cam advance

[1993blazerlt]

Would i be able to run a cam with 4 degrees advance or retard with out getting a new TBI chip? Also i forget which gives you more low end advance or retarted cam timming?

[ZR1-S10]

Yes your need a new chip because the injectors relay on the cam sensor. Advancing the timing gives you more low-end. What brand timing set do you have?

[1993blazerlt]

i am looking at getting a summit timing set it has 4 degrees either way on it and this is a TBI engine so there are only two injectors does that make a difference?

[Matt 4.3 TBI]

Which cam are you going to use? Cam advance or retard will still make a difference in how the engine performs, regardless of how it gets fuel. My timing set had 4 retard, 0 and 4 advance. The Edelbrock insists you install it at 0*, since it has advance built into the grind. I haven't found a reliable calculator to tell how far the powerband will shift in rpm's by advancing or retarding.

[1993blazerlt]

this is just with a stock cam i think i will advance it

[Matt 4.3 TBI]

I would really consider changing the cam if you're already tearing it down. The stock TBI cam has a pretty low grind, even the stock CPI cam is much better.

Here's the lobe lift specs for comparison:
TBI intake .390 exhaust .410
CPI intake .434 exhaust .442
And the Edelbrock I'm using: intake .479 exhaust .488

I haven't found valve timing info from each of the stock cams to get and idea how advancing it will affect the performance. The TBI can definitely benefit from more duration and lift (can get more lift with rocker arms though).

[1993blazerlt]

how much cam can i put in with out a new chip?

[Matt 4.3 TBI]

Edelbrock gives you a chip with their intake, but it's not much better than stock, just more timing advance. I was using my Hypertech at the time of my rebuild (again, basicially stock fuel maps, just more timing) and it handled my cam fine.

[1993blazerlt]

how much power do you think you are getting out of your set up?

[Matt 4.3 TBI]

The estimate jjwalker and I came up with from his engine builder program was about 209 hp and 255 ft/lbs at the flywheel. I've done quite a bit more than just a new cam, though :D

[Matt 4.3 TBI]

Oh, I forgot to reply about the cam sensor.... in short, there isn't one on a TBI engine. The ECM controls fuel with the TPS, MAP, CTS and O2 sensors according to it's programmed fuel maps. It won't go into closed loop and start reading from the O2 to fine-tune until the coolant temp sensor gets over about 150*.

[1993blazerlt]

ok now i am looking to get more bottom end out of this and because of the cost will stay with a stock cam should i advance it or retard it for advance . It is not even my engine so i am not being cheap i am helpi0ng a friend on his and he is very low on money

[Matt 4.3 TBI]

I would advance it then.

[Bubba32716]

were did you get the stock cam spec from?