Little about me I am a Technology teacher who grew up doing woodworking and teaching it for 7 years. This year our automotive teacher retired and I was told I would need to take over the Auto program. I have very little auto background but am certified to teach it. So I bought a 1977 Formula Firebird as a little class project. We have torn the whole care apart and looking to redo the engine.

I am redoing the 403 out of my 1977 Firebird Formula. I am trying to do a budget build.

I am working with a 403 block and 330 #3 heads which are being sent to the machine shop this weekend to be maged and cleaned

I am looking to do a street cruiser and get 300hp or so.

The rear end gear ratio is 2.41

So that’s where I am starting. Where do I go from here??

 

Send the block along with the heads and let the machine shop clean and determine if it needs to be bored and how much. Then you can determine piston sizing. If the crank has wear, you might consider sending it along with it.

 

Look into putting a 3.73 rear in it, with a Detroit TrueTrac limited slip differential. There is a $50 rebate at Jegs until March 31.


You can also put a FiTech throttle body on it in place of a carburetor. They self tune, run better, require less maintenance, and give much better gas mileage than the carb, and are easy to install in place of a 4 barrel carb. Pretty much plug and play. You do not need a high pressure fuel pump, but an electric one would probably work better than the mechanical one.


You do not say how many miles are on the engine. If the bores are in good condition, you may not need to bore it. Check them, and if useable, hone them with a flex hone of the correct size, and put new rings in it. For your application a .020" gap should be sufficient. A little on the open side is better than too little. You should check the bearings and if they are good, check the clearance as well. If you decide to replace the bearings, have the crank turned, and get correct bearings.


Other than that, a roller cam with retrofit roller lifters will make it a lot easier to succeed. You do not have to worry about the flat tappet cam break-in.


A new timing set is almost imperative.


While you are having the heads done, have them mill them a little to raise the compression ratio. You may need higher octane fuel, but you will get more power out of the engine.


I believe this would constitute a budget build, and give you the best engine for the money. You could rebuild the carb, or if it is not a 4 barrel, replace it with a 4 barrel (rebuild a used one). The fuel injection is nice because you can drive the car at any altitude, and the system will compensate. A carb will cause power loss at higher altitudes.

 

If you are using this car as a project for your class then definitely make sure you disassemble the motor in the lab so students can get experience. You should teach them how to use a dial-bore gauge to check the cylinders for out of round and plasti-gauge to test the bearing clearances. As others have said hopefully the motor isn't so worn that you can't use a ball hone to put new cross hatch in the cylinders. The more work you and the students do the more valuable it will be as a learning exercise.

 

I have had the class measure and dissemble the engine while taking a lot of pictures and labeling everything. And it has been a great learning experiences. Last year we completely took apart a ford 302 and just reassembled it with a new gasket kit and they were so pumped when we were done and it ran.

 

You can use a bore gauge and micrometer to measure the crank and rod journals as well.

I put the parts in labeled ziplock bags to keep them together.

There are some "Power Nation" "Engine Power" videos (usually on TV Sunday morning) that go over a number of the techniques for measuring and fitting parts when rebuilding engines. I am sure the kids would like a homework assignment that required them to watch TV. The episodes are also available at powernationtv.com. Look under programs and select "Engine Power"

 

A high pressure fuel pump is needed with EFI. You can use a mechanical pump to supply a small surge tank, which contains a high pressure electric pump.

http://www.robbmcperformance.com/pro...owersurge.html

 

This is a throttle body fuel injection, and it may not require the high pressure of the port fuel injection. It has a built in pressure regulator. Other throttle body injection systems usually require 9-15 PSI. Jegs can give you further information about exactly what pressure system is needed. You may have to make a return line from the fuel pressure regulator to the tank. An inline pump may be enough to support the system without the expense of the overkill systems offered to make it work. If it does not have a regulator, then you can get a regulator fairly cheaply. The throttle body fuel injection is still far better than the original carb.

 

wouldn't rebuilding a carburetor be a good project for an auto shop class?

 

I understand it's throttle body EFI. I have FAST EZ-EFI on mine and considering going to Holley as an upgrade. FiTech fuel pressure regulator is set at 58psi.

I agree rebuilding the carb would be a fun class project to at least help them understand how it works. However, not really a necessary skill for any teenager looking to get into general automotive repair.

 

Maybe this will give you some guidelines.
https://classicoldsmobile.com/forums...403-build.html

 

x2

I'm surprised more gear heads don't feel confident rebuilding their own carburetor.

 

Not to hijack, but as an education student, certifying in social studies and then continuing for my tech cert, I'm happy to see this! It's cool you guys are digging in on this project in a class. Auto classes are not as common as they once were, and more so, its cool that you guys are hands on to that level. It takes a good dedicated class to accomplish that depth of work!

 

Thank you, the students are really enjoying the project. But this project is not going to be possible with out all you guys helping. Being a first build for my students and I, we will be keeping it with mechanical fuel pump and a carb. Keeping it simple. Again I am on a small budget, this all comes out of my pocket school doesn't help, but then again it is my car when we are done.

 

Thanks for the pic. It's awesome that you're willing to buy parts and materials so the students can learn by rebuilding your motor and such. It takes a big heart to be a teacher.

 

If you are going to go to 300 HP, you should have at least a 650 CFM carb. A cam and retro fit hydraulic roller lifter kit will make your life better. You did not state whether you had a stick or automatic trans. If you are keeping the stock gears, and have an automatic, you should get a 2500 - 3000 rpm stall torque converter, or your driveability will be poor at minimum. If you have a stick, you may find that the engine does not like the low rpm range with the tall gearing, when driving in the city. I have 3.23 gears in my wagon, and they are good highway gears (6000 RPM = 200 MPH with .70 overdrive). Your engine will not come on the cam until about 2000-2500 RPM.


So, if you are going to up the HP, you should change your rear ratio to at least a 3.23, or maybe shorter gears, like 3.73. 3.73s are still driveable on the highway, but will make around town driving a lot more pleasant. The 2.41s are only there to make CAFE mileage ratings for the government. Make sure you check for compatibility with the different ratios before you open the rear.

 

This is an Automatic.

 

Since you have an automatic, you should consider both the gear change and the torque converter change. The HP range you are going to usually needs the gearing to get into its RPM range to be reasonably smooth to drive.


My BBC needs a 2500 RPM torque converter, and the 3.23 gears are marginal for an around town car.

 

Changing rear gearing is a good idea. That car should be a stock 8.5" 10 bolt, which should be plenty strong for what you are building. With a th350, you will probably not want to go much above 3.23 if you take it on the highway much. If it doesn't see much highway use, 3.42 or 3.73 could be an option.
Also agreed you will need a converter. There are plenty of people more qualified than myself to suggest a converter, but I'd think a 300 hp 403 would like something around 2500 stall or less. It will be making power down there, and any higher will be wasting power.

Let us know what the machine shop says you need for a bore, maybe we can help find a piston that suits your needs.

 

That will have the factory 800 cfm carb but may need idle circuit mods with a noticeable cam. With no machine work, you will be at 9.25 to 1 minimum with those 330 heads.

 

Many look for #5 heads and I believe they are missing the #3 and #4 330 heads they are large valve and closed chamber. A great choice

 

What intake would you suggest for a 403 with 330 heads?

 

The Performer is a good stock replacement and will work properly if you have the shaker hood. The Performer RPM intake is good but too tall for the shaker hood.

 

There are companies that make the shaker drop for the Performer RPM intake. On a 403, I would definitely use a Performer RPM...

 

edegraaf, may I ask where you live? I'm certified as a teacher, have built cars featured in magazines, but can't find any schools that will consider me to teach auto shop since I've not been a "professional' mechanic.


First, keep things simple. Make ONE change at time. Use this car to exemplify the Scientific Method of testing.


MATH: TONS of examples in this. Have the students measure everything. Have them think of different ways to determine the CC's of the valve reliefs in the pistons, and test their methods. Show them the volume of a cylinder formula, and how to use it to determine compression ratio.


CHEMISTRY: stoichiometric ratios, how 14.7:1 is theoretic. Then obtain a wideband oxygen sensor system (such as Innovate) and actually measure the ratio. Test different idle ratios against the theoretic, and have students record their observations and draw conlussions & make hypothesis. Maybe a daytrip to a chassis dyno, and see how max power comes at around 12.8:1.


All sorts of Physics you can tie into this, mass, inertia, energy conversion, Newton's laws. Try to tie YOUR classes in with the core subject teacher's lectures when possible.


If you can find a local chassis dyno, they may make you some sort of deal in exchange advertising in the school newspaper, annual, and such.

 

I've seen the factory pre-EGR iron intake run well into the 13's at the dragstrip.


My stepbrother's 403 had the iron intake, Q-jet, 3.08 NON-posi rear, 235/60-14 cheap radials, stock torque converter, a header on the passenger side and a stock exhaust manifold on the driver side (LONG story...) and still ran 13.7's in his daily driver.

 

Even at the bright age of 30...I still don't trust my back to put a cast iron intake back on any V-8 while it's still in the car....ha

 

Ok so after 4 months at the Machine shop I have a short block. Now I need to know what I should do for an intake, carb (can I rebuild the original), Distributor, torque converter.

The Engine has been..
bored to 4.3510 and has new pistons and rings
deck height is 9.3120
compression is around 9.5
330 heads
roller rockers
comp cam intake .453 exhaust .456 Valve timing .006
duration .5 intake .212 exhaust .218

 

4.351 is the std bore.
And you have your cam specs all screwed up. Just sayin.

 

Thanks Bud,

.020 over on the bore

Cam specs

 

Either use the stock iron intake or get the Performer. Yes, get your factory 800 cfm Qjet custom tuned, as it will be way lean for your new combo.

 

Why so small on the cam?

 

I am not sure why, thats what the machine shop suggested.

 

Thing it may be a tad bit pingy on 91-93 octane with that cam and those heads on stock 403 pistons but if not the torque will push those 2.41 gears good

 

Did you ask them what their reason was for picking that cam? If you didn't then shame on you. It's your money, you should be able to ask anything you feel like asking.

 

I was going to say the same thing with true 9.5 to 1

 

No i didn't ask as I stated 5 months ago when I got on this forum I am clueless when it comes to this stuff. I am new at it and was looking for advice.

What are you suggesting the CAM should be.

 

If you want a little tone then an Erson Viking 100H would work well, done a bunch of those for 403's. Its' 222/222@.050 with .478 lift.

 

I agree, need another 10 degrees, at least, on the camshaft.


Are you teaching the auto shop class?? If so, send me a PM.

 

Thanks for making it fun for the kids! Helps keep the interest. I recall in 1982 having the shop teacher who raced boats have me and 2 other kids do rings and bearings on his race boat 273 Mopar. Had a bunch of good used bearings and plasti gauge and let us have at it. Had instruction before we wrenched of course. He was within 2 MPH of his personal best with the engine we assembled.