Performance Timing Table Chevy 5.7 Liter TBI ECM 1227747

[buddrow]

Ok, bear with me here if you will.

1. Are those cam specs cam lift or valve lift?
2. Mark, just out of curiosity what is "too high" for knock counts? my stock asdu runs about 20-40 on average. Conversely my buddies truck ive been tuning on, with the asdu bin had knock counts running ramped at idle not to mention on a drive. Ill try to log some this weekend and share with you. I did get it to idle steady and improved driveability over the asdu with the modded chip. need to lean out the low end a little but over all it runs reasonably well. I know there is still more there being a 383cu. in. though.

Happy Tuning,

Buddrow

[dave w]

Are those cam specs cam lift or valve lift?

Figures below the "Lift @1.5" are valve lift, using 1.5 ratio rocker arms. Cam lift multiplied by rocker arm ratio = valve lift.

dave w

[Fast355]

Figures below the "Lift @1.5" are valve lift, using 1.5 ratio rocker arms. Cam lift multiplied by rocker arm ratio = valve lift.

dave w

Dave the 350 TBI uses the 274 aka gm 929 cam. I was a little off on the lift, but that is due to the goodwrench advertised specs being wrong. I was confusing 156 and 773. They are basically the same with 1* wider lsa on the 156.

[dave w]

Dave the 350 TBI uses the 274 aka gm 929 cam. I was a little off on the lift, but that is due to the goodwrench advertised specs being wrong. I was confusing 156 and 773. They are basically the same with 1* wider lsa on the 156.

Fast,
I often use re-ground camshafts ( http://www.oregoncamshaft.com ), so I'll measure the camshaft to make sure I have a good core. I've only needed to measured a few TBI camshafts. It's been a few years since I last measured a TBI camshaft, but I'm remembering the lift of the three or four I measured was something close to .350 / .380 @ 1.5 rocker arm ratio.

I've used the TBI performance timing table I posted on several different EFI friendly camshaft profiles, up to about .423 / .443 lift @ 1.5 rocker arm ratio. Depending on the vehicle I'm working with, I've needed to make adjustments to the timing table, that's tuning. Camshaft profiles effect cylinder pressures, so there is not a "one size fit's all" performance timing table.

The intent for posting the TBI performance timing table was to help others learn spark tuning by experimenting with a decent / proven timing table to begin with. My method to develop a good timing tables involves using data log analysis with Excel. I use Excel to trend spark advance Kpa vs. RPM vs. MPH. Ever look at Kpa vs. high knock counts?

dave w

[Fast355]

Fast,
I often use re-ground camshafts ( http://www.oregoncamshaft.com ), so I'll measure the camshaft to make sure I have a good core. I've only needed to measured a few TBI camshafts. It's been a few years since I last measured a TBI camshaft, but I'm remembering the lift of the three or four I measured was something close to .350 / .380 @ 1.5 rocker arm ratio.

I've used the TBI performance timing table I posted on several different EFI friendly camshaft profiles, up to about .423 / .443 lift @ 1.5 rocker arm ratio. Depending on the vehicle I'm working with, I've needed to make adjustments to the timing table, that's tuning. Camshaft profiles effect cylinder pressures, so there is not a "one size fit's all" performance timing table.

The intent for posting the TBI performance timing table was to help others learn spark tuning by experimenting with a decent / proven timing table to begin with. My method to develop a good timing tables involves using data log analysis with Excel. I use Excel to trend spark advance Kpa vs. RPM vs. MPH. Ever look at Kpa vs. high knock counts?

dave w

Understand that completely. I use TPS vs MAP vs MPH/RPM alot myself.

I have run the Mellings MTC1 and Federal Mougal CS1014R in TBI engines with no more than a slight fuel pressure and timing tweak with good results.