[TAbird79]

I have a 403 motor in my 79 TA that has 64cc olds 350 heads matched with Mondello flat top pistons. My compression has significantly increased. Right now, the only way for me to stop my motor from pinging is to use half cam2 (110) and half premium (93). Should I be having to do this with this combination......????? The shop that rebuilt my motor says that I should be able to get it to run fine on just premium. Its getting to be expensive having to use the cam2.... By the way, an octane booster didn't help....

[Mr. P-Body]

Assuming (always dangerous...) standard bore, stock gasket, 4 CCs for valve reliefs (I know, Olds doesn't have them... add it in anyway!), .04" gasket thickness and "zero" deck, you're looking at 11.61:1. That's WAY too high for 93. The 50/50 mix is about right to get it to run well.

Jim

[olds]

Put the 4A's back on.

[TAbird79]

Sorry, forgot to add that the motor is bored 30 over. Where did you get that figure from? Thanks for the tip. Some guys in another forum were suggesting that maybe my timing is off, causing premature combustion, which is why i need higher octane. But, I remember my mechanic saying that this is the best he could get it without the motor stalling when but into drive. Also, another guy said that he has an olds 350 motor that has 13:1 compression and it runs just great on 87 octane. Does that sound legitimate to you? Thanks again for all of your help.

[Bandit79403Dave]

The guy who say's he's runing 13:1 on 87 octane is full of it. I entered the Engine Masters Challenge two years ago with a 403 Olds and I am in it again this year with the same motor (head issues kept us from competing) and with 11.5:1 and 93 octane we were able to muster around 700 horse with this motor. You don't want to even ask how much is in that motor. That was the ragged edge of what it could do. Crank case pressure started becoming a serious issue...especially if you start pinging. Like P-body said...assuming you zero decked and now have a flat top...you're in the 11+:1 range. With iron heads and I assume an off-the-shelf cam grind, you just aren't going to be able to get that configuration to run properly on pump.

Give this guy a call: Terry Fritsch FCR Performance 402-596-1800

He'll set you up right and can give you suggestiosn on remedying your problem.

BD

[TAbird79]

Finally, someone into the Olds 403 motor. The cam I have in mine is a mondello with .488 intake lift and .496 exhaust lift with a 260/266 Adv. INT/EXH degree duration. Like I said, the motor is bored 30 over with mondello flat top pistons, and 64cc olds 350 heads. The motor also has msd ignintion, an edelbrock perfromer intake and hooker headers followed by true duals with flowmasters. Just wondering how many horses I may be running here? Also, I was wondering if you could give me a rear end gear reccomendation? Right now I have 2.41, but I am looking at a 3.23 or 3.42. Would that be a good match up with what I have under the hood? It's and automatic trans by the way, with a stock torque converter. Thanks for all of your help, I will definitely give that guy a call.
Thanks

[Bandit79403Dave]

To ballpark your power estimate, based on your combo, I am figuring you are somewhere in the 400 horsepower area easily...more than likely more, but you are leaving SO much performance on the table with mismatched combos. That performer intake is a good intake but your combo needs the RPM. Blockers Performance or Larry Navarro sell the drop-base for the shaker. You never really mentioned what carb you are running but make sure that is functioning properly...that goes without saying. As far as gears, go with a 28 inch tire: 275/60-15 or a 235/70-15 (these are 28 inches tall) and 3.73 gears. At your power level and combo you need more converter and the 403 just likes 3.73s for some reason. As far as the converter, without seeing a dyno run of it I am gonna stab in the dark and say a 2800-3500 stall is in order based on where your power starts to come on. 3500 is about the limit you want to stick in there and still drive this thing on the steet. Heat will become an issue real quick with all the slippage in the converter.

Probably should step back and ask this: what is the ultimate goal of this car...btw...403 is an excellent choice good sir...

Bandit Dave

[TAbird79]

The carb I am running is the stock carb for the 403. My goal for my motor is to have as much performace possible, while still having it as a frequent driver. Do think I will have cooling issues with using the 3.73 gears because my car will be running at higher rpms on the highway? Im really scared of overheating this motor because it overheated after I put the 350 heads on it and a new cam. It spun a bearing in the crank and I had to have the whole motor rebuilt. Thats when I had it bored and added the falt top pistons and an oversized oil pan. Right now Ive only put about 300 miles on the new motor so it is still in the break in stage. I replaced the stock radiator with a 4 core, and added a heavy duty fan clutch along with a coolant additive. Im really paranoid about this thing overheating again so it has a 160 degree thermostat. So far, it hasn't passed 160 degrees, even on an hour long trip on the highway. When should I begin to worry about it overheating? At 220? or higher? Also, when should I change out my break in oil and then what type of oil would you reccomend me using after the break-in? Sorry if im picking too much at your brain, I've just never been able to talk to anyone about this that is so knowledgable and helpful
Thanks again,
Joe

[TAbird79]

I forgot to add one question..... Do you think that my maiinline will be a problem if it is not strapped? I was reading an articlle on Mondello's website which reccomended srapping the 403's mainline to make up for the support....

[harry k]

which casting 350 heads do you have , 5 or 6 ?
how much total timing ?

[TAbird79]

#5 casting. And I'm not sure about the timing. I talked to my mechanic yesterday about it and he said that the timing was good and I should just slowly back off on the cam2 until the pinging starts again that way I will know if I can use less mixture.

[harry k]

since you don't know where the total timing is at , have your mechanic do a one cylinder a static cranking compression test , if the compression is above 175-180 psi then you will need to do mechanical change .

[olds]

TABird,
Is that stock carb reworked ? I have #4 heads on my 403 (60cc) and the qjet did not provide enough fuel at idle. I had Cliff redo it. Just wondering.

[TAbird79]

The carb is the original carb. It was rebuilt about 3 years ago.