Be sure to report back on your progress and the final results. I don't plan to do this to my Blazer but I for some reason find this fascinating.

 

No problem. I'm unsure about the max lift with TBI heads. The only differance i have heard of is that they flow poorly compared to the CPSI heads, and are commonly replaced with CPSI heads for that reason.

I know that doesn't answer your question, but swapping heads is something you may want to consider if you're trying to gain power from the TBI engine. - and as a bonus, you'd be working with heads that you know the tolerances of

 

Just about to order my valves, springs, retainers and stuff for the oddball 1994 TBI heads.

Have to measure a couple things this week to determine how to machine the guides. They will need K-Lines and will get a set of valves from Manley or Milodon.

I'm also considering the 1995 upward CPI heads as they have the (heart or kidney) shape combustion chambers. If I can get by a cheap set of heads I'll probably go that road but that could open another can of worms for my build. (Just for thoughts - different knock sensors - manifold from dry to wet flow, retain the TBI manifold and machining for the ports. Headers. Accessory bolt thread locations etc.)

Probably going first with my mild ported OEM heads and see what the COMPCam 260AHR will need on ECU modification of the EPROM.

56-440-8 - Magnum? Computer Controlled

The nice thing is that I have a complete set of two engines including ECU and wiring harness and a vehicle that I can test with the completely stock engine and afterwards the modified one.

Not sure yet if I can come by the engine dyno at a low rate then testing will be done with the factory ECU and with the modified one as I should be able to do a complete ECU rigging to run it on the dyno.

At the moment figuring the proper springs and retainers and locks for the respective valves. Have to take more measurements this coming week to get that right the first time.

I'll let the forum know in my build thread about the parts that finally to into the project as this would be a nice base and know-how for an intermediate build with some machining.

 

Hey, error 401, j just noticed you're a mod now!

Why would you have to change knock sensors with the head? Don't they thread into the block, or am I mistaken?

I'll be watching your build thread to see what you come up with for springs/retainers. I'm interested to see if there's any differences in that area.

 

Thanks - just made that additional step.

You are right about how they just thread into the heads or block.

For me the knock-sensors would be a grey area. If changing only the heads that would mean a different head to the ECU. A wild guess on my part would be that the frequency of the knock sensors should be pretty much the same as the heads have a generally similar design.

The "kidney-shape" combustion chambers are from hearsay less prone to detonation than the old LB4 heads. Still modern EFI has some spots in the VE tables where it gets close to knock in part throttle operations where they advance ignition as much as possible to get best power out of the fuel.

If the knock sensors were off because of the different design or the sensor has other characteristics (freqency filter) you could run into trouble.
A careful evaluation may be necessary with such modifications in order for the engine to last as long as the OEM.

Just a word of caution and a nudge to investigate such things in depth.

If I can get a pair of the newer heads I'll see if the knock sensor is "exactly" the same part number. Then you had to make sure you understand the sensors output. Some are "switches" some just deliver the signal to the ECU or an auxiliary box. If it is just the signal and it is compatible between the ECU that is in the truck and the one of where the heads came from - you may just go for it.

 

I was looking around and I talked to someone that said comp cams makes a kit that would take the place of buying the ls6 springs and the 787 retainers. The part number for it is 982-KIT. It was for an 8cyl engine but it would still work with a 6cyl. Looks like it comes with all the springs, locks, retainers, and seals.

 

Error 401- I never would have thought of that with the knock sensors, I didn't know about the difference in function of knock sensors. Let me know what you find between the two sensors if you get the opportunity.

You just dropped a whole bunch of knowledge on me, thanks!



Tkos15, that seems like a pretty good deal on that kit, especially since it comes with the seals and locks.

 

I'm just looking into the compcams kit's as well for my build.

The pockets for the OEM springs in the 94 heads are small but it should fit a beehive springs. Not sure if the LS6 kit (i had a look at that too) will fit. the old heads have quite a bit of a boss around the valve guide. May need machining.

have to download these pics from my phone. I'll post back over the weekend.

 

what kind of numbers can I expect with a 266 comp, cam and LS springs and 787 retainers.

 

So if tkos15 and Micmak haven’t found a cam yet and you are looking to stay stock with your motor, Crower Cams has a killer reduced price I just looked up (happen to be a crower fan have used them in most my muscle cars) although I was too late at the machine shop for my 4.3 rebuild a few weeks ago. Anyway cam only price $29.00. 114 degree lobe center grind, duration 240 intake 248 exhaust, lift 386 intake 389 exhaust hydraulic flat tappet cam for enhanced throttle response and low end torque with better gas mileage. Go to crower. com and check it out. You will have buy the other stuff but the other slightly bigger cams are 171.00 and up for cam only