DarkObsession

My 85 Corvette has an intake manifold gasket leak up in the front driver's side of the engine. We did a pressure check yesterday and could see water bubbling where the manifold plate meets the heads.

What I'm wondering now is if there are any performance upgrades that I should do while changing these gaskets. I've looked around but haven't found much outside of porting the existing intake system or putting on a TPIS intake.

Anything else I should think about? Thanks for whatever thoughts you might have.

Joe C

if you open up the intake side to breath better, you'll also have to open up the exhaust side. remember it's air in and air out. now you have to ask yourself, how much $$$ am I willing to spend? if you do the intake and exhaust, you'll need better heads. heads are big ticket items, headers cost money, tpis or slp intake systems cost money, and the list goes on. performance cost money.

confab

Oh my gosh, FIC injectors! Mine is like a whole new car after that.

IMO, if you have to pull the plenum/intake for anything at all, dump the stockers for Bosh III.

aklim

Those are old and dirty or Multecs so new rebuilt ones will work better especially when, not if, when you encounter ethanol in the gas.

As far as performance goes, the question is not "What can I do?". It is "What money can I spend?"

DarkObsession

The problem is I don't have big money to spend right now. My hope was to buy a second L98 and start building it up at some point but this manifold issue is throwing my timing off for that. I just wanted to make sure there wasn't something obvious I was missing (like injectors). Just trying to get my ducks in a row before tearing into the car.

ghoastrider1

Eldebrock is making a new style "ram" manifold. cost is around $500 bucks tho. don't know how much imptovement you will get without other upgrades tho.

aklim

Get a set of reman injectors from FIC, new gaskets, take the TB off, bypass the coolant line, take top plate off, take IAC off, take IAC housing off, clean passages, reassemble with fresh gaskets and be done with it.

Any further down the road and you will have to spend money to get results. Intakes, headers, tuning, to begin with.

confab

Cleaning that stuff will make your car perform better and save you trouble down the road. Do a search (sorry I don't have a link) about setting the IAC if you need it.

Also, the TPI is like bolting a bag of snakes together and it helped me a lot to leave the plenum bolts loose till I had them all installed, then snugging them to pull the whole thing together.

Also, be sure to use a good Torx socket, because they can strip and then it's a mess to get them out.

(I used the opportunity to powder coat all this stuff because it's so hard to clean otherwise.)

aklim

I wouldn't. The usual procedure is from the FSM. Cheap, easy and will ASSUME a bunch of stuff. Set it with a scanner

confab

I don't think that works on the 85/Early OBD1 cars.

Actually, I saw a post of yours that talked about setting it with IAC counts, and I tried that but when you connect the scanner (Apparently any scanner? I tried both Snapon and Mac.) it instantly puts it into "Field Test Mode" and jacks the idle to about 1K.

Which is irritating in the extreme, but I don't know how to get around it. I don't think you can.

Silver85

I think that can be programmed out of the EPROM. I have been told it's a timing bump that goes into effect any time a scanner is connected?

OP - $187 for a set of re-man Bosh IIIs from FIC is worth every penny. Mine had the early Bosh's instead of the Multecs and it was still a huge improvement.

confab

Cool.. TY.

If I keep this PCM, who can do that for me? (Or can I do it myself with something like the Moats APU1?)


If it's timing, it is too bad yanking the distributor advance connector won't bypass it, because I bet it is trying to hit 1K and adjusting the IAC accordingly.

aklim

I'd agree with you on that. Thing is, injectors get build up slowly and you don't notice it till you get a new set. ECM compensation is good enough and your SOTP dyno is so inaccurate you can't feel slight changes

DarkObsession

Are these the injectors I'd need for my 1985? Want to make sure I'm getting the right part so that I'm not causing trouble with something else.

https://fuelinjectorconnection.com/c...esign-iii-24lb

Silver85

I had Greg at Blower works kindly burn an EPROM for me. Mine had the early 85 program that locked the TC at over 15mph and I wanted that changed. He took the timing advance out and lowered the coolant temp fan initiate setting as well.

confab

Yes.

That is what he sold me anyway, and I'm thrilled with them.

If you have any questions just call him.

gerardvg

Hi
The 85 runs 24lb injectors with a 30 psi fuel pressure regulator,
The inlet manifold may be ok you wont know until you remove it.
Could be a gasket failure or intake manifold water jacket corrosion,
if it is corroded away you need to replace it or upgrade?

VikingTrad3r

if its corroded hylomar will seal it.

try simply checking torque values first.