Hey everyone,

Things are slow at work so I'm spending time around the car tomorrow. I bought a whole gasket kit for my intake, plenum, manifold, and throttle body (along with black RTV/Right Stuff) because I discovered I have a leak in the intake system on both sides. I've read up what I can online, and in my Haynes* book, but any additional advice is always appreciated. I always seem to get something helpful from you guys.

While the intake, runners, and plenum are off I'm cleaning them out thoroughly, and possibly sanding down the crappy paint left behind by the previous owner.

ALSO! Should I take advantage and try to port them?
Never done it, but then I'll have to bring them to work another day, so the car will be out of commission longer. Plus, I REALLY don't want to take off the whole system again in the next few months to port them because I don't want to ruin the new gaskets.

Thanks for anything.

 

Unless you upgrade [at least] the runners, most of use agree the benefit of porting stock intakes is negligible. IOW, you wouldn't notice the result.

If you convert to large-tube runners or siamesed SLP tubes...or even siamesed Edelbrock tubes, the value of porting is much more measureable.

Large base wouldn't hurt either...but then you start the debate of swapping to another intake.

 

Whoops... forgot to mention that I have SLP High Flow runners. Is it worth the effort?

I have yet to find an AM intake that's CARB/SMOG legal, aside from a converted LT1 intake, with a working EGR(?). Plus, an AM lower manifold is still being looked into for the same fear as stated.

Don't remind me that I can't buy any headers... I might cry because for once, I didn't look at the possible modification of my purchase, before buying it.

 

here it is some good stuff from you tube

 

http://www.eecis.udel.edu/~davis/z28/buildup/plenum/
http://www.eecis.udel.edu/~davis/z28/buildup/runners/

No CARB # but the Edlebrock intake base has provision for Vette style EGR
http://www.summitracing.com/parts/edl-3861

but as Greg mentioned there are arguments for bypassing the TPI altogether
http://www.digitalcorvettes.com/foru...ead.php?t=1793

 

Advice if you have not removed the plenum, runners and intake:

1) **Before you start removing things, start the car and run it then pull the fuel pump fuse and let the car run until it dies from lack of fuel. Loosen the gas cap to relieve any pressure. You will need a couple of rubber plugs to fit over the fuel lines when you remove them from the fuel rails. IF you don't plug them, they WILL leak fuel. You should use flare wrenches to un-screw the fittings on the fuel lines.
2) Disconnect the battery....negative first always!
3) I would put a 5/8 (six point socket) on the damper center bolt and turn the crank until the timing marks line up.
4) Remove the distributor cap and note the position of the rotor. (I draw a picture and tape it to the windshield so I know where it was).
5) Label the distributor and each plug wire as you remove it.
6) Label all hoses and wires as you remove them. Pictures always help.
7) Label all bolts removed and place in plastic bags.
8) The runners to the intake have different length bolts depending on their position on the intake, so be sure to label each bolt.
9) There are two I believe (it has been a long time since I did standard runners) on the inside of the runners (under the plenum) that attach the runners to the intake.
10) When you start to put things back together, wipe down the front and rear "china wall" with a good solvent to remove any oil. Then take a center punch and dimple the china walls. I also use the punch and dimple the portion of the intake that matches the front and rear china walls. This will give your "Right Stuff" something to grip. Chevy has had a problem sealing these areas for years and years. Dimple the walls and you will not have a future problem.





PM sent to you this morning.

 

http://forums.corvetteforum.com/1582598471-post13.html

 

Talk to member SlickFX3 about header options. It may be that you can install newer LT1 exhaust manifolds...or even LT1 shorty headers. They may be CARB compliant...though I've no idea what rules are for interchanging years.

Even with the stock manifolds, people have pulled them and ported them. There appears to be a big restriction at their mouth that can be opened up. Also, McJacks makes some "pretty" coated/ported modified stock manifolds -- if no other option is afforded you in CA.

Taking the video on SLP porting one step further, you'd end up getting tubes that look like this -- if you really try porting all the way thru AND remove most of the upper divider. (The YouTube guy eluded to this, but didn't show you a visual comparison...)


The modification above should net you at least 20hp and raise your effective rpm at least 500 higher.

 

/\ Wow! That's a huge difference from the standard runners. Thanks for the visual, Greg!

Very good info, thanks guys! About to get started... this should be fun.

 

There will be a pretty big port mismatch between any LT1 manifold and a stock 85 exhaust port. The LT ports are raised D port. I have Pacesetter LT1 shorties and a stock 85 head on my bench. I was going to just redrill the holes on the headers, (raising them up) a luxury you do no have on stock LT1 exhaust manifolds.They will work without drilling, but if you saw the mismatch, you would not want to do it. In the end, I purchased some Edelbrock RPM heads which are D port.

 

Also, when you remove the manifold, all bolts are not equally long. The (four) bolts at each end are longer - at least this is the case with my '91





I usually have all the bolts in cardboard in the actual 'pattern'.

 

The bolts go through from the opposite side as shown in red;
do not try to crack the stuck on runners loose from the base ( crowbar / sledgehammer / etc ) unless you have all 12 bolts in your hand
Need a 6" long 3/8" extension to gain access to them under the plenum

 

While you are in there you might as well replace the injectors with new Bosch III. Not a bad idea to get a new EGR valve and thermostat and an adjustable fuel pressure regulator.

 

all of the help you've gotten so far has been excellent. I just want to put a pitch in for you to consider chucking the stock intake man. and runners and go with an aftermarket setup. I put on the Accel, but would not recommend it due to the super PITA of the install. Instead, you may want to take a very close look at the mini-ram from TPIS. Knowing them, the install is reasonable and one you won't hate like I did on the Accel/Lingenfelter. My '89 now pulls hard thru the entire RPM range!

Also, I ported my heads and exhaust manifold.

 

/\ Are you passing emissions with the mini ram, or is your C4 a track car? I've heard that it lacks provisions for the EGR, and would most likely fail the visual. If it works for you then this might be considered.

Greg, thanks again for the pics. Turns out my whole intake system had already been ported by a previous owner. My 2 left runners in the picture, for both sides, lack a center divider. Not sure if this is good or not, but it'll have to stay for now while I save.

 

There was a version of SLP runners with "hybrid" full/partial siamesing from the factory. The idea was to provide more low-mid from 4 cylinders -- with better mid-high rpm performance from the other 4 cylinders.

Maybe you have a set of those?

OTOH, if all four dividers are completely removed, that is home-grown and quite rare. It also improves either your "need" for a better cam. Or even a bigger curiosity about what cam is in your car now?

 

Mine after hours of porting. Do it, you wont regret it.

 

That sounds right on the money, but there are some uneven edges around the tubes. Not amateur work... but someone didn't care 100% about looks so I still suspect porting because of the same evidence on the upper+lower plenum.
Or maybe just SLP's lack of craftsmanship?


EDIT: My runners look exactly like those in the pictures that "ch@0s" attached above.


I've been curious about what cam could be in there also. After removing the valve cover and peeking into the head everything looks like it's in good condition. I suspect new internals were put in at some point, but who knows how long ago.

 

The You Tube video of porting the runners, I had that guy port my intake base to what he called "Stage 4+". When i got it back I was amazed how how much that intake was opened up, golf ball would fit in it. But it was a hell of a chip shot to get it back out...

If you are going to do large tube runners, I recommend porting your intake base or buying a new base.

Best of luck...

 

Finally got the intake back together earlier today, but I forgot to pull the overdrive throttle cable under the left runner. Doh!!!
Anyway... bracket's getting a new facial to align with the cable while I'm at work tomorrow. Whole process took a few days of spare time after work, but I was working slow and carefully.


However, this whole experience showed me that I'm definitely switching to a converted LT1 intake/manifold in the next few months. This whole process would have literally been cut down to about 1/4 of the time if that was the setup. I couldn't care less about the possible performance gains... I just don't want to go through this process again to change an injector, or anything else.