Those damn little Elves switched my Windsor out for a Cleveland!

Steve,

C302 heads are great heads, I won't call them the best, but they are very near the best. I lean towards thinking the Blue Thunder & Brodix BF300 heads are better "canted valve heads", BUT the C302 heads have smaller ports which may translate to better performance on the street. Especially for a 351 cubic inch motor. It would take dyno testing to sort out the SUBTLE differences. So if you don't want those heads, sell them to me!

The 2V motors were equipped with 2 barrel carburetors & the heads featured smaller ports and valves, the 4V motors were equipped with 4 barrel carburetors, large port heads and larger valves. There are many subtle differences like the size of the harmonic balancer, adjustable valve train, camshafts, compression ratio, combustion chamber design, etc. But I beleive the difference you are concerened about is the blocks.

The 1971 351 Boss, 1972 351 HO & 1972 - 1974 351C 4V/Cobra Jet had 4 bolt main caps. No big deal. The 2 bolt blocks are just as strong in every way. In fact, some 4V/cobra jet motors were assembled with 2 bolt blocks, and I have seen a 2V Cleveland with 4 bolt mains, seems sometimes the assembly lines borrowed from one another. From 1972 to 1974 the 2V & 4V/Cobra Jet blocks had the same casting number (D2AE-CA), you had to pull the pan to determine if it had 2 bolt mains or 4 bolt mains.

You must understand, the issue with the main bearing caps is that they twist & squirm under load. The extra 2 bolts per cap is supposed to reduce this, and maybe they do to a small amount, but if you really want to control main cap squirm you install a main cap girdle, period! The only other way to design main caps that are stronger than those assembled with a girdle is to cross bolt them, like those in the 427 side oiler or the 4.6 modular V8.

The Cleveland engine is not known to be weak in the main caps, that is not a normal mode of failure for this engine. You can use either block knowing they are equally strong, and resort to a girdle if the power level or rpm warrrants it, which you should do even if you have a block with 4 bolt main caps.

There are MORE high performance parts on the market today for the Cleveland than there were in it's heyday back in the '70s & '80s. Many of the important parts are still listed in the Manley, Milodon & Moroso catalogs.

your friend on the DTBB, George

Hey George,

what is acceptable for leakdown numbers.

I had the car on the dyno today. It put down 293 hp and 318 tq. Problem is that they had to back out of it at 4600 RPM because of pre detonation. Evidently it has some high compression pistons that require more than 91 octane.

They speculated that it may have gained another 50 or 60 to the wheels if I had had the fuel.

Steve

Hi Steve,

Run a compression test first, all plugs removed, carb set wide open, cranking with the starter. Look for uniformity among the readings, if they all check within 10% go on to the leak down test.

Assuming the leakdown tester is set correctly & in good working order, assuming each cylinder tested is set at TDC on the compression stroke, an average number is 5%, 2% is excellent, anything worse than 10% is taken as a sign of trouble. However, uniformity plays a factor here as well.

If all test good at TDC, test each cylinder at a few settings past TDC by rotating the crank a bit, a cylinder may have a problem in a cylinder wall somewhere in the middle of the stroke.

To detect small leaks it is sometimes necessary to reduce the pressure setting of the tester, less pressure flows less air through the tester's orifice, and leaks will create a greater pressure drop, makng the tester more sensitive to small leaks.

The compression & leak down tests together tell the whole story.

Did your dyno guys have an O2 sensor in the tailpipe, checking for a lean carb mixture?

George

Yes, I believe they did have the exhaust analyzer as they made carb adjustments and tuning on the Dyno.

I know that you are planning on rebuilding your Cleveland this winter, would you be interested in building another one along side of it?

I am interested in a 408, and reusing my C302's. Let me know if you have any interest, and at what cost. I don't expect you to do charity. As the car is Minnesota bound, there is no rush. You could have the engine until next April or May.

Just a thought

Steve

I'm sorry Steve I don't build motors for others any longer. I'm flattered you even asked. That period of my life came to an end in 1991.

I believe you live in OC, have you spoken with Fulps? He did Antenucci's motor. Dennis speaks highly of him.

George

quote:

Originally posted by gandalfthegray:

I had the car on the dyno today. It put down 293 hp and 318 tq. Problem is that they had to back out of it at 4600 RPM because of pre detonation. Evidently it has some high compression pistons that require more than 91 octane.

They speculated that it may have gained another 50 or 60 to the wheels if I had had the fuel.

Steve

Steve,
Your 293hp is very respectable. Even more so since the engine is probably out of tune and you're using soccer-mom gas to fuel it. I've seen stock-smogged Panteras running low-mid 200 hp..

I never used anything less than 93octane and at times will even deposit octane boost into the tank. Good luck.

Kevin

Just curious - but what octane fuel can you get in the USA.
In the UK it's 95, 97 or 98 and my Pantera pinks on 95.

Derek,

Here in the US we have 87 as regular; 89 as plus; and 92, 93, or 94 as premium (depending on which brand you use).

Are octane ratings the same in the UK as in the US?

Michael

Michael, that thought hadn't occurred.

But Google has the answer, it's 'No'.

In the UK Octane ratings are by the Research Octane Number (RON). In the US it's Anti Knock Index (AKI).
AKI is an average of the RON and MON rating for the fuel. MON is the Motor Octane Number.

87 AKI = 92 RON
90 AKI = 95 RON

Hmmm so 98 to me is 93 to you in the US, mystery solved. It's amazing what you find on the internet...

Forgot to say..
In the UK the ordinary stuff is called 'Premium' and it's 95 RON (87 to you).

The better stuff is usually called 'Super' and is 98 or 97 RON (92 or 93AKI).

Also there is LRP (Lead Replacement Petrol) which is 97 RON. This is for cars designed to run on leaded fuel (we are thirty years behind the US on this one!). This one is starting to get difficult to find.

Mainland Europe seems have 95 & 98 RON.

Great info, Derek! I'm now well informed should I take a wrong turn and wind up in the UK or Europe!

Michael

I was able to find 100 octane at the pump in southern CA. but it is rare.

quote:

Originally posted by gandalfthegray:
I was able to find 100 octane at the pump in southern CA. but it is rare.

100 proof will increase your hp output considerably over the soccer-mom stuff you were using. Try it, then dyno.

Yes, I plan to try just that.

Hoping then that they can run the dyno pull up to say 6000 rpm or so. Plan to have this done before the PI gathering in Dec.

I will try to bring the dyno sheets for anyone thats interested. And post the numbers as well.

Little disapointed however with having to run the expensive hard to find fuel.

Steve

quote:

Originally posted by gandalfthegray:
Little disapointed however with having to run the expensive hard to find fuel.

Steve

Steve, welcome to the wonderful world of Panteras Its expensive appetite is just a nature of the beast.

Regardles, you should run fine on 93 and can always add octane boost if needed.

Unless the motor was designed intentionally to run on high octane fuel, there seems to be a mismatch between camshaft & compression ratio. These things can be fixed, for the price of pistons, rings & gaskets.

Flat top pistons in a standard displacement short block & C302 heads should yield 9.5 to 10.0 compression ratio. With any kind of a performance cam, that should not be too much compression for 92 octane pump gas. So I would expect to see pop up pistons in your motor, or a stroker crank with flat tops.

George

George,

Remember the engine is supposed to be a 373. I wonder if it could be a 393 as this seems to be a common displacement among Clevelands.

Steve,

before the advent of the inexpensive crankshaft castings & fordgings manufactured in China, a 377 Cleveland was the most popular Cleveland stroker! That is a 3.70" stroke and a 0.030" over bore.

The 3.70" stroke crankshaft was achieved by off set grinding the rod journals of the stock cast iron crank to 2.10" diameter (small block chevy size). This increased the throw of the crankshaft from 1.75" to 1.85". This was then combined with a set of 6.00" Chevy connecting rods and custom pistons with a compression height of 1.35".

Because your motor was referred to as a 373, that probably means the cylinders are only 0.010" over bored ranther than 0.030". This is a good thing, as it means this block has more life left in it.

Going "over-board" with your friend on the DTBB, George