Vortec bottom end/TBI top end: timing?

[RaysnCayne]

Hey guys,
I'm looking to put the top end parts of a 5.7 TBI (heads, intake, TBI, TBI ignition) on a late-90s Vortec 5.7 bottom end (short block).
My question at the moment is: will I be able to set timing with the TBI HEI (run by the factory TBI ECU) using the molded-in timing mark on the factory, plastic timing chain cover of the Vortec?
As in: that mark is 0º just like it would be if I had the original TBI bottom end with the timing "tube" on the original sheetmetal timing chain cover?
It doesn't look like the TBI and Vortec timing marks are in the same spot to me.

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[xm20k]

You can swap the timing cover, my Vortec block is running a stamped timing cover and an adjustable timing tab.

 

[RaysnCayne]

But what if I want to keep the plastic OE timing cover? (Say, for budget/already have it in-hand reasons.) Will this Vortec cover work?

 

[77Dmax]

You would be miles ahead to buy the TBI intake and run the vortec heads. Huge power increase.

But, yeah you can leave the plastic cover in place. The timing mark will work just fine.

 

[RaysnCayne]

And about $500 behind for that unicorn intake.
(Missed out on a used one a year ago for $200. )

Just trying to do a cheap, roller-cammed TBI 5.7 for my daily with parts I have lying around. Not lookin' to make any real power with this build.

 

[77Dmax]

You can buy a square bore intake for relatively cheap and use the TBI adapter. That's what i was going to do, but sold my 93 before I had the chance

 

[AyWoSch Motors]

But what if I want to keep the plastic OE timing cover? (Say, for budget/already have it in-hand reasons.) Will this Vortec cover work?

What i would do, is roll the engine over to TDC. Put a straw or something down the spark plug hole,or if you have a bore scope even better. Get the cylinder right at top deap, and middle of its dwell period, and see where your timing mark on the balancer sits against the timing cover.
If it lines up, perfect, if it doesn't, either swap out for a vortec era balancer, or use a dremel and make your own mark on the cover, wherever it lines up.

 

[xm20k]

Find TDC and see if it lines up if not a cover gasket set and pointer are really not that expensive. If the balancer is from that block no reason to change it, and it should line up if your just swapping heads and intake and the bottom end is all the original parts.

Pardon Our Interruption

Honestly going to a TBI your loosing 40-50HP the Vortec heads are superior even with a carb will make better power. The stock Vortec made 255 and the TBI around 210. Both are still better than the 150-160HP turd that came in these trucks.

 

[RanchWelder]

Here. Look up my sig and read my build details.
Take what works for you and do what you like.
The cover on my 1998 Roller block WAS plastic and is now the steel cover from my 1987 reman engine.
I bought taps to drill the extra bolt holes the old steel cover uses and never needed them. They seal up OK without the extra 2 bolts.

Timing marks differ from the size of the balancer and the 305 vs 350 timing covers.


Timing any TBI engine, no matter which heads, really does not require a timing light.
You point number one cylinder to the number 1 rotor and cap it.
If you are off a tooth, you fix it. 180 out, same fix but frustrating with the hood in place.
Take off the hood, don't do it alone, don't break the windshield, time it.

If it starts and you rotate till it drops out or stalls, put it back where it was a few degrees from where it dropped out and drive it.
You'll have plenty of time to adjust it back and forth as you get the drips from the TBI or leaking o-rings repaired everywhere.

Vortec Heads are worth the money over remanufacturing TBI heads any day of the week.

Skip a beer or save a few bucks up and find the nice machine shop guy with reliable castings and have him build you a set from his inventory.

Read as much of my build threads as you can instead of asking here, then come back with a plan you can afford and show us what you did?

xm20k is helping you to be satisfied with your investment after all the work is done.
Using the 87 TBI heads is a waste of time.

Everyone comes here to cheat the cost, but the labor vs what you end up with can be very disappointing, with poor head and cam selection.
No matter how you feed it fuel and air, select a good for your power cam, clean OEM lifters, new oil pump and good heads from a machine shop.

Good Luck!

 

[Ricko1966]

If you are using the vortec balancer and cover it will be fine time it to 0* just like factory. I think you're going to be pleased with the power you're going to pick up below 4000 just having the vortec cam in it. The tbi cam is tiny you'd make a little bit more with vortec but still what you have will be a good engine for a DD and will get decent mpg. Resist the urge to bump the timing,TBI heads don't like lots of timing and it will just hurt your mpg. That's part of the swirl port design,get a really homogonized mixture that lights easy and light it off later. That way the engine does less negative work trying to overcome the rising cylinder pressure on the way to TDC ,by lighting it a little later the piston isn't being pushed backwards by the expanding air and fuel. The result is more torque and MPG

 

[RaysnCayne]

Resist the urge to bump the timing,TBI heads don't like lots of timing and it will just hurt your mpg. That's part of the swirl port design,get a really homogonized mixture that lights easy and light it off later. The result is more torque and MPG

Hmm... I'm 4º advanced on the L31 roller cammed-305 TBI I'm currently running, Rick.
I did a basic gasket/oil pump rebuild when I first got my R10 a few years ago.
While I was doing that, a buddy gave me his old L31 cam and told me to jab it in. So I grabbed the roller cam parts from the junkyard. Bought a set of new, proper-length push rods, and jabbed it in. He was adamant I advance it closer to 7º. But I decided to try 4º.
I'm pretty pleased with how it runs the last 2ish years I've had it on the road. (It's gotten 18mpg on long, flat 74mph highway trips.)
But I guess I could dial it back to 0º just to see if that helps.

 

[Ricko1966]

It's the tbi heads specifically that do better down in the 30* total range. If the engine you are talking about isn't swirl ports then we are talking apples and oranges. To find best MBT (minimum best torque) start your timing low check your mph standing start to 500 or 600 hundred yards,use 2 trees as markers. Take off from 1 check your mph at the 2nd ET is irrelevant,looking for mph keep bumping 2 degrees at a time checking mph each time. Mph is going to peak and then plateau. Set your timing at fastest mph that had lowest timing. The short version is,there is no reason to add timing past the point of maximum mph anything more is creating negative work and costing you gas milage,with no benefit. Edit reread your post you say it's tbi heads,sorry. Anyways just check trap speeds maximum trap speed with lowest timing is the goal.

 

[bucket]

I think we've had this discussion before @Ricko1966 but my personal testing over the years has shown that advancing the base timing to 8-10° gives a performance improvement with no negative impact on fuel economy. Regarding the TBI truck engines.

 

[Ricko1966]

I think we've had this discussion before @Ricko1966 but my personal testing over the years has shown that advancing the base timing to 8-10° gives a performance improvement with no negative impact on fuel economy. Regarding the TBI truck engines.

All you have to do is check trap speeds the point where it quits going faster is the point where you stop adding. TBI is kind of a weird case though,because the computer will start pulling timing,unbeknownst to you unless you are data logging.
edit: IMHO trap speed is your best tuning tool for 90% of things Jetting,ignition,tire size,gearing,etc. if you don't have access to a dyno. It shows if you are really making gains or not. Did it go faster or slower that will tell you a lot.

 

[Rustisbest]

Verify TDC, slap a timing tape on there, then shoot it with some satin clear paint so it doesnt come off.
I like the Summit brand. Black with neon yellow numbers make it easy to read and they're marked every 90 degrees making valve adjustment easy too.