TPC Racing Marine 850DP 4165 Sprd/Bore

[Hotcrusader76]

I wanted to pass some pertinent information with regards to overhauling one of these types of Holley carburetors.
This is a Holley 850 Marine Double pumper, which is configured as a 4165 style. It might look very similar in alot of ways to the #4781 Holley 850s but differs in just about every way. Not only does the baseplate have a stamp "made in Japan" but also not even are the carburetor gaskets the same. The fuel bowl gaskets might look identical to the 4150 style or even the 3-circuit HP versions, but they aren't.
In order to overhaul one of these 4165 carburetors one must first locate the correct gasket set.
The primaries of this carburetor are very small and definitely add to the throttle response of this size carburetor but when the secondaries are open, all 2 inches of blade open up with a 50cc shot of fuel from the secondary accelerator pumps. The squirters are 25 primary and 37 secondary, which show quite a difference.
Without going into much detail on the pros and cons of this set-up I will say that this carburetor is an "iron-horse". It was my honor to overhaul this carburetor for aka"Propless" here on the threads. As some may already know he bought a New TPC carb from me last year and wanted this one re-done for a spare, and a nice one it turned out.
http://www.tpcracing.com/images_temp/4165_450.jpg
http://www.tpcracing.com/images_temp/4165d_350.jpg
http://www.tpcracing.com/images_temp/4165_450.jpg
As you can see this little fuel tube connects the accelerator pump passage from the metering blocks to the mainbody orifice that joins to the squirters. Most carburetors use a superimposed boss which mattes to a gasket to act as a passage. For some Marine carbs this device was used as a safety device to prevent fuel leakage between the two surfaces. I recommend purchasing a new one vice changing the rubber o-rings on it otherwise you risk fuel leaks under acceleration. http://www.tpcracing.com/images_temp/4165Fueltube_350.jpg
http://www.tpcracing.com/images_temp/4165Fueltubea_350.jpg
Here you can see another modification that all TPC Racing carburetors receive and that's the primary throttleshaft hole. All carburetors have the remaining shaft extended out as seen in the bottom picture which allows the use of a choke. Now since most people don't utilize the choke mechanism they remove the linkage parts and the shaft remains exposed. Well by removing the excess material from the shaft and plugging the hole you lessen the risk of vacuum or fuel leaks which the carbs are very prone to in that area.
http://www.tpcracing.com/images_temp/4165a_350.jpg
http://www.tpcracing.com/images_temp/4150a_350.jpg
http://www.tpcracing.com/images_temp/4165e_350.jpg
Thanks again guys.
~Ty
[ February 17, 2003, 10:17 AM: Message edited by: Hotcrusader76 ]

[superdave013]

Looks real nice!

[01RENEGADE]

looks good, have you done any Edelbrocks?

[Hotcrusader76]

Thank you for the kind words guys.
I have rebuilt Edelbrocks, but not with the attention to detail that these receive. I have started overhauling Rochesters by popular demand for the street guys as well. I have one that will be done this week that came out bitchin! It's a Q-Jet 500cfm carb destined for a SBC 67 Chevy.
If you need an Edelbrock done give me a call. They aren't much different than the Rochesters except they look great when polished and or anodized.
~Ty
[ February 17, 2003, 01:51 PM: Message edited by: Hotcrusader76 ]

[Hotcrusader76]

Rd,
The preliminary tuning is done here base on a calculated density altitude that the “client” normally operates at on an average. This allows a base calibration to be set with regards to his or her application and once installed minimal tuning is required.
We all know that the best tune is done when the motor and carburetor are happily matted together and are dyno run to a base calibration. Then the final dial in can be done in the water or on the street where the other factors come into play such as g-forces on the floats during acceleration, different drags on the crank which water-brakes and eddies have a hard time simulating on dynos, and of course with many, varying fuel pressures. Without running EGT probes or fuel flow meters on the destined engine getting her properly tuned is a matter of doing the math, using you weather calculations, reading plugs, and knowing what works and what doesn’t. These tools prove to be very useful for the guy who can’t afford $600+ per day for a dyno run, let alone the tools to get her yanked out and into a facility.
We are planning to have our dyno facility next year which will allow our local base customers to have there engines matched to there carburetors, all the way down to the last 1/8th float turn. I spoke with Dan Roberts up at DTS, who is going to give us the full two-day tour here next month. We also spoke with Superflow up in Colorado who has been very helpful in the past for us, but just doesn’t cut the cheese when compared to DTS engine dynos (that might be a controversial comment). Now when it comes to flowbenches, that’s another story…
Rarely does a “client” have to tune any further than the jets or primary float height on their TPC Racing carburetor. The air-bleeds, emulsion, and idle circuits are always on the money for the average performance motor and usually never see any change unless something was drastically changed since the base calibration.
Hope that answered your questions(s).
~Ty

[Blown 472]

Are you changing the emulsion tubes?? if so how do you get them out without wreaking them??

[Hotcrusader76]

Well you don't, "remove the emulsion tubes" persay as you would remove the plugs that seal them. Sometimes the emulsion wells as they are called, will contain emulsion tube pick-ups which are often seen in 660 center squirters and smaller cfm carburetors.
You can remove them by drilling a hole down inside, not so far as too breakthrough the emulsion tube pick-up but enough to get a sheetmetal screw down-inside and pry up on it to remove it. Now some people might try using the caps over again, bad idea! I highly recommend reinstalling new ones so that the proper depth can be acheived when press fitting them back in.
I use an small arbor press to accomplish this.
~Ty
[ February 17, 2003, 06:56 PM: Message edited by: Hotcrusader76 ]

[Froggystyle]

I am stoked to have a genuine carb guru around. This is the one area of high performance that I have always found to be at least 2 parts voodoo.
I will check the plugs, and change jets like it is cool, but when it comes to actual modification of the carb... I consider that thing one sealed unit!
Great pics Ty. Good to see someone else obsessive about detail!

[Hotcrusader76]

Thank you for the compliments Wes. I make it a personal mission on every carburetor built that it runs without flaw and adheres to the highest of visual standards.
A little show with alot of go! wink