i had my motor completely rebuilt and had afr 190cc heads and crane rockers installed and it doesnt seem any faster then it did before with the factory heads. what could the problem be? other mods listed below.

 

Did you up the compression for alluminum heads or did you leave it the same?

 

Also, have you burnt a new eprom to take advantage of those new heads? AFRs can generally handle a lot more spark advance than stock heads, and that is key to making more power.

Also, that TPI intake is probably not helping you as much as you could with a Superram or Miniram. What about the cam?

 

the heads were supposed to be kept to factory specs as recommended by afr. i beleave they milled them to 64cc.

 

Perhaps when the motor was rebuilt the timing was set back to stock? Have you checked that?

 

i know for a fact the timing was set back to factory settings at 6 degrees. would that make that much of a difference? does anyone know what the slp cam timing should be set at?

i have a thermomaster chip would a custom chip be better?

i also have an adjustable fuel regulator and i told him to set it at 50psi he might of changed it back to a lower setting.

 

I belive in the KISS method of troubleshooting:

1. do you have optimum compression (aka new properly installed head gasket?)
2. new spark plugs (or even a spark in all cylinders?)
3. cylinders recieving proper amount of fuel
4. timing was already mentioned
5. operable maf/O2 sensors

if everything is on track look at the rest of your mods, your intake side kicks @$$ but your rear end gears and exhaust (except headers) are killing you.

The rest is politics. Good luck!

 

I'd say give it more timing and check how it is running fuel wise, definitely check the plugs.

 

when are the gears getting installed??? whats the fuel pressure set at??? what is your base timming??? with your current mods you should notice an improvement but, your mods with those gears you are not going to get the performance you want...

zroc

 

Oh yes. I also notice the comments about "changing the timing back to 6*". This is NOT the way to advance the timing on an EFI car. It should be done within the eprom.

Just advancing your timing say 4* can trigger knock retard in areas where the engine cannot tolerate it (such as lower rpms before peak torque). Once detonation occurs (whether audible or not), you performance is killed.

Basically, you need the spark advance to start building just before peak TQ to max HP, along with a mixture somewhere between 12.6-13.1. Those AFRs should probably make max power somewhere around 34-36* near peak TQ. Most of the stock eproms for GM cars have the max timing occuring somewhere around 28-30* with up to 12* of knock retard at the slightest hint of detonation.

Remember also that the your peak TQ is occurring at different points most likely with those heads, so where you're max timing is going to occur is also going to change.

If you were to talk to a "racer using a carb" about your swap, he'd recommend you change the "curve" in the distributor to get max HP to match the new heads. EFI is even more particular - "mechanical fixes" are not the answer. You have to do it inside the eprom.

 

Also how amany miles do you have on this rebuilt engine? I just rebuilt a 350 and droped it into the firebird last month and it took over 500 miles before that sucker loosend up, 780mi.
SSC

 

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