questions about roller cams

[Gramps]

I’d like to do a little preventative maintenance on the engine in my 78 K20

Here’s the scoop, the engine is a 350, it runs fine, has 70 thousand original miles on it.

My brother having owned a 78 Blazer with a 350 since new, tells me that this particular year motor is prone to having cam lobe problems (lobes go flat) and suggested that I replace the cam in it with a good quality roller cam setup, he said with his, his problems all started about the time it hit 70,000 miles, right where I’m at now.

The engine in my truck as it is right now is completely rock stock right down to the air cleaner, never has had anything done to it except the recommended oil changes through out it’s life, and the engine runs just fine, I have no issues with it at all.

Here’s my thinking: I would like to get 150,000 or more miles out of it before I have to look at any major engine work, I may never hit 150,000 miles on that truck in my lifetime, but want to be sure that I have something good and reliable anyway,

The only thing I’ll be using the truck for is trips to the dump (land fill) on trash day, taking the boat to the river, and hauling the travel trailer on an occasional camping trip.

I’m thinking I’d like to have an RV cam, or torque cam, something that will give me mid range torque, plus maybe a double roller timing chain, and doing a cam and timing chain upgrade doesn't seem all that difficult, I’d rather not pull the engine out for any major work, so something easy would be right up my ally.

Looking on ebay for roller cam kits brings up stuff for 87 and newer, my 78 is HEI, and carbed, From what I’ve read, the cams I’ve looked at point towards applications with fuel injection and hi performance,

What I want is maybe a little more torque mid range, and I like the grumble of an RV type cam, but I don’t want to lose much fuel millage, I’d be happy to keep it in the 10 to 15 MPG range, and closer to 20 mpg would be even better, but maybe I’m asking for the world and am just not going to get it.

I have no idea what cam kit I would be looking for, can someone help me out and get me pointed in the right direction?

Thanks, Gramps

 

[bucket]

What's your gear ratio and tire size?

You're going to want a "retrofit" style roller cam meant for your older engine. As well as retrofit style roller lifters, they are paired together with a link bar.

It would be a good idea to replace the valve springs and have the heads freshened up at the same time.

 

[Jims86]

What's your gear ratio and tire size?

You're going to want a "retrofit" style roller cam meant for your older engine. As well as retrofit style roller lifters, they are paired together with a link bar.

It would be a good idea to replace the valve springs and have the heads freshened up at the same time.

Gonna need to change the dizzy gear too.

 

[Gramps]

Gonna need to change the dizzy gear too.

I was told that also, my brother was saying the the metals aren't compatible and that's the reason for the dizzy gear change.

I suppose freshening the heads wouldn't be that bad beins how it's going to be torn down almost that far anyway.

I don't know what the gear ratio is, I was trying to look that up the other day and couldn't figure it out, the tires are 9.5x16.5LT

I can post a picture of the option sticker that's in the glove-box door if that helps.

here's a picture of the glove box option sheet if that helps with the gear ratio question.

You must be registered for see images attach

I'm planning on having the work professionally done, I don't want to attempt it myself, but would like to collect the correct parts before I take it in to have the work done. it will be a little easier on the wallet that way.

 

[bucket]

The pic is too small to read what it says. If there isn't a specific gear ratio listed, then it's the standard ratio that would be used in a K20. Probably 3.73 unless you have option like Trailering Special or Camper Special.

Combined with the relatively tall tires, you're going to want a cam that starts making power down low. Maybe 1500 rpm or so. Without overdrive, you don't want to have the powerband so low that you run out of steam on the highway, trying to pull your camper/boat up an incline.

 

[Gramps]

photo bucket did some sort of software upgrade and now I have to learn it all over again, so for the meantime, here's a link to that picture where you can blow it up and make it bigger: http://s1239.beta.photobucket.com/user/mrlinfoot/media/100_2850-2.jpg.html

there's nothing on the sheet that says anything about the gear ratio, it does say the tires should be 8.75x16.5, a little smaller then what I have now I believe.

the grand daughter and I are headed out for an evening at the arcade fun center, so I'll have to do some further looking when I get back, I'll find a roller cam I think is what I need and post up a link to it and maybe someone can tell me if it's what I'm looking for or not.

with so many options out there, I'm still completely lost as to exactly which one I want or need short of someone posting a link up here saying, "this is the one you want"

I'm not entirely helpless, but when it comes to cams, I really have no clue.

thanks, gramps

 

[Gramps]

I was doing a little research for retrofit roller cams on ebay and came up with this: http://www.ebay.com/itm/360505317332

if I'm understanding "buckets" suggestion about the torque being down around 1500 rpm, I'm thinking the one in the link I just posted is probably going to be the one I want, can someone take a look and confirm that?

I'm also going to need to figure something out for push rods and the gear on the bottom of the distributor and not sure what else I'm going to need.

my goal here is to buy all the needed parts, then take the truck to the shop and have the stuff installed.

 

[bucket]

I was doing a little research for retrofit roller cams on ebay and came up with this: http://www.ebay.com/itm/360505317332

if I'm understanding "buckets" suggestion about the torque being down around 1500 rpm, I'm thinking the one in the link I just posted is probably going to be the one I want, can someone take a look and confirm that?

I'm also going to need to figure something out for push rods and the gear on the bottom of the distributor and not sure what else I'm going to need.

my goal here is to buy all the needed parts, then take the truck to the shop and have the stuff installed.

Good price, but that's going to be too wild. Probably don't need push rods, but a decent set is cheap and can't hurt. The dizzy gear is cheap too, but you can get a complete, ready to run dizzy for cheap. HRPC is in love with it.

Hey HRPC, got a link to the ebay dizzy?

 

[bucket]

This is more what you would want, although it's a little more $ because Comp stuff just tends to be. http://www.ebay.com/itm/COMP-350-40...Parts_Accessories&vxp=mtr&hash=item2eb29c5ddc

The lift is still a touch on the high side, hence the recommendation of matching valve springs.

 

[HotRodPC]

So are you looking for someone to tell you how it is, or someone to agree with your brother? Looks like alot of posts here discussing a new cam putting the cart before the horse, or are you just wanting upgrade the pep a little and do some mods and telling this line of crap to the wife that it needs a cam?

There were a FEW 305's in that era in the last 70's that wiped out a lobe or 2, but I never heard of 350 doing it. And if you were going to have premature cam lobe wear, I'd say without a doubt you'd have for certain had it by now. At 70,000 miles you're way beyond the threshold of possibly having a bad cam.

UNLESS you're wanting to do add some performance, and it currently runs fairly well for a 30 year old motor, then I think I'd leave it alone since it sounds to me that is pretty much OEM and unmolested.

That's just my .02. Welcome to GMSB BTW.

 

[Gramps]

So are you looking for someone to tell you how it is, or someone to agree with your brother?

good point, glad you brought that up, I'm looking for someone to tell me how it is, because, this full size chevy stuff is completely new to me, your dealing with a Subaru and Volkswagen guy here, the last chevy I owned was a vega back in the 80's and it was nothing like this.

Looks like alot of posts here discussing a new cam putting the cart before the horse, or are you just wanting upgrade the pep a little and do some mods and telling this line of crap to the wife that it needs a cam?

maybe the cam isn't what I want or need? I'm interested in upgrading the pep, the last camping trip I went on was in our Subaru wagon that went up the mountain so slow, even the semi trucks were passing us, it was embarrassing to say the least, and I'm sure those guys were all laughing, I ain't goin there again, and grandma only has the boat and the river on her mind, and how fast I can get it back out on the water, so she's really not interested in the nitty gritty of getting the truck a little more pep.

There were a FEW 305's in that era in the last 70's that wiped out a lobe or 2, but I never heard of 350 doing it. And if you were going to have premature cam lobe wear, I'd say without a doubt you'd have for certain had it by now. At 70,000 miles you're way beyond the threshold of possibly having a bad cam.

ok, that's the second time I've heard that, so I'll go with the majority vote on that one, yes the truck runs just fine the way it is, nothing abnormal at all, so maybe my cam worries are in vain.

UNLESS you're wanting to do add some performance, and it currently runs fairly well for a 30 year old motor, then I think I'd leave it alone since it sounds to me that is pretty much OEM and unmolested.

my main concern, not knowing 350's at all, is that I'd like to do some preventative maintenance on it now, that will give me something reliable for many miles to come and in driving the truck, for a stock V8, it just seems like it could use a little more power, so I'd like to give it a little more oomph, but not sacrifice reliability or gas mileage, and was thinking that a cam upgrade might be the way to go and I could solve the potential future cam lobe problem at the same time.

I do have an air-cleaner housing for it off a 454 that has the bigger inlet with the tube that attaches to the firewall, although I haven't installed it yet, I'm told that will help the engine breath easier.

I've also got an extra rebuilt HEI dizzy that's been rebuilt with some stiffer springs, with some corvette parts or something like that, that is supposed to help with the gas mileage, but that's just sitting in a box, not yet installed in the truck.

That's just my .02. Welcome to GMSB BTW.

thanks

 

[HotRodPC]

The late 70's and early 80's were bad years for expecting alot of power out of anything. The Chevy 350 is a tried and true very durable motor. To date, a good chance the 350 was the best motor Chevy motor to be produced which could explain why it made a 30+ year run from 69 to 99 in trucks and even a few years later in Vans. As far as real power though, they did good early on in 69 then as smog emissions and EPA standards choked them, they became less powerful to meet the gubment demands up until about 96 when OBD II was installed along with SFI (Sequential Fuel Injection) otherwise they were lacking in hp but still had some torque.

Not sure how much more power you're looking for, but an aftermarket intake like an Edelbrock intake and a true dual exhaust will help some and certainly help with throttle response. If you want even more power an RV cam will sure help, but I would NOT go thru all the trouble and expense of a roller cam in that motor. It's an old school motor and to retrofit a roller cam would be expensive IMO. If you're willing to do that, I'd just find a good used Vortec 350 (96 and later) set up that is a roller motor from the factory, and convert the truck to the SFI. But, keeping it real and balanced, a standard flat tappet hydraulic RV camshaft and Eddy intake, along with dual exhuast should give you plenty of get up and go even towing a small boat with the proper gear ratio.

 

[woodsrider250]

It's a good idea to add zinc to your engine oil...esp on older motors with soft cams. EPA said take zinc out, cams get wiped all over the US...bikes, cars, trucks, etc.

 

[HotRodPC]

It doesn't hurt to add the Zinc, but once the cam is well broke in, it's really not needed. For sure you have to add it for a new cam break in and I'd leave it in for 1000 miles if it were a new motor, then change my oil, and I'd add it the second time too to run 3000-5000 til my next oil change but past that, it's likely just fine without it.

 

[Gramps]

I was looking up that zinc stuff, it looks like royal purple as some 10-40 that's got zinc in it and Edelbrock has some 10-40 that's Zinc Enhanced.

so next time I change the oil, you suggest that I go to something that got some zinc in it or at least ad an additive?

I'm also thinking at the very least, I should probably change out the timing chain and gears, if any of that were to ever give up, then it would wreck the whole engine. on the subaru's with the flat 4's, that's the first thing you change out, although those are belts and not chains.

I was just looking over the mileage records that came with the truck, and from 1978 to 1985, it was driven a total of 40,000 miles,

From 1985 to 1989, it was driven another 16,000 miles, which brought it up to a total of 56,000 miles.

from 1989 till now it was driven another 14,000 miles to bring it to the 70,000 it's at now.

I do have records of all the oil changes since new, and it looks like from reading through the records that the guy was fairly consistent about changing the oil every 3,000 to 4,000 miles, there's a crap load of oil change listings, but there's nothing in there that says what kind of oil he used.

Gramps