Wild Mango
Member
No need to hope, HAceT, all 400's are torque rich rubber torchers. Rest assured that you will be able to light up the rears at most speeds whenever the fancy strikes. What Fun!!!!
Need help on 400sbc
- Thread starter HAceT
- Start date
No need to hope, HAceT, all 400's are torque rich rubber torchers. Rest assured that you will be able to light up the rears at most speeds whenever the fancy strikes. What Fun!!!!
sschutze
Member
You'll like that Cam. It will give the engine just enough of a stutter at idle to notice, but won't be too extreme.
I'm not a pro engine builder, but I've built enough to have figured a few things out.
A good rule of thumb on Cam selection for a "slightly modified" engine: Stay under .500" lift. The closer you get to .500" lift or more, you run the chance of the rocker studs lifting out unless you convert to screw-in studs.
It's less likely to occur if you don't race it, but even the occational burnout will put a lot of stress on the valve train if it hasn't been set up.
I'm sure there are going to be plenty of guys that will disagree, but I have found that to be a good guide for the weekend mechanic.
Wild Mango
Member
IMHO you have done yourself a disservice by going for low compression. That is really going to put the hurt on low end torque even if the low dynamic compression makes the idle sound nasty. With the bigger inlet valves and the cam I would say you cost yourself well over 50 ft/lb torque and as much as 30 -40 HP, all of it in the low to mid range where its specially useful.
Easy to change slugs in a bucket so save up your pennies and get a set of good flat top hypers like the Kieth Blacks and pop them in. I guarantee you will be suitably impressed. Guarantee it.
Mike
Well-Known Member
In this part of the country, we have to keep an eye on compression ratio. In the kind of weather we've been getting, it's pretty tough to run static compression in the 9.5:1 range. Unless you're ready to pop for racing gas. In the spring and fall of the year, when temperatures are cooler, you can get away with it, but not in this kind of humid heat. You can always dial a bunch of timing out of it, to keep it from detonating, but that's no fun either. If I'm faced with a $5/gallon difference between pump gas and race gas, I'm opting for the lower CR every time.
You're right in saying reduced CR will result in reduced power, but we all have to draw the line somewhere. :down:
You're right in saying reduced CR will result in reduced power, but we all have to draw the line somewhere. :down:
HAceT
Member
Well I'd have to say the car runs GREAT....except for the heat. She likes to run warm but heck at this time of year I guess it's common. I just don't like it though. I am running a 165 thermo and 34 degrees advance. I have some telling me to take some the timg out and one that tells me that I should run a 180-185 thermo. Whats the masses opinion on this.
P.S. I want to Thank everyone for all your help on this build and words of wisdom I've recieved about this 406. I love it.
P.S. I want to Thank everyone for all your help on this build and words of wisdom I've recieved about this 406. I love it.
one finger john
Active Member
At what temp does the car run now? The thermostat is fine @165*. How many more degrees does it take before it stabilizes? Anything under 200 degrees on a fresh engine is o.k. Does it run good, smooth, no misses? Are you running an oil additive (if it has regular hydraulic lifters)? Break it in nice for the first 500 miles, varying loads and rpms, change the oil & filter (if you can, cut the filter open to look for signs of bearing failure), then drive it like a regular car. Because that is what it is, a regular car with some extra oomph.
Enjoy, John
Wild Mango
Member
THanks for the comments Mike. I'm on the other side of the world and of course not familiar with your climate.FYI= Here a cold winters daytime temp is 8degC, high summer say 25degC. My 2 400's are 10.5:1 and I run 96RON pump gas with 34deg total and the vacuum puts 16deg on that. Both Comp 280Magnum cammed.There is enough cam there to keep the dynamic compression reasonable at low speed so I have all the timing in by 2600. I run Shell Rotella Diesel oil, remote tandem filters that also give me another quart or so of oil and a 200F TStat. Finest mouse ever, the 400 and his bigger brothers the 427 and 434. Just wonderful.
HAceT
Member
It gets up to 210 driving and has seen 220. Yes it runs smooth great with no misses and it does have oil additive for the breakin. The 327 usewd to run warm too but it sometime took it longer to get there. Yesterday it reached about 210 in about 10 miles. I had a car show I was putting on and it was 10 miles from the house.
one finger john
Active Member
Ron, 38 -40 degrees total? Hmmm ... I dunno, sounds a bit much. Try straight distilled water with Water Wetter, the biggest steel, nonflex fan (19 in. if possible) with a close fitting shroud, check the timing again, is the carb properly set (not too lean), do you have a high stall speed converter, could be free wheeling in 3rd gear with low rear end gears. What is your trans temp? Does the trans share the radiator with the engine? Is the vacuum advance hooked up and operating properly?
The more you know and tell us, the more we know and can help you, John
My blower motor was doing the same thing, running hot going down the road at speed. Had 34 degrees of timing in it so it would not detonate with boost. Bumped the timing to 40 total and what a difference in power and no more overheating. I always ran 38-40 degrees total in the race cars. Give it a try and see.
one finger john
Active Member
Could be. I have never run a vac advance on any performance motor. Just mechanical advance and of course the initial advance. With big cams there is usually not enough vac to make the advance very predictable.
Wild Mango
Member
The Mallory HEI vacuum diaphragms are adjustable for (lack of) pressure. You poke a 3/32" hex key through the hose hole and wind tension on or off the diaphragm spring to adjust the pickup vacuum. As the vacuum advance kicks in the manifold vaccum goes up another couple inches as well, and my 280deg cam 400's run a lot more "docile" at a 2500rpm cruise. Certainly helps mileage, engine doesn't load up with unburnt crud, haven't noticed any effect on engine temp.
In 35 years a lot of the running hot problems I have attended to are crappy instruments. A lot.
one finger john
Active Member
I have thought about this and I think that what HaceT needs it to first determine what the total advance in the distributer is and at what rpm. Then figure out at what rpms the car cruises at. If the distributer is not fully advanced at cruise rpms then it is not receiving enough advance at cruise speed to operate efficiently. Also find out how much vacuum is being pulled at cruise rpms. That will tell you which vacuum can may be used to advance the timing at cruise rpms. The NTBA has a good article in the tech section on vacuum advances.
Example ... HaceT's car cruises @ 70 mph @ 2500 rpms. The distributer is fully advanced @ 3500 rpms @ 24 degrees. Initial timing is set @ 12 degrees before top dead center. Total timing @ 3500 is 36 degrees. At 2500 rpms (1000 rpms less), advance in the distributer 14 degrees. Initial timing 12 degrees plus dist @ 2500 rpms (14 degrees) = 26 degrees total @ 2500 rpms. Ten degrees short of the needed advance for real efficiency. The vacuum advance can will pull 10 - 16 more degrees into the distributer @ cruise speed (2500 rpms) and the engine will be more efficient. 40 - 46 degrees total with vacuum advance is NOT uncommon. Remember that HaceT's car is a very mildly warmed over rebuild (sorry, it is what it is) and needs the extra advance to ensure smooth operation. Because of the compression (8.5 cr) he can get away with the extra advance.
After the distributer & timing are taken care of then look at the carb and jetting. (90% of all carburetor problems are in the ignition). Do yourself a favor, take the distributer to a place that has a distributer machine, tell the operator everything that is pertinent to the car and engine, don't fudge or exaggerate on specs (set the distributer up for the way the car is at the present), have the work done, and then plug it back in. You will be miles ahead.
John
P.S. I invite any and all additions or corrections.
P.P.S. Used properly, vacuum advance can tame a race motor (for driving thru the pits & staging). Only limitation is the amount of vacuum that is available from engine/profile of camshaft.
Example ... HaceT's car cruises @ 70 mph @ 2500 rpms. The distributer is fully advanced @ 3500 rpms @ 24 degrees. Initial timing is set @ 12 degrees before top dead center. Total timing @ 3500 is 36 degrees. At 2500 rpms (1000 rpms less), advance in the distributer 14 degrees. Initial timing 12 degrees plus dist @ 2500 rpms (14 degrees) = 26 degrees total @ 2500 rpms. Ten degrees short of the needed advance for real efficiency. The vacuum advance can will pull 10 - 16 more degrees into the distributer @ cruise speed (2500 rpms) and the engine will be more efficient. 40 - 46 degrees total with vacuum advance is NOT uncommon. Remember that HaceT's car is a very mildly warmed over rebuild (sorry, it is what it is) and needs the extra advance to ensure smooth operation. Because of the compression (8.5 cr) he can get away with the extra advance.
After the distributer & timing are taken care of then look at the carb and jetting. (90% of all carburetor problems are in the ignition). Do yourself a favor, take the distributer to a place that has a distributer machine, tell the operator everything that is pertinent to the car and engine, don't fudge or exaggerate on specs (set the distributer up for the way the car is at the present), have the work done, and then plug it back in. You will be miles ahead.
John
P.S. I invite any and all additions or corrections.
P.P.S. Used properly, vacuum advance can tame a race motor (for driving thru the pits & staging). Only limitation is the amount of vacuum that is available from engine/profile of camshaft.
HAceT
Member
Cruise varies because I do drive the car all over. not just highway. But to answer the question at 55mph i'm taching 2500rpms. On the main roads at 70mph i'm doing about 3100rpms. I have a vac gauge in the car and it's a steady 17-18psi while idle and driving steady. My gears are 3.42 with 26.6" tall tires and I am running a th350 tranny. Rad is for a 1965 Mustang. Using the adjustable timing light and taching 2000 I set the total timing with Vacume advance hooked up 34 degrees.
Yesterdays drive my temp was 220 most of the drive and got to 230 a couple times. I can cut the car off and leave the fan oon for about 10 minutes and the temp will drop alot. I'm starting to think the rad is too small.
Yesterdays drive my temp was 220 most of the drive and got to 230 a couple times. I can cut the car off and leave the fan oon for about 10 minutes and the temp will drop alot. I'm starting to think the rad is too small.
There is the problem! You don't set the timing with the advance hooked up. Unplug the line and plug it off, Then set it for about 38 degrees at 2500 RPM then gently test drive.
Hook the vac line back up before test driving it.
one finger john
Active Member
Thank you Ron, the only thing I did not mention was disconnecting the vacuum advance when setting the initial timing. Also I believe that the vacuum source should be manifold vacuum (below the throttle plates), not ported vacuum (above the throttle plates).
John
John
one finger john
Active Member
By the way, how much advance was taken out when the vacuum line was disconnected? If you have a Mighty Vac hook that up to the vacuum can to see how many degrees are in the can. Not rubbing you the wrong way, but I don't like dial back timing lights. Not the most accurate. Try using a straight timing light and see if it makes a difference. Also, Jim (Ex Junk) I think supplied the article from an ex-GM engineer that explained the workings of vacuum advances, ported vs unported vacuum, the whole 9 yards, Very good article.
John
John
ruggs
Member
I've been watching this thread all along and just have to ask this question. If you had a 327 that used to run on the warm side and add another 79 cubic inches to that wouldn't you think that it's going to run even hotter? What shape is the radiator core etc? Just trying to spark more thought into this since HAceT says it runs great....Ron (ruggs)
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