425 Super Rocker V8 Increase BHP

[DAN76]

Hello from the UK,
I've just purchased a 1965 Oldsmobile Delta 88 Holiday Pillarless Sedan. It's got all the available factory extras from the time, including twin exhausts and pleated upholstery.

It's in pretty good shape as was only imported to UK from SF in 2005 and has been dry stored over the winters.

My intention is to fully restore but in the meantime i would like to make some engine modifications to increase the BHP. I'm not very clued up when it comes to American cars so would like some advice - this seems like the ideal place to get it.

If i were to replace the carb etc, what model Holley would i need for this engine and is there anything else i can do to increase power?

According to log book it's currently 310bhp from a 425ci block with 3 speed Turbo Hydramatic Transmission.

Thanks
Dan

[citcapp]

Welcome aboard, Sounds like you are going to have a fun time ahead. This is a great resource for all of your questions. Please post pictures of your ride. There are several people here who can help you with carb selections. I prefer Hollys myself but there are several members who are going to suggest that you stick with an updated or modified version of the carb that came with the 425 which if your plan is restoration I agree with with. The will chime in and I will take some heat for using a 770CFM double pumper on my built 455. Good luck and stay in touch

[DAN76]

Cheers.
Any info you can give me on my car would be greatly appreciated!
I'll add some pics to the gallery now.

[Jamesbo]

Originally Posted by citcapp

Welcome aboard, Sounds like you are going to have a fun time ahead. This is a great resource for all of your questions. Please post pictures of your ride. There are several people here who can help you with carb selections. I prefer Hollys myself but there are several members who are going to suggest that you stick with an updated or modified version of the carb that came with the 425 which if your plan is restoration I agree with with. The will chime in and I will take some heat for using a 770CFM double pumper on my built 455. Good luck and stay in touch

Not that anyone cares about this mundane subject but when you swapped to a 770 CFM double pumper, what did you MPG do?

Last year I took one off a 455 and replaced it with a Q-jet and I am much happier.

Just MHO

[Run to Rund]

1. get a moderate camshaft like a Comp Cams HE268 or small magnum or XE, keeping the .050" duration around 218-225 degrees.
2. dual exhaust, low restriction mufflers
3. consider a 66-up intake manifold with a properly jetted Quadrajet.

[65Delta88]

Originally Posted by DAN76

Hello from the UK,
I've just purchased a 1965 Oldsmobile Delta 88 Holiday Pillarless Sedan. It's got all the available factory extras from the time, including twin exhausts and pleated upholstery.

It's in pretty good shape as was only imported to UK from SF in 2005 and has been dry stored over the winters.

My intention is to fully restore but in the meantime i would like to make some engine modifications to increase the BHP. I'm not very clued up when it comes to American cars so would like some advice - this seems like the ideal place to get it.

If i were to replace the carb etc, what model Holley would i need for this engine and is there anything else i can do to increase power?

According to log book it's currently 310bhp from a 425ci block with 3 speed Turbo Hydramatic Transmission.

Thanks
Dan

Dual exhaust manifolds are a must, I have a holley 750cfm vac secondaries carb and a edelbrok performer intake manifold and I am very happy with the results.

[DAN76]

Originally Posted by 65Delta88

Dual exhaust manifolds are a must, I have a holley 750cfm vac secondaries carb and a edelbrok performer intake manifold and I am very happy with the results.

do you know what power output that gives?

[citcapp]

Originally Posted by Jamesbo

Not that anyone cares about this mundane subject but when you swapped to a 770 CFM double pumper, what did you MPG do?

Last year I took one off a 455 and replaced it with a Q-jet and I am much happier.

Just MHO

I have less then 100 miles on the engine so I have done MPG test yet. I will let you know in a week or two. My 57 is a play car and when I get my build sheet done and posted you will see that MGP was not my concern when I built the engine. How you comming with tranny and interior mods?

[DAN76]

Originally Posted by citcapp

Welcome aboard, Sounds like you are going to have a fun time ahead. This is a great resource for all of your questions. Please post pictures of your ride. There are several people here who can help you with carb selections. I prefer Hollys myself but there are several members who are going to suggest that you stick with an updated or modified version of the carb that came with the 425 which if your plan is restoration I agree with with. The will chime in and I will take some heat for using a 770CFM double pumper on my built 455. Good luck and stay in touch

Would you be able to tell me what the factory fitted carb spec is for this car and how to modify/upgrade ?

[geckonz08]

Originally Posted by Run to Rund

1. get a moderate camshaft like a Comp Cams HE268 or small magnum or XE, keeping the .050" duration around 218-225 degrees.
2. dual exhaust, low restriction mufflers
3. consider a 66-up intake manifold with a properly jetted Quadrajet.

hi there,
welcome --some real smart guys here with good knowledge--wish I were one !!
BUT
What R TO R says above would have to be a good start.
YOUR OLDS will be a real eyecatcher in London. Not sure how you will negotiate your way around the streets !!!
good luck
mike

[66 Olznut]

Your car came with a 4gc (I think it's called) and there's not many performance options to choose. I would get a Edelbrock Performer, paint it to match the engine and get a Quadrajet from here http://www.sparkyscarbs.com/ built for it which will wake it up nicely and improve mpg.

[DAN76]

Originally Posted by 66 Olznut

Your car came with a 4gc (I think it's called) and there's not many performance options to choose. I would get a Edelbrock Performer, paint it to match the engine and get a Quadrajet from here http://www.sparkyscarbs.com/ built for it which will wake it up nicely and improve mpg.

Excellent, thanks. I've had my eye on a Holley 750 on ebay but am being advised more to go for the Q-Jet. Are they similar in power increase?

And do these items simply bolt on or will i need someone with considerable experience to do the job for me?

[BILL DEMMER]

Originally Posted by 66 Olznut

Your car came with a 4gc (I think it's called) and there's not many performance options to choose. I would get a Edelbrock Performer, paint it to match the engine and get a Quadrajet from here http://www.sparkyscarbs.com/ built for it which will wake it up nicely and improve mpg.

agreed that the quadrajet will be a nice improvement. you could also use a factory 4-bbl. intake from a pre-egr application, '70 and up. the reason i start at '70 is, that was the first year for the integral choke, no "hard to find" stove coil in the manifold.
alternatively, you could use a pre-egr 4-bbl. intake from '66 and up, with a '70-'75 carb(would need a custom throttle end).

second on www.sparkyscarbs.com


bill

[66 Olznut]

Originally Posted by DAN76

Excellent, thanks. I've had my eye on a Holley 750 on ebay but am being advised more to go for the Q-Jet. Are they similar in power increase?

And do these items simply bolt on or will i need someone with considerable experience to do the job for me?

Simple bolt on stuff, take ya a few hours with basic tools. Just make sure you torque everything down correctly.

[DAN76]

I've been offered an Edelbrock Performer carb here in the UK. It's a 750 model tuned for moderate to high street performance. (part No. 1407)

is this as good as a Quadrajet?

[66 Olznut]

I had one, wasn't impressed by it at all.

[DAN76]

Originally Posted by 66 Olznut

I had one, wasn't impressed by it at all.

what was the issue?

[66 Olznut]

Originally Posted by DAN76

what was the issue?

Didn't have the power I expected, driveability wasn't great and economy was in the toilet. I put the QJ back on.

[Jamesbo]

Originally Posted by 66 Olznut

Didn't have the power I expected, driveability wasn't great and economy was in the toilet. I put the QJ back on.

X2

That has been my experience.

i actually have the edelbrock carb and love it. been trouble free for over ten years. i have it on top of a performer manifold with a mild crane came and dual exhaust. the engine is bored 30 over and has dual exhaust. its been a very dependable "street rod" not to wild but not too mild....as far as gas mileage goes....who cares...its a a street rod its not supposed to be good on gas...gas mileage is for my cavalier.

the edelbrock carb is a copy of the carter carb...mine is also the spread bore design so it will sit on a stock 4bbl manifold and replace the rochester "stumblejet" directly

[DAN76]

Originally Posted by blkmonday

i actually have the edelbrock carb and love it. been trouble free for over ten years. i have it on top of a performer manifold with a mild crane came and dual exhaust. the engine is bored 30 over and has dual exhaust. its been a very dependable "street rod" not to wild but not too mild....as far as gas mileage goes....who cares...its a a street rod its not supposed to be good on gas...gas mileage is for my cavalier.

the edelbrock carb is a copy of the carter carb...mine is also the spread bore design so it will sit on a stock 4bbl manifold and replace the rochester "stumblejet" directly

i'm not too fussed about mileage either. The car only comes out when the sun's shining anyway (not very often in UK!!!).

Well i've bought the carb anyway. It's a performer 750 (1407) so now all i need is the performer intake manifold. Will i need anything else to fit this lot, like a gasket fitting kit??

What have you done with your choke?

[Oldsguy]

You will need a new gasket set if you remove the intake manifold. Do you have a catalog like Summit, or Jegs, or Speedway? Can you order from them and get delivery there in the UK? One of those would be a great help. You can get all that kind of speed stuff from them. I have piles and piles of them. Once you order from one you become a customer and receive catalogs about twice a year from them.

[DAN76]

Originally Posted by Oldsguy

You will need a new gasket set if you remove the intake manifold. Do you have a catalog like Summit, or Jegs, or Speedway? Can you order from them and get delivery there in the UK? One of those would be a great help. You can get all that kind of speed stuff from them. I have piles and piles of them. Once you order from one you become a customer and receive catalogs about twice a year from them.

They charge £24.99 to even consider shipping anything overseas, then it's the actual shipping cost on top plus 21% duty.

seems a bit much for a set of 15 dollar gaskets!

i'll just have to wait until i have more items to order.

i actually switched over to a manual choke. i dont drive the car in the winter at all...so the manual choke isnt really an issue

[Oldsguy]

Manual chokes aren't really that bad, we have become spoiled by the automatics.

[DAN76]

Originally Posted by blkmonday

i actually have the edelbrock carb and love it. been trouble free for over ten years. i have it on top of a performer manifold with a mild crane came and dual exhaust. the engine is bored 30 over and has dual exhaust. its been a very dependable "street rod" not to wild but not too mild....as far as gas mileage goes....who cares...its a a street rod its not supposed to be good on gas...gas mileage is for my cavalier.

the edelbrock carb is a copy of the carter carb...mine is also the spread bore design so it will sit on a stock 4bbl manifold and replace the rochester "stumblejet" directly

My Performer 750 carb is Square bore and the Performer intake is Dual Plane. Does this require a mounting kit?