Valve spring upgrade with gt40p heads

[Mamigacz]

TRBenj,

When I was looking for a cam for my boat, I found from earlier posts, that you had a lot of good things to say about the cam research cam. I'm assuming that you went through the process of changing springs when you did the upgrade. Did you get springs from cam research? What did you use? Are you also running gt40 heads?

[TRBenj]

When I was looking for a cam for my boat, I found from earlier posts, that you had a lot of good things to say about the cam research cam. I'm assuming that you went through the process of changing springs when you did the upgrade. Did you get springs from cam research? What did you use? Are you also running gt40 heads?

GT40p's in my '90.

Yes, I upgraded springs... it seems the stock P valvesprings are only good up to ~.500 of lift, and I was near that, so decided to pull the trigger. Most dont. Not sure if the regular GT40's have such poor stock springs... but I suspect not, since they came in high performance vehicles, unlike the p-heads. Be sure you keep the 2 head styles straight, as they are very different. I let Cam Research select and supply the springs for the reasons I mentioned above. I dont recall the brand.

[Mamigacz]

I should of asked Cam research for springs when I ordered the cam. It would of made my spring search a lot simpler. Thanks.

[TRBenj]

What would prevent them from recommending the proper springs now?

[Mamigacz]

I did give Cam Research a call today and they have a drop in spring kit for GT40P heads and the cam I bought ($100). Unfortunately, I bought springs from Summit racing on Tuesday. For some dumb reason, I made the assumption that Cam Research didn't carry springs. Oh well, I should not assume.

[TRBenj]

It has been my experience that cam shops are usually more than happy to sell you other valvetrain parts... anything that improves the odds of their parts being used in the application directly is something they have a vested interest in. At a minimum, I try to get cam/lifters/springs from the cam guy.

[Mamigacz]

I finished installing my rebuilt 351W today. Even though I went with the cam break in service from Cam Research, I still went through a 15 minute, 2000rpm additional break in. I was only running the motor on the Fake a Lake, but the engine seemed more responsive when I cracked the throttle. My crank and rod bearings must of been really worn, because the oil pressure came up to 40 psi at idle, warmed up (was 5 psi at idle before the rebuild). Wisconsin summers are too short, I can't wait until spring to see how this engine performs on the lake!

[Zach@n3]

Good Job fella looks good. Did you do all that wire loom yourself? Is that a broadband 02 sensor in the manifold to tune the carb with the motor box off? 5 psi is a little weak at idle. If you have done an extended WOT run in mine on a hot day it never drops below 20 psi at idle.

Bet she will be a whole different animal now!

[Mamigacz]

Yes, I bought a custom wire kit from Accel. It comes with 8 long wires and you cut them to the desired length. Installing the ends is a little bit of a pain, but in the end it turned out pretty nice. It funny you noticed the interferance with the motor box (I didn't while planning this change). I already switched the risers, so the O2 sensor points towards the carberator. I have a wide band air fuel/ratio guage in my 69 Camaro. It's so nice to see where your at while changing the jetting. I'm going to take the wide band set-up off my Camaro and install it in the boat for the 2013 season. After I get the boat's carb dialed in, I'll probably take it off.

[Zach@n3]

I was going to suggest just swaping the risers if it would clear haha. I have never tuned anything with a wide band but I'm sure it takes out all the guess work and probably gives you a more accurate guess on what jet selection you need to make. No need for it to be there once its been tuned properly. I would like to do what you did to mine some day but it runs like a top as is for now and gets the job done especially with the new prop.

[81nautique]

I used a tuner when I rebuilt my 351, different manifolds but you get the idea. Mounted the meter on the front motor mount stud. My sensor was much closer to the wet exhaust than yours will be and it did eventually fail but my tuning was done and I never replaced it.

[Mamigacz]

So you had water running on the O2 sensor? The way I have it, it shouldn't get wet. The bung is passes right thru the water jacket into the exhaust port. Water can travel around the bung, but not thru it.

When you say meter, do you mean the gauge?

[81nautique]

So you had water running on the O2 sensor? The way I have it, it shouldn't get wet. The bung is passes right thru the water jacket into the exhaust port. Water can travel around the bung, but not thru it.

When you say meter, do you mean the gauge?

No it was a dry system using an adapter I made but in the log style manifold the sensor was too close to where the water entered the elbow so it could get some spray on it. It doesn't take much to ruin them but your setup looks like it should work fine. You can see where I mounted the gauge in my first picture. My system also had a USB cable I could attach to a laptop to record the A/F ratio at any rpm and load. I was concerned about high rpm tuning as this was a 10:1 Compression ratio motor and I didn't want to burn it down with a lean mixture.

[TRBenj]

Mami, can you explain how the 02 sensor goes through the water jacket and is able to seal off (keeping water out of the dry portion of the riser)? I cant picture it.

[Mamigacz]