I'm new to this board, although I've been reading and searching posts on the boards for a few months to help me plan my engine buildup on a 91 RS 305 LO3 engine.

Here's my plan:

Step 1
Good tune up
Hooker 2055 headers (coated)
Catco hi flow cat
Hooker 3" cat back
14" open element air cleaner
All these parts are in my garage waiting for a free weekend to install

Step 2 - I'll probably wait until winter and pull the motor
Edelbrock Performer TBI intake manifold (#3704)
LT1 cam (205/207, .447/.459, 117 lsa)
World S/R Torquer II heads (58cc)- ported and polished
Ultimate TBI mods
HEI ignition and wires
TIB.chips prom to get me started, then custom burn myself


Step 3
Swap 3.08 open rear end with 3.42 posi
Suspension mods

I have realistic goals for this buildup since I realize the 305 isn't the ideal building block for big hp. I don't plan on being the fastest guy on the block, just want to wake up the L03 from 170 hp stock to something in the 250 to 270 hp range.

My #1 concern is using an intake, cam, and heads that are balanced and compliment each other. #2 is engine driveability as good as stock, meaning no hesitations, no backfires, good idle, etc.

Questions:
1. I'd like to keep the car emissions legal even though I'm not in an emissions controlled county, although I soon could be. That's a big reason why I plan to use the Edelbrock TBI #3704 manifold, it's EGR ready. How much of a penalty will I pay in hp to use this manifold as compared to a better carb manifold with a tbi adapter plate?

2. Assuming I use the Edelbrock TBI manfold, is this a good match with the LT1 cam and World S/R Torquer heads?

3. Should I do the Ultimate TBI mods or just go with a Holley 670 cfm TBI or GM 454 TBI? I realize that with the Holley or GM TBI's I'll need to bore the intake ports to 2". I'd rather not waste the money on a bigger TBI if the stock TBI with the ultimate mods can deliver enough fuel and air.

4. I think I will probably need a larger fuel pump, especially if I go with the larger TBI. I plan to use the 190 lph size since I think the 255 lph size will be too much.

Comments are welcome, especially from those who have experience with a simialr setup. Thanks,

91Rocks

 

Sounds like you have it planned out pretty well. I like your parts selection and it seems organized. I would change a couple things though.

First, I would put the gears and posi before the cam and intake and heads. You'll want the gears to be there already to get you in the power band quicker. Also, the posi will help you put the power to the ground and not just light them up.

Second, I would get the chip burning stuff right away and start messing around with the car asap. I just did a header install and intake manifold. It already really needs to be tuned. These cars lack a lot in the PROM department. Start doing that as soon as you can.

Also, I just installed the Holley TBI intake manifold and I really like it. I did the ultimate TBI mods and am using the stock one for now, but the manifold comes with 2" bores if I want to upgrade later, much simpler than boring out the Edelbrock. It also has a larger plenum. The manifold takes a bit more fabricating to get it to work, but they're fairly simple changes. It also has EGR so you can stay legal. Just check it out as an option.

 

Forgot to mention, Another good reason to start the chip burning early is that you will get comfortable with it fast and maybe feel more daring with your build. That is, go with a bigger cam instead of the LT1 cam. If you're comfortable tuning the chip on your own, you can throw a pretty good sized cam in that motor and make some real good power.

Right now the LT1 looks good with no experience tuning it'd be easier to dial in. But, if you have the experience you may feel that you can step it up and still tune it easily.

 

If I were you, i'd do gears and rear after the motor is in running and tuned.

Who would do gears before figuring out the powerband? I dunno.

Last thing you want to do is get everything done and find out you have to little/not enough gear at the end of the track.

Tuning the TBI ECM. Well. Enjoy. I tinkered a little bit with them.
I'm not a big fan. Some of the guys over in DIY_PROM have used
'730s.

-- Joe

 

BronYrAur, thanks for the feedback. The intake manifold is what I'm still debating. I need to look into the Holley TBI intake a little more. Can you give me the p/n? If I go the Edelbrock route, I'm not too worried about boring it out. I have friends who are machinists who can do it for me, plus sounds like others on this board have opened it up to 2" despite what Edelbrock says. What mods or fitup issues did you run into with the Holley? Sounds like the Holley may provide a little more performance, but for my buildup, I doubt either will be the limiting factor.

 

I can see where you're coming from but either a 3.42 or 3.73 gear will be fine for that combo. But, I would hate to see all that work go into the engine and then have it be a dog because he's still got a 2.73 gear. I was just looking at it from a different perspective.

As for the ECM's they aren't really difficult to deal with if that's what you were implying. Any novice can easily tune in the fuel and timing on a TBI ecm with some knowledge and practice.

I bought the Holley intake used but I believe the part number is 300-66. You can find it on the Holley site to check, but I'm sure some place like Jegs carries it.

 

3.42 to 3.73 is a big jump.

Lets look at it this way. Say he's running a 24" tire. In his 1:1
gear, say his redline/shift point is 6k. With a 3.73, that will be 114mph.

Say he uses the same tire but chooses 3.42, his MPH will be 125 at 6k.

Now I dunno what his powerband and shift points will be, But I think saying a 3.42 or 3.73 will work is a huge error. He's gonna want his trap MPH to be just under his redline point. Personally, I don't think hes gonna be trapping 114, or 125mph in the 1/4.

Now if he decides to get some 16" tires, and the outside diameter is greater than 24", and he decides to get a 3.42 rear end, then I wouldn't even bother shifting into his 1:1 gear. Car will bog.

-- Joe

 

The Edelbrock intake is a great intake as fas as "true bolt on" is concerend. It literally bolts right up without splicing, cutting, fabbing or relocating anything. It is a nice step up from stock and shares the same basic design of the performer carb intake yet has the TBI unit centerd as to increase equal distrobution to each runner. It can be bored to 2" to accept a larger TBI down the road which also helps unshroud the top making it perform more like the carb version. The Holley intake is a little bit better than the Edelbrock intake from everything I have read about it. It already has 2" bores and comes with EGR. It will require you to relocated a few things including converting to an older style EGR to have it clear the TBI unit. This can be avoided though by using a TBI spacer. Your best intake choices are carb intakes. Some can be had with EGR and most will perform better than either the Holley or Edelborck intakes. Plus depending on what cam you go with, it will be easier to select an intake that matches. Both the Edelbrock and Holley intakes are well suited for the LT1 cam. Both have great midrange power making capabilities that matches the cam's profile and behavior in a 305. Carb intakes are also cheaper but come at the cost of relocating stuff (small expences for hoses and fittings and such) and the cost of an adapter plate. You should still come out slightly cheaper than the $200 price tag on the Holley and Edelbrock units. You may howver, have TV cable problems because of bracket missalinment. If you have a T5 car don't worry about this. Now, if ease of installtion and downright simpleness are in favor instead of a few mesely hp, than go with either the Holley or Edelbrock.

 

91RockS,
I have a very similar setup to what your wanting to build, except I didn't port the heads and use an Edelbrock carb intake with the Holley adapter. The TBI unit is unmodified with stock injectors.

After I moded mine I was able to add a load of ignition timing (over 10 degrees).

My engine is running to the limits of the stock throttle body unit. At about 4000 rpms under full throttle the engine starts to make vacuum and the wide band dyno readings show that it's starting to lean out at 4500 too. I've already tuned the chip for maximum fuel at this point. I tried the Holley TBI last year and had ignition problems with it got over 4500 rpms that went way as soon as I returned to the GM TBI. It I was you I would start looking for a 454 TBI. I would be using a 454 TBI now if I wasn't going to switch to multi-point injection.

You definitely need a good fuel pump, specially if yours is getting old. I'm running a 255 lph TPI pump.

You will lose a bunch of torque, but the torque peek will move up about 1500 rpm (from ~2000 to ~3500) and you will gain a load of horse power.

 

Anesthes,
The point I was trying to make with the gears is that he has a bad gearset in there now. The car is going to pick up a little performance but still be a low 14 second car. If he were choosing gear ratios for optimum performance based on 1:1 at your shiftpoint he'd have something more along the lines of a 4.10 gear. I just said 3.42 or 3.73 depending on what you would rather drive on the street, it's a matter of comfortability, it's not exactly a race car.

As for the Holley intake, Like Shifty said you have to use an older EGR valve that'll clear ( I just blocked it off with a plate). My throttle cable was off by about an inch so I had to make an extension out of a piece of metal and bolt the original throttle bracket onto that, worked fairly well. The coil didn't bolt onto the manifold right because the bolt holes weren't the same distance apart as stock. Relocated that. The fuel lines also had to be cut and lengthened because we didn't want to try to bend them up over the new bigger plenum to reach the TBI.