Installing a carb set up on a 91 L98 with 86 light heads. What type of intake/carb setup works well? Im suto calculating about a flow of 600 cfm with these heads at or near 6000 redline. Should I get a bigger carb and choke it back with smaller jets? Anyone go to FI and have carb set up stuff they want to sell?

Thanks,

Matt

 

Ahhhhh, another convert :) The intake and carb setup that works best depends if you are changing the TPI camshaft or not. If you are retaining it and plan to do so for a long time, then a performer RPM intake combined with a 650 CFM Holly works great. If you are changing the cam pick one with .485 lift and around 230 duration @.50. If you have a manual trans go with a lobe cntr at 110 and 108 for the automatic. That combined with Performer RPM and a 750 Holly would work great. On both carbs I personally like the double pumpers, however, for fuel economy you could go with vacum secondary versions. The performer RPM responds well to 1 inch spacers. Hood clearence is an issue so be carefull the first time you shut the hood with your new combo. A good Idea is to temporarily remove one of the inner fender wells from the hood so you can peek under it while it's being lowered down.
Good luck :cheers:

 

11sec84,

Thanks for the advice. i am looking forward to this. Did you change heads as well? I think I am going to buy the camshaft that you described and go mechanical double pupmper. What air filter will fit? I also want to run a 200 shot of juice. Any ideas?

Matt :D

 

NONE!

If you go with Performer RPM and 1" spacer, than you will not be able to close the hood. I have done this coversion, (with help of the 11sec84, that's why he said "another one"?), and I cut out big hole for the air cleaner in my hood. I am planning on installing cowl induction scoup, which should give me planty space for any kind of air cleaner. For now I am driving with the air cleaner exposed (only sunny days). I can't give you any details on the engine, because I went to 383 with AFR heads and aftermarket cam. I too run Holley double pumper 750 and I have Holley 650 also, but that's for autoX and small road courses. I got 450 #tq at 4700, and 459 hp at 6100 from engine dyno.

Ziggy

 

Hey Ziggy, how's it going? Glad to see those #'s from your combo. :cool:
Red 5:
Ziggy is right, you won't find an air cleaner to fit under the hood when the spacer is used. Even without it, hood clearence is tight.
When I first did my carb conversion, I did so utilizing the stock crossfire heads. It ran with typical 5.0 Mustangs and Z28's. I later swapped to the entry level Dart S/R casting heads and it woke up the car. With headers and the cam I reccomended to you I was running consistent 12.70's @ 109 on pure radials. It wasn't until I got into the 400 engine that I aquired the 11sec84 status:) Don't forget, once you change to carb, you might as well delete the smog pump and related devices since they will no longer serve any purpose.

 

RED5's mechanic here(SC'ED 66 VETTE), I have already removed all the smog stuff before I sold it to him. However, we have found a manifold/carb/aircleaner that will fit under the stock hood, but you are right , a very tight fit ! ! ! I am going to put all this stuff on for him. I will get him to get the heads and cam as soon as I can talk him into it. Hopefully that won't take long. :) Thanks for all your help, I will take a look at the heads and cam you have recommended to RED5.

Will

 

I am still waiting for the oportunity to go to the track and see what it will do in the 1/4 :)
My Winter project is to put on the scoup so I can drive in the rain if needed.

Will,
What's the intake/carb/air cleaner combo the will fit under the stock hood????? (just wondering).

Ziggy


[Modified by 88WHITE VETTE, 10:56 PM 12/18/2001]

 

Weiand (stealth) manifold, 600,650 or 750 carb, and any of the low profile air cleaners, you know the ones that kinda fit over and around the carb. 14" or so. This will fit under the stock hood.

 

Will,

Glad to see your working with me on this search for knowledge. What was the part that the 85 vette had that used the same in tank fuel pump and had the return line located on it? I can't seem to locate one in Summit.

BTW: When I put the edlebrock performer intake on the L98 heads the seem to fit a little loosely. Im concerned that they may be cut at a different angle. And the intake to the heads don't match the output of the intake :crazy: .

Are there specific angles and hole patternes in the heads I need to be concerned with?

 

As you recall, Steve said there was a little difference but he also said how to fix this easely. As far as the return style regulator, It is a Mallory 3-port return style in the Summit christmas catalog on page #85 @ the bottom left. The number is MAA-4309 Three port $74.95


WIll

 

Steve had mentioned that he had a machenist re-cut the intakes angles so it would fit better. Since we are starting from scratch would't it be easier to buy one that has been made with our intent in mind? Do they make the carb intakes that fit the stock L98 head assemblies?

 

What are some of you that are converting doing about the wiring harness in respect injector harness.and ,more ect ? I have been thinking about this also.


[Modified by mountainmotor, 4:11 PM 12/19/2001]

 

The 383 conversion (carbed) 85 that I saw had the wires still attached. Just wadded together and stowed in the corner.

 

Get rid of them. If you are going this far, then get rid of them all together. I called GM parts and they sell the fuel injection harness seperate, so this means that it can be unpluged and removed. Now don't get me wrong, I have not done this that is why I called and ask about the harness. I will remove RED5's harness to get it out of the way. No need to clutter up the engine compartment or burn the harness on the headers.

WIll

 

I have almost brand new (installed it and than I took it out, never run) regulator MAA-4309 that I purchased from Summit, but I decided to go another way and installed low pressure fuel pump and Holley regulator.
If you interested, I can sell it to you for $45 (shipping included).

To answear the above question, I did cut all my wires that I am not using. That includes all the distributor, knock sensor, MAF, etc.. wires, only thing that I left is the information system wires(temp. sensor, psi etc..). If I ever go to injection, I will be using Speed Pro system that comes with all the wires that you need for the FI.


Ziggy

 

Ziggy,

What made you decide to go he other way with the different pump and regulator? What type of set up are you running? ie: heads, cam, carb?
Did your convesion go well? Do you think your car is More or Less powerfull than when it was Fuel Injected?


Thanks,

Matt

 

Hi Matt,
This is partial post that I made after I had my engine dynoed:

It's 383 stroker, with 10.5 compresion ratio, Performer RPM intake, Holley 750 double pumper carburetor, XR288HR cam (int. lift @valve .555 / exh. lift @valve .576 / int duration:236 / exh duration:242)AFR 190 heads (no porting)and 1" spacer under carburetor.
This run was with 36 deg. timing advanced. We did couple of runs with 39 deg. but there was no power gains or losses. Nice thing about this engine is that it has over 400 #trq over 3000rpm.
Weather was HOT, and tempatures were in high 80s low 90s, barometric press:29.3

RPM Trq Hp
3000 402 230
3100 404 238
3200 402 245
3300 408 256
3400 406 263
3500 414 276
3600 411 281
3700 411 290
3800 417 302
3900 424 315
4000 425 324
4100 435 339
4200 440 351
4300 441 361
4400 446 373
4500 447 383
4600 451 395
4700 449 402
4800 448 409
4900 444 415
5000 439 418
5100 442 429
5200 440 436
5300 432 436
5400 430 442
5500 427 447
5600 422 450
5700 416 451
5800 406 448
5900 401 451
6000 399 456
6100 395 459

As you see, it was still making power after 6100 rpm, but I did not want to spin it over that. Since, I had the car at 6500 and still pulling very hard. Before that motor, I had 355 with Mini RamII on it and had nothing but trouble with the motor and other problems that unable me to enjoy the car. After it couth on fire whille road racing, I decide it was time for motor work. Just so happened that Monty was selling his old bottom end and next thing you know it was in my garage waiting for AFR heads and intake. With this set up, car feels so much more powerfull, but I still need to work on it to get good throtle response for autoX and road course.


As far as the pump/regulator, I changed it because after I installed it, I had couple of small leaks and I just did not want to mess with it and went to low pressure set up. If you going to use your old fuel lines, they must be "tailored" in order to work.
I will e-mail you some pictures of my set up tonight.

Ziggy

 

Red 5, i used the edelbrock performer intake and a holley 600 carb. changed to a vac advance distributor and use the holley red pump. still have to dial in a few things but its running. the intake i used is the 14 inch type but its only about 2 inches high. one of those cheap chromy ones you can get at a parts store. its just temporary until i fashion one so i can use the stock cleaner. its bigger than the little chrome job, plus i can get colder air up there. anyway it does not hit the hood. if i use a spacer, i dont think it would fit, its pretty tight in there.

 

Ziggy,
Loooks like you have been having some fun with your vette. :cheers:

When you run solo 2 events do you have trouble with fuel delivery during hard turns?
What are the drawbacks to running a carb in solo events?

Matt

 

There was no problem with the fuel delivery. At the time it was not tatally done and I had some throble keeping it running and it wanted to die when braking, but's all gone now (other problems that I mentioned to you in the e-mail).
Ziggy

PS,
you might want to spend some money and go for the road race floats to stop slosh in the bowls from interfering with float drop and needle and seat opening. They are available from the Barry Grant catalog, they are not cheeeep but worth it. I am putting them on my 650 that I am building.