Tips & opinions for a possible 403 swap, good idea?
#1
Tips & opinions for a possible 403 swap, good idea?
Is the '78 to '79 Olds 403ci engine a viable performance engine?
I currently have an Olds 350 and read up on the 403 as being a large bore short stroke engine and I assume it may have some "revy" characteristics.
Is the bottom end relatively strong?
What kind of power can I expect? (flat torque curve, higher rpm performer, poor low end, etc.)
I know Pontiac and Buick also used this engine. What is the availability in terms of after market performance parts?
Any information, tips, or opinions you may have would be most appreciated. Just a side note- I am most likely going to turbo the 403 (if I go that route) or the 350 I currently have.
Thank you
I currently have an Olds 350 and read up on the 403 as being a large bore short stroke engine and I assume it may have some "revy" characteristics.
Is the bottom end relatively strong?
What kind of power can I expect? (flat torque curve, higher rpm performer, poor low end, etc.)
I know Pontiac and Buick also used this engine. What is the availability in terms of after market performance parts?
Any information, tips, or opinions you may have would be most appreciated. Just a side note- I am most likely going to turbo the 403 (if I go that route) or the 350 I currently have.
Thank you
#2
Is the '78 to '79 Olds 403ci engine a viable performance engine?
I currently have an Olds 350 and read up on the 403 as being a large bore short stroke engine and I assume it may have some "revy" characteristics.
Is the bottom end relatively strong?
What kind of power can I expect? (flat torque curve, higher rpm performer, poor low end, etc.)
I know Pontiac and Buick also used this engine. What is the availability in terms of after market performance parts?
Any information, tips, or opinions you may have would be most appreciated. Just a side note- I am most likely going to turbo the 403 (if I go that route) or the 350 I currently have.
Thank you
I currently have an Olds 350 and read up on the 403 as being a large bore short stroke engine and I assume it may have some "revy" characteristics.
Is the bottom end relatively strong?
What kind of power can I expect? (flat torque curve, higher rpm performer, poor low end, etc.)
I know Pontiac and Buick also used this engine. What is the availability in terms of after market performance parts?
Any information, tips, or opinions you may have would be most appreciated. Just a side note- I am most likely going to turbo the 403 (if I go that route) or the 350 I currently have.
Thank you
#3
Thanx Joe. Like I said, I already have an original Olds 350ci (unfortunately #7 heads though) and will probably boost it if it is a better candidate.
What about in a N/A application? Hows the 403 compared to the 350?
Whats a better investment: sticking with my 350 (more than likely boosted) or buy and build up a 403?
What about in a N/A application? Hows the 403 compared to the 350?
Whats a better investment: sticking with my 350 (more than likely boosted) or buy and build up a 403?
#5
Thanx Joe. Like I said, I already have an original Olds 350ci (unfortunately #7 heads though) and will probably boost it if it is a better candidate.
What about in a N/A application? Hows the 403 compared to the 350?
Whats a better investment: sticking with my 350 (more than likely boosted) or buy and build up a 403?
What about in a N/A application? Hows the 403 compared to the 350?
Whats a better investment: sticking with my 350 (more than likely boosted) or buy and build up a 403?
#6
Theres absolutely nothing wrong with big blocks like the 425 or the 455. BBO's are a dime a dozen and the build ups are just as numerous. I just want something different. I can't help it, I love turbos. I love seeing what they do to small displacement engines. That said, engines that have higher redlines are usually better candidates than low rev-ing BB.
Besides, BB are known for there low end & torque. The jetting and timing required for turbos, as well as the low compression, causes the low end to suffer which defeats the purpose... at least for a good streetable engine.
And another pro for boosting a 350 is MPG. With a 700r4 I bet I could still get 20+ miles to the gallon. I don't have any experience but I'm guessing a typical 425/455 averages 12 mpg (TH350/400 equiped)...?
Besides, BB are known for there low end & torque. The jetting and timing required for turbos, as well as the low compression, causes the low end to suffer which defeats the purpose... at least for a good streetable engine.
And another pro for boosting a 350 is MPG. With a 700r4 I bet I could still get 20+ miles to the gallon. I don't have any experience but I'm guessing a typical 425/455 averages 12 mpg (TH350/400 equiped)...?
#7
Aren't the pre-77 350's also windowed? And I thought 75 and later 350's were SBC? with four bolt mains? I could be wrong....
I do understand that the "Olds" 350's can have the bottom-end reinforced (girdle, alloy mains, etc.) and that the 2bolt mains can be as strong as a 4 bolt from other GM engines because the Olds foundry used higher nickle content in the steel during casting... per-75... I think.
#8
- GoldOlds
#9
#10
Yep, I have #7A heads. Itty bitty intake ports. I don't know the cost but I wonder if hogging them out is cheaper and as effective as buying a new set of heads....
#11
I can't answer the first question above, but Olds kept making their own 350 up to about 1979 or so. True, the mid-70s was an era of GM mix and match, meaning every division was borrowing engines from the other three. Pontiac used a lot of Olds 403s in their '78 and '79 Trans Ams, which brings me to my next point. From what I've seen first hand, the 403 is a stronger engine than people give it credit for. A few friends of mine were HUGE fans of the 403; one had one in his '79 T/A, the other in an '80 T/A (originally a 301 car) and later an '84 Grand Prix. They kicked the living snot out of those motors and they never broke down. Putting a 330 crank in a 403 sounds like a good idea to me; you don't lose any cubic inches and you have yourself a forged steel crank. Just my 2 cents.
- GoldOlds
- GoldOlds
In a bone stock 403 I am sure it would hold together even with a factory crank. Would it hold up to 500+ street horsepower? Boosted or not...?
#12
You are.
Windowed mains did not enter production until the 1977 model year.
As noted previously Olds made 350 gas engines until the 307 came out in 1980. Some SBCs were used in the downsized 77-up Oldsmobiles and were the subject of a famous lawsuit, but the Olds 350 was still in production.
Windowed mains did not enter production until the 1977 model year.
As noted previously Olds made 350 gas engines until the 307 came out in 1980. Some SBCs were used in the downsized 77-up Oldsmobiles and were the subject of a famous lawsuit, but the Olds 350 was still in production.
#13
Don't confuse the the 1972 7a (small upper case A) heads (casting number 409147) with the late 1980s 7A (large upper case A) heads (casting number 0142) used on the 307. The 7a heads are fine, the 7A heads are crap.
#14
You are.
Windowed mains did not enter production until the 1977 model year.
As noted previously Olds made 350 gas engines until the 307 came out in 1980. Some SBCs were used in the downsized 77-up Oldsmobiles and were the subject of a famous lawsuit, but the Olds 350 was still in production.
Windowed mains did not enter production until the 1977 model year.
As noted previously Olds made 350 gas engines until the 307 came out in 1980. Some SBCs were used in the downsized 77-up Oldsmobiles and were the subject of a famous lawsuit, but the Olds 350 was still in production.
So 7a (small capital "A") are good heads (casting #409147)? Right?
#15
- GoldOlds
#16
Thanx Gold Olds. I appreciate your input.
My main goal is determine the strength of the 403. People have said good and bad things about the block and I think I'm just gonna stick with the 350ci.
What helped me make this decision was the notion that the windowed block reduces the maximum redline to approx 4000-5000 rpm. With the bore to stroke geometry as it is the 403 should love to wind-out. While 5000 isn't bad, I'd like to see a 6000 rpm redline or even in the neigborhood 6800 (dreaming maybe). I'd bet I could achieve a 6000+ redline with a 350 after balancing and blueprinting, roller rockers, knife edged crank, etc.
My main goal is determine the strength of the 403. People have said good and bad things about the block and I think I'm just gonna stick with the 350ci.
What helped me make this decision was the notion that the windowed block reduces the maximum redline to approx 4000-5000 rpm. With the bore to stroke geometry as it is the 403 should love to wind-out. While 5000 isn't bad, I'd like to see a 6000 rpm redline or even in the neigborhood 6800 (dreaming maybe). I'd bet I could achieve a 6000+ redline with a 350 after balancing and blueprinting, roller rockers, knife edged crank, etc.
#17
So are the plain #7 heads any good? Just the number "7" with no other letter. Casting number is 409147 near the exhaust ports. The heads are a bit dirty and caked with grime/oil but I see no letter.
#19
I'm not convinced the valve sizes in the FAQ are correct. I was sure all 350s except W-31s used 1.880 intakes and 1.567 exhausts, but you'll need to mike your valves to be sure. The main difference between the 1971 #7 heads and the 1972 #7a heads is the valve spring pockets. Olds used rotators on the valve springs on some heads. The rotators were thicker than normal retainers so the spring pockets in the heads were cut deeper to provide the same spring installed height. #7 heads should have rotators (and thus deeper spring pockets) on the exhaust valves only, #7a heads should have deeper spring pockets on all valves. Not a big deal since you want to ditch the rotators for high perf use anyway (the added weight isn't conducive to high RPM performance). Depending on the spring pockets, you can add shim washers to get them where they need to be. Except for this spring pocket difference, the 7 and 7a heads are equivalent and are also equivalent to #5 and #6 heads as well.
#20
Thanks for the info Joe, but if I'm not mistaken don't the #5 heads have the larger intake ports? taller ports? #7 are of a small square type and the #5 are a tall rectangular shape I believe.
#21
#22
Thanks again joe.
I have yet to pull and tear down my 350. Its running so I figure I'll wait to I'm good and ready before I pull it apart. until then I have been trying to gather information on engine components in order to identify what I have and what i want to replace. If the #7 heads (no "a" or "A") are as good as you say they are then I'll clean them up, do some porting, maybe oversize the valves, and polishing as opposed to dumping $2500+ into edlebrock units. Most of the information online has been extremely helpful but I keep running into "sometimes" and "some engines were different because", you know, just like the way you said some have deep spring pockets and some had just half within the same year. Just gettin as prepared as I can get.
I have yet to pull and tear down my 350. Its running so I figure I'll wait to I'm good and ready before I pull it apart. until then I have been trying to gather information on engine components in order to identify what I have and what i want to replace. If the #7 heads (no "a" or "A") are as good as you say they are then I'll clean them up, do some porting, maybe oversize the valves, and polishing as opposed to dumping $2500+ into edlebrock units. Most of the information online has been extremely helpful but I keep running into "sometimes" and "some engines were different because", you know, just like the way you said some have deep spring pockets and some had just half within the same year. Just gettin as prepared as I can get.
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