Introduction

[Danoby]

Hello everyone. I have been doing extensive research on swapping vortec heads onto the TBI 350 in my Caddy (in signature). While doing research, I was led to this site. My biggest hesitations with doing this swap are: not making the car run worse, not dealing with a check engine light, and not getting buried and overwhelmed with details like making a custom EGR setup or eliminating it altogether and tuning becoming a nightmare, not hurting gas mileage at all or too much. Anyway, I am a mechanic by trade, and thus very capable. I have a few other toys too including a '69 GTO project car, an '86 F150 Flareside 4x4, an '02 Harley Low Rider, a '71 M35A2 deuce and a half, and an '88 Baja Sunsport. My Caddy is my daily driver and my baby. It's a great cruiser that's just a little short on power. I get about 12 MPG city and 18-20 highway. I'd love to get some help getting the Caddy some more power. I want to retain the TBI EFI and swap on a good set of vortec heads I have. I don't know if I should make a separate thread for that in the GM EFI section or delve right into it here.

[dave w]

I had excellent results using TBI heads on a roller camshaft Vortec 5.7 liter short block assembly. Using TBI heads saved money, time, and several headaches. Admittedly, the Vortec heads would yield slightly better performance. The Vortec roller camshaft required some timing and fuel table adjustments to the PROM chip programming to get things dialed in.

dave w

[Danoby]

I have read that I can expect a minimum of a 30 HP gain switching to vortecs. My current heads need valve seals pretty bad. It smokes on start up. And when it's fully warmed up - and I mean after driving for at least 15 minutes - I start getting a knock signal under load to the point where the ECM pulls out timing causing a significant power loss. I suspect the oil is getting past the seals enough to contaminate combustion. I am pretty sure being a car engine that it's equipped with flat tops, putting SCR at about 9.8:1 which is pretty high with pump gas. The vortecs would increase SCR further to about 10:1, but that should be okay with it's superior chamber design. You see, the vortecs would solve a few different problems I am having plus I would see a nice power increase.

I am now realizing all the headaches I will endure, like tuning and EGR. I am fine with the mechanical aspect or doing the work, but I am not familiar with tuning an engine electronically, and I am not sure what I would do about the EGR. I guess I would either find a way to make it work, which is a headache, or forget about it, eliminate the system, and deactivate that part of the programming.

I am not sure what to do here. There are lots of things to consider. I guess what I need to know is approximately how many hours would it take for me to learn how to program? How many hours would it take to learn how to program and burn a chip and then execute the process? How much would it cost to have someone else do it for me? In fact, I probably need a new tune already, so regardless of if I do the head swap or not, I need some programming done, just perhaps not as extensive. I guess I would need to log some data somehow and then send it to someone so they could burn me a chip? I had talked to Brian Harris at TBI Chips, but I am a bit wary of using a chip from him based on things I have read. He was very informative about how to upgrade TBI engines though.

[Fast355]

I have read that I can expect a minimum of a 30 HP gain switching to vortecs. My current heads need valve seals pretty bad. It smokes on start up. And when it's fully warmed up - and I mean after driving for at least 15 minutes - I start getting a knock signal under load to the point where the ECM pulls out timing causing a significant power loss. I suspect the oil is getting past the seals enough to contaminate combustion. I am pretty sure being a car engine that it's equipped with flat tops, putting SCR at about 9.8:1 which is pretty high with pump gas. The vortecs would increase SCR further to about 10:1, but that should be okay with it's superior chamber design. You see, the vortecs would solve a few different problems I am having plus I would see a nice power increase.

I am now realizing all the headaches I will endure, like tuning and EGR. I am fine with the mechanical aspect or doing the work, but I am not familiar with tuning an engine electronically, and I am not sure what I would do about the EGR. I guess I would either find a way to make it work, which is a headache, or forget about it, eliminate the system, and deactivate that part of the programming.

I am not sure what to do here. There are lots of things to consider. I guess what I need to know is approximately how many hours would it take for me to learn how to program? How many hours would it take to learn how to program and burn a chip and then execute the process? How much would it cost to have someone else do it for me? In fact, I probably need a new tune already, so regardless of if I do the head swap or not, I need some programming done, just perhaps not as extensive. I guess I would need to log some data somehow and then send it to someone so they could burn me a chip? I had talked to Brian Harris at TBI Chips, but I am a bit wary of using a chip from him based on things I have read. He was very informative about how to upgrade TBI engines though.

I wouldn't follow any of his TBI build-up advice to be honest. As for the heads you won't gain 10-15 HP with Vortecs over the TBI heads running your stock cam. The cam in that Cadillac is the same weakling that came in the LG4 and L03 305 engines. You are a full 30 HP down on a TBI truck with the same engine and a non roller hydraulic flat tappet cam. Best thing you could do is get your current heads cleaned up, new guides or more likely new valve stem seals and put a '395 marine cam in it. That being said your current engine is being held back more by the stock exhaust manifolds than anything else. If you switch to vortecs the compression ratio will be unaffected and stay right at 9.6:1.

[Danoby]

I really appreciate your input. I don't want to be rude, but how do you know what cam came in my engine? I have searched endlessly and cannot find any information to verify what cam came in my engine. It would seem really stupid of GM to put the same cam from lower compression and smaller cubic inch engines in a flat top 350 with 9.8 CR.

I bought 906 L31 vortec heads for either my Caddy or my SBC powered boat. I was going to put them on the Caddy but now I am rethinking that. If you really think the cam is tiny and holding it back, maybe I'll go back to my original plan of retaining the swirl heads and doing the valve seals and changing the cam. The 906 heads I bought came with a stock L31 roller cam in good shape. I measured the lobes and got .411/.426. Based on the lift I believe it is the same cam that comes in a brand new L31, like off of Jegs where I got these specs: 191/196 .414/.428 111 lobe centerline. It's really not that much smaller than the 395 cam that comes in the Ram Jet 350 and HT383 with 196/206 .431/.451 with a 109 LSA. Correct me if I'm wrong, but that L31 cam might be a good upgrade, plus it was free and in good shape. And if I use 1.6 rockers I'll get .442/..457.

I still don't know what all will be involved in tuning this thing with all of these changes...

[Fast355]

I really appreciate your input. I don't want to be rude, but how do you know what cam came in my engine? I have searched endlessly and cannot find any information to verify what cam came in my engine. It would seem really stupid of GM to put the same cam from lower compression and smaller cubic inch engines in a flat top 350 with 9.8 CR.

I bought 906 L31 vortec heads for either my Caddy or my SBC powered boat. I was going to put them on the Caddy but now I am rethinking that. If you really think the cam is tiny and holding it back, maybe I'll go back to my original plan of retaining the swirl heads and doing the valve seals and changing the cam. The 906 heads I bought came with a stock L31 roller cam in good shape. I measured the lobes and got .411/.426. Based on the lift I believe it is the same cam that comes in a brand new L31, like off of Jegs where I got these specs: 191/196 .414/.428 111 lobe centerline. It's really not that much smaller than the 395 cam that comes in the Ram Jet 350 and HT383 with 196/206 .431/.451 with a 109 LSA. Correct me if I'm wrong, but that L31 cam might be a good upgrade, plus it was free and in good shape. And if I use 1.6 rockers I'll get .442/..457.

I still don't know what all will be involved in tuning this thing with all of these changes...

I know the cam well. Its the same one that came in the civilian L05 Caprice, as well as Olds and Buicks variants of the B/D-car. 179/194 @ .050, .350/.385 lift, 109 LSA, 106 ICL.

Your engine is ~9.6:1 with the stock 6cc valve relief flat top pistons, stock deck height, and the stock headgaskets.

I am not a big fan of the factory Vortec cams. I have had them piled up like cordwood in the shop and started tossing them recently.