Hey guys,

Just swapped in a 350 TBI into my ex-L03 Car. Used the top end from the 305 on the 350 bottom end. What would be my best bet to get the most power out of this engine? The cam is new, and fairly mild, but better than stock. I forget the specs, and I'll have to dig them up. Still running the 305 PROM too.

Right now I'm looking to keep all of the work on the top end of the motor. Intake manifold and TB are what I'm thinking of next. Anyone have any suggestions for mods, or part numbers for decent hi-flow TB's or intake manifolds?

I've also heard that a 454 TB will fit on a SBC intake manifold and work w/ my emissions system.

 

Sounds like you just slapped it in and hoped it would work! A comp. from a 350cu. in. car would help!

 

You need to ditch those heads as soon as you can. They will kill any power you can hope to make with that engine. Decide on heads first before intakes so you get one to match. I'd say its not worth buying an intake manifold to match those heads and want to change it later. Just use your stock manifold until you get new heads then replace all at the same time.

As far as the prom goes, I wouldn't start with a 350 prom like he said. With those heads you're not going to be making much more power probably so I wuold say try to tune off the current 305 chip, the tables would probably be closer than a 350 chip.

 

Well, I'm not sure what kind of heads you're running, but I believe SDPC was selling a kit to a make a 350 Vortec TBI. If you get the vortec heads and vortec intake manifold, EGR adapter and a Holley 670 TBI you should be happy with the results. Of course some chip tuning/burning will be necessary to get it to run right. I know some guys throw in a 350 TBI Caprice Cop chip as a band-aid until they can get a custom chip burned. You can usually find those for sell on Ebay.

Here's the link to SDPC

http://www.sdpc2000.com

 

if you used a the 305 Head's as you said upper end. your 350 is going to have a 14:1 comp. ratio, and small valve's that want breath.
to get every thing right you may get away with a prom from a 350TBI truck if not you can swap the computer's but it react's funny in the 305 wiring.............i'd also get the 670cfm tb and the tb spacer's with a set injector spacer's.
But then again i could be wrong and just a Retard .
But after all i am building a
:hail: dual TBI 406 in a 91 GTA Ramair2:hail:

 

Ok, first of all with those heads you will not be at 14:1 compression or anywhere near that. The LO3 swirlport heads will kill any power you hope to make though. your compression shouldn't be too bad, whatever the L98 Vettes had I'm guessing around 9.5-10:1.

You cannot use a prom from a 350 TBI truck because the trucks used a 7747 ecm and you have a 8746 ecm, if you needed a 350 prom you could use one from a Caprice with the 350, but honestly with those heads and a mild cam the 305 tables will be closer than the 350 tables I think.

Ditch the heads and intake and until you do that don't bother with a 670 Holley TBI either.

Also, what exhaust are you using? If you're using the 305 exhaust, that is by far your weakest link in the setup. You NEED headers and full 3" exhaust all the way back. If you have stock LO3 exhaust on there now you probably have 30hp or more to pick up from just headers and full exhaust.

 

Ok ok I stand corrected.
I was Told that 305 head's on my 400 would give me like 14:1 or some crazy thing.
But thats ok i want with dart american eagel's.

 

Thanks for the info guys. I'll be planning on swapping the heads first, then the intanke manifold and TB / spacers.
I'm running the 350 now on the 305 ECM and the engine runs perfect. Correct powerband, and smooth idle. The only thing ECM related I am having issues with is my tranny not finding 4th gear, and not wanting to shift until 4000+ rpm sometimes. Another problem for another time.

As for the exhaust I'm running, its 3" flowmaster catback. No headers yet. I'll hold off on getting those until i get the new heads.

Any reccommendation on parts for heads, headers, tb, intake manifoldS?

 

Along these same lines, guys, I have an L98 out of a 1989 Formula that I am dropping into my 1992 L03 Firebird. I want to reuse the TBI on top of the L98. Does anyone know what replacement parts I will need? Will I have idle problems if I leave my stock chip in?

 

It Will Run ok.
But your still going to have a 2.73 rear end and I don't think your going to gain much go power...

3.73 gear's Behind your L)-3 will run decent....

eun some 235/60r15's on the font and 245/60R15's in the rear with 3.73 geat's get some TB spacer's nice Dual exhasut you run just as fast as the L-98.......

But I my self if i was going to do and engine swap in a TBI car I'd but a 400 chevy under it man with some 3.73 gear's you will rule the road's but even if you left the 2.73's in it.
You'd still kick some Tail...
But it's your car...
to Run the L-98 it should run Fine.
just drip ot on and swap intake's Fire it up......

 

Along these same lines, guys, I have an L98 out of a 1989 Formula that I am dropping into my 1992 L03 Firebird. I want to reuse the TBI on top of the L98. Does anyone know what replacement parts I will need? Will I have idle problems if I leave my stock chip in?

 

Okay, I DID kind of forget to mention that I have a 3.23 disc brake rear out of a 1996 Camaro. I also will be installing headers at the front of my already convertorless (Great to live in the rural South!) exhaust. By the way, the post I read on here about single plane intakes was right on time. Is there one that will bolt on to L98 heads?

 

I'm going with an L98 setup just like that actually pretty soon. I'm going to use the Holley 300-66 TBI manifold, but if you want single plane the popular weiand 7525 will bolt right up to those heads. I think that setup should be a pretty good one then. Personally, I'm still thinking about either keeping the stock L98 cam in there or go with something a little more aggressive.

 

ok. Getting back on the original topic after my thread got jacked :

"Thanks for the info guys. I'll be planning on swapping the heads first, then the intanke manifold and TB / spacers.
I'm running the 350 now on the 305 ECM and the engine runs perfect. Correct powerband, and smooth idle. The only thing ECM related I am having issues with is my tranny not finding 4th gear, and not wanting to shift until 4000+ rpm sometimes. Another problem for another time.

As for the exhaust I'm running, its 3" flowmaster catback. No headers yet. I'll hold off on getting those until i get the new heads.

Any reccommendation on parts for heads, headers, tb, intake manifoldS?"

 

Transmission shift Problem Solved:
You have to adjust the TVR cable.
If it's nit right on it will shift funny for a while.
But it normally Reck's the tranny............
The GM OD's are very Touchy when it comes to that cable.
hop fully you did drive it to much and fried it.



Head's&Intake:
L-98 Head's are Just Fine Not My pic of choice but work's.

you need EDELBROCK intake number EDE#-3704 $219.95 or
EDE#-3704 $364.95.

Part's sugested you use:
#3704 Intake, #6085-Head's, Cam kit #3702,Holley 670cfm TB,
TBI spacer#RDP-2433,injector Raiser#EDP-2457. yield's
380Hp & 435FTLB@Fly wheel.

Estimated Cost:

EDE#-3704 $219.95 ,tb spacer TDP #2433$76.95,injector Raiser#EDP-2457 $24.95,Head's #EDE-6085$569.50each-X2,cam kit #EDE-3702$129.95,670Cfm TB$312.99.

Yourbill: $1,903.79

Wow thats exspensive.

forget the Head's run the L-98's head's. you'll save almost $1,200.

Now me i'd get a set of used Rebuilt Dart iron eagle's $600.00 for the set,Holley intakeDual plan High Rise. www.jegs.com #510-300-49.
then get the edelbrock cam kit with the holly TB,and spacer's........
you get more power less moneyYa might have $900 invested instead of $2,000. and end up 30hp and 80ftlb more power.

 

thanks for doing the math. What sort of power could i expect from a good intake manifold, cam, and throttle body with the l98 headS?

 

340Hp & 425FTLB@Fly wheel about give or take 5hp.

Your torque will stay about the same.

335hp-345hp & 425Tq-445TQ Fly wheel. With the holley intake the jazzed up 670cfm TB witch will be 710Cfm.,and L-98 Head's.

But with them Dart,Head's and the Shnazzt TBI intake from holly you'll have.

410Hp & 520-535 Tq @Fly wheel with $900 vested assuming,
9.5:1-10.5:1 c/r.

I'd swap the 3.23's out for some 3.73's,But see what it dose first.