I am finishing up on the "LT4 Hot Cam/Vortec Heads" setup that was in CHP a while back. I used the SDPC manifold.

I can't seem to find any documentation on what this port is for. It is right next to the EGR passage. There are fine threads in it, so I am betting it is not just a bolt hole. Two quick questions.

1) Has anyone else had to plug this hole? If so, what did you use - size, etc.

2) Does someone make a blockoff plate for this style of EGR? I will eventually be hooking the EGR back up, but would like to plug that hole for the time being (not sure if that would cause a vacuum leak being open)

 

It might just be the mount for the coil bracket. Does it go all the way through?

 

Yeah, it goes into a hole of some sort. The bracket that holds the distributor bolts into the hole just to the right (in this picture). It could be for the coil, but it really looks like it connects into something (possibly the exhaust passage).

Possibly it is for an exhaust sensor for the egr...was this sensor maybe not on the valve itself on corvettes? But then I would think it would be on the other side of the valve...

 

Check if that goes into the coolant port. It looks like it does.

 

It does go into the water (coolant) So plug it, it is not needed.

 

That's a coolant temperature sender hole for the Corvettes. It's takes 1/8-27 NPT plug if you decide not to plug it. There's a coolant passage that runs along the rear of the manifold and that hole taps into it.

There are two EGR mounting flanges on this manifold. One is on the top (for Camaros) and the other is in the rear (for Corvettes). You need only to use one. For block-off plates, I'm actually not sure where you would find one of those- maybe some place like Moroso?

 

Both TPIS and Street&Performance have egr block off plates.

 

Great, thanks all! (That definately woulnd't be good to leave open! )

 

No, it isn't.

On a Corvette a small fitting goes into it and then a tube attaches there that crosses over to the upper heater hose. It aids in bleeding off any steam pockets that are created in the rear of the manifold and also promotes more coolant flow in the rear of the manifold to help prevent aluminum heads from warping if things got a little too hot.

 

I blocked mine off, on a camaro you dont need that port. I also fabricated my own EGR block-off plate and coil bracket (coil bracket is still in factory location!)


To scorp - what all is to your combo in the vette (heads, cam, compression, porting......etc..)? It looks awesome! Is it n/a or juiced?


Mike (1bad91Z)

 

It was NA but I believe that he bought a bottle for it over the winter.

With a proper tune, I have a feeling he'll be knocking on 11s before he knows it.

 

Heh I hope so. First I gotta get the damn thing back together.


Everything is listed here...

http://personal.tmlp.com/scorp/vette/upgrade.html

It made 322hp and 369 ft/lb at the wheels naturally aspirated with a horrible fuel curve. Haven't had it running long enough to tune it yet.

 

Scorp - have you had your heads flow benched, or do you know pretty close to what they flow at .500, .550, .600? Are you running a speed density 730 ECM or is it MAF?

Mike (1bad91Z)

 

Sorry, I wish I knew what they flowed, but I don't. I bought them with the port work and larger valves already done. It is a 165 ECM MAF system.

 

Scorp - Thats too bad that you're running a 165, I had a killer 730 PROM for your combo! You picked a decent cam for your Super-ram, but Vortec heads seem to like a split pattern duration (they need a little more exhaust duration cause the exhaust side is where our heads are lacking). Good looking motor though!

Mike (1bad91Z)

 

Thanks!

I've actually been debating going back down to 1.5 rockers instead of these 1.6s. I think I'm opening the valves too much (.560") for these heads. I might do some before/after dyno tuning later this summer to see what works out better once I get the thing squared away and tuned.

I may be going to SD this fall, I haven't decided yet.

 

Scorp - another thing you can try is running 1.5's on the intake valves and 1.6's on the exhaust. And yea .560 is a little much for our heads beings they fall on their face after .550. Thats why I went with less lift more duration.

My heads flowed their peak at like .550. Thats why I went with the cam that I'm running now.

.503 / .510 lift
224/230 duration @.050
112 LSA
108 ICA

and those specs are with 1.5 rockers

Mike (1bad91Z)

 

here's the #'s on the heads I had done, what are the #'s on your stage III heads if you don't mind me asking?
INTAKE
LIFT------- STOCK---- PORTED-- GAIN
.1---------- 59--------- 64--------- +5
.2---------- 117------- 132------- +15
.3---------- 170------- 187------- +17
.4---------- 214------- 236------- +22
.5---------- 226------- 255------- +29
.6---------- 219------- 259------- +40

EXHAUST

.1---------- 42----------46--------- +4
.2---------- 83----------90--------- +7
.3---------- 123--------139--------+16
.4---------- 136--------161--------+25
.5---------- 143--------174--------+31
.6-----------147------- 178--------+31