Like Dan said. You can put headers on a stock slant, and also the 390 carb, but without other mods, you won't get much improvement. You would probably be better off, taking weight out of the car, rather than your wallet.
| Slant Six Forum https://www.slantsix.org/forum/ |
|
| Stock/6 too much carburetor https://www.slantsix.org/forum/viewtopic.php?t=32472 |
Page 1 of 1 |
| Author: | flatiron [ Fri Nov 28, 2008 2:28 am ] |
| Post subject: | Stock/6 too much carburetor |
I would like to put headers and a carb on my stock slant. Is a 390 Holley to much carb. |
|
| Author: | SlantSixDan [ Fri Nov 28, 2008 6:27 am ] |
| Post subject: | |
Instead of deciding you want to put such-and-such a particular part (or parts) on your car and then trying to predict if that will spoil the car's performance, driveability, and economy, it's usually best to start from the other end of the question and define your goals for what you want the car to do that it doesn't presently do, or what you want it not to do that it presently does. Be specific, "go faster" isn't particular enough. The more specific you can get, the better will be the advice you get in return. Or, to put it another way, why (specifically) do you want to install headers and a 4bbl? |
|
| Author: | Charrlie_S [ Fri Nov 28, 2008 7:25 am ] |
| Post subject: | |
Like Dan said. You can put headers on a stock slant, and also the 390 carb, but without other mods, you won't get much improvement. You would probably be better off, taking weight out of the car, rather than your wallet.
|
|
| Author: | Joshie225 [ Fri Nov 28, 2008 7:49 am ] |
| Post subject: | |
I put a Holley 390 on my 225 recently, but I also installed a head with larger valves, porting work and milled enough to have a true 8.5:1 compression ratio. My engine was right about 8:1 before the work. Another 225 of mine was 7.7:1. No headers, but 2 1/4" exhaust off the stock manifold. Made for a big difference in power, but it wasn't a strictly bolt-on deal. |
|
| Author: | rock [ Fri Nov 28, 2008 12:09 pm ] |
| Post subject: | Flatiron, well yes and no |
Flatiron, I don't see the mention that you want to add a 4bbl intake, and fer sure you will need it with a 390 cfm. So, headers, 4bbl carb, and 4bbl intake...so ype, you can put it on and run along in a just for looks mode, and it will look ok. And no, what a bunch of money for looks...carb used $150, offy intake used $160, headers from somone who couldn't make em fit..$150, plus time to figger out the carb linkages and do the mounting. Every man has a right to spend his cash how he sees, but at least (in my opinion) as a compromise in the $250 range you oughta try a 2bbl carb and intake, and gasp, even the stock exhaust manifold as a compromise between getting SOME improvement and some looks. For a true performance enhancement, plan on doing a head as many of us here have posted about ($600 to $1,000). Not only will it run better, you won't believe how a slant can sound like a 383 til you hear a good head and cam at work. And no quick fixes seem to exist on the way to power, I did all my work and it took about two years, cause I had to tend home fires too. rock '64d100 |
|
| Author: | wjajr [ Fri Nov 28, 2008 3:35 pm ] |
| Post subject: | |
So Rock, for 600 to a 1,000 bucks what did you do to your head? Mill head, over sized valves, and some level of porting I guessing. Did you do any of the work your self, or did you farm it all out. What kind of performance improvement did you receive from the head work. Was it obvious the engine had been modified at first turn of the key, or not? I have been kicking around the idea of purchasing a die grinder, and performing a little gasket matching this winter with the guidance of others more skilled than I on this board. I suspect porting is rather time consuming, and expensive to have a shop perform. I would have to have a machine shop do the valves & planing. |
|
| Author: | Reed [ Fri Nov 28, 2008 3:51 pm ] |
| Post subject: | |
I did the calculations once, and a stock slant six with 90% volumetric efficiency only needs 390 CFM to turn 6000 RPM. Most slant sixes never see anywhere near 6000 RPM, and most slant sixes aren't anywhere near 90 efficient. A more realistic 75% volumetric efficiency motor turning 4000 RPM (also more realistic) only needs 260 CFM. The Carter BBD (biggest stock carb ever put on a slant six) flowed 280 CFM. On a stock slant six you can do most of what you want with a one or small two barrel carb. I wouldn't spend the money on a four barrel uintil you did some serious porting or swapped to a much bigger cam and exhaust than stock. |
|
| Author: | runvs_826 [ Fri Nov 28, 2008 10:17 pm ] |
| Post subject: | |
Normally if they were aftermarket heads I would be afraid to tell someone this, but the iron slant heads are a great tool to learn on. Take a gasket and bolt it down to the head and take the die grinder and go to town. The big thing is don't bother trying to make the runners huge, but simply make them flow. I believe you could reach %85 VE at home with a die grinder which is actually a real nice flowing head for factory. The big thing is to clean up the intake and polish the exahust. If your anything like me you won't punch through, if your impatient maybe more likely. I think with a nice cam, the super six, and the head work you would be more satisifed than an offy, 390, and headers. |
|
| Author: | Aggressive Ted [ Sat Nov 29, 2008 10:07 am ] |
| Post subject: | |
Quote: What kind of performance improvement did you receive from the head work. Was it obvious the engine had been modified at first turn of the key, or not?
When I started mine up for the first time for break-in I thought that is what it was going to do.......break........It started right up with heck of bang and stayed running. After 40,000 miles it still has the same explosive starts on first revolution after hitting the key. No more grind, grind, grind then trying it again. One pump of the gas and bang! It is allot of fun to drive now. Very, very, spunky and peppy!
|
|
| Author: | DusterIdiot [ Sat Nov 29, 2008 5:44 pm ] |
| Post subject: | But... |
Quote: I did the calculations once, and a stock slant six with 90% volumetric efficiency only needs 390 CFM to turn 6000 RPM. Most slant sixes never see anywhere near 6000 RPM, and most slant sixes aren't anywhere near 90 efficient.
A more realistic 75% volumetric efficiency motor turning 4000 RPM (also more realistic) only needs 260 CFM. The Carter BBD (biggest stock carb ever put on a slant six) flowed 280 CFM. On a stock slant six you can do most of what you want with a one or small two barrel carb. I wouldn't spend the money on a four barrel uintil you did some serious porting or swapped to a much bigger cam and exhaust than stock. You can think of it like that... but the Holley 390 won't pull the full 390 cfm all the time (especially if he uses the stock stiff secondary spring). the 280 cfm gives you the whole 280, but if your engine wants 'more' you have now limited it and will have to change it later anyway. If you raise the VE of the engine through some compression, port massaging, etc... then the carb becomes the bottle neck in the build (this explains why my Hpak duster goes flat at 90 mph with the BBD, yet is still pulling strong in Overdrive at 127mph with the Holley). Given the 'logic' the street engine will not see the 4000 rpm range, but at lower rpms the 4 barrel will not have the secondary side open either, so he's limited to 180-190 cfm during 'normal' street operations, but instead of having one big 'whopping' plate to open causing a large 'dip' in vaccuum when stepping on it, the two smaller plates should give better signal throughout the throttle range.... -D.Idiot Recently one of our local performance guys had commented that carbs are not flow rated the same at all...a Holley 780 cfm carb at WOT on a flow bench at 0.5hg vacc(which is what an engine should read about WOT) only flows about 360 cfm.... |
|
| Author: | emsvitil [ Sat Nov 29, 2008 10:37 pm ] |
| Post subject: | |
1 & 2 bbl carbs are flow rated at 3.0in Hg 4bbl are flow rated at 1.5in Hg. So an identical carb rated at the 2bbl flow will be higher than if it was rated at the 4bbl flow You can convert by multipling or dividing by the square root of the difference in the flow values..... in this case the square root of (3/1.5) or 1.414. |
|
| Author: | rock [ Sun Nov 30, 2008 5:57 am ] |
| Post subject: | Hello Flatiron, glad to see your "wheels" turning! |
Flatiron, To answer your question, I did the porting but left the serious machine work to a serious racing machine shop. Just like Runvs says, I taught myself to port and it is so easy you can ruin a head! I ruined one that was done and ready to bolt on, just by wanting oooone more litttle cut, and it was in the exhaust. As someone here says, you don't need to make the exhaust side equal to the intake, and I was trying. I was matching the holes in the Aussie gasket and that took making trumpet outlets of the ports, then blending. That's were I hit the water jacket. I shared my pains in a thread about a year ago, and that thread has lots of info and related contributor comments. I know a harbor freight die grinder will work for you but I use a big dremel as detailed in the thread. But basically for that money you will install the large stainless engnbldr valves, 340 springs, new guides, 5 angle valve job, mill .100, have the shop port the pockets where the air turns under the valve, clean and polish the combustion chambers, surface the side where the manifold bolts on, and have the combustion chambers cut to unshroud the big valves. Then cc the head and block to know your CR. With a felpro gasket you will probably be in the 8.5 range. then add a set of Dutras and a tuned exhaust...can you tell a difference? Oh man yes. I don't go racing like the other guys here cause I am too scared to blow it up after all the work, but I drove the same vehicle with a stock 1bbl for nearly 40 years before I redid it, and I know how much more power I have instantly than I used to. I built for low end torque, not high end, and thus don't have the highest lift cam I lusted for, but I realistically wanted to live in the world below 4500 rpm. When 70mph is 2500 or 2800 rpm, you rarely hit 4500 on a highway! As others here, I have done lots of other tweaks too and started out with a Eddy 500cfm. I can tell a slight difference between the 390 now and the 500 I had, and that is a matter of when my secondaries open up, airflow between the two carbs open and closed, and plenty of gages and instruments to measure what is happening., plus the differences between holley and eddy innards. Ted and I have pretty similar engines but very different drivelines and weight so look at some of his, DI's and Reed's explanations as to what they did/do and results. I am running a drool tube head now because I wanted the easier removal of the tappets if I recammed as compared to the peanut plug head, but started with a so called RV cam. You do not want to overcam to hear a lope and then have NO power. So I guess my advice would be keep running stock, save bucks til you can afford a good head and study and learn why folks here have made certain choices. Read Emsvitil's posts and those of DI and Reed re. advance curves. Get an old junk head and practice porting. I am taking two to the scrapyard this week and will be glad to give you one for cost of shipping 80 pounds, but you should be able to get one locally. How 'bout that! rock '64d100 |
|
| Author: | Ron Parker [ Sun Nov 30, 2008 4:11 pm ] |
| Post subject: | |
When I was driving my car on the street, stock 69 Dart the best two bangs for the buck were a electronic iginiton, and a 3.23 rear gear ratio. Both were cheep and it worked better on the street. Hell I got pulled over by a police friend of mine running 104 mph on a county road. Still got a warning and it said doing 74 in a 60 mph zone. Sweet, Thanks Ron Parker  It Aint Over Until I Win |
|
| Page 1 of 1 | All times are UTC-08:00 |
| Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/ |
|