameter then my current set up and do not sit over the spring locators.
Called Jegs tech support and was told that the difference between the old and new springs was not enough to worry about changing them. (Would make my life easy!)
Can any one tell me if I should go with this? Or do I need to find a different spring that fits? Different locator?

New springs;
Comp 981-16
Single Outer Valve Springs
  • Rate: 373 lbs
  • .880'' ID, 1.254'' OD
  • Seat Load: 105 lbs at 1.700''
  • Open Load: 273 lbs at 1.250''
  • Coil Bind Height: 1.150''
  • With Damper
Existing springs;
Comp 972-16
Single Outer Valve Springs
  • Rate: 308 lbs
  • 1.060'' ID, 1.460'' OD
  • Seat Load: 124 lbs at 1.800''
  • Open Load: 293 lbs at 1.250''
  • Coil Bind Height: 1.195''
  • With Damper
 

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They are right, what you've got is fine and actually a little better.
The smaller 981 spring is just the lowest cost way good enough to run with that cam.

They also won't be the cause of a wiped cam, if that was your worry.

New 981 is 105 lbs seat, 280 lbs open @ the actual .470" valve lift.
Old 972 is 124 lbs seat, 270 lbs open @ the actual .470" valve lift.

The higher seat pressure will be better able to control any seat bounce, which is what creates "valve float" .
 

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You probably already knew this, but after wiping the first cam, that engine needs to be completely disassembled and all the cam shavings thoroughly cleaned out. Then find out why????. There are lots of reasons a cam can be wiped.
 

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That is also quite a bit of cam duration for a heavy vehicle with a stock TH350 converter and 3.73 gears. It will work fine for most normal driving, and may sound good, but will probably be pretty “soft” for acceleration at low RPM.
 

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Discussion Starter · #5 ·
Thank you guys for your input. Helps a ton.
I will be adding a stall. I am only looking for cruising. 20 miles to town and then cruising main street.
I believe the last cam was wiped from bad break in, poorly adjusted valves. I know I never used break in oil or zinc additive. Probably didn’t change the oil out very well. (I built it in a shed with little knowledge and even less money) Then took it to a shop, they tightened the valves some more assuming that took them the rest of the way out.
 

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Comp is trading the damper’s contribution for less main spring pressure.

The damper adds a bit spring pressure and of rubbing friction between it and the outer spring.
The pressure contribution is probably not all that much; but the rubbing friction between it snd the outer spring is a function much like suspension system shock absorbers in that it dampens the run away natural oscillations of the bare spring. The result is more stability with less total pressure which these days reduces impact loads on the valve train that eventually end up at the lifter to lobe interface which add to the wear on these items. This is just plain smart engineering. It is the point of beehive springs which use a variable wind in both diameter and coil spacing to produce the same effect as a dampened coil without the frictional losses between damper and spring.

If you look at competition type nested springs that often consist of either an outer spring with damper and an inner spring or an outer spring and two nested inner springs; you will see the damper and or the nested inner springs are wound in counter directions. This is done to develop countering natural frequencies to damp the frequency modes that result in natural vibrations ganging up to cause spring surge.

As far as digested cam and lifter clean up through engine disassembly I’m not convinced this does much. This failure mode mostly creates fine particles rather than larger chunks of metal. To a high degree the filter traps most of this stuff. The damage done is the damage done as not all the oil is filtered all the time. So if the circulating wreckage was large enough to cause damage to the oil pump gears and bearings that damage is what it is. If the engine has held normal oil pressure through this whatever the damage is it is nominal. So opening the motor up to just clean it probably has little value, At the other hand if there is visible damage then some level of rebuild is in order which goes beyond cleaning the pan with a solvent soaked towel.

Oil changes are vitally important, they always have been. Engines are mighty hard on oil. The combustion process subjects oil to high temperatures with acid and water contamination that doesn’t exist in gear boxes and rear axles. The temperatures bake the oil molecules to failure, these are mostly found on the underside of the pistons where oil mist is a need to cool the underside of the piston crown. The combustion process through blow-by (simply a name given to engine exhaust that escapes into the crankcase) puts the waters of combustion and burnt as well as unburnt fuel products into the crankcase. These mix with oil to create all sorts of undesirable compounds from acids to semi-poly compounds that form sludges and varnishes. To some sensible degree this stuff is like pouring pouring polyester resin and alkyd paint into your crankcase. So the concept of oil changes is to get this stuff out of the engine before the acids etch the metals mostly bearing and piston and the esters and varnishex goo and glue everything up. For those of use that have opened up engines from people who never changed oil we know that you are first greeted by a crankcase full of what looks like jellied grease.

Once when I worked in an all night garage back in my flat rate college days I had a customer that had so much sludge and varnish build up in the rocker boxes of a small block Chevy that the guy brought it in because a few minutes after start up the good oil pressure fell to zip. Opening the valve covers was a pry bar project. Once inside the only space was where the rocker arms, pushrods and valve springs were working. Everywhere else was near solid goo. I left a note for the day boss to ask him about oil changes? The valley looked about the same When the engine was started the oil that pumped to the top end couldn’t drain back fast enough to resupply the sump so the oil pressure died. Left overnight the oil succeeded in oozing back to the sump so morning fire up showed pressure for about 10 minutes. The response to my question was he didn’t believe in oil changes “it’s just a rip off“ as he knew that oil lasted forever. My response was WTF? How about an engine rebuild?

Bogie
 

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In my opinion catalytic converter safe low zinc oil, higher spring seat loads, cheaper made cams & lifters, plus improper initial adjustment(more than setting lifter lash or preload, tune) are all factors in flat tappet cam failures these days.

Next time set the springs up at lower seat or use weaker/old springs for initial break in. Cheaper than break-in rockers, 80ish lbs seat Obviously don't rev it to the moon before swapping in the new springs. I like to prime the oil pump right before until all rockers show oil also, sometimes gotta turn the engine a bit to get em all to oil

Some cam lubes have the break in stuff needed but I like to also add redline additive to my oil instead of buying high priced flat tappet cam safe oil. and Lucas assembly lube is really sticky(wear gloves). Also like to use a box fan in front of the radiator.

As mentioned bit of stall should help.
 

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In my opinion catalytic converter safe low zinc oil, higher spring seat loads, cheaper made cams & lifters, plus improper initial adjustment(more than setting lifter lash or preload, tune) are all factors in flat tappet cam failures these days.
The most important one to note is the cam technology has evolved to more aggressive cams than ever before and higher spring pressures with added rpm then ever before.
It's hard to kill a long cam with a slow lazy ramp than a cam with higher lifts and short duration.
40 years ago the go too cam was the 292 cam with .450ish lift, 250lb springs at 6500 and now were looking at 270's and .550 lifts and 400lb springs at 8000.
 

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The most important one to note is the cam technology has evolved to more aggressive cams than ever before and higher spring pressures with added rpm then ever before.
It's hard to kill a long cam with a slow lazy ramp than a cam with higher lifts and short duration.
40 years ago the go too cam was the 292 cam with .450ish lift, 250lb springs at 6500 and now were looking at 270's and .550 lifts and 400lb springs at 8000.
Another good point. Still I'd say the most important one is, it's less common knowledge/skill to tune or break in flat tappets cams than 40 yrs ago.
 

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I’m old enough to remember when Isky broke the .5 inch barrier with the 505 cam. It was like “rocket science”!

I agree the old cams were bolt in and go, yeah they wore on occasion but it was rare. As I’ve said if you were having problems you bought a set of hard faced tappets which you can still do. The Ford Y-blocks ran a cam thrust plate with a mushroom shaped tappet that gave very little trouble in cam or tappet wear, which was fortunate because the the only way in or out for their tappets was through the bottom end.

But in today’s ‘brave new world’ of high output with lower compression ratios the emphasis is toward less overlap and earlier closing intakes using more lift to substitute for the breathing of these features.

A big problem with older engine designs was the fairly steep valve angles to the bore center these result in a fairly deep chamber that provide a pocket that hides a burnt mixture volume that is hard to vent out toward the end of the exhaust cycle. Both Chevrolet on the W engine (348, 409, 427) and the Ford MEL (383, 410, 430, 462) tried getting over this with a flat milled head which resulted in discovering other problems of mixture management in the cylinder that were detrimental to power.

There are compromises and other porting techniques that get around the flat milled head chamber or chamber in piston designs by flattening the chamber wedge angle and in the example of the early LS cathedral port head restoring good in cylinder in late flow management with achieving a high order or late cycle exhaust evacuation without so much overlap. The overlap being used for the incoming mixture to do the final evacuation of exhsust from the chamber and of course the exiting exhaust adds early velocity to the incoming mixture which helps fill the cylinder at the cost of increased fuel consumption and air pollution by the unburnt fraction. Which you can at least burn off in the exhaust system with air injection snd a cat converter but while scrubbing pollutants doesn’t do much for improving mileage. In the end Chevy realized that cathedral ports work well with carburetors and TBI but are unnecessary with port or direct injection so they went back to more conventional ports.

None of this is new the early Ford Indy engine used a 9 degree wedge chamber, this was an application not a discovery, as the effect of a flatter wedge chamber was already well known by the early 1960’s. The Chevy W motor and Ford MEL a case in point.

Back to cams and the reduction through elimination of overlap with earlier intake closing with fast ramping on the lobes, here it is especially advantageous to pay attention to improving flow across the back side of the valves, hence back cutting as this gets the early flow well increased. Along with this the elimination of old style valves with their glob welded head to stem greatly improves flows past the valve.

So there are a lot of elements to be considered in the never ending hunt for more performance, they all blend toward an optimal solution that is a set of compromises depending exactly what the designer needs for outcomes. We all tend to get stuck in our thinking and this really shows in the many years it took the OEMs to recover from the imposition of mandated emission and fuel conservation laws. However, the government thinking that every individual needs “ivory tower” guidance slowed much progress by putting the onus for wear compensation on the manufacturer designed system rather than mandating personal responsibility by requiring annual inspection and repair of failures, which maybe wouldn’t have flown well in our world of ‘rights’. But keeping up on maintenance as a requirement rather than a choice would simply removed the requirement for most of the damn emission gadgets and technical compromises of the 1970’s and 80’s made before the electronics technology was capable of carrying the needed number of instructions and fast enough to be real time useful plus reliable enough to do the engine management functions over the projected vehicle life span.

Bogie
 

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Discussion Starter · #13 ·
”If you‘re going in circle you may be cutting corners”
Looks like I’m going to do it again. Lesson learned. Trashed the cam and lifters again. As far as I can tell everything was done correctly minus flushing the engine. (The important part) Got in a hurry and thought I’d get lucky.
Before I did the cam, lifters, etc. It ran just well enough to pull itself in the garage. While doing so I put fresh oil in. Ran it a few minutes, did the cam work, cleaned things out, flushed oil where I could, and dumped the oil. Didn’t notice metal shavings.
Ran the break in procedure. Used all the right lube, break in oil, etc. Dumped the oil, had terrible metal shavings. Buddy convinced me the damage was done and try again. Well I did, ran it about 10 and dumped the oil again. Less but still enough to know it was bad.
Tore it apart and 2 of 6 lifters were trash. (#1 intake, #3 exhaust) No point looking past that.

Obviously it needs tore apart, inspected and hot tanked.
I’m not ready to attempt to build again. I‘ll take my shot when I have more time.

Do I expect full rebuild? Crank, pistons, the works. Paying someone else to do the rebuild, is it safe to assume I’m looking close to the price of a long block crate engine?

I have a new distributor, wires, plugs, new carb, good intake, decent heads are 10 years old with not many miles on them. All new chrome pulleys, alt, pwr steering, dress up kit etc. sitting in the box.

Yeah I want to get out with as little as money possible. But I’m not cutting anymore corners.
Greatly appreciate the input. I‘ll make sure to advise this time.
 

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Do I expect full rebuild? Crank, pistons, the works. Paying someone else to do the rebuild, is it safe to assume I’m looking close to the price of a long block crate engine?
If the block was fairly fresh, not much run time on the cylinder wall finish and no gouges/skuffing happened during the cam fiasco's....it is likely fine with just a light re-hone.
Crank same, likely just a polish, shouldn't need a regrind.
Rods should be good as they are
Pistons likely have to be replaced due to embedded iron in the piston skirt, but a close inspection may get lucky and they are okay.
Block washed out, new main/rod and especially cam bearings, new rings and the possible new pistons, new oil pump, new timing set
Then just choose your cam package

Should be able to do that better and cheaper than a crate short block.
Maybe not if paying someone else to do the assembly.

If you do go this route, and assemble yourself, and you are going to try flat tappet a third time....absolutely verify that turning the cam by hand in the block makes every one of the lifters rotate in its bore, and swap fast turners for slow turners to try to get a happy medium.
Do this cam/lifter test in the clean block BEFORE you do any other assembly step....so if there are lifter bores that need some deburring or honing it can be done while the block is still empty and easy to wash..
 

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Discussion Starter · #15 ·
Really leaning towards a long block crate engine. Take out the lack of knowledge on internals a waiting on a machine shop as they are all booked for 6 months. Also on a little time crunch. (Would Iike to get things going for prom) Save this block and learn/build over the years with my son. I can put in the corner for the moment, then slowly go through it and learn properly, convert it roller and do it up right. Then he can drop it in something else. Ill be back for more advise when the time comes.

In the mean time, if anyone has suggestions on where to start with a crate engine. Preferably that will work with the intake, carb etc. that I have. I’m all ears!

Again thank you for everything.
 

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Might look at Blueprint engines. I just saw one of these a few weeks ago and it's done well.
 

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Discussion Starter · #17 ·
Might look at Blueprint engines. I just saw one of these a few weeks ago and it's done well.
Thanks for the sugggestion. I’d prefer to stick to a long block, heads, pushrods, lifters etc. all assembled. I don’t mind taking it from there up. If I understand correctly, everything from the 350 will bolt up to the 383 correct? Minus possibly the intake and flywheel dexpending on the year? It’s a tough time to get ahold of a crate engine that will ship within the next 6 months. The more options the better.
 

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They make plenty of long blocks too. Peruse the site.
Externally the 383 and 350 are identical. You need to match up seal style and flywheel/flex plate (internal/external balance style).
Id bet if you call them they can help you get you something that will minimize your struggles.
 

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If it keeps eating lobes and lifters I‘d certainly consider that the lifter bores are suspect an being out of line with cam which could also be cam position in the block. This can also be too much lifter clearance or lifter bores that are tapered or angled.

It may well be the block needs major machining correction.

I seldom build a Chevy flat tappet cam SBC without adding a thrust button of the type used for roller cams. I am of the engineering mind set that the cost savings Chevy did by eliminating the thrust plate on flat tappet cams which nearly everybody else of the era did use puts too much work on the lobe to lifter interface. I think this was a design mistake. Chevy tried back prior to the cost reduction efforts of the 1970’s to get around this by Parkerizing their camshafts and using a hard faced lifter. Once the finance guys cut this expensive process out cam troubles arrived to such an extent that there was a class action suit. The factory one it in Detroit Federal court so while the US government held GM as not at fault the problem persists to this day. We currently blame the EPA for banning ZDDP oil additive and while that may be a contributor it is hardly the root cause.

Back to the dynamic at the lobe lifter interface using a cam bumper on a flat tappet cam relieves the interface of supplying the means of offering thrust control. Figure that everybody has always used an angle on the lobe an a convex face on the lifter to promote rotation of the lifter in its bore and everybody but GM still felt it good engineering to use positive thrust retention. It becomes obvious that GM tried to use the existing shapes of the cam lode and lifter face to also supply thrust control of the cam. Ford tried this early on with the FE and had noticed lobe and lifter wear in the test phase so they used a factory installed thrust button through the 62 model year then went back to a thrust plate as they used on the pervious Y blocks. So on my Chevy builds I simply set then up with a cam button and have not had any lobe and lifter wear issues.

That’s not to say that you shouldn’t invest in Parkerized cams or cryogenic hardened flat tappet cams and hard faced lifters but given the mess that cam failures make if your not going to a roller at least spend the time and money to crowd the odds in your favor.

Bogie
 
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