[Zooguy]

Okay i picked another 66 full size (Bonneville) as a parts car for my 66 Star Chief. Turns out its way to good to be a parts car!! So im making it the wifes car so we can have his and hers rides at car shows/meets/ cruises.

Mine has the 389 but will be BBC swapped. Hers DOES NOT have original motor in it. Hers is a 1970 400 with some #15, 1968 heads. Sooo i have a few questions about this combination and what it could be capable of.

#1 ... From reading up about my car i learned that the 1970-74, 400 blocks are stronger and improved over the 1965-66, 389 blocks. Did i understand that correct?

#2 ... I assume its a stock shortblock. If so what are going to be the "weak points" of the 1970, 400 bottom end?

Im going to check a few things to determine the "health" of the motor

#3 ... What is the stock oil psi for a 1970, 400?
#4 ... With #15 heads what type of compression psi should i be looking for?
#5 ... What should my compression ratio be with these heads?
#6 ... What is the factory piston ring end gaps that the 1970, 400 came with?
#7 ... What is the durability of the stock pistons, rods, crank for a 1970, 400?


Ive done lots of racing with nitrous builds in the past and am thinking about putting a little shot of the giggle gas on her car. 100-150 shot. I know its a big heavy car and i AM NOT building another race car. Just tossing a "lumpy ish" cam in it, electric cutouts way up front on the exhaust and a small shot of the juice im sure would feel "really fast" for her in such a big car.

If the motor gets a poor bill of health after checking it over really good ill pull it out and rebuild it with new bearings, rings, timing set, oil pump, cam, lifters, springs, pushrods, gaskets,and call it good. Toss it back in.

[Zooguy]

https://youtu.be/rckYLcOTtVc

All i did before this point was add trans fluid cause it was low.

Cleaning up the paint some;

https://youtu.be/qKcykJEXuQU

[Tom Vaught]

Originally Posted by Zooguy

Hers is a 1970 400 with some #15, 1968 heads. Sooo i have a few questions about this combination and what it could be capable of.

#1 ... From reading up about my car i learned that the 1970-74, 400 blocks are stronger and improved over the 1965-66, 389 blocks. Did i understand that correct?

True in both cases.

The 67/68/69 400 blocks are even a bit stronger vs the 1970-74, 400 blocks
but harder to find a good one still out there.

1967 400 2 barrel engine with "steel program splayed main caps" has made over 1500 hp in a turbocharger application.

NA 70 400 block should live a long time (with proper machining during the rebuild).

Tom V.

[steve25]

1)
Yes, you have the best 400 block you can have other then a non production ram air V block.

2 & 3)
If I recall right your block started life as a 2bbl motor .
This means that it only has a 40 psi oil pump and not the 60 psi oil pump needed for 4 bbl and performance usage.
This also means that the stock rod and main bearings are only the low grade Moraine 200 type, not the Moraine 400 type used in all the 4 bbl motors.
The auto trans B body 2 bbl motors had there Governors set to up shift at 4100 rpm, so that gives you a good idea of what the factory engineers considered a safe red line.

4)
Your motors cranking compression besides being ware dependent is also cam dependent.
If you tested and found you had 150 psi I would call it average for your motors age.

5)
Your motors factory stated compression ratio is 10.5 with those heads.
Note that all production factory compression ratio’s where overstated by .5.

6) see my photo.

7)
Your motor has the same rods and crank as any other 400 cid motor of that year.
The crank is plenty strong for racing and holding up to big power levels, the factory rods I would not use beyond 5600 rpm with stock rod bolts, but since you only have the 40 to 45 psi oil pump I would not buzz the motor to more then 5000 rpm and even then only if running a synthetic oil .

In short, even if your motor leak down tested at less then 10% I would not even think about adding a 100 Hp shot, no less 150!
I might even think twice about a 50 Hp shot on those 200 series rod and main bearings.

Don’t do something foolish that will kill a good block and crank!

[Zooguy]

Originally Posted by steve25

1)
Yes, you have the best 400 block you can have other then a non production ram air V block.

2 & 3)
If I recall right your block started life as a 2bbl motor .
This means that it only has a 40 psi oil pump and not the 60 psi oil pump needed for 4 bbl and performance usage.


5)
Your motors factory stated compression ratio is 10.5 with those heads.
Note that all production factory compression ratio’s where overstated by .5.

So if I hook up an oil pressure gauge and I'm reading anything above ~43-44 PSI oil pressure with regular 10w30 oil. It should have the "high pressure" pump and better bearings in it but with potentially worn bearings causing a reduction in oil pressure due to larger tolerances?

If I get readings 40 PSI or lower safe to assume it was indeed a 2v with the lower PSI pump and lesser bearings.


So being a 1970 400 with 1968 #15 comes out to approximately 10.0 CR? I it's kind of hoping it would be around 9 or 9.5

[steve25]

If you have the 60 psi pump in the motor and you have no rod knock sounds taking place when the motor has run for 20 minutes, then when starting the motor cold even with 10W30 oil you should see at least 55 psi of oil pressure show up.

I would not sweat the difference right now between 9.5 and 10 to 1 on a used motor especially if you will be stuffing a bigger cam in it.