Can't decide. stock 350 or 403! help

[sh1ft]

If it is in the original car check the mileage, if not I would go thru it from top to bottom while it is out. How does that old saying go do it right the first time. Do not short cut if you suspect then rebuild unless you like pulling motors out. Either way good luck.

 

[CHRIS.O]

Just dont want regrets down the road with smoking, using oil, etc.

Then rebuild it if you want peace of mind. BUT rebuild it dont just re ring it. All new, then your talking 2-3 grand though for a complete rebuild with good parts. Running a used engine is always a crap shoot. If it is selling cheap enough then I wouldn't worry about it. Run it, if it needs a rebuild a year from now so be it, it probably would of needed it even if you re ring it, thats kind of like a band aid. Goodluck bud.

 

[brian_wms]

Just found a 455, that has low knock. Any suggestion i'm so confused right. Dont know what to do. How hard is that swap? I want to keep all my accessories from my 307 and keep the stock look.

 

[sh1ft]

455 is not stock. Dont care what anybody says big block does not look stock in a small block car. BTW any noise could be the end of a motor, if one makes no noise and the other does why deal with more issues?

 

[CHRIS.O]

If your confused then don't do anything until you know what you want. Spirited street car or a pavement pounding monster? Figure that out. From the sounds of it your inexperienced so I bet a stock 403 would be plenty good for you and keep you grinning from ear to ear for quite some time.

 

[Minion1186]

Agreed my cutlass salon has a new 1968 350 in it. Its dead stock with #5 heads with the only things not being stock is the RPM intake, headers with 2 1/2" duals and distributor and boy does it set you back good. I didint run it yet but I figure with 373's posi and th350 I should be in the late 14's at least.

If you had the opportunity to grab a complete stock 68-70 350...that would be the way to go.. while the later thin blocks motors make good street motors it remains obvious that the 403 is the way to go..

I had one in my Cutlass..bone stock I was able to run 14.40 with it.. Early 350 heads and a nice comp cam allowed me to go 13.30s..

403's make killer street motors... as long as you dont plan on spraying it or run 10s-11 with them 😉

 

[brian_wms]

Yes, the stock exhaust will work but seriously look at getting dual exhaust. I had single stock exhaust WITHOUT a catalytic converter and a glass pack muffler. Ran hard off the line then fell hard on It's face after that. Added a Cat back dual outlet exhaust, ran much better. I would run the stock early 307 HO cam or smog 455 cam, 197/204 .440/.440 vs 194/198 .400/.402 stock, lament. You only have around 7.8 to 1 compression, stay small on the cam. The Lunati high efficiency series 207/207 .461/.461 would also work, wouldn't go much bigger.

went with the 403 engine. The Lunati cam doesnt come with lifter, can i just buy more stock lifters? Or do you recommend any other brand.

so let me get this right. All stock except intake, cam and headers, And I should be smokin right? bidding on a intake on ebay now. Will those headers clear my oil filter looks real close.

 

[DoubleV]

so let me get this right. All stock except intake, cam and headers, And I should be smokin right? bidding on a intake on ebay now.

All depends on your goals. That 307 HO cam isn't very good and was suggested to you only because your CR is very low ( though on a stock 403 I think you can still go a bit bigger ). If you want to go 'fast', all you need is a set of early 350 heads. These will bump up your CR ( more power ), allow you to run a better cam ( more power ) and flow better than the stock 403 heads ( again more power ).

An RPM intake is a good intake, but the standard Performer isn't going to do much of anything. Obviously true dual exhaust is a no brainer and yes headers will definitely help but you could always add headers ( and a better intake ) later on down the road since they are just simple bolt-ons.

So if I were on a strict budget, had a stock 403, and wanted some good get-up-and-go, I would get a set of decent older 350 heads ( with a good valve job if funds permit ), get a mild street friendly cam that matches well with my higher CR ( which I believe would be around 9 to 1ish ) and just run the stock intake and exhaust ( with true duals ) for now. I would then add an RPM intake and headers later on when I had more money saved. This all assumes I already have good gearing and a transmission that would last. If you don't have either of those things, you're looking at even more money. Going fast even on a budget isn't cheap!

 

[brian_wms]

So since i'm running a stock engine, and don't have the 350 heads, running a mild cam isn't going to do much?

 

[DoubleV]

I don't remember the stock cam specs for a 403, but they're pretty lame. I guess I can't really say a 'mild' cam combined with your pathetic CR would be worth it or not though but if I would lean towards 'yes, but not a world of difference'. If you're on a real tight budget and don't want to address your low CR, I personally would look at the el cheapo generic 204/214 cam. I think it would be big enough to make a difference and still work with your low CR.

If you don't have decent gears, you may not get as much oomph out of this build as you may think.