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Cam Swap?

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Post by 76 Malibu Wed Nov 23, 2022 2:55 pm

I have my '76 350 engine apart doing the valve seals, water pump, new clutch fan, distributor recurve, performer intake and Q-jet carb.  I am also cleaning the block to paint and detail it or at least as much as I can without pulling the engine.  I was thinking that since my car rolled over years ago the timing chain is probably due and if I go that far, maybe I should look at the cam.  The stock cam is pretty mild and it is likely worn as I know the cams from this era are pretty soft.  From looking at the rocker movement, some cylinders seem to have less movement than others (I haven't measured).

So I was thinking this might be the time to swap the timing set and a new cam too.  The bottom end on my motor is strong and not worn.  It just has 882 heads and low compression so I know I can't go too crazy in the cam department.  Ultimately, I will build a high hp engine down the road, but I'd like a bit more power now to make the car a bit more fun to drive.  I was looking at Summits 1102 cam:

https://www.summitracing.com/parts/sum-1102

Camshaft Use:
Street/Towing
Camshaft Manufacturers Description:
Smooth idle, low -midrange torque, towing in 350 c.i.d. engines. Works with stock converter and lower compression.
Basic Operating RPM Range:
1,500-4,800
Intake Duration at 050 inch Lift:
204
Exhaust Duration at 050 inch Lift:
214
Duration at 050 inch Lift:
204 int./214 exh.
Advertised Intake Duration:
278
Advertised Exhaust Duration:
288
Advertised Duration:
278 int./288 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:
0.421 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:
0.444 in.

I'd probably do new springs too (summit has a spring kit for a decent price), but other than that I didn't want to invest too much money into this old smog era 350.  From reading the reviews it seems that this cam works well with smogger 350s. I am concerned with the low quality of flat tappet cams and lifters these days, but I am not looking for this to be a long term solution.  That said, I don't really want to have a wiped cam after break-in.

Any thoughts, or opinions?
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Post by Joe73 Thu Nov 24, 2022 7:23 am

I think that cam would work well for the time being. It does state 1500-4800 rpm. Id like a bit looser convertor than stock for it. Have a you taken a look at the torque (towing) cams? Might find something in the rpm range of idle on up. As for a little extra insurance against wiping out the cam, I run crower cam saver lifters. They have a few thousandths of an inch removed on one side and allow a bit of oil to slip alongside the lifter and drop on the lobe. And, again before the manifold goes on, I take a sharpie and put a dot at the 12 o'clock position of each lifter. Then I rotate the engine a couple times and check the dot. The dot location should move which would mean the lifters are rotating like they should. If they dont rotate it will wipe the lobe out. After your all done and broken in, Id get the timing set to 34-36 degrees total using adjustments on initial, vacuum and dist. advance weights. It will really liven up the engine. Heres a good read on how to do it. Its a long read but well worth it. Good luck with the install.

https://www.chevelles.com/threads/ignition-101.189195/
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Post by 76 Malibu Thu Nov 24, 2022 9:53 am

I started doing some reading and didn't realize how bad the lifter situation has gotten in the last couple years. Now I am all paranoid that I am going to lose a lifter or wipe the cam if I do the cam swap, which of course means a full tear down. I'd hate to ruin my bullet proof 350, as it has been literally the most reliable engine I have ever owned (this if the first time in 46 years it's been opened up ever). And I don't have the money to do a full tear down and rebuild right now. Maybe I will just swap the timing set and live with this stock cam for now until I can do a full performance build when I might to a roller conversion.

It seems the lifters are all made by a couple of suppliers regardless of the brand. The quality control and hardness isn't there. I have read that these Chevrolet performance are hardened and are good:

https://www.summitracing.com/parts/nal-12371044

But they cost more than the Summit cam and lifter kit. I would think the Chevrolet parts would be not made off shore, but who knows anymore. Chevrolet also makes a cam, but it has more duration so may not be the best for my car with a stock converter:

https://www.summitracing.com/parts/nal-24502476

I will have to think about it, really not sure what to do.
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Post by bucket Thu Nov 24, 2022 2:19 pm

I've got a Summit cam and lifter set in my '70 Impala. It was properly broken in and has lasted 15 years or so now. At the time of the instal, flat tappet lifter longevity was already a big issue and a hot topic. Much like today.

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Post by Iggy Fri Nov 25, 2022 11:32 am

That cam is an excellent choice for a low compression smog engine - with the 882 heads and dish piston you have 7.8:1 compression. When I use a flat cam, I like to use GM lifters, they have a hardened base that is attached rather than hardening the lifter body like most aftermarket lifters. Summit Brand Lifters were that lifter re-boxed until a few years ago, here is a link to the GM lifters https://www.summitracing.com/parts/nal-12371044/make/chevrolet

Since there are only a couple of lifter manufactures, you will find some "white box" brands that are re-boxed GM - you just need to know what you are looking for, that hardened base that has been added.
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Post by Joe73 Fri Nov 25, 2022 11:49 am

My stock 73 engine had the dished pistons with 882 heads and it was 8.5 to 1 stock compression. I ran the crane cams copy of the Chevy 327 350hp cam in it. It ran well.

As for the lifters, do some research, obviously buy quality, make sure they are rotating in their bore and do a proper break in with the proper oil. As for the oil, do some research and go with what your comfortable with. Remember, too much zinc makes the oil acidic which will pit metal surfaces. I know two guys running 5w30 full synthetic right from break in and its been a couple years now without issues. My new build is running a Comp Cams 292 duration which I purchased in the mid eighties brand new. I matched them with the Crower cam saver lifters. It broke in fine and the motor still runs well. Good luck with your choice.
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Post by zucchi Mon Nov 28, 2022 11:18 am

Joe73 wrote:As for the oil, do some research and go with what your comfortable with.  Remember, too much zinc makes the oil acidic which will pit metal surfaces.

Flat and hydraulic cam/lifters need oil with zinc dialkyldithiophosphate (ZDDP). The zinc deposits onto the steel surfaces forming an atomic thin layer against which the metal-to-metal shear force is greatly reduced. Essentially, it acts as a sacrificial protectant. Most modern and synthetic oils have insufficient ZDDP because practically all modern cars are made with roller cams which don't have shear stresses on their valve trains thus negating the need for high levels of ZDDP, not to mention the detrimental effect of zinc and phosphorous on catalytic converters. Many "racing" oils have around 1500-2000ppm zinc. What happens with increased levels of ZDDP is the zinc deposits becomes thick enough to where it will become "sticky". Mind you, you'll still get excellent wear protection but your engine will work a little harder thus reducing fuel efficiency. Back in the 1970's and 80's, ARCO sold graphite infused oil. All the hype aside, it was formulated with about twice the ZDDP as it's competitors but the graphite was added to compensate for the stickiness of the higher zinc level.

As for it making the oil acidic… the chemistry that forms this molecule slightly resembles that of soap; a fatty alcohol that's acidified then neutralized with an ionic salt. However, its structure sets it appart in that the alkyl chains don't have an ionic terminus, they're covalently bonded to the thiophosphate ester which is covalently bonded to the zinc atom which makes them nonpolar. In other words, they're not water soluble. Any compound that's not water soluble will not have a free proton, the main characteristic of an acid. On the other hand, one of the raw materials that's used to make ZDDP, phosphorus pentasulfide (PPS), is water sensitive and can hydrolyze to form phosphoric acid. Mind you, that's only in the presence of moisture. So, in order for that to happen, the ZDDP will need to contain some unreacted PPS and your crankcase will need to have some water in it. Water in the crankcase can be the result of condensation like water in the fuel tank. If you're driving your car as a daily driver, there isn't time for condensation to cause problems. For those who only run their cars a few times in any given year, this may be more of an issue.

I would really like to see the experimental studies and test data that show that too much ZDDP makes oil corrosive to steel; that's sort of an occupational quirk of mine.
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Post by Joe73 Mon Nov 28, 2022 11:44 am

Im not looking at getting into a discussion about the pluses or minuses of zinc. Thats why I mentioned that the op does his research and goes with what he is comfortable with.

I spent a few days trying to figure out what oil I wanted to go with when I was building my flat tappet engine. I was obviously concerned with zinc amounts that everyone spoke of and have seen people doubling the amount of zinc during break-in. Then I looked at what zinc is actually doing for the flat tappet and came upon what too much can do. Then knowing a couple of people who have never run zinc in their flat tappet engines made me do some more research.

I liked that the synthetic oils 'shear' ratings are pretty high which I was comfortable with for flat tappet protection. And the fact that I know people using it exclusively with their flat tappets. Then reading that zinc levels over 1200ppm (if I remember correctly) could have negative effect on the metal surfaces in the engine.

So the quandary began on what to run. Valvoline VR1 says they have 1300 ppm of zinc. Thats what I went with. For me, its readily available and reasonably priced.

Anyway. Along with hours of googling "too much zinc oil acidic" came up with alot of info on corrosive attributes of too much. Similar to this. https://aaoil.co.uk/123579-2/

As for current oil testing in reference to shear and psi ratings, again lots of good google info, including https://540ratblog.wordpress.com/ Long read but very interesting.

Everyone should do their own research and go with what their comfortable with.
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Post by bracketchev1221 Mon Nov 28, 2022 11:50 am

My honest opinion, I don't know that the cam will be enough of a change to even make a difference. What gears, and other modifications are done to the car?
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Post by zucchi Tue Nov 29, 2022 9:13 am

A simple bolt-on, instant HP option would be one of those low-profile, under hood B&M forced induction units. With the large combustion chamber in that engine, you'll have a nice, big air/fuel charge.
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Post by bracketchev1221 Tue Nov 29, 2022 9:18 am

I had one in the 90's. Does B&M even still sell them anymore or is it all Weiand now? I had the whole kit, with the B&M super Street charger cam. .488/.510 234/244@.050. Ran good until it sucked a teflon rotor strip. Then I removed it and just built a 10.7:1 355 with a solid lifter cam.
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Post by 76 Malibu Wed Nov 30, 2022 5:45 pm

bucket wrote:I've got a Summit cam and lifter set in my '70 Impala. It was properly broken in and has lasted 15 years or so now. At the time of the instal, flat tappet lifter longevity was already a big issue and a hot topic. Much like today.

My issue is that it seems the new Summit cams are made off shore now, and they used to be made in the USA.

Iggy wrote:That cam is an excellent choice for a low compression smog engine - with the 882 heads and dish piston you have 7.8:1 compression.  When I use a flat cam, I like to use GM lifters, they have a hardened base that is attached rather than hardening the lifter body like most aftermarket lifters.  Summit Brand Lifters were that lifter re-boxed until a few years ago, here is a link to the GM lifters  https://www.summitracing.com/parts/nal-12371044/make/chevrolet

Since there are only a couple of lifter manufactures, you will find some "white box" brands that are re-boxed GM - you just need to know what you are looking for, that hardened base that has been added.  

Which cam do you think would be good? The Summit cam or the Chevrolet 476 cam? I haven't measured the compression, but I have heard others say it is only 7.8:1 too for these engines despite Chevrolet's claim to be 8.5:1. That is really low, and I'd be worried about too little DCR with a bigger cam. I definitely like the idea of the Chevrolet lifters though.

bracketchev1221 wrote:My honest opinion, I don't know that the cam will be enough of a change to even make a difference.   What gears, and other modifications are done to the car?

There are no other real mods to the car. Stock converter, 2.73 gears. All it has (or will have) is dual exhaust with Magnaflows, a new Edlebrock intake, a Q-jet carb, and a recurved distributor. The main reason I pulled things apart was for the carb swap as the 2GC was in need of a rebuild anyway, and to fix the valve seals.

The more and more I think about this, I think I am leaning at sticking with the stock cam for now. The engine runs really well now and I'd hate to take a chance with new cam and take out the engine with a flat cam. I may still do the timing set though regardless, as I am sure it is well worn. My long term plans is to do a full performance rebuild and I will likely go to a roller cam with some decent heads and compression, long with corresponding transmission and gear upgrades.
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Post by Joe73 Wed Nov 30, 2022 5:55 pm

If it were me and your current engine is running well, I'd put some gears in it. To me, your going to need them anyway and it's the best bang for the buck. Should be able to install the on an afternoon. The difference in the car will be immediately noticeable.
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Post by 73ss Wed Nov 30, 2022 7:15 pm

In my old 454 motor I used a summit 1302 cam & the better comp lifters with the snap ring, & comp springs. I went with the summit cam for the specs. One of the few cams ground on a 114LSA. (vacuum). I removed the inner valve springs and shims for the break in. After the break in I re-installed the inner springs & shims. A lot of work but the cam held up for 8 years. I've since pulled the motor and built a new one, but the cam was still good, Showed minimal wear. A big block has a lot heavier valve-train and stiffer springs than a small block but the do use the same lifter. For oil I used Brad Penn, Lucas, Valvoline VR1, what ever was on the shelf at the time. For my new motor I went with a Roller cam with beehive springs this time. It's quiet, revs nicely, and It's a nice piece of mind.

As Joe73 said, lifter rotation is key to survival as well as reduced spring pressure during break in.
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Post by bracketchev1221 Wed Nov 30, 2022 7:48 pm

Joe73 wrote:If it were me and your current engine is running well, I'd put some gears in it.  To me, your going to need them anyway and it's the best bang for the buck.  Should be able to install the on an afternoon.  The difference in the car will be immediately noticeable.  

A set of 3.23 or 3.42 gears will wake that car up more than a small cam swap will.
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Post by 76 Malibu Thu Dec 01, 2022 6:10 pm

Yeah you guys are probably right that a gear swap would be better, especially if that is part of my long term plans.

I will see if I can borrow a dial indicator and make sure the existing cam is ok. If it is maybe I will just skip it for now. I guess I was just tempted by the cheap price of the Summit Cam and lifter kit.
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Post by bracketchev1221 Wed Dec 07, 2022 9:00 am

Years ago I had a 79 malibu with the stock rearend in it. Now I don't know for sure if it was a 2.56 or a 2.73 rear, but I went to a 3.73 gear in it and picked up 1 second in the 1/4 with just that change. Now I will admit it was a bit much with a 24" tall tire.
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Post by Iggy Wed Dec 07, 2022 10:57 am

As you have figured out, if the stock cam looks good - leave it and replace the rear gears. A new timing set is in order no matter what you decide. If the cam is worn and you need to replace it, I personally would go with the Summit cam over the stock cam. The stock cam is 1950's technology that was used until the end of the 1980's and is still used in the 260 HP crate 350. The Summit cam by comparison is about 20 years newer technology and a little more efficient - it will do a little better job of filling the cylinders and creating a little more power, but if it is not broke, don't fix it!

As for the advertised compression, the calculation was based on a dish piston with a 64cc head, but the engine came with a dish piston and 76cc head reducing the compression to a real 7.8:1 rather than the advertised 8.5:1. If you need to replace pistons, go with a 4-valve relief flat-top and the 76cc heads you will get an honest 9:1 compression (which was the "low compression" 350 used in 1970 trucks).
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