Fuel Pump in earlier V8s

[Kevin H]

Originally Posted by john smith

Geo
Remember - the Canadian '383' was manufactured for use in California which then had very tight emission controls + lead free fuel.

This engine was fitted with a Carter Four Barrel carburettor which met those emission controls by restricting the airflow through it.

The Four Barrel Weber carburettor allows some 40% more air (cubic feet per minute).

John, are you sure about this?
Where was your 383 made? (what's your engine number?)

I thought Chrysler only started making changes for the emission standards late in 1971, when they started to restrict air flow in the cylinder heads.

383's manufactured from 68-70 (and possibly into 1971) would have had the heads with a casting number 2843906. These were a relatively high performance head with very good air flow, so I can't imagine why Chrysler (or Bristol) would put a restrictive carb on a 383 engine with these heads.

As for air flow and carbs, I'm no expert but I did a bit of research on the topic a few years back and wrote this on the old BEEF mail list;

----

There must be many a V8 Bristol out there with a tired or non original carburetor, so for those who are thinking about fitting a new carburetor I thought I might share a few facts I which learned recently about carburetor selection, and possibly explode a few myths in the process. This is a fairly simplistic view but it should at least point people in the right direction!

Carburetors are rated according to the airflow capacity, that is the volume of air which they can supply or 'flow' in one minute, this is measured in Cubic Feet per Minute or 'CFM'. The air of course combines with a measured quantity of fuel on the way through, which ideally will be vaporized by the time it gets into your engine's cylinders.

There is a 'rule of thumb' formula which can be used to match carburetor size or capacity to engine size;

engine capacity (CID), multiplied by maximum engine speed (RPM), divided by 3456 = Carburetor CFM

CID x RPM
__________ = max CFM
3456

For example for a Bristol 411 series 4 or 5 the formula would be (400 x 5500) / 3456 = 636 CFM

However this formula assumes 100% volumetric efficiency (VE), which means the 400 CID engine actually consumes 400 cubic inches of air/fuel mixture for every two revolutions. Which in the case of a normal 400 CID Chrysler engine produced in the 1970's, it doesn't. In fact of the Chrysler V8's used by Bristol, the 400 CID engine, fitted to the 411 S4 & S5 and 412 S1, probably has the lowest VE because of the anti pollution, or 'smog' measures in force in the USA at that time. It is effectively 'de tuned' and probably has a maximum VE of about 70%. All other V8's used by Bristol probably have a maximum VE in the region of 80% to 85%.

An engine's VE varies with engine speed and is highest when peak torque is produced. So taking into account the VE of the 400 CID engine fitted to Bristols, it really only NEEDS a carburetor which flows about 445 CFM.
CFM ratings are only a guide and it is possible for a four barrel carburetor to flow at least 20% more air than it is rated.

At the other end of the scale they can of course flow a lot less, in fact the secondary throttles on some four barrel carburetors are activated by manifold vacuum controlled air valves (commonly known as 'Air Valve Secondaries'). If these are working properly the carburetor will only flow the amount of air required by the engine (Manifold vacuum varies with engine speed and load).

However, most carburetors are fitted with jets, metering rods, etc, which provide a fuel supply in keeping with their air flow rating. So the greater the CFM rating the bigger the standard jets will be and vice versa, (to allow the correct maximum air/fuel mixture). Jets are of course changeable (as are often metering rods ) so there's nothing stopping you from re-jetting a carb that is slightly too small or too large for your engine to make it more suitable. There are however, other specifications which may need to be modified to achieve optimum performance from a wrong sized carb. Including but not limited to; metering rods, air valve adjustment, inlet 'needle and seat' size, air bleed, float level, float drop, accelerator pump adjustment, enrichment circuit timing. Most of these modifications should not be attempted by anyone other than an experienced specialist.

When a carburetor is significantly larger or smaller than the engine requires, these issues are exacerbated because the manifold vacuum becomes too high or too low. Larger carbs, for example, have larger throttle bores and venturi area, which means the manifold vacuum will not reach anywhere near that which the carb is rated at WOT wide open throttle (1.5-inch/Hg), unless the engine is highly tuned to a greater volumetric efficiency and probably higher maximum engine speed. Generally speaking any significant variance in manifold vacuum from the standard at which a carb is rated will make carburetor tuning very difficult.

Many people have been, and probably still are, led astray by the carburetors fitted as standard by American muscle car manufacturers in the 1960's. According to the formula given above, it would seem they fitted oversize carburetors to some particular production model Corvettes, Camaros and Mustangs. Well they did! But that's because these cars were frequently entered in sanctioned competition events where the standard equipment carburetor had to be retained. So when competing they tuned the engine 'up to' the capacity of the carb.

The moral of this story is, if you need a new carburetor for your Bristol, unless the engine has been seriously modified for performance, use the formula above to correctly size your carburetor and it will likely work very well 'straight out of the box' with very little alteration.

NB: Carter, and most other manufacturers of 4 barrel carbs, made different models for different engines (Chevrolet, Pontiac, Ford, Chrysler etc). Make sure you get the correct one for your engine or the throttle linkages won't be correct, the choke actuation will likely be incorrect, and it probably won't fit your intake manifold without an adaptor plate!

Kevin Howard

[pasini s]

Hello,




I have read Kevin's remarks about the carburettors and I would like to add
that the 'large' Edelbrock 1406 (600cfm) that I tried on my 409 was probably
a bit of an excess for the engine. As my Carter was beyond repair I bought a
1403 (500cfm, similar to the old Carter 3131/3249) and having enlarged the
holes for the secondary throttle valves on the intake manifold (pls see



http://www.stefanopasini.it/Bristol_...nifold_Mod.htm

for details) it now seems to work pretty well. The 1403 is cheap (I bought
it for $200), its linkages are not as different from those of the Carters as
the 1406 are, and has the advantage of an auto electric choke as well.

Cheers


Stefano

[Claude]

Originally Posted by pasini s

Hello,
I have read Kevin's remarks about the carburettors and I would like to add
that the 'large' Edelbrock 1406 (600cfm) that I tried on my 409 was probably
a bit of an excess for the engine. As my Carter was beyond repair I bought a
1403 (500cfm, similar to the old Carter 3131/3249) and having enlarged the
holes for the secondary throttle valves on the intake manifold (pls see
http://www.stefanopasini.it/Bristol_...nifold_Mod.htm for details) it now seems to work pretty well. The 1403 is cheap (I bought
it for $200), its linkages are not as different from those of the Carters as
the 1406 are, and has the advantage of an auto electric choke as well.
Cheers Stefano

Reviving an old thread. I am currently in the USA, and may have a few kgs extra allowed on my luggage allowance when I head home in three weeks. My 411 S1 came with a 383 which my rebuilder says blew up at some point and the block was replaced with a 400, but the Bristol 383 heads (which he reported were "high performance" were bolted on to the 400 block.

The barn-find car's carb was corroded, so when I was packing the container to move to NZ 13 years ago, I bought a new replacement, which from memory was a "Carter" by Weber. When the engine came back from rebuilding, it ran awful, but as I had other problems with the work done by the shop, so I just stuck the car in the garage for another day.

That day is now coming, and last time I was in the states I picked up a used 383 with transmission that I popped in the container. The 383 is now down with Bob Schmidt's mechanic in South Island, NZ to be sold or rebuilt and sold. However, I kept the carb off that engine, to add to my choices when I open the hood (bonnet) and try to get the beast running right.

Given the very inexpensive prices from folks like JEGS ($229), however, my best solution may be to buy a bolt-on carb and sell the old ones on NZ's auction site. Thus, my question:

What carb should I buy? What number is a direct bolt on that will have the least problems. I am not looking for performance, but economy is fuel use.

Edelbrock 9906 Edelbrock Performer Factory Remanufactured Carburetors looks interesting and is priced right. It is a rebuilt 1406. Bob Schmidt pointed me to a Chrysler web site that speaks highly of Edelbrock, but before I make the decision, I would appreciate experience or knowledge from others in the Bristol fraternity.

Thanks
Claude

[RGSchmitt]

At 08:20 AM 10/10/2010, you wrote:

"That day is now coming, and last time I was in the states I picked up a used 383 with transmission that I popped in the container. The 383 is now down with Bob Schmitt's mechanic in South Island, NZ to be sold or rebuilt and sold. However, I kept the carb off that engine, to add to my choices when I open the hood (bonnet) and try to get the beast running right."

To update Claude's "spare" 383. It is at Leitch Motorsport & Restoration (Leitch Motorsport and Restorations, Ltd.), the shop that completed the restoration of my Frazer Nash Mille Miglia in 2005. Their engine specialist, Greg Hunter, has torn down the 383 and pronounced it "good". He also sent me a list of parts needed to rebuild it to original specs. However, he explained that most buyers in NZ would prefer to buy the engine "as is" and complete it to their own tastes, or by their own shop. We have not yet tried to sell it either as is or completed and I'll confer with Claude soon. He'll set a price and make all decisions but I'll be involved in any rebuild.

So if anyone wants/needs a 383, contact either of us - or Barry Leitch.

Bob (Burbank)

PS I have a high regard for the work by Barry and his staff. I now have two more projects with him: 1977 Ford Ranchero and Vespa Restoration in New Zealand

[pasini s]

Hello,

I must make some amendments to what I wrote about the Edelbrocks several months ago. The difference in linkage from the standard Carter was not as little as I thought initially and, though the 1403 was quite good, the kick-down never worked well and arrangement was awkward. At the end I found that rebuilding the original Carter 3249 (once again, but this time with a brand-new quality kit) was enough to have a good result. Then the engine blew, and now that I am waiting to get the parts from the US I have also bought a brand-new Carter 3131S (NOS, never installed) and I'll have this one rebuilt too and fitted to the 318. BUt the Edelbrocks were good, well built and worked well.

Cheers

Stefano

[Claude]

I found a vendor on EBay that offers the Edelbrock carb for $199, and then includes setting it up for the car. He has asked for the following information. If someone can provide me with the ones that I mark with underline, I would appreciate it. Thanks Claude

TYPE OF CAR OR TRUCK........Bristol
WEIGHT.........._____________
CUBIC INCHES: 400
ALTITUDE YOU LIVE AT........ sea level
GEAR RATIO.............. _____________
TYPE OF TRANSMISSION.............727 Chrysler automatic
CAM SIZE............ ____________
HEADER TYPE AND SIZE............ _______________
MAX RPM'S............. factory redline or less which is __________

[GREG]

Why not send these questions to Bristol Cars ?

Just a thought !

[Kevin H]

Originally Posted by GREG

Why not send these questions to Bristol Cars ?

Maybe because they have a service department which they would understandably like to stay in business by servicing cars and selling parts, rather than offering free advice to people who want to bypass them and buy their parts on ebay

[Kevin H]

Originally Posted by Claude

CUBIC INCHES: 400

Shouldn't that be 383 or have you changed the engine?

Max RPM is probably 5200 for the 383, but it you do have a 400 I'd say 5000 to be on the safe side.

Gear Ratio probably means the final drive and I believe a couple of different options were available, but most likely 3.07

Weight - 1 ton, 13 cwt (imperial)

Headers will presumably be standard 4 into 1 cast iron but I don't remember whether they are rear exit or centre exit.

Haven't any idea about cam size.