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Username Post: HP Gain?        (Topic#359387)
probelair 
Gold Supporting Member
Posts: 65
probelair
Reg: 11-01-19
01-06-20 06:21 AM - Post#2783802    

Just wondering. So the 61 impala I bought 2 months ago has a 283 2 barrel 170 horse motor.

I have a 4 barrel intake and carb on the shelf.

Putting new exhaust on because of the Transporter was wondering what the potential HP gain would be and if worth the time.

If we decide to keep the Imp she will be getting a new motor down the road.

Want to drive her this summer and see if this is the car for the wife and I.

Thanks again



 


dcairns 
Frequent Contributor
Posts: 2103
dcairns
Loc: Orange CA
Reg: 11-07-03
01-06-20 09:05 AM - Post#2783813    
    In response to probelair

If you do decide to keep it and put a new (probably larger) motor in it, then you will want to consider what you do with the exhaust now, rather than have to do it twice.

A stock 2-1/2 inch dual exhaust is great on a 327 or larger. I don't know if it would help on a 283. I think the 283 only came with single or dual exhaust in the 2 inch size.

For some reason, the 2 inch is a bit smaller than 2 inches and the 2-1/2 inch is a bit larger than 2-1/2. So there is a bigger difference that you might think:






- Dave
1964 Impala 4-door sedan



 
probelair 
Gold Supporting Member
Posts: 65
probelair
Reg: 11-01-19
01-06-20 11:01 AM - Post#2783818    
    In response to dcairns

Yeah was thinking going 2.5 as long as there is no repercussions to the existing motor.

Car runs just needs exhaust and a few things.

Waiting on spring.



 
305c1500ext 
Member
Posts: 256

Loc: Auckland,NEW ZEALAND
Reg: 10-23-06
01-07-20 06:26 PM - Post#2783951    
    In response to probelair

Hi. I went from a 2 barrel to a little 500cfm four barrel with a cast iron four barrel intake on my `65 Impala with a 283. Made a big difference.Not earth shattering,but enough to keep up in and with modern traffic.Also running a twin 2 inch exhaust with a `H` pipe.My car is no where near a prime example...But she is mine!

Philip
1996 c1500 305 vortec.1st truck so far!350 crate motor is in....had to rebuild the engine first!!
1986 mazda 323 turbo road race car 400hp.SOLD
598 bbc in 56 chev drag car 8.62 second
1965 Chev Impala sedan 283-now 327 + turbo 350


 
probelair 
Gold Supporting Member
Posts: 65
probelair
Reg: 11-01-19
01-08-20 06:25 AM - Post#2783973    
    In response to 305c1500ext

Thanks very much.



 
Verne_Frantz 
Member #574 "61-64 Subject Matter Expert"
Posts: 5700
Verne_Frantz
Loc: Hightstown,NJ USA
Reg: 08-22-00
01-10-20 02:09 PM - Post#2784148    
    In response to probelair

Your '61 283 probably has the worst flowing small block Chevy heads they ever made. The heads are your limiting factor. Adding a 4bbl and 2.5" dual exhaust with those heads will not make much of an improvement at all. Either go with a set of 856 heads or all the way up to the 461 heads with those other changes.

Verne



 
probelair 
Gold Supporting Member
Posts: 65
probelair
Reg: 11-01-19
01-10-20 05:09 PM - Post#2784153    
    In response to Verne_Frantz

Thanks, didn't know that. Trying not to make a major changes. Probably yanking the motor and trans next fall.



 
Cmb62 
Newbie
Posts: 35

Loc: Sydney, Australia
Reg: 04-28-17
01-14-20 02:12 PM - Post#2784391    
    In response to probelair

I have a 62 Belair with 283 and had a 2bbl carb. I ended up replacing it with a 4bbl carb and manifold. I found there was a significant improvement, but I guess that is mainly due to the old 2bbl being quite a bit tired. I'm not disagreeing with other comments made here, but thought i would give my experience so far. I may one day rebuild the old 2bbl, but for the moment i'm happy to cruise around as it is.

Go with the flow


 
probelair 
Gold Supporting Member
Posts: 65
probelair
Reg: 11-01-19
01-16-20 05:20 PM - Post#2784505    
    In response to Cmb62

So a quick question. i need a exhaust. Transport damaged this one.

If i go with 2.5 so i don't have to change it later. will i cause any problems?



 
Original58 
Contributor
Posts: 538
Original58
Loc: Manitoba, Canada
Reg: 10-30-13
01-16-20 07:31 PM - Post#2784513    
    In response to probelair

No problems thst I can see. I run 2.5 inch duals with an H pipe on my 58 w/a 283. Turbo mufflers. Nice quiet rumble.
Jeff

1958 Biscayne 283 Turbo-Glide 31,000 mi (now 35,000 and counting) driven daily
1966 Mustang Inline 6- C4 57,000 mi and growing daily
1929 Graham - Paige 612- the eternal headache that I will never sell


 
japete92 
"6th Year" Silver Supporting Member
Posts: 1294
japete92
Loc: No. Virginia
Reg: 01-18-13
01-17-20 08:07 AM - Post#2784526    
    In response to probelair

  • probelair Said:
So a quick question. i need a exhaust. Transport damaged this one.

If i go with 2.5 so i don't have to change it later. will i cause any problems?



Not if you stay with the sbc V8. But, you do need to decide what engine/heads you are eventually going to use. The 2 1/2" ram horn manifolds do not 'bolt on' to 'vortec' heads.

Other than that, as long as you stay with the traditional sbc (I have no experience with the LS-x types), and buy all the requisite parts (don't forget the heat riser valve, or the spacer, that goes on the passenger side), you may drop in any displacement (383 would be my recommendation) sbc V8 engine.

ALL GM V8s (300 hp + as I remember) in their full size X frame cars came with 2 1/2" manifolds and exhaust pipes with nominal 2" tail pipes. Muffler inlet/outlets were accommodating. The BB manifolds were different from the sb.

You may see some acceleration improvement from your 283 2 barrel with the 'free-er' breathing exhaust (dual 2 1/2").

I (just my opinion) would not bother changing the carb on the 283 along as the car ran properly. I'd wait for the 'new' engine.

Just trying to be helpful.

Pete






Edited by japete92 on 01-17-20 08:13 AM. Reason for edit: No reason given.

 
probelair 
Gold Supporting Member
Posts: 65
probelair
Reg: 11-01-19
01-17-20 09:00 AM - Post#2784532    
    In response to japete92

Thanks everyone




 
back2chevy 
Newbie
Posts: 35
back2chevy
Loc: Burlington
Reg: 10-31-15
01-17-20 09:45 AM - Post#2784534    
    In response to japete92

Is that true that 2 1/2 exhaust manifolds won't bolt up to vortec heads?
I bought a set of off-shore manifolds and they bolted right on. Just curious if I should take them off again. (engine not in car yet)

63 Impala 283
92 VR-4


 
japete92 
"6th Year" Silver Supporting Member
Posts: 1294
japete92
Loc: No. Virginia
Reg: 01-18-13
01-17-20 12:36 PM - Post#2784545    
    In response to back2chevy

  • back2chevy Said:
Is that true that 2 1/2 exhaust manifolds won't bolt up to vortec heads?
I bought a set of off-shore manifolds and they bolted right on. Just curious if I should take them off again. (engine not in car yet)



The aluminum Vortec heads with the "D" port exhaust WILL NOT FIT the Ram horn exhaust... They will bolt up, but they will not seal in the port area becuase of the larger raise port. I mis-spoke when I said they won't bolt up. Sorry.



 


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