tbichips.com (Brian Harris). Useful or Not?

[Fast355]

A few years ago, I had a 93 GMC K2500 4x4 with an NV4500 5 speed that I swapped a 97 Vortec engine into. I scored a "CRUSADER" marine tbi to vortec intake with no egr on EBAY for $100. Based on Brian's recommendation, I installed an LT4 "Hot" cam that my brother had bought for his 1996 Impala SS but didnt use. Bad choice. No torque from that cam in a truck. It didnt have a lift or even bigger tires than stock. I swapped it for an "Extreme 4x4" grind recommended by Comp Cams (I forget the specs) . It made a WORLD of difference. The LT4 cam may have been fine in a high RPM mud truck, but not a street truck. The other problem I had was the spring he sold me for the stock fuel pressure regulator gave me the exact same fuel pressure as the stock spring (?) I tried the adjustable regulator he recommended, but it was a bear to get to and the head stripped off shortly after install. Frustrated, I installed the fuel pump from the donor Vortec truck and an aftermarket adjustable fuel pressure regulator to get my fuel pressure up to the recommended level.

I have no way of knowing whether any power was "left on the table" as I bought the truck with a blown engine, but it seemed to run and tow well for a 350 equipped truck. I always wondered how much power I was missing compared to going to a larger CFM EFI system, or 700 cfm carb. I sold it a few years ago and bought an 01 Silverado HD with a Duramax.

I am now working on a 1991 Olds Custom Cruiser wagon. It had a tired 200k mile TBI 305 that still ran with 0 lbs oil pressure indicated (!). I will be swapping another Vortec 350 into this car. I have a "take out" Ram Jet 350 cam, Comp beehive springs, full roller rockers, GMPP parts vortec to tbi intake ($150 Ebay score). Undecided if I will sheel out cash for headers, or run stock manifolds and full duals. I plan to get it running and see how it runs. Not look for a barnstormer, maybe tow a small pop up camper, etc. I see that the RAMJET intake that bolts to the vortec heads is a possible upgrade. I wonder if it would be worth the extra coin...

If the LT4 Hotcam was not making torque it had a bad tune or was timed wrong. That cam will BOIL tires off even at lower RPMs. In an engine under 10:1 it needs to be advance 3° and installed on a 106° ICL.

I have a Ramjet cam and 1.7 rockers in my Express van and even pulling my 6,000 lbs Jayco travel trailer I find it lacking above 4,000 rpm which I spend ALOT of time at. On steeper hills the 4L80E is in 2nd gear at 70 mph, spinning 4,500 rpm with my foot on the floor.

With my old G-van I had a 10.5:1 Vortec head 383 with TPI using SLP runners that had been siamese ported and tri-y headers. I ran a 232/240 @ .050 cam on a 110° LSA and towed heavy with it. It had a 4L60E and 3.08 gears. Only ran a 2,600 rpm converter in it. 70 in 3rd gear was only about 2,700 rpm.

[Steveshow]

If the LT4 Hotcam was not making torque it had a bad tune or was timed wrong. That cam will BOIL tires off even at lower RPMs. In an engine under 10:1 it needs to be advance 3° and installed on a 106° ICL.

I have a Ramjet cam and 1.7 rockers in my Express van and even pulling my 6,000 lbs Jayco travel trailer I find it lacking above 4,000 rpm which I spend ALOT of time at. On steeper hills the 4L80E is in 2nd gear at 70 mph, spinning 4,500 rpm with my foot on the floor.

With my old G-van I had a 10.5:1 Vortec head 383 with TPI using SLP runners that had been siamese ported and tri-y headers. I ran a 232/240 @ .050 cam on a 110° LSA and towed heavy with it. It had a 4L60E and 3.08 gears. Only ran a 2,600 rpm converter in it. 70 in 3rd gear was only about 2,700 rpm.

Im not sure what the compression ratio of the stock vortec was, but the cam was in fact installed straight up. I did consider doing as you mentioned and advancing the cam to increase torque, but when asked,Brian only told me "it should work as is". Of course comp cams is in the business to sell cams, not give advice on how to make an existing cam work, so i guess i shouldnt be surprised that they didnt suggest advancing the existing cam.

btw, i know that a cam can be installed advanced or retarded by moving the timing gears, but how do you "alter" the centerline? This is how the cam is ground...


on a related note i dont think any cam would make a used vortec 350 with tbi in a 4x4 3/4 to. Truck with 265 70r16 all terrain tires "boil the tires"...

[Fast355]

Im not sure what the compression ratio of the stock vortec was, but the cam was in fact installed straight up. I did consider doing as you mentioned and advancing the cam to increase torque, but when asked,Brian only told me "it should work as is". Of course comp cams is in the business to sell cams, not give advice on how to make an existing cam work, so i guess i shouldnt be surprised that they didnt suggest advancing the existing cam.

btw, i know that a cam can be installed advanced or retarded by moving the timing gears, but how do you "alter" the centerline? This is how the cam is ground...


on a related note i dont think any cam would make a used vortec 350 with tbi in a 4x4 3/4 to. Truck with 265 70r16 all terrain tires "boil the tires"...

When you advance or retard the cam you change the intake amd exhaust centerline in relation to the crankshaft. The LSA or LCA is what is ground into the cam and cannot be changed.

My cammed L31 BOILS the 255/70R15s in my heavy Express van despite having a 4L80E with a very tall first gear and 3.73s.


This was the aftermath of a burnout on dry concrete.