Slant Six Forum :: Engine Build Advice

I was searching around the net, and found offenhouser offers 2 choices for intakes: a 4 barrel option and one for two seperate single barrels. What is the benefit of two singles?

Quote:

I was searching around the net, and found offenhouser offers 2 choices for intakes: a 4 barrel option and one for two seperate single barrels. What is the benefit of two singles?

They look cool

I think that is the SMART answer in deed. Tuning a single four has to be a lot easier.

That's definitely going to depend on the specific carb in question.

I used a 625 (600? not sure) AFB, and that required a LOT of "fiddling". I could never make it run just right if you floored it below about 2000. It always bogged and missed, no matter what I did.

I have no idea how many jet, rod, spring, float, and accel pump changes I did before I declared it "as good as I can get it".

Quote:

I suspect you had difficulties getting the carb to run right because a 600+ CFM carb is WAY to big for a stock slant six, or even a moderately warmed up slant six. A 500 CFM Carter/Edelbrock AFB (or, better yet, AVS) would be the biggest four barrel carb I would run on a slant six, and then only if it had lots of mods or was a dedicated drag car. THe Holley 390 is the most popular four barrel carb, but a Holley 4360 might work too. Much harder to find, but it is a spread bore carb that flows 450 CFM.

On a street driven slant without lots of modifications, a two barrel is where you usually want to stop. You can actually do quite a bit with a one barrel.

Author:	RAMW150 [ Tue Dec 14, 2010 6:05 pm ]
Post subject:	Engine Build Advice
I have been toying w/ the idea of building a slant for my truck that will have a lift and 35" tires. My tuck has a 4spd and 3.55 rears and 33'' tires now and does ok. It lacks on long uphill grades or towing a medium weight trailer. I am asking for all advice i can get such as :what year blocks are best,how much can you bore, what cam is best for torque, 2bbl or try 4barrel, head work valves etc. Any advice would be great!

Author:	Reed [ Tue Dec 14, 2010 6:25 pm ]
Post subject:
If I were you, I would follow AggressiveTed's build exactly. Send him a PM for the details. In a truck that pulls trailers, you really don't need to go even to a two barrel, much less a four barrel carb. For a daily driver, a block is a block, so long as you stay in the forged vs. cast crank families of engines.

Author:	sandy in BC [ Tue Dec 14, 2010 6:33 pm ]
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If you really want to run 35s you will need to change out your gears for something lower...or the thing will be a pig. I run 4.11 gears with 31" tires and over 300 hp......I used to have 3.73s and they were too high.

Author:	RAMW150 [ Wed Dec 15, 2010 9:01 am ]
Post subject:	forged vs cast engines
Am I correct that an early 1976 and older block would have a forged crank vs a later block w/ a cast crank? Ideally these are better for building, right?

Author:	Reed [ Wed Dec 15, 2010 9:23 am ]
Post subject:
Yes on the early 76 being forged, probably not on the forged cranks being better. There have been several documented cases of people building high performance cast crank motors. Again, for a daily driver truck motor, even a warmed up one, I don't think it will make a difference.

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Author:	66aCUDA [ Wed Dec 15, 2010 11:26 am ]
Post subject:
I tow with my cast crank Hydro motors all the time. No issues. Frank

Author:	RAMW150 [ Sun Jan 02, 2011 3:11 pm ]
Post subject:	Intake choices
I was searching around the net, and found offenhouser offers 2 choices for intakes: a 4 barrel option and one for two seperate single barrels. What is the benefit of two singles?

Author:	Brussell [ Sun Jan 02, 2011 6:32 pm ]
Post subject:
As far as I'm aware the benefit is tuning, can be finely tuned a little better.

Author:	Reed [ Sun Jan 02, 2011 6:41 pm ]
Post subject:
I think the annoyance of synchronizing two carbs outweighs any other benefits. I would go with a four barrel offy intake, if you really must have a four barrel.

Author:	emsvitil [ Sun Jan 02, 2011 6:54 pm ]
Post subject:	Re: Intake choices
Quote: I was searching around the net, and found offenhouser offers 2 choices for intakes: a 4 barrel option and one for two seperate single barrels. What is the benefit of two singles? They look cool

Author:	Reed [ Sun Jan 02, 2011 7:06 pm ]
Post subject:	Re: Intake choices
Quote: Quote: I was searching around the net, and found offenhouser offers 2 choices for intakes: a 4 barrel option and one for two seperate single barrels. What is the benefit of two singles? They look cool That would have been my smart-ass answer.

Author:	runvs_826 [ Sun Jan 02, 2011 9:29 pm ]
Post subject:
I think that is the SMART answer in deed. Tuning a single four has to be a lot easier.

Author:	65CrewCabPW [ Mon Jan 03, 2011 1:01 am ]
Post subject:
Quote: I think that is the SMART answer in deed. Tuning a single four has to be a lot easier. That's definitely going to depend on the specific carb in question. I used a 625 (600? not sure) AFB, and that required a LOT of "fiddling". I could never make it run just right if you floored it below about 2000. It always bogged and missed, no matter what I did. I have no idea how many jet, rod, spring, float, and accel pump changes I did before I declared it "as good as I can get it". It's all but impossible to find today, but back when I did it, I had a Carter "strip" kit that included myriad springs and jets and rods and even acclerator pump squirter nozzles. They're out of production, as far as I know, and the kits you can buy now are far less complete and cost big bucks. Back then, it was about 25 bucks or so. The AFB is relatively easy to tune, once you understand the basics, and back then, I had the Carter "how to tun an AFB" book to follow, which I had read from cover to cover repeatedly before I even started. I've found nothing better to explain the basics of the AFB and how to understand what's going on. My experience says use the later model carter BBD 2 bbl, but again, finding tuning parts is, well, very hard. My old super six carb is now on a poly 318, where it runs very well. Again, I had benefit of the Carter book on how to tune it many years ago (long since lost), and still wish I did. My advice is use a small 4bbl if you have to, and listen to the carb selections by the gurus here, but if I had had it to do over again, I would have probably stayed with the 2bbl.

Author:	Reed [ Mon Jan 03, 2011 8:52 am ]
Post subject:
Quote: That's definitely going to depend on the specific carb in question. I used a 625 (600? not sure) AFB, and that required a LOT of "fiddling". I could never make it run just right if you floored it below about 2000. It always bogged and missed, no matter what I did. I have no idea how many jet, rod, spring, float, and accel pump changes I did before I declared it "as good as I can get it". I suspect you had difficulties getting the carb to run right because a 600+ CFM carb is WAY to big for a stock slant six, or even a moderately warmed up slant six. A 500 CFM Carter/Edelbrock AFB (or, better yet, AVS) would be the biggest four barrel carb I would run on a slant six, and then only if it had lots of mods or was a dedicated drag car. THe Holley 390 is the most popular four barrel carb, but a Holley 4360 might work too. Much harder to find, but it is a spread bore carb that flows 450 CFM. On a street driven slant without lots of modifications, a two barrel is where you usually want to stop. You can actually do quite a bit with a one barrel.

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Author:	65CrewCabPW [ Mon Jan 03, 2011 9:21 am ]
Post subject:
Quote: Quote: That's definitely going to depend on the specific carb in question. I used a 625 (600? not sure) AFB, and that required a LOT of "fiddling". I could never make it run just right if you floored it below about 2000. It always bogged and missed, no matter what I did. I have no idea how many jet, rod, spring, float, and accel pump changes I did before I declared it "as good as I can get it". I suspect you had difficulties getting the carb to run right because a 600+ CFM carb is WAY to big for a stock slant six, or even a moderately warmed up slant six. A 500 CFM Carter/Edelbrock AFB (or, better yet, AVS) would be the biggest four barrel carb I would run on a slant six, and then only if it had lots of mods or was a dedicated drag car. THe Holley 390 is the most popular four barrel carb, but a Holley 4360 might work too. Much harder to find, but it is a spread bore carb that flows 450 CFM. On a street driven slant without lots of modifications, a two barrel is where you usually want to stop. You can actually do quite a bit with a one barrel. Correct... But, it was "what I had". It came on a 72 Chrysler T&C wagon that I converted to Holley Pro-Jection, and so I had the carb. I don't think any amount of tuning, other than doing some fundamental re-engineering could have "fixed" the big carb. Until the engine rpm's came up a bit, those air shutters just looked like a "leak" to the motor and the back cylinders (1 or 2) saw lean until it could pull enough cfm to act like a carb on the secondaries.