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Old 02-15-2017, 05:31 PM   #1
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My 5.7 needs a cam

I have come to the conclusion that my G30 needs a new cam/lifters. Does anybody have any suggestions for the right cam?part#? Fuel economy and cost our primary concerns and towing secondary. I'm pretty sure the turbo 400 transmission and 410 geared rear would tow great with just a stock Truck cam.

I'll be throwing on a new timing chain and water pump at the same time. Just for safety sake

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Old 02-15-2017, 07:08 PM   #2
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I am assuming you are talking about a 5.7L/350 small block.

If you are, the upgraded RV cam would be ideal for your purposes.

If you don't have it already upgrading to EFI would be a great idea. Fuel mileage may get a little bit better but the driveability will be greatly enhanced.

Opening the exhaust up and getting a cold air induction system installed will go a long way towards improving the burn in order to take advantage of the improved cam profile.
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Old 02-15-2017, 07:14 PM   #3
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+1 on an RV cam... what yeasr is that? is it later than 87?

the chevy 350 in 87 started shipping with Roller cam and roller lifters. thats adds to the cost of things and gives you a bit fewer choices,..

86 and older engines have flat tappet cams and lifters which drops the cost and offers many choices..
-Christopher
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Old 02-15-2017, 07:59 PM   #4
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Its an 85

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Old 02-15-2017, 08:38 PM   #5
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also you need to know what the engine speed is at the normal speed you travel, you want a cam optimized for that engine speed for best power and economy
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Old 02-15-2017, 08:56 PM   #6
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did you wpe a lobe on the original? or just trying to beef it up a bit?

do you have an idea of what your preferred cruising RPM is? I rememebr you have a TH-400 trans (1:1) but cant remember what rear and tires you have...

we cant go with anything too wild as the stall speed on the converter is likely 1400-1800 on that bus..


I have used the comp cams in the past with good success..

COMP Cams: Dual Energy™ 255DEH; Hyd. Flat Tappet; '58-'02 Chevy Small Block

this one is a smooth idle.. gives good low end torque but will not be as aggressive in power at the higher RPM (above 4000)...

they make a 265 which is a bit more aggressive but also creates a bit more rough idle... rough idle sounds bad-ass but can be cumbersome if the torque converter stall is too low..

-Christopher
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Old 02-15-2017, 09:17 PM   #7
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My cruising rpm is in the 2500-3000 range. I think 2700 is about 60. Rear is 4.10 gears. Th400 is 1:1 tires are 215/85r16.

One of my cyl isnt firing. Rocker arm is barely moving. Compression is great across all the cyl. Holds pressure too.

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Old 02-15-2017, 09:32 PM   #8
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wiped Lobes are common in older engines with modern oils... flat-tappet cams dont like the new oils...

I ran a product called ZDDP-PLUS in my old hotrods for this very reason... I may still have some of the stuff in my garage in ohio...

you may also just have a flat lifter... the first step would be to yank the intake manifold and examine the lifter for the affected rocker... on a 350 they can be plucked from their bores with the heads on.. is there excessive play in the pushrod for that valve?

when you get the lifter out you can use a micro camera to examine the cam lobe visually.. and of course the bottom of the lifter...

if the lifter is a ^&*%^&* to get out of the bore it usually means the cam ate up its base...

pullinfg the intake also lets you make sure thats the original bloick and someone didnt stuff an 87 or later block (with roller lifters) in..
-Christopher
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Old 02-15-2017, 09:44 PM   #9
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Could very well be a flattened cam lobe, I'd recommend converting to a roller cam and lifters for durability alone. It wouldn't be cheap, but with the lack of ZDDP in today's oils it would mean only having to do the job once.
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Old 02-15-2017, 09:58 PM   #10
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Theres no tapping or noise. If it is the original thirty-year-old lifters and Cam I really don't mind replacing it before we go all the way to California from Florida. If I convert from Flat to Roller do I need new pushrods?

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Old 02-15-2017, 10:12 PM   #11
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we would have to look that up to see if the pushrod lengths are different.. I believe they are different length..

converting to roller is an option. there are retrofit roller cams for non-roller blocks..

you'll likely need a timing cover with a roller-cam button..

flat tappet camshafts, the lobes are slightly angle.. both to make the lifters spin in their bores and wear evenly.. and also so that the lifters hold the camshaft in position (front to back).. roller cams require retainers for the lifters so they dont rotate in their bores and also a button on the front cover to keep it in position and not allow it to "walk" forward.

roller cams also dont have that critical make-or-break run-in period when you first install them..

anything I built that was at all radical i used roller cams as i wanted the steeper profiles and more Lift...

dont let me build that engine or you'll have one mean-ass Tyr-Fryr (license plate on my old monte carlo.. 520 HP 387 stroker.. (350 with a 400 cam)
-Christopher
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Old 02-15-2017, 10:13 PM   #12
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Yes, roller lifters are taller
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Old 02-15-2017, 10:15 PM   #13
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Maybe i'll just keep it simple. https://m.summitracing.com/parts/sum-k1100

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Old 02-15-2017, 10:18 PM   #14
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thats not a bad profile, should have decent low end torque and at your cruise RPM be respectable.. as wel las maintain a good idle quality...

of course in your case just having 16 valves that open and close and 8 cyklinders firing would help!!
-Christopher
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Old 02-15-2017, 10:32 PM   #15
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I had a rig very similar to yours-85 GMC 14' cube van. 350 -th400-4;10's. 10k lbs. I put over 100k miles carrying race car or bikes all over the east coast. Mileage was a big battle I kept fighting. And I was one of those obsessed types that kept notes of every fill up + mileage.
I had headers with 2.5 " pipe-h pipe-flow masters--edelbrock carb + performer intake--extra bright ignition--fresh air intake. And over the course of 15 years I got a fresh engine also.
My best mpg ever was in the tankfull that would take me thru NC/SC. (Meaning flat as flat as can be) was 9.8. Thats it. If I would get hilly like Vt + Nh., 8.2 mpg. And I could do the same numbers repeatedly. A measured 10mpg was my holy grail. Which i never saw. But not for the lack of trying.
You're basically pushing a house thru the air. Your roof looks a bit lower than mine was -that might help. I had a truck air dam built on the cab-it made going down the road MUCH nicer.
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Old 02-19-2017, 04:31 PM   #16
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Missing lobe.


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Old 02-19-2017, 05:26 PM   #17
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yeooow!!! seen that one enough times!! how do the cam bearings look? wiped lobe means that metal went someplace..

the pure engine builder in me says tear it down and rebuild it..

the '2 tears in a bucket' in me says put in a new cam with fresh oil... run in the new cam with break-in oil.. change the oil and use a good quality oil with the proper ZDDP. and go drive for probably 100k miles..

(ive done this both ways and had good luck)

im assuming you will stay flat tappet or are you going to go roller?

heres a good article on CAM oils .. I used an additive called ZDDP-PLUS in all my hotrods with flat tappets... though of course if you can spring the $$ roller is the way to go.. just dont go too aggressive on stock springs... they will break.. esp with high amounts of lift..

Camshaft Break-In Guide - How To Properly Break In A Flat-Tappet Cam - Hot Rod Network


-Christopher
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Old 02-19-2017, 06:39 PM   #18
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Ive been using rotella in everything without a cat for a while now. Looks like some rotella has high enough zddp levels for break in. Hmmmm. Ive got plenty of 10w30 on the shelf.

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Old 02-19-2017, 06:52 PM   #19
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some of it pretty much does.. Rotella is good stuff..

I learned about the rotella trick after I was done building flat tappet cam engines...

if your bus is staying in warm climates you could probably get away with running the same rotella most of us run in our diesel busses..

ive run 15W40 in small blocks without issues.. though im sure theres some nay sayer that will tell me I shoulda never done that... but I was HARD on engines... ran em like I stole em.. Lots of tire smoke!... and wanted good heavy oil to handle the way I drove...

the diesel guys made smnoke out their exhaust... i made more smoke with the Tires.. their way was much cheaper..


-Christopher
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Old 03-13-2017, 09:16 AM   #20
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8.5 mpg with the new cam on a rural drive to the beach running 55 most of the time. Engine runs perfect i think. Sometimes a hair rich at idle. I wish i could find a junk yard rear with 3.73 or 3.55 gears.

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