Always lurked on here for valuable information, today is the day I need to ask for help. Son and I built up a 355 recently and decided to try the Vortec head route for cheap power. After doing some online reading about what can and cant be done with stock heads we decided to just copy the build sheet used in a Motortrend build to be safe and known that the parts worked. This is the link to the article we followed : https://www.motortrend.com/how-to/1...en-junkyard-dog-small-block-into-a-performer/ We used all the same pats they did and used the stock rockers and pushrods as well. So before first break in all proper assembly lube, break in oil used. 1/2 turn preload used on valves primed oil pump with drill to confirm oil flowing correctly through all lifters/pushrods to rockers -cranked over no plugs in to watch everything opening and closing as should -re-checked valve lash Got the engine fired and started the break in procedure, after break in set the timing and had all running properly. Pulled oil filter and opened up for inspection and found nothing alarming. After 45 min of testing the truck through gears and other tests it starts to run badly like a timing miss, start chasing the simple solutions that eventually leads to pulling rockers and finding #2 cyl has both bent pushrods and collapsed exhaust lifter that was destroyed on the mating side to the cam and the cam was wiped out. After trying to figure out what happened maybe we thought it was a bad backfire or a bad lifter(s). We bought new camshaft and lifters the same as before, cleaned everything up, re installed and last night started break in procedure again. 10 min into break in and i start reading header temps and see #2 is cold. Shut down the break in and inspect. Pulling valve cover I find #2 cyl again with both collapsed lifters/not springing or pumping back up. What am I missing here ? I feel so bad for my son right now and feel embarrassed as this route of the build was my idea to go with old technology vs just the LS swap route. Any help please. Jamie
What lift cam?? Vortec heads have limited lift [some say .420" and others claim .480"] You need to pull the valve spring and reinstall the retainers ,then measure the maximum clearance between the guide and the retainer. You can buy offset keepers from Summit to get extra clearance [+.050 Offset Keepers # SUM-174003-4] With the correct selection of retainers and beehive springs you can get up to .550" lift [but you still need to measure the clearance] Summit .550 Springs # SUM-174002 Summit Retainers # SUM-174003-3
So, I scanned through the article, they first verified the heads had .500 lift capability, then used a .480 lift cam. Did you verify that before hand?
Cam /lifter failure has become all too common on flat tappet engines. There are many thoughts on the cause. Wrong oil, too heavy valve spring pressure, bad cam metal, bad lifter metal, wrong angle on lifter. Im sure there are more. The second cam/lifter may have died from metal left in the engine from the first failure. If it were mine I would take it a part,and really clean the inside,and all oil passages, and buy a roller cam conversion cam set. Your no where near the only guy to have this problem. Im done with flat tappet cams myself. Roller cams are easy break in with fewer worries.
No I didnt verify, I was under assumption that all the Vortec heads were good without machining to go up to .480
That would be my issue then. You read Kerry’s reply, seems to be a range of possible “max lift” from heads to heads. Always “trust, but verify”.
Im starting to think that also , will check tonight and report back after measurements. Just seems funny that its on 3@ cyl again. Lifter journals all looked and felt ok. Also confirmed lifters were rotating as they should .
It’s possible (being the MT engine had a flat tappet cam in it) someone may have used the tool in a hand drill to get more clearance for lift. The cutter has a pilot that goes in the valve guide. If done by hand, maybe all were not repeatable. Just another thought.
You’ll want something like this. Pre-measure the tool with a caliper and set to desired height. https://www.amazon.com/Micrometer-M...1&psc=1&mcid=5f9ef957fda63fd1af833f459e1559f7 . It may work without having to pull the head and removing the valves. I’ve only done it off the engine. Put the spring and parts needed together, the tool goes inside the spring pocket. More I think about it, it would need to have the head off to compress the spring in a drill press, ect. also when I say “desired height” I mean from installed height to lift height, ie take the smaller number (measure installed) and then start there and go to lift height and .020 fudge for safety
If you have bent push rods and collapsed lifter something is hitting or binding. A .060 coil clearance is a good rule of thumb. When the valve is fully open do you have enough clearance between the retainer and the valve guide. Do you have adequate valve to piston clearance. IMO this is not due to a bad cam or lifter but maybe too much lift for your set up. If the retainer is hitting or the valve spring is coil binding a roller cam is going to have problems also but more expensive problems. Dan
Another MT article on Vortec heads. https://www.motortrend.com/how-to/148-0208-vortec-heads-valve-lift/ Which has a highlighted paragraph: Because these heads are meant to work with a 1.5:1 rocker, their tall valve guides can only handle maximum valve lifts of around 0.420 inch. Good luck, keep us posted on what you find. Dan
Lifters should be rotating while on the base circle of the cam . But that does not show the whole setup binding at maximum lift [over the nose] One guide could be slightly taller, or the valve seat/valve is shallower so the stem sits lower or if you're using stamped rockers one could have slightly longer ratio. Measure everything
^^^ This. A bad lifter or improper break-in procedure doesn't bend a pushrod. Good thing is, the engine has engine run time on it that you should be able to see the witness marks where it's binding.
I understand how a collapsed lifter can bend a pushrod but you would think that would show up very early on the break in. Dan
That was supposed to say "doesn't bend a pushrod". Sorry for any confusion. Proofreading on my phone isn't my strong suit.
Measure measure measure tolerance stack up has bit yer ass, something is too long, till you find it your bound to fail.
Thanks all for replies, appreciate all the input. Ive pulled the engine and going to go over it again this weekend. Will post findings (even if/when realize I measured wrong) Jamie
You wrote "break in procedure" twice now. Once on the first attempt and then again "10 minutes into the break in procedure" for the second attempt. Just to be clear since you didn't actually come out and explain your specific break in procedure--> then I read the article you posted "We first treated the cam to a proper break-in procedure by exceeding 2,400 rpm for over 30 minutes to get the cam and lifters properly acquainted." This is the first article i've read stating to spin it up above 2400 for 30 mins. Every other break in info i've ever read or heard always stated somewhere in the 1,500-1,800 range swinging up to the 2000-2200rpm range as different rpms throw the oil in different areas of the crank case to get that splash lube happening. Followed by typically a 20minute break in session with complete cool down (I do 10minutes, cool down, then another 10) I'm not saying that it's the smoking gun by any means, but you did state both lifters on #2cylinder died. I dont know the location of specific bosses and block webbing around an SBC lifter gallery, but could you have had insufficient splash on those lifters due to sticking to an RPM that was over 2400, but non-varied? -rick
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