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73 400 Rebuild Questions


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#1 TJTA

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Posted 2 weeks ago

I have found out that a rebuild on my 73 400  would be in order and make sense at this point since the engine is out. We removed it to replace the oil pan and a rear main seal for assurance with the 2 piece bop seal. 

 

After removing the oil pan with my engine builder, it became apparent that the bearing had wear and the cylinder walls were showing some possible blow by. So he said it would be a good idea to do the rebuild now as oppose to replacing the bearings, oil/rear main seals and pulling the engine again in a couple of years to do the rebuild. Looks like the bearings were last change in the early 80's. Currently has flat top forged pistons.  

 

 

My question is, where do I go from here?  Do I do a standard rebuild which he said could bring me to around 375 hp / 460 torque or so ( according to the builder ) . The engine will be broken in and dyno before it goes back in.  Or do I go for a stroker kit?  If I do put in a stroker kit, what other components need to be upgraded to handle the extra torque? Rear end is 3.08 posi. It is a 80 TA with T-Tops that originally had the 301. Are there any disadvantages with a stroker kit in this 1973 400 block?

 

 

The present  comp cam with the 230/236 duration at 50, new lifters, new chain have about 1300 miles. They were changed by previous owner. So I think these part could be reused?

 

Thanks


Edited by TJTA, 2 weeks ago.


#2 ponyakr

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Posted 2 weeks ago

Cam should be OK, IF the lifters are put back on the same lobes. Some say a 230° cam, in a 400, is a little soft at lower rpm. OK for 428 or more cubes. 

 

Only disadvantages I can think of for a stroker are:

 

(1) Cost more. Most recommend a forged crank, since there have been failures with the Chinese cast cranks. The forged cranks are $400+ more.

 

(2) Will use more gas

 

(3) Could break stock auto trans if it gets good traction on a WOT 1-2 shift

 

(4) Could break rear end IF it gets good traction

 

If you run hard street tires, it will probably just spin the tires, rather than breaking parts. 

 

Some recommend the 1-piece BOP seal. 

 

Most recommend zero deck height, or very near it. This will keep the quench distance below .050. Most say .040 or slightly less will help reduce the chance of detonation. .050 & up will increase the chance. 

 

Many recommend 1-piece stainless valves. 

 

The 4X heads seem to be rather crack prone. 6X heads are the most popular, for stroker engines. 6x-8 cores are still cheap & plentiful. Usually $200 a pair, or less. I'd go with 6X, rather than 4X. But hey, there are still lots of 4X heads doing fine. OR, for a couple of thousand more, you can go with alum heads, rather than having iron heads correctly rebuilt.  


Edited by ponyakr, 2 weeks ago.


#3 TJTA

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Posted 2 weeks ago

I was thinking about the Butler stroker kits which I think I saw a forged piston in the package. But they are about $1900. Then I have the shipping and conversion to deal with on top of that price.

 

 

TH350 Tranny was rebuilt already last year and the engine builder said he did a HD rebuild. I asked him about doing the stroker kit and he mentioned it will be fine for the extra torque. Also the torque converter was rebuilt and now has 2500 stall. ( I kind of like it ).

 

 

Can't comment on the rear end since it was original from the factory 3.08 posi. Does the car having T-Tops cause any concern with this added torque from the stroker? Can't remember if 455's were put into t-tops cars back in 76 ( first year of t-tops ).

 

Not sure what you mean but "hard tires". My tire presently are the Bf goodrich radial ta.  Don't know if they qualify as being hard. What are considered hard tires?

 

I already bought the 2 piece BOP since I was going to change the rear main before the situation took a different turn. Can't we just put in the 2 piece during the rebuild?

 

If I don't change upgrade the 4x heads at the present, will I be losing at lot of hp/torque?

 

 

I appreciate your knowledge and comments. 



#4 ZumpTA

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Posted 2 weeks ago

The softer the tire, the more grip (rolling resistance) it has.  Toyota Prius has a very hard tire, it doesn't need much grip and the little rolling resistance they have improves fuel economy.  A hard street tire as stated above has very little grip.  It will just spin without ever grabbing the pavement and getting traction. They are also slippery as snot in the wet, and have a very high treadwear rating, some can go 60,000+ miles.  A very soft street tire has no treadwear rating and barely last for 10,000mi on the street under normal driving conditions. They grip so well, you'll blow out your rear end, snap an axle, shred a diff, maybe even eat up the transmission internals if they are not hardened for all the extra torque the tires will put down.

 

I can't speak on the old style radials, the standard radials you have are probably in the middle.  Something like a Drag Radial would likely ruin your day. 

 

I had a set of super sticky tires on my T/A.  The grip was so good I could barely spin the tires wet or dry.  Second would barely chirp under even the hardest shift.  One step down in rubber and I can not only roast my tires into 3rd, I can break them loose @45MPH and "drift".  One step down from there and even a 2nd gear start at idle can break the rear loose in the wet.  I have to start in 3rd applying no more than about 5% throttle, and even then the potential for wheelspin is real.

 

When I had my 80 Z28, I ran the BFG Radial TA, Cooper Cobra, something from Firestone (FireHawk maybe?), and once a Mickey Thompson Indy Profile L60-15 on the rear.  All "standard" radials were about the same,  but the L60s were a blessing and a curse.  Inflated to a normal pressure, they spun easily and loved to hydroplane.  Breathing on the throttle in the rain in 4th could kick the rear out.  Bouyant is an understatement for those things.  At a low pressure, they hooked so good, the car could wheelie a little. 

 

For the time being, stick with your radials and see how they perform.  But, when you put a stickier tire on it, be aware that as you're increasing grip, you're increasing the forces everything from the flywheel back is under.  Too much grip, something will give.  In the case of my '93 T/A with the highest performing street tire money could buy, it was a few teeth on my ring gear.  On my '80 Z28 with the MT L60s, I shot a spider gear thru the differential cover.  :)


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#5 js292

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Posted A week ago

I was thinking about the Butler stroker kits which I think I saw a forged piston in the package. But they are about $1900. Then I have the shipping and conversion to deal with on top of that price.

 

 

TH350 Tranny was rebuilt already last year and the engine builder said he did a HD rebuild. I asked him about doing the stroker kit and he mentioned it will be fine for the extra torque. Also the torque converter was rebuilt and now has 2500 stall. ( I kind of like it ).

 

 

Can't comment on the rear end since it was original from the factory 3.08 posi. Does the car having T-Tops cause any concern with this added torque from the stroker? Can't remember if 455's were put into t-tops cars back in 76 ( first year of t-tops ).

 

Not sure what you mean but "hard tires". My tire presently are the Bf goodrich radial ta.  Don't know if they qualify as being hard. What are considered hard tires?

 

I already bought the 2 piece BOP since I was going to change the rear main before the situation took a different turn. Can't we just put in the 2 piece during the rebuild?

 

If I don't change upgrade the 4x heads at the present, will I be losing at lot of hp/torque?

 

 

I appreciate your knowledge and comments. 

 

Not all Butler rotating assemblies are forged cranks, it's a option you have to select for more $$$'s.

 

Your TH350 will be fine for a while depending on how hard you drive and it's condition to start with.

 

rear end should also survive as long as your not running drag radials, most street tires just spin anyway. I have what is suppose to be sticky Nitto's and they spin through all three gears if I mash it to the floor. 

 

With a t-top car and increased torque I'd defiantly install sub-frame connectors.

 

No issue using you BOP two piece seal during the rebuild

 

If your rebuilding your 4x heads mag them to make sure there are no cracks, and cc the chambers so you can calculate you comp ratio.


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