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Old 11-08-2012, 09:37 PM
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simple 400 questions

My questions are prob easy I'm using a timing chain cover and tab off a 350 I'm wondering if the balancer is the same size are the timing marks the same also while the engine is apart can I put the balancer and tab on to see if its correct as that seems like a no brainer my next question is the rod bolts I have heard not to use tread locker and there's a few that say yes what do u think I have blue locker is it worth it? I'm building this basicly stock another question is I have dished piston any pros cons to this aslso where most 400 flex plats for th350? Because I'm worried that my plate bolts won't match the tourch converter

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Old 11-08-2012, 09:55 PM
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350 used several different covers/balancers. Any of them will bolt on a 400. You have to check the diameter and position of TDC on the timing tab, as it was changed several times.

Install rod nuts with oil or assembly lube only. There is no use for locktite. Once the nut is correctly torqued its not going anywhere.


Most 400 flex plates have two torque convertor patterns.
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Old 11-08-2012, 10:05 PM
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Great thank you so much that's what I figured but as I'm putting it toghear and have the dots on the cam and crank lined up can I put on the balancer and timing chain cover and tab and just make some marks so I kno exactly where the tdc is
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Old 11-08-2012, 10:29 PM
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Quote:
Originally Posted by mistagoodbadguy View Post
My questions are prob easy I'm using a timing chain cover and tab off a 350 I'm wondering if the balancer is the same size are the timing marks the same also while the engine is apart can I put the balancer and tab on to see if its correct as that seems like a no brainer my next question is the rod bolts I have heard not to use tread locker and there's a few that say yes what do u think I have blue locker is it worth it? I'm building this basicly stock another question is I have dished piston any pros cons to this aslso where most 400 flex plats for th350? Because I'm worried that my plate bolts won't match the tourch converter
• Timing tabs and lines for the sbc are explained here.

• Determining TDC is outlined here.

No thread locker on the rod bolts- you want to lube them w/oil or the manufacturer's lube if using ARP hardware. Threadlocker doesn't work w/oil.

Dished or FT pistons depends on the target compression ratio and what size the combustion chambers are. The compression ratio depends on the cam specs.

Something else to consider is the quench measurement.

Last edited by cobalt327; 11-08-2012 at 10:36 PM.
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Old 11-08-2012, 11:24 PM
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simple 400 question

You have to be careful with the balancer and flexplate or flywheel you use. The 400 motor is external balanced and the 350 up to 1985 is internal balanced. On the 400 balancer there is a weight bolted to the inside hub. The flexplate has a piece of metal for weight welded to it along the ring gear. In 1986 the 350 was external balanced with a weighted flywheel or flexplate. The balancer was still neutral balanced meaning no weight on the back side. I take it that this engine has not been to a machine shop before rebuilding. You can line the dots on the gears and install the timing chain cover. If the cover does not have a scale welded to it you will need a bolt-on one. Then you can check if the balancer line aligns with zero on your scale. Like cobalt327 says you can use 30w oil or thread lube on the rod and main bolts. You need to know the cc of the chamber of the heads you will use to determine the compression ratio. I would want to be close to 9.5 compression. You can go to KB Pistons for Automotive Applications to look at pistons. Once you pull up the piston it will tell you the compression ratio with the head chamber cc. When you have the short block assembled you can measure the distance the piston is from the top of the block at TDC. This measurement + your compressed head gasket thickness is your quench. You want to be close to .040.
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Old 11-08-2012, 11:48 PM
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Actually the factory 400 balancer has a scalloped outer ring. But you're totally correct that some aftermarket balancers use a bolt-on weight.

The 400 balancer has a 2 o'clock TDC line. The aftermarket sbc timing tabs are also for the 2 o'clock TDC line unless otherwise specified.


SBC 400 factory balancer- note scalloped outer ring
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Old 11-09-2012, 12:42 PM
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Thanks guys and that's the balancer that I have I just want to make sure I can adjust the timing correctly
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Old 11-09-2012, 01:28 PM
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As stated be sure you use a 400 Flexplate and not a 350. Good luck
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Old 11-09-2012, 02:20 PM
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Yup I do have the correct flex plate
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Old 11-09-2012, 03:10 PM
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Apart of the run test function I did while at Chevy engine plant was to pound in balance pins into the H/B'ers on 400's.They are not the same as 350's or 302's or 262's(yeah on the V8 262's sure am telling my age huh lol) or 307's.
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Old 11-09-2012, 06:41 PM
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One other question I have is about my intake gaskets I noticed the wholes on eather the front or rear... Dident have a real good look is blocked off should this be like this or not I have heard 400s have cooling issues so I would assum the more flow the better should I remove these or keep them in? I will be using org heads from a 307 and a stock intake from a 350 with a crab with the choke that I assume gets heated by the collent or exhaust in the center port sorry to sound like a dumb *** but wanna do it right and when ever iv done intakes iv never used block offs what's the perspose of these and are they needed?? Anyways all the help I can get is very helpfull I love to learn and want to make this perfect for the lady
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Old 11-10-2012, 02:32 PM
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No ideas on the intake manafold gaskets also I have never used gaskets on my exhaust manafolds should I
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Old 11-11-2012, 02:13 AM
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Quote:
Originally Posted by mistagoodbadguy View Post
One other question I have is about my intake gaskets I noticed the wholes on eather the front or rear... Dident have a real good look is blocked off should this be like this or not I have heard 400s have cooling issues so I would assum the more flow the better should I remove these or keep them in? I will be using org heads from a 307 and a stock intake from a 350 with a crab with the choke that I assume gets heated by the collent or exhaust in the center port sorry to sound like a dumb *** but wanna do it right and when ever iv done intakes iv never used block offs what's the perspose of these and are they needed?? Anyways all the help I can get is very helpfull I love to learn and want to make this perfect for the lady
Think twice before using the small chambered small valve 307 heads on a 400 SBC. The compression could be way too high to run on pump gas depending on the chamber volume and whether the pistons are dished or not- but the chances are very good the CR will be too high. The small valves used in 307 heads (unless they were changed) will choke the engine.

As far as the intake gaskets go, they're made to fit either side of the engine. So having the coolant crossover holes both front and rear does not matter.

The heat crossover blockoffs are used to keep the intake from warming up as fast. On a daily driven non high performance engine it is better to leave them both open or maybe only close one side off and leave the other side open- your choice. If it was ME, both would be open- especially if you are going to use it in cold weather.

The choke adjustment, etc. depends on the type of choke you have. Some are electric and need only a power wire to make them work. Some use hot air from either the intake (most common) or hot air from the exhaust manifold. The hot air gets to the choke through steel tubing that fits into the holes in a cover over a "stove" on the intake manifold. Then there is the divorced choke that has the thermostat coil mounted to the intake and it used a linkage rod to actuate the choke. The carb itself does not contain a choke housing like the hot air choke or electric choke, in other words. If you can show what you have or describe it we can help further.
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Old 11-11-2012, 08:46 PM
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They are dished pistins and the heads where org made for 307 327 350 and the carb has the stove also does the 400 use the same thimisat and spark plugs? And what about the exhuate manafold gaskets and can the choke mech be changed to electric? And where would I put the power wire too the alt also are there any simple vac dieagrams
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Old 11-12-2012, 07:06 AM
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Quote:
Originally Posted by mistagoodbadguy View Post
They are dished pistins and the heads where org made for 307 327 350 and the carb has the stove also does the 400 use the same thimisat and spark plugs? And what about the exhuate manafold gaskets and can the choke mech be changed to electric? And where would I put the power wire too the alt also are there any simple vac dieagrams
The intake is where the stove is located. Any chance you could post a photo of the carb (choke side) and the intake right below the carb? Otherwise we could be chasing our tails here.

The exhaust manifold gaskets are the same between the 307 and 400. I would recommend the metal foil backed gaskets if you're using cast iron manifolds. Retighten them after the engine has run. Keep checking them until they take a set.

Use a 180 degree thermostat.

You can use an electric choke. The exact type of electric choke depends on the carb you have. If you can't post a photo of your set up use eBay to copy a picture from that looks like your carb: quadrajet carburetor | eBay

307 SBC engines were made during the years that the tapered seat plug was introduced, so unless you know what year the heads are (date code under the valve cover), the heads need to be looked at to see if the plug seat is for a tapered or gasketed plug. I would use a 44 heat range AC Delco plug.

Vacuum lines:

You need vacuum to the modulator if you have an automatic trans. Usually from the carb base.
You need a vacuum source for the vacuum advance. Usually from the carb base.*
You need a vacuum source for the power brake booster if you have one. Most often this is a port on the intake manifold, not the carb. Should be same size as the port on the booster.
You need a vacuum source for the PCV system. This is usually a larger port at the rear of the carb base.
*See the section on what vacuum source to use for the vacuum advance here.

Alternator wiring:

10SI: Wiring a Delco (GM) Alternator
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