Frequently Asked Questions

Q: 350 HO Codes for 1968

What were the possible options and codes on my:
1968 Firebird 350 H.O.
L-76 H.O. Engine, 4Bbl Carb, Dual Exhaust, “H.O.” Side Stripes

A:
Engine:
350 H.O. Man. Trans. “WK” 320 H.P. 10.5:1 Compr.
350 H.O. Auto. Trans. “YM” 320 H.P. 10.5:1 Compr.

Trans:
3-Spd. Standard (C/S) Saginaw “RJ”
3-Spd. Standard (F/S) Dearborn “DB”
4-Spd Optional Muncie “FX”
2-Spd Auto ST-300 “MB”
2-Spd Auto (w/A/C) ST-300 “MC”

Cylinder Heads: “18”
Carburetor: M.T. 7028269 A.T. 7028266
Intake manifold: (same as all 4Bbl) 9790140
Exhaust Manifolds: (same as Std. & 400) 9794320RH/9777755LH)
Distributor: M.T. 1111447 A.T. 1111282

*There were 2,087 400 H.O. Firebirds made in 1968. I’d guess that there were close to that for the 350, perhaps less.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: 350 H.O. Components

What components were used on a 350 HO that made it special from a regular 350?

A:

TH400 –

Definitely used on 350HO but TH350 on std 350 engines (if ordered with Turbo Hydramatic)

Carb –

7029268 is correct. I bought the same one when I needed a carb.

Suspension –

It sounds like you have air shocks. And I don’t think they were used, even in the heavy duty suspension. I looked at the AMA spec (https://FirstGenFirebird.org/firebird/1969/ama/ama_page9.html) and it never mentions air shocks. Probably a previous owner put them on???

Manifolds –

I e-mailed Paul Spotts (formerly of Performance Years) and asked him and he too says they used STD manifolds. The casting number I gave you was from the ones on my wife’s car. I was told that they were from 1969-1972 full size car manifolds, based on a “Foundry Parts List”. Sounds like, from your casting dates, that they are correct. Good for you! Oh, one last check might be to see you if you the oil filter adapter that would have to be used if you had the long branch, since they interfere with the normal oil filter location.

Heads –

I also asked Paul about this, and he said that they were in fact different for the 350, but that some 400’s (like Judges other Hi-Po cars) may have gotten the 350 #48 heads for even more compression, because of the low demand for the 350HO, and thus having extra parts around the factory.

Valve Reliefs –

The 350 HO cars must have had the valve reliefs since the size of the valves, even if they were right next to each other (2.11+1.77=3.88) is larger than the bore of 3.875 (.) But recently I heard it suggested that maybe all 350’s got the valve reliefs so they didn’t have to cast and stock two different type of blocks. Plus I know of people who have put the Large Valve heads on their 1969 350 2-bbl blocks and did not crash the valves, so the must have had the valve reliefs.

Power Steering Loop –

Asked Paul about this too. His recollection was that is was used on cars with high numeric gear ratios, like 3.73 or higher, or 3.90 or higher, since they would typically be revving higher, thus spinning the pump faster. What is the rear end gear ratio on your car?

Cam –

I’ve only heard lately the story that they used the 744 cam in 350HO cars, but that’s not what the AMA spec says or any other literature I have. 067 cam for Auto, 068 for std trans.

“Hood Scoop” –

I noticed this passenger side “hood scoop” that looks like a hood tach on some factory literature too, which also shows it on a lemans. Was supposed to be used for cold air induction. Maybe this falls in with the long branch manifolds….planned but never put into production????

Side Notes –

From the picture you sent, I noticed that you still have thermostatic vacumm switch on the intake. That’s good news, I almost never see a car that still has this, the manifold is usually plugged. Also noticed that you are missing the second alternator bracket that seems to duplicate the one from the water pump, but attaches to the front bolt on the thermostat housing.

If you want some info on my wife’s car, go to:

http://www.angelfire.com/on/geebjen/jensbird.html

There is only one picture of the engine compartment there, and it was taken by the previous owner. Since then, I’ve gone to std black plug wires, painted the intake, valley pan, valve covers, brackets, water pump etc, and will be replacing the chrome air cleaner with a factory single snorkel with black lid and pcv vent tube etc. I’m hoping to get some newer pictures of the updated engine compartment soon. When I do, I’ll post them on the site.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: 350 HO Codes for 1968

What were the possible options and codes on my:
1968 Firebird 350 H.O.
L-76 H.O. Engine, 4Bbl Carb, Dual Exhaust, “H.O.” Side Stripes

A:
Engine:
350 H.O. Man. Trans. “WK” 320 H.P. 10.5:1 Compr.
350 H.O. Auto. Trans. “YM” 320 H.P. 10.5:1 Compr.

Trans:
3-Spd. Standard (C/S) Saginaw “RJ”
3-Spd. Standard (F/S) Dearborn “DB”
4-Spd Optional Muncie “FX”
2-Spd Auto ST-300 “MB”
2-Spd Auto (w/A/C) ST-300 “MC”

Cylinder Heads: “18”
Carburetor: M.T. 7028269 A.T. 7028266
Intake manifold: (same as all 4Bbl) 9790140
Exhaust Manifolds: (same as Std. & 400) 9794320RH/9777755LH)
Distributor: M.T. 1111447 A.T. 1111282

*There were 2,087 400 H.O. Firebirds made in 1968. I’d guess that there were close to that for the 350, perhaps less.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Difference Between a 400 H.O. and Ram Air Firebird

Whats the difference between a 400 H.O. Firebird vs an identically equipped Ram Air Firebird?

A: Functional (cold air) ram air induction came on the 1969 RA III. 1968-1969 400HO cars did not have this. Besides this, they are 100% identical (ie ra III did NOT have a different carb settings, cam, heads, exhaust manifolds etc)

As I recently mentioned, if you wanted all the hardware and performance upgrades that the “Ram Air Performance Package” truely offered (i.e. cold air induction PLUS better flowing heads/stiffer valve springs, 3.90/4.33 rear, radical cam, stronger valvetrain, etc) you HAD to get the RA IV (not the RA III/400HO ) in 1969. In 1968, the RA I or RA II (and not the 400HO) had to be ordered.

Think of it this way…. RA III Firebirds (and Trans Ams for that matter) came with *Ram Air Induction* while RA I, RA II and RA IV ‘Birds and TAs came with a *Complete Ram Air Performance Package*

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Verify a 350 H.O.

Up until about 5 minutes ago I thought my bird was originally an inline 6. Well I now know it was a V-8 after checking the VIN. Is there anyway to tell if it could have been a H.O. through the vin and trim or would I have to go through PHS?

Could I tell from strips, engine code, hood holes, tires, or other distinct H.O. markings?

A: As far as I can tell, the only 350HO info on the car would have been atttached to the engine – such as code WK (manual trans) with cam 067, carb 7028269 and distributor 1111447 or YM (automatic) with cam 066, carb 7028266 and distributor 1111282, both with casting number 18 heads.

Checking for other options is a more questionable. Since the 2 barrel 350 could have optional dual exhausts, evidence of that option is not a guide either. Both the 350HO and the 2 barrel had the same hood emblems and related holes, so this is useless info. The stripes could have been a option deleted.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Difference Between a 400 H.O. and Ram Air Firebird

Whats the difference between a 400 H.O. Firebird vs an identically equipped Ram Air Firebird?

A: Functional (cold air) ram air induction came on the 1969 RA III. 1968-1969 400HO cars did not have this. Besides this, they are 100% identical (ie ra III did NOT have a different carb settings, cam, heads, exhaust manifolds etc)

As I recently mentioned, if you wanted all the hardware and performance upgrades that the “Ram Air Performance Package” truely offered (i.e. cold air induction PLUS better flowing heads/stiffer valve springs, 3.90/4.33 rear, radical cam, stronger valvetrain, etc) you HAD to get the RA IV (not the RA III/400HO ) in 1969. In 1968, the RA I or RA II (and not the 400HO) had to be ordered.

Think of it this way…. RA III Firebirds (and Trans Ams for that matter) came with *Ram Air Induction* while RA I, RA II and RA IV ‘Birds and TAs came with a *Complete Ram Air Performance Package*

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.