I have a 1995 3000gt and my friend has a 2004 blazer LS 2wd that he has built a motor for and wants to trade for my car. The blazer is in good condition and has a cowl hood. The bottom end of the motor is a non vortec 4.3 from an older s10 truck that was carbureted. It is rebuilt with the 2004 vortec heads on it. The crankshaft and rods are stock but has .125 dome pistons (i think 10:1 compression). The motor is bored over .30 i believe, and has roller lifters with a roller cam. The blazer will crank up and runs good when its cold (check engine light is on) but no knocks. but when it warms up the ecu retards the timing and makes the motor start knocking. And when the motor is shut off it will not crank back until its cooled back down and the battery has to be disconnected. Oh and its got the stock 700r4 tranny.

Any help would be greatly appreciated im trying to decide what to do.


Andrew

 

[quote=amorgan93;451158

Any help would be greatly appreciated im trying to decide what to do.


Andrew[/quote]

Run Andrew Run!

 

+1!!!

 

I would very politely decline the swap.

 

that picture makes the blazer look hella long, rims look nice on it tho

 

Back away slowly....... To make that motor run decently you'd need to go the rest of the way and put a carb on it, pre-computer HEI distributor, and disconnect the O2 sensors. Or, you'd need a seriously custom re-tune for the PCM chip but with the transmission you'd always have emissions related codes anyhow. Kiss emission inspection goodbye.

 

ok so it actually has a 90 or 91 block & bottom end with the vortec heads that have been ported and polished. There has been a lot of money spent on the engine. The engine runs great when its cold, runs like a scalded dog, but when it reaches operating temp is when it starts the knocking. Why would i need to go carbed? I know the computer is capable of running it because it runs so good when cold. why disconnect the o2 sensors?

my 3000gt isnt exactly in pristine condition. Its been hit on the other side and could use some body work, and paint. The blazer is a nicer vehicle. And the 3000gt isnt my daily driver, i have a toyota daily driver.

really need some explanations other than just "avoid"

thanks again

 

An explanation of everything the PCM (powertrain control module) computer is way beyond me but I suppose it's the problem. I suggested carbing it and an HEI distributor (with simple mechanical and vacuum advance) for ease in tuning and they're well understood parts and an average person can access all parts to tune the engine in properly. When you start the truck (cold) the PCM automatically enriches your fuel sytem. I "think" it locks out EGR actuation at first but it monitors some sensors (like block temp and O2 sensors to make sure they're responding to fuel curve and timing adjustments) It's called "open loop" As the engine warms up it'll go into closed loop monitoring all sensors adjusting fuel pulse width and ignition timing as it feels its appropriate to keep the engine running well and to keep it within emission parameters. What is "appropriate values" and how it all interacts is based on programming and values entered at the factory appropriate for your motor. Raising the compression ratio from 8.5:1 to 10:1 is a significant change in terms of how the fuel is burned in the cylinder and the composition of the exhaust gases. It also changes what is appropriate ignition timing. The camshaft profile change also sounds very significant compared to the stock baseline once again changing your exhaust gas composition. When the PCM makes changes to the fuel and timing curves based on input from the O2 sensors they're no longer correct decisions because those pre-programmed values aren't appropriate to *that* engine. This is how 3rd party companies make a living selling EEPROM tuners. The PCM in the vehicle can adjust for small changes but the allowed range of variance values isn't large enough to accommodate *that* motor without significant reprogramming. I also mentioned the transmission because that truck was originally equipped with an electronically controlled (and monitored) transmission. To mention one problem alone not being able to monitor "slippage", which an excess amount qualifies as an emissions related failure, is a guaranteed check engine light and emissions trouble code. Get the engine running right and it sounds like a "fun" vehicle to drive but I have my doubts in terms of work and money involved to make it what I think of as a a daily driver including regarding annual emissions inspection as a minor annoyance.

 

there is no way i could carb a 2004 and pass emissions. if it was a 95 or below yea. but i still need to pass emissions. im pretty sure i could use Apexi SAFC-ii to trick the computer and provide it more fuel, but passing emissions is gonna mean getting the check engine light to go away. Could the knock sensor be whats causing it to knock? misreading the high compression/cam as knock? and i noticed there are virtually no aftermarket parts for the 4.3 (injectors, headers, etc...).

from what im reading the crankshaft in these motors is extremely weak, and can break even below 250hp. Several google searches have yielded me the same information about the crankshaft and 4l60e being weak. So i'm not sure that it would last long even if i did get it running. i mean my 3000gt motor has forged crank, and rods stock. Its only a 2 bolt main but they hold up to about 700 hp. DId the typhoon and cyclone have the same crank?

 

Y'know it'd be interesting to know just what codes are being set. Also what octane fuel are you feeding this thing? Originally the motor was about 8.5:1, I hope you're using some better fuel than 87 octane. Rereading the original post I realized I have no clue what type of cam is in there, the original cam was a roller too.