Was there ever a high compression
Thread Starter
Pro
Joined: Jul 2009
Posts: 503
Likes: 0
From: Gambrills Maryland
I found a 71 for sale down the street from me that has the engine plaque on the console that says 350hp....380 torque...and 11 to 1 compression. Does that make any sense? The ownwer does not know much about the car. How can I tell from looking at the engine what it really is?
Tx
Mike
Tx
Mike
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
There were no 11:1 compression engines built by the factory in 1971. In '71, all C3 engines were required to reduce compression and were either 8.5:1 or 9.0:1 heads. That doesn't mean that the engine in that car is not what is shown on the shifter plate. However, since the owner doesn't know anything about the car/engine, you should assume that only the data plate has been changed.
If he will allow it, you could remove one of the valve covers to get the casting numbers and date codes off the heads and query the Forum on what they may truely be.
If he will allow it, you could remove one of the valve covers to get the casting numbers and date codes off the heads and query the Forum on what they may truely be.
Thread Starter
Pro
Joined: Jul 2009
Posts: 503
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From: Gambrills Maryland
I dont know if I can take the valve cover off but thats a good idea. Ho about thecarb...doesnt the L46 have a different size/make carb then the "72 V8 had?
The vin says its a 71. The tach redlines at 5400 and it does not have air. Does that tell us anything?
The vin says its a 71. The tach redlines at 5400 and it does not have air. Does that tell us anything?
Drifting
Joined: Jul 2002
Posts: 1,697
Likes: 3
From: Woodinville WA
The tach suggests it was originally a 270hp 350.
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Burning Brakes
Joined: Oct 2003
Posts: 1,090
Likes: 74
From: New Carlisle IN
That is the standard casting number for small blocks for many different years. The more valuable info should be found on the pad up on the front of the motor just below the passangers side head. It should have a sequence of numbers that should match part of the vin number and then a set of three letters that will tell which engine is in the car.
Racer
Joined: Jan 2010
Posts: 402
Likes: 1
From: Medford NJ
Those specs only match the '70 L46 or LT-1, so it sounds like the owner changed the console plate. The other possibility is that the owner replaced the '71 engine with one of these '70 engines OR built the '71 engine to '70 specs. Then the console plate is telling the truth.
1970 specs: http://www.vettefacts.com/c3/1970.aspx
1971 specs:http://www.vettefacts.com/c3/1971.aspx
1972 specs:http://www.vettefacts.com/c3/1972.aspx
1970 specs: http://www.vettefacts.com/c3/1970.aspx
1971 specs:http://www.vettefacts.com/c3/1971.aspx
1972 specs:http://www.vettefacts.com/c3/1972.aspx
Last edited by vettes4evr; Jun 14, 2010 at 09:12 PM.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
Too bring a 71 low compression engine (76cc heads) back too a 70 LT1 spec isn't hard. A head & cam swap will do it. That's why the head numbers are needed to confirm it's an LT1 11 to 1 compression
Melting Slicks
Joined: Jan 2004
Posts: 3,247
Likes: 210
From: Detroit MI
A bit more involved than that, the pistons would need to be replaced as well with domed units instead of flat tops (or dished but I don't think 71's were dished but I could be wrong).
Last edited by 69autoXr; Jun 15, 2010 at 08:53 AM.
Thread Starter
Pro
Joined: Jul 2009
Posts: 503
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From: Gambrills Maryland
If I do just have the stock 270Hp 1971 350, what can I do to get it up to 350-370 without having to change out the pistons? Or is it ceape/easier to just drop a turn key crate motor in?
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
a pr of massaged gm vortecs & a cam like summit K1105 can take an OE dished L48 to about 350 fwhp at crank. Before you go an inch farther ... suggest you first verify pistons, rings, bearings etc are in good shape.
