Had one of those 403's in a Jet Boat. The Harden Marine 403 did not have the window mains in the block..I was told they don't have them in the 77-78 GMC motorhomes either. They used a cam with specs about the same as a 70 455 4sp cam..like 475 lift and 295 duration if memory searves. The thing Ran so close to a 455 jet....it was scary!
One of the most underrated Small Blocks of all time , as the years go on people realise the 403 is not weak at all , many at 400 000 miles, that huge bore of 4.351 is 100 tho bigger than a 454 chev , bigger than a 500 caddy big block , and the magic 86 mm stroke all modern engines have, its a brillant engine , raise compression and intake, cam and exhaust it more than doubles power , all the burnouts in Smokey and the Bandit were done with a 403 olds Trans Am. Many these days are reving that " weak" bottom end to 6750 rpm snd 675 hp , no brakeage ! That massive bore is very good !
@JosephCowen-fz8vj actually the bandit car was a pontiac 400, the trans am used in the bridge jump had a 750hp Nascar engine which was a chevy. Another fun fact is the 403 Olds motor didn't come in the trans am until 1979.
@@tdog6437 Actually, the 403 was standard in the Trans Am, and optional in the Formula, in California in 1977 and 1978. California was no longer allowed to use the Pontiac 400 engines at that point. Of course, in 1979, the 403 became the standard TA engine, and optional for Formula, nationwide.
@grand73am you are correct, California and colorado both had the 403 as a no charge high altitude option in 77 and then became standard for all automatic transmission trans am cars in 79. The only way to get the 400 trans am in 79 was to order it with a 4 speed manual.
@@tdog6437 yes I've had a few , although big , that combustion chamber is well designed , like all Olds , in 1990 the Olds V8 was the only engine that year to be released with a carburettor, it passed emissions with a carbie , every other GM and infact all US V8s needed fuel injection in 1990 to pass , except the Olds . That shows an efficient combustion chamber.
you say stock heads i see there A heads my 1965 425 big block has the A heads did you do anything to the heads or block to make up for the larger cc heads which i think would lower compression if you just throw them on i might be wrong though but that's what i've always thought
@@christopherpatterson8833 I can work on that for a future video. In the meantime have you seen this one yet? There’s some tuning on my friends Camaro if that helps. th-cam.com/video/YfsjJvTk1gk/w-d-xo.htmlsi=o0dKwxDKZyANRTd3
I'm running a Street Demon carb on my 1970 350 olds in a cutlass supreme. It works good with the edelbrock performance rpm intake. Stock exhaust manifolds, cam and valve train. I am going to put some shorty headers and a mild cam on it. Curious what power numbers you expecting from your 403?
@@mason5540 since I stuck with the stock 8.0-1 or less compression I’d be happy to make 250 honest horsepower. It makes tons of bottom end, that’s for sure!
Question. I have heard that it is not good or difficult to get a good reading from an engine running it without a properly weighted flywheel. Either a manual trans fly wheel or having a torque converter attached to the flex plate is best when running on a stand? Love the video and a big van of the 403
First off let me say I’m a big fan of yours! I’ve watched many of your videos and I loved that 79 H/O you had with the 403 many years ago! I’ve never heard that it’s bad to run an engine on a stand. I’ve heard it can be dangerous because they want to flip over when you rev them up! That’s why I keep a come-along attached from my second floor ceiling beam to the engine to give it some support. You definitely need to run a flexplate or manual trans flywheel on it. If you didn’t I don’t know how you would start it because there’s no way for the starter to turn it over. Thank you so much for watching!!
I went with a Olds factory cam part #400165 made by Supercars Unlimited. It was used in the 69 Hurst Olds, the 70 442 with automatic trans and W30 with automatic trans, the 1970 W33 Delta 88, the 1970 Toronado GT W34 and I believe in the 71 442 automatic also.
@@jimmy_olds I only got 60 miles on it before it got cold here so I'm still breaking it in. I like to put 100 miles on my rebuilds before I really get on them. It feels strong though and has lots of bottom end power. It spins the tires effortlessly so I'm hoping it makes a decent amount of power.
Casting number is 22504068. Look for the A4 cast in by the thermostat housing too. That’s the easiest way to tell. You don’t want the A5! That’s the roller cam intake and has tiny ports.
Hey man is there any way i can pick your brain a little bit. You mentioned being familiar with oldsmobile motors. I have an 85 cuttlass with an 1978 oldsmobile 350 but instead of machining the engine debating on buying a 403 i found. I have questions regarding torque converter/ transmission bolt ups. As well as questions on motors themselvs. Thank you if you read this!
@@jamesweaver7262I’m running the original 403 4A heads on it. People do run big block heads on 403’s though. The 4A heads have a 83cc combustion chamber while big blocks are usually 80 cc or slightly less (I believe E heads are 77 cc). As far as I know you need to use the Performer RPM intake or Holley Street Dominator intake since they have enough “meat” in the port flanges to port them out to big block size.
@@tdog6437 no I haven’t. I’ll probably just put it in the car as-is. The oil pump is just a Melling replacement pump with their high pressure relief valve spring so I’m not sure what’s going on there. I’m using Lucas straight 30 break-in oil so I’m sure that’s bumping the pressure up some. I usually run 10W30 or 10W40 synthetic oil after the break-in period so it’ll probably come down a bit from that
Seen many cracked main webs in 403's in the 12 years i was in the machine shop.
I haven’t had that misfortune yet. I’ve only been inside about a half dozen 403’s in my life though
Had one of those 403's in a Jet Boat. The Harden Marine 403 did not have the window mains in the block..I was told they don't have them in the 77-78 GMC motorhomes either. They used a cam with specs about the same as a 70 455 4sp cam..like 475 lift and 295 duration if memory searves. The thing Ran so close to a 455 jet....it was scary!
Love those M/T valve covers on the 455. Have a set for my pontiac
@@sjd7188 yeah those are classic! Thanks for watching 👍
One of the most underrated Small Blocks of all time , as the years go on people realise the 403 is not weak at all , many at 400 000 miles, that huge bore of 4.351 is 100 tho bigger than a 454 chev , bigger than a 500 caddy big block , and the magic 86 mm stroke all modern engines have, its a brillant engine , raise compression and intake, cam and exhaust it more than doubles power , all the burnouts in Smokey and the Bandit were done with a 403 olds Trans Am. Many these days are reving that " weak" bottom end to 6750 rpm snd 675 hp , no brakeage ! That massive bore is very good !
@JosephCowen-fz8vj actually the bandit car was a pontiac 400, the trans am used in the bridge jump had a 750hp Nascar engine which was a chevy. Another fun fact is the 403 Olds motor didn't come in the trans am until 1979.
@@tdog6437 Actually, the 403 was standard in the Trans Am, and optional in the Formula, in California in 1977 and 1978. California was no longer allowed to use the Pontiac 400 engines at that point. Of course, in 1979, the 403 became the standard TA engine, and optional for Formula, nationwide.
@grand73am you are correct, California and colorado both had the 403 as a no charge high altitude option in 77 and then became standard for all automatic transmission trans am cars in 79. The only way to get the 400 trans am in 79 was to order it with a 4 speed manual.
@@tdog6437 yes I've had a few , although big , that combustion chamber is well designed , like all Olds , in 1990 the Olds V8 was the only engine that year to be released with a carburettor, it passed emissions with a carbie , every other GM and infact all US V8s needed fuel injection in 1990 to pass , except the Olds . That shows an efficient combustion chamber.
Was going to do an ls swap on my 79 trans am but I think I’ll keep my 403.😂
Sounds great! Thanks for all the R&D better you than me!
@@scotts439 hey you’re welcome! You know what a man of the people I am 🤣
you say stock heads i see there A heads my 1965 425 big block has the A heads did you do anything to the heads or block to make up for the larger cc heads which i think would lower compression if you just throw them on i might be wrong though but that's what i've always thought
They're the stock 4A 403 heads. I think the "4" is covered by the PS bracket so it looks like they just say "A".
Cool but show us how you set cabs timming ect thanks
@@christopherpatterson8833 I can work on that for a future video. In the meantime have you seen this one yet? There’s some tuning on my friends Camaro if that helps. th-cam.com/video/YfsjJvTk1gk/w-d-xo.htmlsi=o0dKwxDKZyANRTd3
18 degrees is the factory spec for timing for nationwide 403 use in 79. The spec for 403 in California is 20.
I'm running a Street Demon carb on my 1970 350 olds in a cutlass supreme. It works good with the edelbrock performance rpm intake. Stock exhaust manifolds, cam and valve train. I am going to put some shorty headers and a mild cam on it. Curious what power numbers you expecting from your 403?
@@mason5540 since I stuck with the stock 8.0-1 or less compression I’d be happy to make 250 honest horsepower. It makes tons of bottom end, that’s for sure!
@@olzkng word. so probably pushing 400 torques?
Question. I have heard that it is not good or difficult to get a good reading from an engine running it without a properly weighted flywheel. Either a manual trans fly wheel or having a torque converter attached to the flex plate is best when running on a stand? Love the video and a big van of the 403
First off let me say I’m a big fan of yours! I’ve watched many of your videos and I loved that 79 H/O you had with the 403 many years ago!
I’ve never heard that it’s bad to run an engine on a stand. I’ve heard it can be dangerous because they want to flip over when you rev them up! That’s why I keep a come-along attached from my second floor ceiling beam to the engine to give it some support. You definitely need to run a flexplate or manual trans flywheel on it. If you didn’t I don’t know how you would start it because there’s no way for the starter to turn it over. Thank you so much for watching!!
Sounds good, what cam did you pick?
I went with a Olds factory cam part #400165 made by Supercars Unlimited. It was used in the 69 Hurst Olds, the 70 442 with automatic trans and W30 with automatic trans, the 1970 W33 Delta 88, the 1970 Toronado GT W34 and I believe in the 71 442 automatic also.
@ that’s amazing, I’ve always wanted to try that grind! Too bad Supercars Unlimited shut down.
@@jimmy_olds yeah that was a bummer. I hope someone picks up their inventory or decides to supply the same cams they did
@ absolutely! How’d the engine turn out? Decent amount of power?
@@jimmy_olds I only got 60 miles on it before it got cold here so I'm still breaking it in. I like to put 100 miles on my rebuilds before I really get on them. It feels strong though and has lots of bottom end power. It spins the tires effortlessly so I'm hoping it makes a decent amount of power.
Nice build if you don’t mind me asking what is the intake manifold part number
Casting number is 22504068. Look for the A4 cast in by the thermostat housing too. That’s the easiest way to tell. You don’t want the A5! That’s the roller cam intake and has tiny ports.
Hey man is there any way i can pick your brain a little bit. You mentioned being familiar with oldsmobile motors. I have an 85 cuttlass with an 1978 oldsmobile 350 but instead of machining the engine debating on buying a 403 i found. I have questions regarding torque converter/ transmission bolt ups. As well as questions on motors themselvs. Thank you if you read this!
I can try to answer whatever questions you have. You can email me at olzkng@aol.com if you want.
I genuinely appreciate you my man! Ill shoot you an email sometime this week. I’m picking up the 403 this week
How can you run big block "A" heads with those giant dishes in the pistons? Am I missing something? Compression should be super low.
Or are they 4A?
@@jamesweaver7262I’m running the original 403 4A heads on it. People do run big block heads on 403’s though. The 4A heads have a 83cc combustion chamber while big blocks are usually 80 cc or slightly less (I believe E heads are 77 cc). As far as I know you need to use the Performer RPM intake or Holley Street Dominator intake since they have enough “meat” in the port flanges to port them out to big block size.
The only thing that bothered me with the 403 was the main webbing having the windows.
Yup, that limits how far you can go with them. I’m not going to push this one too hard though 👍
@@olzkng did you try a different oil pressure gauge yet
@@tdog6437 no I haven’t. I’ll probably just put it in the car as-is. The oil pump is just a Melling replacement pump with their high pressure relief valve spring so I’m not sure what’s going on there. I’m using Lucas straight 30 break-in oil so I’m sure that’s bumping the pressure up some. I usually run 10W30 or 10W40 synthetic oil after the break-in period so it’ll probably come down a bit from that
LS motors have windows in exactly the same place ! Are they weak ?
@@JosephCowen-fz8vj LS motors have 6 bolts and other advantages