L98 Performance question
 

Hey folks, i am curious about a couple things about the L98 injection system and what its capable of handling forHP.

I have a GM 604 400hp crate engine (350) that looks like it will more or less all bolt up (other than maybe the knock sensors)
so my questions are

1. can the TPI feed this motor? there is a fellow locally that can tune the ecm he said. or am i better to pull the stock one and get it somewhat re and re?

the job itself seems simple swap of oil pan and intake and in theory it looks like it will bolt in


thanks in advance

It will run, but it won't make anywhere close to 400hp with a TPI on it. The stock intake can't feed the heads/cam enough air at the higher rpms.

It will actually run OK with the TPI intake but it will be down on power from the rated 404 HP since the intake will restrict the airflow into the engine. The bigger issue I see is the fastburn heads may require the STPC vortec manifold to seal the intake to the heads. (More money to be spent one the intake but it will work)

can u elaborate on the STPC vortec manifold.
im not looking to make huge power, this engine is looking for a retirement home and the corvette would be a fun place for it.

i figured it would be a good fun little project if i can get the TPI to work or get a miniram or somthing to make it work.

guess i should say my car is an 87 as well dont think it matters

The fast burn heads have vortec style ports that are taller then standard sbc ports and the factory intake manifold may not cover the port. If that happens you will need to purchase a sdpc intake manifold that is designed for the fast burn heads so the ports are covered.

The rest is fine, a mild tune and it should work well.

excellent thanks folks,
is there any harm in not having the knock sensors? the crate engine doesnt have a spot for them.
(this will be a work in progress but just want to get my ducks in a row)

Yes it does. Remove the block coolant drain plugs (1/2" NPT plugs) and screw your knock sensor(s) into that hole. :thumbs:

hey thats awesome thanks for the help folks im not to familiar with this stuff (mostly race cars and the newer 5.3 and 6.0l vortecs)

ill keep yeah posted if this deal goes through on this motor

Another option is a converted LT1 intake will breathe better
enter david frederick in the search box he does (or did ) them quite a bit
Poor guys miniram

Edelbrock pro-flo xt vortec style works with fastburn heads and fits under the c4 hood.

Make sure that the cam in the crate motor is profiled for EFI. You may want to install an after-market TPI system if you want the motor to breathe better in order to get the intended horsepower.

eDELBROCK PRO-FLO
 

RWDsmoke How would a First TPI do on that motor? Not trying to steal a tread. TIA:thumbs:

If it has the 52mm Throttle Body and 28-30 pound injectors it should be Ok.

First TPI intake comes with a I believe is a single blade 90mm TB.

https://www.firstfuelinjection.com/services.html

If you port the Base and Plenum you could get close to your power numbers.

good news i just talked to my race car owner and i have inherited this motor for freee!!!!!!
so this year im going to start accumilating parts and then do the job next winter most likley.
i dont need it to make 420 but if i can get it there with some better headers and intake that would be swell.
so far i need an intake, headers (not sure what to do here with the egr crap not totally familiar with this area)
will stock injectors and such work? or shoudl i go into new fuel rails and injectors? what about throttle bodies?

looks like that edelbrock intake is the way to go.

not sure what you mean by profiled for efi all i have are the specs on the cam (these motors are glorified truck engines :P lots of torque, this one was rebuilt and blue printed)
Cam lift: .474" intake / .510" exhaust
Cam duration @ .050": 208° intake / 221° exhaust
112° lobe separation

hate to bring the ld thread up but im going to start acquiring parts for this job over the summer. but before i do i have a couple questions.

The egr is under the TPI right? will the crate motor be fine with an EGR (or should i delete)
is there any issue with it being deleted, i dont want to stare at a check engine light all the time :P.

Headers are the next issue, i dont believe my stock shorties will fit with the fast burn heads, is there a certain brand i should be looking at like off of an LT1?

can i use my stock injectors or should i be getting different injectors and rails?

im not trying to make it reach the HP it was dynoed at. but still want it to run properly and make the car a bit more unique for me. plus its a fun project for me and the old man to tinker with this coming winter

so things im planning on getting done.
edelbrock intake
new headers
EGR block off?
new oil pan
get trans serviced
redo all ujoint in driveshaft and half shaft
new exhaust.
get the chip burned from a local fellow here that tunes all sorts of vehicles

ill start a build thread when it starts to happen :)

Dont apologize for bringing back your own build thread! Can't wait to see how it goes!

Sadly I won't be much help for you but I'm pretty sure you can get the EGR codes deleted in the programming so the CEL doesn't glow in your face constantly.

Good luck with the build! Take and post pics, we would love to see.

In regards to the EGR - mixed opinions on that from what I've researched. Some say the lack of one heats up the cylinders a bit since they would otherwise have some exhaust (and therefore non-combustible) air in them. I haven't had that issue yet though. The EGR check engine light only comes on when it does a diagnostic test which requires certain conditions that only really occur on a cruise control freeway drive. You mentioned having a custom chip so you can just disable the EGR on the chip and never see/hear from it again. I opted for an Ostrich 2.0 (though I wish I would have gotten their all-in-one instead now) and just installed it this past weekend.

But if you did want to install the EGR, it goes on top of the intake under the plenum. I just reinstalled mine since I've got to pass a visual test in California in a few months. :-D

Other notes:

- An 87 ECM expects there to be a cold start injector so if you don't have one it may require a little longer than you'd expect to start. My fix for that was to upgrade to a 1989 ECM .bin ($6E) which uses the other 8 injectors to help it start.
- You'll likely not have the AIR pump system installed. When it's activated the ECM expects extra oxygen to be in the exhaust so it offsets the oxygen sensor value for what it considers lean/rich. Without the AIR system, it'll end up running lean when this happens. This can also be disabled in the ECM though I have yet to do it myself.

Once I get an EGR tube back on the car I'll have both of the block off plates which I can send your way. It'll be a few months before I get that far though.