Hello,

I wanted to know if someone could give me a to the point answer on a specific car or cars that have the stock valvetrain and roller cam setup to replace a flat tappet cam.

I have a '92 350 tbi. I don't know the block casting code, but I do know that it has the lifter guide hold down bracket holes factory drilled and tapped, so it was machined to accept a roller cam. It also has the proper lifter bores.

I have tried searching the forum but I haven't found exactly what I'm looking for. I did read the sticky about the LT1 cam swaps and so on, but I am new to anything mod-wise on Chevy stuff so its all a bit overwhelming for me to figure out what is what or if the LT1 cam is in fact the roller cam I'm looking for. I'm specifically looking for a list of cars so I can reference them on sites like rockauto for parts. Also so I could go to a JY in hopes that I could find those cars and be confident I could take the cam and valvetrain out knowing it will swap right in to my block with the flat tappet cam.

I'm not looking for any aftermarket performance recommendations. I understand I won't be gaining anything performance-wise with the swap into an otherwise stock block. I am only doing this because I have a few bad lifters as it is and don't want to mess with replacement lifters and break-in risks.

Thank you.

 

Any 305/350 from 87 forward that isn't from a truck will have everything. Starting 94-95? trucks are all roller cam too. If it's a "vortec" 305 or 350 it'll be roller. That's on the cheap but depending on what's in your local JY.

You can get these parts new https://www.jegs.com/i/JEGS+Performa...EaAnrdEALw_wcB
Pick/order whatever cam you want whether new or used just make sure you get proper valve springs. LT1 camshafts from fbodies/corvette ised to be a common upgrade because people were throwing them away to step up their cam and tbi owners could use those specs without much fuss due to factory TBI tuning is/was a little less accessible. Much harder to find a factory LT1 cam for sale than it used to be.

 

Gm 14101116 for the spider plate
Gm 12550002 for the dogbone retainers
gm 10168501 for the cam retainer plate

amazon has all 3 for 60$. Then you just need lifters, which you can get from any 80’s roller or late 90’s/2000’s ls1 stuff

 

I did this exact same thing for my 91 K1500. I swapped in a stock L31 roller cam along with the bars, lifters and pushrods. Runs like a champ on the stock tune.

 

I have an extra GM #049 L98 cam. 207int, 213exh. 415 lift so easy on press in studs and stock springs. Great upgrade for a TBI engine as I am running one myself and have used them on several other builds. May have an extra set of stock lifters to go with it. Id sell it if u interested.

 

Thanks that does help out. I might go that direction if I can't find anything usable at a JY or used online.

That's good to know. I didn't know it was that cheap to get those parts new. If I cant get a JY assembly for cheaper then thats definitely what I'll do.

Ok thanks for referencing it as the L31 cam. Looked into it and that is indeed the cam I am trying to source.

I would be tempted to do anything outside of factory stock options, but the issue is where I am the smog laws are pretty bad. They already want these things off the road, and I had to battle to get the thing to pass last year. If I was confident the exhaust gas profile wouldn't shift outside of what's considered passing, I'd be more inclined to. Thank you for the offer either way.

 

An update on what I've gathered the last few days from some more digging and help from you guys.

I believe that everything I am looking for would be found in a '96 suburban C1500. I was cross referencing part numbers for things to try and spot what is different from my tbi setup and the swap I want to do. I noticed that the valve spring retainers are different part numbers from the flat tappet spring retainers. Does this matter? I know it needs the stiffer springs that the roller setup came with, but I haven't come across anyone mentioning this detail. For reference: 96 retainer vs 92 retainer. I know the Melling p/n's are the same, but I know I have the GM retainers.

The other thing I came across was some people saying they ran into issues using a vortec roller cam with their stock tbi distributor because of the gear on the dizzy shaft. I believe I already have this taken care of. I read that people solved this problem by buying a new distributor altogether to get the proper gear that would fit the shaft diameter properly and work with the roller cam, which is where the issue was.

When I cross reference the distributor on rockauto, the upgraded one is the same part for both my tbi and the vortec 96 suburban, and I already replaced it a while back with this part so I seem to have that solved. In case anyone was wondering it's the United Motor Products 9362

Another question I had was about the timing chain set. I see the chain sets are different for my tbi vs the 96 suburban. Is the Cloyes C3092 (suburban part) the one I need? Just want to make sure everything will be direct fit for my crank snout and block clearance. The one I currently have is the Cloyes C3055. I see that the tooth width is the same on both chains so I think the suburban one would be direct fit on my block?

 

Just get the stock distributor gear from the same truck. Pull the distributor and knock out the pin. The gear will slide right off. I used one from one of the many stock LT1 oil pump drives I has sitting in a drawer.

 

Any roller cam timing set should work fine.

 

Good to know. Thanks for all the info, helps a lot. Confident in what I need now.

 

All TBI distributors have the melonized gear. No need to dick with the gear unless it's excessively worn.

Vortec (96--newer) SBCs have a known issue with distributor gears. Apparently GM saved another nickle on the assembly, and doomed the gear to premature failure.

SBCs have two possibilities for the cam retainer. I guess some moron in the engineering department invented a cam retainer for SBC with wide-spaced bolt holes; and the earlier roller-cam block was cast and machined to accept bolts in the wide-spaced locations. Some time later, they realized their mistake and used the retainer plate that was designed for the BBC about a thousand years ago, which was already in their parts inventory. The "second design" SBC plate is the same as the "BBC" plate. The blocks were changed to more closely-spaced bolt locations.

GM sells a timing chain, two sprockets, BOTH retainer plates, and the hardware to attach it all. Downside being, the crank gear has a single keyway--and is therefore not "race-y" enough for many folks.

https://www.summitracing.com/parts/n...make/chevrolet

One alternative, of course, is to verify the timing set is in good condition on the donor vehicle; and grab the entire timing set along with whatever cam retainer that engine happens to have, and hope it fits the block you intend to use it in. If your block needs the "other" retainer, just buy that separately from the GM stealership or aftermarket sources. The unknown-mileage Vortec short-block core engine I bought to rebuild, had a timing set so unworn that when I degreed the cam, I was within about one-and-a-half degrees of perfection. Close enough for me.

 

Great info. If I happened to run into that different retainer plate I'd be stumped for a while thinking I got my compatibility vehicles wrong haha.

 

Just an update.

I found the cam/lifters/pushrods/brackets at the JY out of a 98 suburban. I’m in the process of cleaning everything and ordering the springs and all that.

Im running into an issue cleaning the lifters though. I have rebuilt these same lifters before in other vehicles so I’m familiar with the parts they have inside them. These lifters are just gummed up pretty bad, probably from sitting in one position for a while. I can’t get the inner cylinders out. I have them soaking in berrymans chemdip, and they’re still fighting me. Anybody know of any tricks to make this easier? I got two free by using one of those expanding concrete anchors as a puller from a trick I learned a while ago, but I’d rather not use something metal to metal if I could help it. Even if the lifter is hardened.

I know that an obvious solution is to just buy new lifters. The problem is I’m not sure which to buy. I can see the direct replacements on rockauto, but I don’t want to buy those since that is what got me in this situation in the first place with the replacement solid lifters I bought being bad. I trust that the factory lifters are better quality. I know only like three main companies make stock lifters replacements these days, and the general consensus is they’re all made from cheaper materials.

So with that, can anyone direct me to a set of quality stock compatible lifters from a site like summit or others that cater to more quality aftermarket parts? I looked and think I found what I need, but I get lost in the lift specs and all that. Summit answers questions about the lifters in the reviews but it basically boils down to “you may or may not have to change pushrod length since these lifters fit so many applications”. I don’t want to buy the wrong parts, and trying to find a straightforward answer for stock application with stock everything else seems hard to find. At least for me. I don’t really do valvetrain mods enough to get into customizing the stock geometry so I get lost fast.

 

I typically use a pick with a slight hook to pull the plungers out. Sometimes they can be super sticky.

 

Or, after you remove the spring-retainer, pressurize them internally, so the plunger is forced out.






I fill the pump-oiler with clean ATF. Flows easier than engine oil at room temperature.

 

You should contact Mortorq regarding that cam. He could send it off to Jones Cams and have it reground to the specs he's looking. Mike (Mike Jones of Jones Cams) has no step nose cores in stock. And no idea when there might be.
You've been here:
https://www.thirdgen.org/forums/tech...toplite-4.html

 

Already offered it to him. I gave an L98 cam to a friend who put it in pretty much stock Vortec 350 in his S10 and went low 13s. Of course it had gears and loose converter + carb, full exhaust but still. It ran extremely well for a truck you can drive anywhere. Bought up several more and running one on my car now and very happy with it for a mild TBI build. Car revs easy to 5300-5500.

 

Yea I don't understand. The Caprice cop cars with TBI ran that can.

 

Thanks for the tip. A few more days in chemdip did the trick and I was able to get them fished out with a pick.

 

I wish I felt more comfortable going for more performance. It seems like a no brainer but because I strictly need this for utility purposes and more importantly because of my states strict emission laws, I want to be as close to stock as possible. I know, super boring.

 

I have a new issue for you guys. This one has me stumped. I have the cam and valvetrain swapped in. Everything going smooth so far. I got to the timing chain and I've hit a stopping point. I bought a timing set for a 98 Suburban C1500, the car the cam came out of. I went with the same tooth width that came stock with the old flat tappet timing gear. I know it shouldn't matter either way.

The part number is Cloyes C3017. The problem is it has a ton of slop in it. There is no way its supposed to be like that. I was pretty confident that this timing set was compatible from doing my research. I gathered that any timing set that was made for a stock vortec roller cam should bolt right on. So I did some more digging. First off I confirmed that each individual component I received was the right part. All stamped numbers line up. Then I looked up a timing set for a '90 caprice thinking maybe the older block had a different center spacing. Nope, same set advertised. So now I'm kinda at a loss. Here's a pic of the slop with the crank at #1 TDC.






The only take I have at this point is that the style of chain and sprocket set won't fit my old block for some reason? The stock TBI chain was the pressed in link style, like a traditional bike chain. The engine the cam came out of had the same pressed link style, but I thought both styles worked either way. Either way, I'm thinking of trying the Cloyes 91157 Street True set. Looks like the original chain set and I've read the quality is much better. I also noticed on the cam dowel pin hole that it looks all ovaled out. I don't know if that's to fit other engines, but the cam sprocket was definitely able to move back and forth due to that wallered out hole.

I don't know if it helps, but I found my block ID. It's 14093638. I couldn't find anything useful with it, just that its a 2-4 bolt main 5.7L with either flat tappet or roller. Just thought I'd throw it out there.

 

I think I might have figured out what’s going on. I looked up the Cloyes set that won’t fit on amazon. Seems like half the reviews are having the same issue I am where it doesn’t fit and has a bunch of slop.

So it’s either the chain set is being incorrectly advertised as fitting a sbc, or something is wrong with the manufacturing process. At least I now have some direction about what’s going on here. Seeing that made me pretty confident to order the Cloyes street true set so I did. Will get here by the end of the week and I’ll update.

If anyone had anything to add about the timing chain issue I’d still be interested. At this point I’m just curious if it’s something I’m missing or just bad manufacturing/wrong fitment guide. Good to know for the next guy who looks for info on this swap in 2022 with all these poorly made parts out there.

 

Looks to be an excessive amount of slack even if the block has previously been line honed.
There are timing sets specifically for that purpose.
But seeing as your investigation found similar issues with other purchasers, it could be a bad batch.
EDIT:
What did you end up with for a cam?

 

Yeah I doubt anything was ever touched on this engine. It’s from a g30 van and when I bought it it was just used as an old work van. Everything I’ve torn into on it had factory parts.

I think you’re right that it’s on the manufacturing end. I mean it even looks rough overall. I get that the faces of the gears don’t need to look pretty, but overall it seemed like a dodgy set even if it fit. Weird because I’ve used tons of standard level Cloyes sets in the past with no issues. Part of me even thinks it might be a reboxed no name with how similar in style it looks to eBay specials. I’d expect that from amazon but not really with rockauto even if they offer cheap junk sometimes. Glad I returned it and got the USA made line of Cloyes parts. Here’s to hoping.

 

Pretty normal for a stock style replacement. GM built them loose enough for a robot to install them and Cloyes is an OE manufacturer for GM. I prefer single rollers myself. The Cloyes "True Rollers" are made with less slack for a performance applications. Look at Cloyes 93157. 91157 is also not a bad chain set.

 

The cam came from a vortec L31 block. I looked up the stock specs compared to my flat tappet cam. It’s close to the same but the vortec cam has slightly more lift but less duration.

 

Flat tappet 350 TBI grind
(Same part number as the LU5 Crossfire 305)
194/203 @ 0.050
.390/.410 lift
112 LSA
108 ICL

L31 Vortec grind
191/196 @ 0.050
0.414/0.428 lift
111 LSA
106 ICL as installed on OEM vortec timing set

 

Update:

I got the new Cloyes set in and it fits like it's supposed to. Tight on both sides. Got everything back together today. Primed the oil system with a modified old distributor and verified oil out of every rocker. Started it up. It clacked a bunch which I expected without priming the lifters prior to install. Eventually they filled up and it started sounding smooth. I have a big problem though. The engine runs like crap. It has a very obvious random misfire pop through the exhaust.

I checked at least 4 times that mechanical timing was set right before I put the cover and everything back on. I always turn the engine over by hand two full rotations to verify the marks line up on 1 TDC. The nature of it being a random stumble makes me think it isn't mechanical related. I know the skies the limit on what it could be due to how much you have to tear into the engine to do the cam swap, but I just want to hear it from you guys before I chase my tail.

The L31 vortec cam doesn't need an ECM tune for the TBI right? Nothing I researched pointed to that, and I cant see the specs of the cams being that close causing it to run this bad.

Things I have done:

• Pulled the ESC wire to set base timing after warmup. Started with factory 0 BTDC and played with up to 4 which is what I usually set TBI engines to.
• Verified injector spray pattern/leaky injector. At least as much as a visual is going to tell you.
• Checked for vacuum leaks and misrouted vacuum hoses.
• Visually checked and cleaned cap/rotor and am certain I don't have the plug wires messed up.
• Verified all the rockers are moving with engine running. I know this doesn't make up for a dial indicator but they all looked to be moving the same and no clacking.
• Verified engine grounds
• ECTS harness has new pigtail along with TPS. TPS sets code when unplugged

I want to believe this is ignition related. The exhaust smells rich. It's not indicating that its a lean misfire like a pop through the intake would. When I increase the throttle, it'll chug and buck till it opens a bit more then starts to smooth out. Quick snaps and it still responds. But when you put it in gear, it isn't going anywhere. It wants to die when you give it throttle but it'll stay alive if you get passed initial throttle. I know it sounds like a classic vacuum leak as well, but the vacuum leak needed to cause it to run this bad should sound massive and obvious. I sprayed with brake cleaner around intake and throttle body and no change at all. I have a smoke machine but it would suck to get it from where its stored so I'd rather not.

I just really want to hear this likely isn't mechanical related with the cam. But it's the only thing I changed. My next plan of attack is to put a vacuum gauge on it and see if the reading is steady, and check spark down to the plug with a HEI tester. I own all this stuff but a lot of it is in different locations. Along with my job it's not going to be done right away. I'll keep updating as things come along.

 

TOTAL waste of time. If you spend one full minute "priming" the oil system, you spent thirty seconds too long. "Priming" is DONE when you achieve oil pressure. Squirting oil out the rockers is a waste of effort.

Connect a scan tool, find out what the computer is trying to tell you. Verify ALL sensors, and computer outputs.

How old is the O2 sensor?

Verify adequate fuel pressure, which may be more than stock spec depending on the rest of the engine. Use the short- and long-term fuel trims as a guide to needed fuel pressure.

I have an L31 cam in my '88; runs fine on the stock tune, although I did add some initial advance and some fuel pressure. Engine also has aluminum heads, aftermarket intake manifold. I expect it could run better with a properly-done custom tune; but that's beyond my skill set.

For ****'s sake, do not ever do that again.
SOME brake cleaners don't burn, which makes them useless for detecting vacuum leaks.

SOME brake cleaners produce toxic gasses when burnt, putting you in the hospital, and maybe the morgue. Effects of the gas can last for days...weeks...months. It can **** you up severely.

I use aerosol carb cleaner. Some guys use an unlit propane torch. DO NOT USE BRAKE CLEANER.

 

Yeah I hear you on the oil priming. I know it’s not like I did a full rebuild or something, and I know it’s generally ok to just go at it briefly, but I like to see oil out of every rocker just to know I did. Im one of those guys with the selective perfectionism.

I would love to get a scan tool on it. Unfortunately I don’t own obd1 diag tools. I used to work in the industry but never really used much obd1 stuff. I do know what I’m looking at on obd1 data though.

If you have a low cost suggestion I’d definitely consider. Can’t buy an old snap on scanner just for this though, or at least I hope I don’t get desperate enough to feel like I need one. I want to say there’s the free software for a laptop and I just need an obd1 to usb cable? Not sure. Or I think there’s an old gm scanner besides the tech 2? Can’t remember if it does obd1 too.

02 sensor was converted to three wire for the heater circuit a while back. It’s basically new, got about 5k miles on it and it was a genuine GM sensor. A common mod done to the old one wire sensors. I left the ability to switch itye heater on and off, and it’s usually left off. This was how I passed smog and that was a saga. Basically the van would fall out of closed loop waiting my turn in line for a smog and I’d fail for excessive hydrocarbons. Put the three wire in so I could force it to stay in closed loop and passed.

About the fuel pressure. I know that if I can’t find a smoking gun soon it’s going to come down to ruling all of that out. I hate checking pressure on the TBIs. The only success I’ve had with the tools I have is plumbing into the filter by the tank. I’ve seen a lot of setups with the gauges on the line near the TB, but I’ve also seen a lot of those setups leak so I’m hesitant. The FPR was rebuilt not too long ago. Got the TB kit that came with everything. If I can’t find a smoking gun soon though I know I’m going to have to suck it up.

Good to hear that you got an L31 cam to work. At least it gives me some hope. I’m wondering if I somehow installed the timing chain on 6 compression stroke vs 1. I can’t imagine it would even run this well if I did that though. It doesn’t hesitate to start up it just misfires severely after a couple of seconds. I’d feel stupid as hell doing that rookie move but it happens. I’d be happy with that even though all that money on gaskets was burned just to know it wasn’t something catastrophic. I’ll check for 1 compression with my thumb and verify turning by hand.

As far as the brake cleaner goes. You’re right, I really gotta stay away from the stuff. I tell myself that every time I use it. The only saving grace is I live in a nanny state that doesn’t have chlorinated brake cleaner. Still doesn’t give off nice fumes when sprayed on a hot engine. I tend to keep my breathing held or away from it as I spray. Still not a good idea so point well taken.

 

Doing quick research, a tech1/2 is just too much for right now. Don’t want to go down that road. But I did find the software combo I remember reading about.

It’s using tunerpro which is free software and a moates ALDU1 and CABL1 connector. Pretty confident that will work, but if anyone can vouch that’s be great. It’s cost effective but I hope I can find the issue before ordering and waiting for shipping due to a time crunch.

 

When I was spending my own money, I bought a Snap-On MTG2500 about twenty years ago, used, from eBay. Very similar to the more-common and less-expensive MT2500. When that died a year ago or so, I bought a Solus Pro, again used, again from eBay. $350 shipped to my door. I've seen folks buy and recommend the various computer software plus OBD cable solution; and then they come back onto the forum saying they can't get their software to read this parameter, or do that function. I guess they get it figured out...in the meantime I'm cruising along with a genuine scan tool having a single problem in twenty-plus years of using it (Won't perform an auto-bleed on the ABS module of my '97 K2500 plow truck. The newer Snap-On software does that, however. My software is 8.2, that feature got added some time around version 10.x.)

The fuel pressure adapters in general, are not meant for permanent installation. Therefore leakage is a minor problem. I have two adapters, the one that replaces the fuel filter, and the one that screws between the fuel supply hose and the TBI unit. I prefer the one right at the TBI; but some vehicles don't have room there. On those, the fuel-filter job is the only one that works.

Of course you did. The cam turns half as fast as the crank, which is why the cam gear is twice as big as the crank gear. Therefore, the cam is installed on #6 AND #1, depending on whether the dots on the gears are both at 12:00 (#1) or crank gear at 12:00 and cam gear at 6:00 (#6) which is how most folks do it. The DISTRIBUTOR can be screwed-up though. If the distributor was half-a-cam-turn off, the engine would not run at all.

Thus the need for the scan tool, and verifying fuel pressure.

Trying to fix a computer controlled vehicle with no way to communicate with the computer is like talking to a deaf/mute person without knowing sign-language. You can brute-force some interaction; but it's easier, faster, and more-efficient while being enormously less frustrating to have the appropriate equipment.

 

Point taken. I can usually get away with a multimeter on older cars but in this case all bets are off with aftermarket parts swapped in.

I did some reading and found an Actron CP9110 that comes with the GM obd1 cartridge and cable. From what I read these were competitor scan tools with the snap on and OTC scanners back then. Tempted to get it since it’s about 90 bucks shipped.

The snap on scanners you mentioned I did find on eBay as well, but most of them only come with the obd2 adapters and/or no cartridges for around the 2-300 dollar range. It’s just a bit out of my spending range right now and it’s also a matter of the time issue to wait for the money + shipping.

 

It's sounds like you haven't got the distributor installed correctly. The just a WAG from the cheap seats but it plays out like it's ignition/timing related. Seeing as the distributor has been removed and reinstalled, there is that possibility.

 

I believe it’s ignition related too. It just behaves like the timing is way too retarded. I think it may just come down to how rushed this has all become and trying my best to not rush through steps but we know how that goes when time is key.

I have the van about an hour away from my job so it’s a non stop game of time management and frustration.

Having time to think clearly about it, my plan of attack is to verify that the distributor is positioned correctly, and I want to check the knock sensor. I’m thinking about what could cause the ECU to retard the timing outside of incorrect distributor install, and the electronic spark control system is what comes to mind. Here’s to hoping I don’t have to pull out the oscope to verify the ICM/ECU signals.

I know I did disconnect the knock sensor when pulling the oil pan to get the timing cover on and I noticed it had some wiggle to it. Could be a broken connector at the sensor itself. I’ll resistance test it and verify the harness wiring. I’m lucky to have the service manual so I have all the specs.

 

IF the timing pointer is correct for the damper; and
IF the damper ring hasn't shifted; and
IF the timing light is connected properly and set to "0" if it's an advance-style light,
THEN the distributor--since it's showing the correct timing with the EST wire disconnected--is positioned where it should be.

Yep, you need to verify the electronic advance, and make sure the knock sensor isn't showing false signals.

 

Yeah I agree, it’s wishful thinking. The balancer was recently purchased, and when it was back off I did inspect it. No separation I can see.

The mark does line up with the tab with a timing light at zero. I’ve pulled the distributor on this engine enough to know where it’s close just by eye when I have to put it back in. No hard start on the engine first time.

The only things that come to mind are somehow the ICM partially failed, the knock sensor is creating false readings, or the EGR is partially opened at idle, which I guess could happen if the vacuum lines were messed up so I’ll verify that. I did buy that actron scan tool, but it’s a waiting game for it to get here. Really hoping I find it on my own before I need it.

Other than that the elephant in the room could be that the mechanical timing wasn’t set right. I just can’t see it being the case though. It definitely gives symptoms of that. I’ve never personally installed a timing set off a tooth or anything. I always turn by hand multiple times and I’ve done much more complex timing jobs than a 350. Anything’s possible though. The timing set I bought was one with three possibilities to install the crank gear for custom timing. I went with the standard configuration for dot to dot and turned it by hand to verify that they both line up. Crank dot at 12, cam dot at 6 to where they point to each other at 1 TDC.

I just can’t imagine this cam has that much in it to make the valve overlap be that long and make it mechanically misfire. It has to be something else. I’m trying to get my compression tester. Also looking to do a leak down test eventually. No reason to suspect bent valves though. Pretty sure the 350 is non interference

 

I also set the valve lash using the up/down play method. Tightened till the very first sign of no slack. Turned the engine by hand in quarter increments, tightened the remaining that had slack to zero lash, and then a final 3/4 turn on all of them. I suppose I could readjust them with it running if I want to rule it out at one point.

Could also check the resistance on the ECT at different temps to see if it’s a reasonable value.

Total shot in the dark, but could it be the higher strength valve springs on the stock TBI heads? The springs seemed to fit fine but I know they’re stronger for the L31 cam. I noticed when I turned the engine by hand after I had this running issue it was much harder than I remember with the spark plugs in. Figured this was because of the stronger springs. Now I’m wondering if that’s making the valves not open fully or something to that effect. Idk, everything I read up on suggested to just swap the parts over and even on a stock TBI head it should work fine. No sign of rocker studs being pulled on the head either. All the rockers seem to be moving normally and no noises.

 

Easy enough to verify the EGR. Take the vacuum hose off of the EGR valve, and plug the hose. The EGR cannot open; although it could be stuck open or partially-open. Perhaps hanging-up on a fleck of carbon. Lifting the diaphragm manually and releasing it might crush the carbon and get it to seal again, otherwise remove the valve and solvent clean the valve and the manifold passages.

This is why I won't install a cam without a dial indicator and a degree wheel. If there's problems later, you're never sure if the cam timing is correct.

A compression test is the quickest/fastest way to check cam timing, but it's not failure-proof. If you have reasonable cranking compression, the cam timing can't be far off. But it can be a little off. In the end, there's no substitute for that dial indicator and degree wheel.

For the record, crank dot at 12:00 and cam dot at 6:00 puts the #1 AND #6 pistons at "TDC", the difference is that #1 is at TDC Exhaust stroke, starting the intake stroke, and #6 is at TDC Compression stroke, starting the power stroke. The distributor has to be set to point near #6 terminal on the cap, not #1 terminal. I tried to explain this in a prior post. When both the crank and the cam dots are at 12:00, the distributor can be positioned so the rotor points to #1.

IF this was wrong, the engine would not run at all.

Yes. It's a fairly-pathetic, stock cam.

Non-interference??? Good luck with that. The piston has valve reliefs so that the piston clears the valves at TDC-Exhaust, when both valves are only slightly open. At full valve lift, the piston will smash both valves.

Did they ALL have slack to begin with? If not, some could very well be over-tightened.

Perfect starter-job for your new scan tool. No need to check resistance when the actual temperature value should be displayed on the scan tool screen.

Aftermarket valve springs are MUCH stiffer than OEM Vortec springs, which by performance standards, are very limp.

 

Got some time to work on it tonight. EGR was really easy as you mentioned. I just pulled the line, verified it had no vacuum, then pulled up manually on the valve and you could hear the stumble. I didn't expect it to be the problem. I bought it a while back as a genuine GM NOS off ebay.


I realized when I mentioned the 1/6 TDC thing that it didn't make any sense after you pointed it out. Laughed at that one. Was really lost in deep thought about the timing and got ahead of myself. I have to get my compression tester and I'll be on it sometime this weekend. I have a dial indicator to at least test lift with it installed and verify it isn't a wiped lobe (doubt it).

When I started it today it fired up instantly, but it got choppy fast. You snap the throttle and it'll respond, but it misses hard still at idle. Obvious popping through exhaust. I was able to test fuel pressure. Drumroll...7psi KOEO and 7psi running. I tried bumping the FPR spring on the stock housing that has the security torx at the bottom, and it didn't change anything. Idk how it was running that low, but it still does. Now I know this seems like I found the problem, but I have some skepticism I wanted to pick your brain about before I put any more money into this including having to drop that gigantic van tank.

There's no doubt in my mind that before I disassembled the engine that the stock cam ran on that 7-8psi even if it's out of spec. Does this actually seem like the smoking gun here or more like a problem added onto an issue I have yet to find? In other words, does that L31 cam need that much more fuel pressure that it's reacting that bad? Even with the very close specs? Because if not I feel like that's just a problem I discovered but might not be the main issue. Especially since if I open the throttle it responds well even if it still has the slight stumble.

The injectors have a good looking cone pattern as I increase throttle, if anything it has some dribbling within the cone but I would say that I've noticed that since having the van and it's never been an issue enough for me to mess with it. It's just at idle that its struggling the most. From my experience fuel related symptoms usually get worse as you increase the throttle. Not to mention the induction firing going on in the exhaust. Seems counterintuitive to think low fuel pressure being the cause of that vs engine mechanical/ignition related.

Also, the knock sensor was way out of spec. Supposed to be 3.9k ohms, mine was at 100k. Replaced it, but problem is still the same.


Thats good to know that it isn't.

They all did. I had each rocker completely backed off and tightened as I pulled up on the pushrod. I made sure I wasn't resting my socket on the rocker too.


Yeah I figured it likely wasn't the springs.

I sorta did do a leak down test on it too when I swapped the valve springs. I just put air into the spark plug hole to hold the valves up. I noticed cyl 1 had some decent leakage past the rings. The pitch would change when I put my hand over the lifter bores before anything was installed. But not enough that I felt concern. All the other cylinders had some normal amount of air getting past the valves for an older engine thats got ~90psi of constant air. Nothing that was some obvious bent/burnt valve. The miss/popping isn't a pattern miss like you would hear with a incorrectly placed plug wire. It's a random popping so I can't say it seems to be related to one cylinder in particular.

 

Runs good until the lifters pump up? I'd look at re-doing the lifter preload adjustment.

Verify that the pump is getting proper voltage/amperage. Verify that it's got proper ground.

If the electrical is adequate...time to drop the tank.

"Spec" is 9--13 psi. You're below spec. That can't be good.

My K1500 has aftermarket heads and intake manifold along with the Vortec cam. Seemed to want more fuel pressure than the 11.5 it had originally. It's 14-ish now.

No, I don't think fuel pressure is the "only" problem here. But it's absolutely not helping things, being low on pressure and probably low on volume.

What is "induction firing in the exhaust"?

I don't understand AT ALL. The lifter bores aren't pressurized by the air going into the plug holes.

 

You may be onto something here. It’s such a brief period of time that it seems to run smooth until you see and hear it start to shake. I think I’ll adjust with it running and see if there is improvement.

I’ll do that when I get down there next time. I have a feeling it’s going to be a worn pump. It’s definitely a factory pump.

Yeah, I know it has to happen. Sucks on my wallet but I’ll try to make it happen sooner than later.

My bad I meant exhaust backfire. I’ve heard induction used as a interchangeable term for intake backfire and I get caught using it sometimes.

Ah what I meant is that when I had the intake off, no lifters or cam in, I was changing the springs so I put constant compressor air into the spark plug hole via a compression gauge hose without the schrader valve in it.

When I did it on number 1, you could tell the air was getting past the rings and going into the crankcase because you could hear the air come up through the lifter valley. I only mentioned the lifter bores because the bore made a pronounced frequency that I could change when I put my palm over the bore to verify where I heard the air coming though. Nothing crazy like “the rings are gone” but not great at the same time. I wouldn’t say it’s the reason I’m having such bad misfires.

 

Hearing leakage in the crankcase means very little. Doesn't take much leakage to make lots of resonant noise.

That's why leakdown testers have gauges--there's something to measure the leakage. The next problem comes with the design of the leakdown tester. But that's another posting.

 

For sure. I know it’s not the proper leak down tool, more so that it had more air escaping than the others that I noticed. Nothing like a burned valve type rush of air though.

 

Figured out the issue. It was an ignition misfire. One plug was fouled for some reason, and the other had the ground touching the electrode. Must have pinched it within the time I had it out as I was doing the cam swap. Did a compression test for the hell of it and all numbers good.

Fixed both those issues and she purrs now. Took it for a test drive and it responded well. I can definitely feel a bump in throttle response and how those jack rabbit take offs feel from a stop. Kinda comical, but still a nice addition to getting the bad flat tappet issue fixed.

Still want to fix the fuel issue. I’ll probably get the injectors flow tested/balanced, do the FPR adjuster upgrade, and replace the pump.

Also had that scan tool come in and it worked out well. Nice to have for future issues.

Thanks again to everyone that helped out. It was really helpful to have people that have done these swaps and beyond to give me direction on what to expect and what could be wrong. You guys are awesome for taking your time with this thread. Maybe I’ll update a little while from now to give anybody else that finds this thread useful some success closure.

 

Excellent.
And thanks for posting the findings. So many times these kind of threads end with no resolution even though the OP may have solved the problem.

 

I can’t send you a pm but if OP isn’t interested I would be.

 

Just wanted to give a 6 month update in case anyone was to do the same cam swap I did and wanted confidence that it held up.

It’s going strong. Still smooth as the day I got it going with the swapped cam. I’ve ran it hard too. Many wot and no issues.

I will give a few more details I learned after the swap. I think I mentioned I ended up replacing my fuel injectors to new ones when I replaced my pump, and bumped the pressure to 14.5 by modding the fpr to have an adjustable bolt at the bottom for spring pressure. When I did that I also bought the raised spacer for the fuel pod. What ended up happening was the fuel was being sprayed so wide outside of the bore that it was just creating droplets of gas all around the Venturi/pod casting area. It also lost some power when I test drove it. What I figure happened was the new injectors having a great cone shaped spray pattern along with the bump in fuel pressure made the injectors have too wide of a spray circumference along with the height increase. I think it may have went as far as having some fuel droplets get sucked into the iac area, and probably just made the o2 sensor wig out trying to get everything in fuel control. It also smelled very rich out the tailpipe, and would do the classic subtle misfire stutter/popping at idle. Maybe because I didn’t have a bored out tb or the 454 tb swap? Not sure. Either way I took the spacer off and everything went back to normal. Not sure if anyone else would run into the same problem, but just in case, those were my findings.

Also to mention, I run shelll rotella t6 5w-40. I initially ran the common 15w-40 but I noticed I had lifter tick a little too long on initial startup than I cared for. I know I don’t necessarily need the rotella due to not having a flat tappet cam anymore, but I know it’s a tried and true oil for sbc’s either way so I continued doing so. With the 5w-40 no lifter tick in the mornings. YMMV.

 

Thanks again for the updates. These keep the thread vital and relevant.

As for the Rotella, while I do understand that not all Rotella is created equally there is some evidence that suggests that some varieties lack the anti-foaming agents that are present in other engine oils.
The diesel engines that they were designed for are typically low RPM and as such don't require the additives needed for a faster spinning engine. Maybe check the label and acquaint yourself with the engine oil specifications.

I've always run a top quality synthetic. At one time I was doing that as well as adding a bottle of GM's Engine Oil Supplement (EOS).
I'm not saying that you do the same however you owe it to yourself to check it out. I'd hate to see that nicely running engine of yours get messed up because the oil gets full of entrained air.

 

Thanks for the feedback. I do remember reading about the anti foaming agents being a cause to have mixed reviews for using in a gas engine. It seems that some people claim it still wouldn’t anti-foam at higher rpm because it was designed to go through high pressure oil pumps, others believe you’re gambling that it may not work as well as is designed for the lower running rpms of a diese engine. I’m no chemical engineer, hard to say even with TDS info since it wasn’t technically designed for what some of us use it for. I know at some point I’ve seen oil analysis results in forums and so on.

It’s nice to know that T6 is a full synthetic oil, but you may be swaying me to go back to traditional full synthetic oil designed for gas engines as I use in my other vehicles. Gotta get the zinc content stuff out of my head now knowing I don’t have that potential issue anymore.

Funny you mention GM EOS. I love that stuff. Used it to break in the new lifters I originally replaced on the flat tappet cam that ended up being bad from factory, which is why this whole swap happened in the first place. But, it did do it’s job in not wiping the cam. I used it because I have the FSM that stated to use the eos for new lifters and to put the rest of the bottle in from what I remember. At least for some reason or another I concluded that’s what I was supposed to do. That’s the only controversy I’ve seen people debate, is how it says on the back of the bottle to not add as an oil additive. I’ve heard that’s more for the emissions concerns of the zinc poisoning the cat, and nothing else.

I know people swear by it as an assembly oil, which I believe and have used it as such. It’s what I used to install this cam as well. Funny when I go to the dealership to get a few bottles and only the senior guys know what I’m talking about and have to check if they have old stock. I know it’s still being produced, but sometimes it’s hard to come by and usually dealers don’t just have it on shelf. Same with the GM X66P piston and ring cleaner. (I own a Saturn as well). Stuff is discontinued it seems, and the online prices are insane. Called around Buick dealerships and the like and some found a couple bottles still on shelf and I grabbed them up. But everything’s harder to come by these days it seems…Anyway, enough of my digression. I’ll update if anything major happens in the future.