Good afternoon gentlemen.

I have been lurking for some time, absorbing the vast amount if info available here. I would like to start by saying thanks to everyone who passes their knowledge on to us less knowledgeable folks.

I am building a 460 for my 77 Lincoln. It came with the smogged out 460, obviously, which is extremely underpowered. I have since purchased a '68 429 longblock to tear into and make something that'll get the old girl moving a bit. I have a few questions, but I'll start with what I have:

C8ve block 30 over and ported c8 heads.
Stock 460 crank, eagle i beam rods
22cc forged pistons, should be around 9.5 compression.
Performer intake
Holley 750 dp
3.5 gear in the back.
Easily 4500lb car.

From what I've read here, a s400 turbo would work well. I was thinking a 75mm. If I'm way outta line, let me know.

I am also unsure of which cam to run with a system such as this. I would probably run a comp 274xe or something similar in the n/a engine to make around 450 horse and 500 tq. Would this need changing?

I'm looking for 700 streetable horse with the addition of a turbo.

What kind of vacuum will I have? Of course, everything on this thing is vacuum operated it seems like, so I'd like to pull a decent amount.

Thanks in advance for your input! It is appreciated.

 

First off kudos for your vehicle choice! I love that body style! We need some pictures!

Turbo:

The big $640 shipped S475 with the 1.32ar T6 would work ok for your goals. Assuming you went with this turbo...

Cam:

I don't agree with the 274xe cam choice paired with the turbo above. Your power goal won't be an issue with big block IMO. You want to limit the overlap on the cam with a turbo build. You are looking at 13* or so of overlap @ .050 and 60* @.006 with the 274xe grind. The S475 is boarder line too small IMO so your back pressure levels will be high. Because of this you want negative overlap @ .050. I'd be looking at a much milder duration. I know it sounds odd but the super conservative RV grinds usually make great turbo cams.

Use this to calculate the overlap. YOu want negative overap @ .050.
http://www.wallaceracing.com/overlap-calc.php

If money isn't a huge concern I'd be looking at S480 with the 1.58ar T6 housing. Or a set of twins.

 

Congrats on dumping the 2.50 gears! Or are the 3.50's the original one's?

I know that T-Birds have always been under geared - 2.75's in a 9" rear until the late 70's, then 2.50's, then the 80's Fox bodies had 2.73's in the 8.8.

Al

 

My dad had a 77 Town Coupe when I was a kid, sweet ride..................

 

Thanks forcefed. Lots of good info there. I'll reconsider the cam specs. If I could track down an RV cam on the cheap, even better for me. I would prefer to go single turbo just to keep it more simple under the hood. The s480 is definitely not outta the question. Thanks for all your input!

T6- I wish the car came with 3.50s! Stock 2.50s in 1977 unfortunately. Sure makes a difference! Fuel economy is as bad as ever, don't know why they didn't put proper gears in to begin with.

 

Actually 2.50s are awesome gears. With a TH400 1st and 2nd act like a glide then 3rd acts like OD. With a 28" tire u can go 140 at 6000rpm in 2nd gear.

Then in 3rd u can cruise 65 mph under 2k rpm.

 

Maybe a turbo BB can mask the anemic nature of those gears, but on the late 70's 200 HP engines, it sucked. 2.50 gears, coupled with a low 5k redline made for a total fail. No acceleration, but decent top end, when you finally made it there.

I had a 74 Charger - a 318 coupled with 2.45 gears. That engine was not capable of 6k RPM, but if it was, I am thinking more like 100 MPH tops in 2nd. And it had L60's on the rear.

What I find ironic is the biggest fail of the 60's - the powerglide transmission - is now a hero trans because it can harness the power of 1000+ HP engines. Converter technology also made that possible. Soon they will have a TH100, top gear only!

The first car I ever drove was a 66 Chevelle - 194 6 cyl with a powerglide. It had a 70 MPH top speed, so you can see where my loathing of anemic gearing comes from!

Al

 

When the current c6 inevitably bites the dust and I'm thinking of a rebuild I'm have to consider that. I'm sure the 3.50s will be OK for now. I'm working on some pictures for you gentlemen. It's in pieces right now, so I gotta go back on my computer to find some old ones from when she was all one piece.

 

I agree that gear is a bit much for a 4500lb car with a 200hp engine to pull, but for comparison I ran a 30" tire and a 3.10 gear on a turbo 323 cube SBC with zero issue. Wheelies at the track 1.3x 60' sub 1.2 second 0-60 times and cruised very nicely in high gear on the freeway.

A Turbo big block can pull a silly low gear no problem. Esp if you only used 1st and second gear. Now the vehicle weight alone will load the turbo plenty on the Mark V, so the 3.50 is still a better choice IMO performance wise. But having a third gear to cruise the highway would also have advantages in a heavy car like that.

 

Fwiw, my Pontiac would
Run 10.90's pedaling with 2.75 gears. Don't be sacred of tall gears in a turbo car, turbo's love load.

 

Oh, I agree that a turbo BB can take full advantage of tall gears. But that's the only setup that can.

Speaking in Mopar terms - a big honkin' 500 cu in BB turbo with 2.76 gear could be a nice street setup, with 3rd acting like OD as mentioned. But I would need the trans to have a wide ratio gearset, like a 2.75 1st gear. Then you would still have a little gear to get the car moving on the street.

Al

 

Everyone gets caught up on the numerical ratio, but its ultimately about the load. You can't really compare sub 3000lb with 4500lb. Even with BB torque, you have to make the converter work for a given application which is tough on a heavy car, high gear, and low rpm big torque. There is some trade off, and I see gear ratio as the first place to look, especially if working on a budget minded setup.