Tbi Vortec swap ignition problems

[Mule89]

So what should have been a simple swap has kinda turned in to a huge head ache dealing with ignition. This is a 99 vortec block with stock cam lifters and heads the rotating assembly is from an 89 TBI engine (extremely low budget rebuild) all new bearings and also has a big block chevy oil pump because I was tired of screwing with the low oil pressure that kill 3 of the 4 engines. When you crank it over it sounds like only 4 cylinders are hitting but it also blows out the throttle body like it has a intake valve not closing all the way, and it is getting plenty of fuel. I have already confirmed it's not 180° out of time. My thought is the rat pump is pumping up the lifters so much that it opens the valves a bit. Usually my dad or my Automotive Shop teacher know what is possibly going on but when I explain and and showed everything to my dad he said "I have no idea" and we are on spring break so can't really get a hold of my shop teacher on tips to eliminate the possible problems because he used to be a GM dealer tech that worked on these trucks brand new and he also has OBD1 scan tool that with live display. I'm trying to figure it out but I'm only 18 I don't have the experience to know what I need to do. I should also note that I'm using 10w-30 should I run a thiner oil like 0w-20 so that the lifters are not being pumped up so quickly or am I way off and sound like a mad man? I'm just really wanting to hear it run because it is my favorite truck. I do not have a compression tester but might be able to come up with something.

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This engine is going to eventually have a turbo on it but I just want to get it running good with out it before I do that also another reason I used the big block oil pump. If anyone can help me out with this it would be greatly appreciated.

 

[Schurkey]

VERY unlikely that you have enough oil pressure to expand the lifters against valve spring pressure. Assuming you don't have broken valve springs, it would take something like 150 psi of oil pressure. More, if you have stiff aftermarket springs.

I'd be more likely to believe you've got leaking intake valves, possibly due to misadjusted lifter preload.

I like to adjust lifter preload with the intake manifold OFF, so I can see the preload. That's not practical now--but you might back off the adjuster nuts and re-set preload. Some guys try to find the zero-lash point by spinning the pushrods. I don't like that, if a person has strong fingers they'll spin even after you have gone beyond the zero-lash point. I prefer to "rock" the rocker arm in it's normal direction (not side-to-side); when it's just tight enough so it won't rock any more you're at zero lash.

I assume you're using the pushrods that came with the Vortec engine. The TBI pushrods would be too long.

Fastest way to set lifter preload: (You might want to start with the crank/damper at TDC, so you have the timing marks to guide you--but you don't have to. The crank can be at ANY position in the rotation to start with.) Back off ALL the adjuster nuts so the rockers rock. Tighten them ALL to zero-lash, but not beyond. Turn the crank EXACTLY 1 full turn. Some of the rockers will be loose. Leave the tight ones alone. Tighten ONLY the loose ones to zero-lash.

Tighten ALL the adjuster nuts "your choice" of preload. Factory spec is one turn. Most guys go 1/2 turn. Anything on that order will be fine. Put the valve covers back on, and have a beer. You're done.

A leakdown test might be useful. You can listen for air pressure escaping at the tailpipe (exhaust valve leaking) at the carb/throttle body (intake valve leaking) at the oil fill cap (leakage past the rings) and look for bubbles at the radiator cap opening (leakage past a cracked casting or failed head gasket.) There will always be leakage past the rings, some is normal, too much is cause for concern. There should be NO leakage past the valves or gasket.

An ordinary compression test can tell you that you have low compression, but it won't tell you why.





Are you using the "special" Big-block pump set up for small-blocks, or a genuine Big-block pump? Is the pickup tube spaced properly from the bottom of the oil pan? Did you check the pressure relief valve for proper operation?

 

[retorq]

If air is coming back out the throttle body you have a base timing issue as in TDC isn't anywhere near where you think it is or there are valves hung open due to improper installation. I would pull the plugs, pull the covers, back off all the rockers nuts and spin it with the starter to see if it's smooth. Then find TDC with your finger, verify with the timing mark and balancer, then stab your distributor in correctly, that should get it started. Then adjust your rockers.

Also since you have the newer block and newer heads you have to make sure your using the right water pump and hook up the coolant bypass correctly.

 

[Schurkey]

since you have the newer block and newer heads you have to make sure your using the right water pump and hook up the coolant bypass correctly.

Good catch. The Vortec water pump (and block face) doesn't have a bypass hole on the passenger side of the block, so you need to create a bypass like the factory did. Or drill the Vortec block using a water-pump gasket as a template to create the bypass hole suitable for the TBI water pump.

Some Vortec blocks have no hole at all, you have to drill all the way through the casting--maybe 3/4 inch before you break-through the casting. Other blocks have the hole started, but not full-depth, so you only have to drill the last (deepest) part, and the location is impossible to miss.

I start with a 1/8" bit to make a pilot hole, then finish up with a 3/8" bit.

 

[Mule89]

I eleminated the oil pump as part of the problem and it is a big block pump. turns out the dizzy had issues with the cap actually, the battery that was "good" only had 43% charge, and plugs that I left in where fouled.

 

[Mule89]

Good catch. The Vortec water pump (and block face) doesn't have a bypass hole on the passenger side of the block, so you need to create a bypass like the factory did. Or drill the Vortec block using a water-pump gasket as a template to create the bypass hole suitable for the TBI water pump.

Some Vortec blocks have no hole at all, you have to drill all the way through the casting--maybe 3/4 inch before you break-through the casting. Other blocks have the hole started, but not full-depth, so you only have to drill the last (deepest) part, and the location is impossible to miss.

I start with a 1/8" bit to make a pilot hole, then finish up with a 3/8" bit.

Already have an external bypass. What doesn't make sense it back fired out the TB blew compression out the intake. It runs now thought but can anyone explain because it sounds like it was 180°

 

[retorq]

It's already been explained, on the compression stroke an intake valve or multiple valves were open, compression was escaping out and back thru the throttle body. Either your cam was installed wrong or your base valve adjustment was wrong. If you have it running now then the cam is probably installed correctly.

 

[Mule89]

It's already been explained, on the compression stroke an intake valve or multiple valves were open, compression was escaping out and back thru the throttle body. Either your cam was installed wrong or your base valve adjustment was wrong. If you have it running now then the cam is probably installed correctly.

Yeah that's what has me puzzled because the cam was installed correctly, distributor was installed and set correctly, and it still acted like it was 180 out