403 or sbc 355

[novadave1973]

hey everyone I just got an 86 regal.. the body is great for an upstate ny car... it has the 307 runs pretty good and drives but my intentions were to thro my 355 in it and do some street strip duty with it...my 355 has forged flat tops an elgin cam with .467 lift vortec heads edelbrock intake and carb. th350 with 3.73 gears...my best time in my old 79 monte was 12.30 and same in my 73 nova....my delema is that my dad offered me his 403 to put into the buick..the 403 is stock right now..im curious what kind of upgrades I will need for the 403 to get in the ballpark performance of the 355...from what i have read here in the forums seems like the 403 is an easier swap..i intend to keep the 200r4and gonna need to upgrade the 2.56 7.5 rear...thanks

 

[81Regal]

Welcome and the 403 would be an easier swap since everything off the front of the 307 will bolt to the 403. Trying to compare the 2 engines performance wise wouldn't be a good idea, the 403 is built for torque and your 355 sounds to be built for horsepower.
If you are going to keep your transmission, I would step up to mid 3.xx for gears.

 

[novadave1973]

I figured I would try to get a set of 3.42...I know that a cam lifters and intake for the 403 prolly cost me $500... but not sure its goin to give me the performance im used to especially with a complete car like the regal the nova was stripped. so I know the regal is a lot heavier especially with the pw pl ps and im gonna try to keep the ac regardless what engine I use...

 

[DoubleV]

An Olds 403 is a very capable motor, but it wasn't really built for high performance raceing in mind. There are plenty of people running around with 12 second street friendly 403's in G-Body's in full trim ( or other cars with similar weight ) so it can be done quite easily. To build a RELIABLE 403 to get you in the 12's though, you pretty much need to rebuild the whole thing with good parts and get a girdle ( to keep it together ). A cam/lifter swap + gears is in no way going to get you there on their own. You need everything else any other engine needs, especially head work. Built properly, a 403 can be an awesome street engine, but you have to build it with the right parts.

 

[shanghaismith]

I figured I would try to get a set of 3.42...I know that a cam lifters and intake for the 403 prolly cost me $500... but not sure its goin to give me the performance im used to especially with a complete car like the regal the nova was stripped. so I know the regal is a lot heavier especially with the pw pl ps and im gonna try to keep the ac regardless what engine I use...

If you keep the 200 4r, I think 3.73 gears would be a better choice. I think the 403 is the way to go if you want to spend the cash to do it right. VV is right, it will take more than what you listed. I have about $5,000 in my 403 that runs in the mid 12's (11.45 on a 125 shot) and is a real pleasure to drive on the street. With the 200 4r at 70 MPH it turns about 2300 RPM and the fastest I have had it is 138 MPH.

 

[L92 OLDS]

An Olds 403 is a very capable motor, but it wasn't really built for high performance raceing in mind. There are plenty of people running around with 12 second street friendly 403's in G-Body's in full trim ( or other cars with similar weight ) so it can be done quite easily. To build a RELIABLE 403 to get you in the 12's though, you pretty much need to rebuild the whole thing with good parts and get a girdle ( to keep it together ). A cam/lifter swap + gears is in no way going to get you there on their own. You need everything else any other engine needs, especially head work. Built properly, a 403 can be an awesome street engine, but you have to build it with the right parts.

X2. No girdle on my 403 and no issues 20+ years later. At the time, I went through the whole motor and did it right. At a minimum, you will need to spend money on some good heads for that 403. The stock 4A / 4B head would need to be worked and you will need to buy high compression pistons if you chose to use them. A poor mans build on a stock 403 is to bolt on small chamber olds 350 heads on to a stock shortblock. It's been done plenty of times with reasonable results. 403's are torque motors which make them fun to drive. I'm guessing your 355 needs RPM to build power and requires a stall and steep gears. Also fun but a totally different driving experience.

 

[novadave1973]

thanks for the help guys....sounds like the 403 could do the trick if I had the money to throw at it...maybe ill get it and put it on the stand and get the parts I need...meanwhile ill put the 355 in the regal..i was thinking I would get the 307 out and use a smallblock mock up and see if I can fabricate the 307 brackets for the ps alt and a/c compressor. has anyone done this before??? use the ps pump and alt off the 307 on a sbc?

 

[DoubleV]

i was thinking I would get the 307 out and use a smallblock mock up and see if I can fabricate the 307 brackets for the ps alt and a/c compressor. has anyone done this before??? use the ps pump and alt off the 307 on a sbc?

Technically, almost anything can be modded to work in an application it wasn't meant for but some things would end up so far off from where they started from that you'd just have been better off starting at a closer point to begin with. In other words, it would be alot easier to just get the brackets from a SBC.

 

[DRIVEN]

That 403 is just going to be too distracting and has absolutely no performance potential. You should probably just drop it off at my house. I'll properly dispose of it for you.

 

[CamaroAdam73]

Just to chime in here, you can't just install a girdle everything has to be re-aligned. I found this out the hard way haha, i'm building a 403 right now and it's a great way to go, I picked up my crank girdle from dickmiller, called the man himself and he told me i don't even need one and my aim is to output around 400HP.

I'd go with the 403, save the 355 for another project man.