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Author Topic:   ENGINE COMBONATION NEEDS FIGURED OUT
pbrcowboy2
unregistered
posted October 06, 2003 04:51 PM           
HERE'S THE COMBO:
1. 350 BLOCK MILLED 5 THOUSANDTHS AND BORED
30 OVER
2. 416 HEADS MILLED AT 25 THOUSANDTHS
3. 11 TO 1 FORGED DOME TOP PISTONS
4. OEM HEAD GASKETS
5. 4412 TWO BARREL CARB
6. STRAIGHT OUT 90 DEGREE HEADERS
7. OFFENHAUSER SINGLE WIDE OPEN 360 DEGREE
ALUMINUM MANIFOLD
8. 1.5 INCH SPACER
9. OEM ROCKER ARMS

ANYBODY HAVE IDEAS ABOUT WHAT KIND OF
COMPRESSION WE HAVE HERE?


sdhnc29
Member
posted October 06, 2003 05:22 PM
It would be absolutely impossible to say without the following info . CC your piston in the hole at exact TDC and give me the number , CC your combustion chamber and give me the number , tell me what the thickness and bore diameter of your head gasket is . Only then can anyone tell you what your compression ratio will be . Other than that , its a shot in the dark .

Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780


smallrock98
Member
posted October 08, 2003 11:06 PM
Well, you are definately over 200 compression. If I had to take a wild guess with the info you gave.......I would say somewhere between 225 and 250.


norightturn
Member
posted October 09, 2003 07:53 PM
that 200 psi number is cranking compression and guaged with a compression tester. it's not the compression ratio. the camshaft overlap has a lot to do with the amount of cranking compression and absolutely nothing to do with compression ratio. listen to steve, you have to know the volume of the variables he listed to know exactly.

[This message has been edited by outlawstock17 (edited October 09, 2003).]

norightturn
Member
posted October 10, 2003 09:06 PM
I just figured that he hasnt put this engine together yet and he wanted to know how much cranking compression he might have. After all, he doesnt really say what type of compression he is looking for so I just threw out a cranking compression number for him compared to one of my engines I built that was similar to his.


pbrcowboy2
unregistered
posted October 12, 2003 09:44 AM           
this engine was already built brand new in car but i put a set of heads on it was wondering if somebody could tell me if i was looking at 12 or 14 to 1 comp.........thats what i wanted to know!!!!!


sdhnc29
Member
posted October 12, 2003 02:31 PM
Refer to my first post . There is a massive difference between 12 and 14:1 compression . 2 points does not sound like much , but it is huge ! A 12:1 engine will use different race gas than a 14:1 engine , and this could be the difference between burning a piston , torching a head gasket , or not . You kind of got the cart ahead of the horse in this instance . So I would back up , do what I mentioned in my first post ........and your question can be answered correctly .

Everyone is trying to help you out here , but you are not providing the info to answer your own question correctly .

Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780


redneck bubbas racing
Member
posted October 12, 2003 05:03 PM
I'll give you an educated shot in the dark. Most pistons that are off the shelf are labeled using a 64cc head for compression purposes. A 416 head has an app. 58cc chamber. On a typical small block 6-7 cc usually equals 1 point. Taking into account your heads and block have been slightly milled I would assume (knowing that assume simply means making a a$$ out of u and me) that you have ABOUT 12.5-13 to 1.


pbracer9
Member
posted October 16, 2003 04:16 PM
I did this when we were karting and seemed to work well. Get a large syringe 50cc or larger. Place engine so that 1 cylinder is vertical and place piston at tdc and fill combustion chamber until plug hole is full with oil. turn crank 180* and fill until full again. Then do the math volume bdc/volume at tdc. Works well for us


racer17j
Member
posted October 16, 2003 06:41 PM
only one problem there 9 the plug hole isn't at the top of the cylender like on your 5 horse


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