Inliners International Forums General Discussion Engines 4 brrl on 250

I have a new stock 250 in my truck running the old 1 brl rochester and factory intake/exhaust. Just wondering if i purchase one of the offy 4 brrl intakes or one of the clifford 4 brrl intakes and put a 390 holley on it with a set of the langdon headers do i need to beef up anything else in that stock engine or will it be ok as is?

To really take better advantage of the induction and exh. You should install atleast a RV style cam.
The lower end will be good to go. Tom

What is the best way to install a new cam? I am very new at this and looking to spruce up my 250 a bit as well.

its a new motor so i dont really want to change the cam or anything, will i overheat or over torque anything in the stock engine if i just add the carb, intake and headers.

Tom has the dyno numbers to say for sure,
but I'd think that you'd be better off
with the headers alone.
It probably won't give any significant power increase,
but it'll provide better sound.
I expect the carb and manifold won't be cost effective until you change the cam and have improved exhaust.

On my otherwise stock 235, I got about a 7 HP increase with an exhaust upgrade

regards,
Leon

0.2 sec and 2 mph gain in the 1/8 mile

I just converted my stock 250 to a 4bbl.
Started off as a stock 250, stock single exhaust, powerglide-3.08 Nova.
Tried both Clifford 4bbl intake and also the Offy 4bbl intake.
Tossup between the Clifford and Offy intakes, but both of them gained a clean 0.2 sec and 2 mph over the best 1bbl intake and carb setups I had.

That change equates to a gain of about 0.3 sec and 3mph in the 1/4 mile, and calculates to a gain of about 15hp in the Gonkulator from just adding the 4bbl and intake.

I tried many different carbs on each intake so the above is just a summary. One interesting note, during all this thrashing, the 4bbl setups got BETTER gas mileage than the 1bbl Rochester carbs.

Is it worth it if you're buying the intake and carb new?
Well, you have to decide that for yourself.

I am curious how did you compare the 2 intakes?
Track,G-Tech, 0-60 MPH,60 ft? I phone?
Butt dyno? LOL

MBHD

Deuce the better gas mileage is what i'm shooting for, not really that concerned about the hp right now. this is a daily driver. mainly looking at the headers because think i have a slight warp in my exhaust manifold. i change the gasket and about 500-1000 miles later its starting to leak again. figure if i change from the exhaust manifold to headers might as well change out the intake at the same time. unless any of you guys have an idea of how to stop my leak.

I'm surprised that the intake improvement showed up with a stock exhaust, but good to know.

Take a look at the MS-19 problem solver gasket kit from Dick Larrowe. From their Website - "The newest product we sell is Remflex intake and exhaust manifold to head gaskets which solve the problem of leaking gaskets and warped exhaust headers."

regards,
Leon

I posted some more detail about the 4bbl Clifford vs Offy vs Stock 1bbl in the Hi Performance Section:


https://www.inliners.org/ubbthreads/ubbth...fdd3f#Post61079

A better gasket is certainly a plus (especially when the engine is in the car), but the cure for a warped flange is to re-face it.
You'd be surprised how accurate your eye is for small irregularities, out-of-parallel, etc. and this allows high spots (clean area with full contact, between carbon spots) to be dressed down with a big file.
A header flange is frequently 1 piece for reason that help the manufacturer:
1. cheaper to make
2. 1 less fixture needed while welding
3. helps prevent tubes from bending during shipment
But... the flange may be too strong to conform to the port surface when it's slightly bent or warped. Sometimes partially slitting the flange between ports with a saw helps - not most of the way, but 1/3 of the way up, then 1/3 of the way down, 1" apart, etc.

If you still have the the "pins" and not bolts or studs at both ends of the exhaust manifold, it could be part of the leak. The pins thread into the head just like the studs. A little WD-40 and a stud puller or visegrips will remove them and then replace them with studs or bolts to tighten up the ends of the exhaust manifold.

I did some experiments years ago with a stock 250 in a 70 Nova.
I put a 2v Rochester from a 307 on the stock intake with an adapter. Got about 3mpg over the stock 1v and a lot of throttle response and acceleration, though no times or anything. 1v was in excellent condition and I tried one from a 292 also. The 292 made more power, no better on economy. The 307 2v was hands down the winner. I had stock exhaust with a "turbo" muffler.
At the time, I had NO money so tests were with what I could get CHEAP!!!
Also, the vacuum advance made 3-4mpg difference. Timing was tested at every step but I don't remember the figures.
I think I got up to 22mpg with a Saginaw Vega 4 speed and stock rear gear.

Hotrodrobert,
Good to know.
I assume the 1bbl on your 70 Nova was an MV?
Mine were the earlier B/BC/BV carbs.
Seems you saw the same trend - the 1bbl, whether BV or MV, is not as good on gas as the later design 2bbl (or 4bbl) carbs.
I thought this might have improved with the MV design but looks like it didn't.