High compression Carb car

[Vanquizor]

Just curious if anyone's really putting the boots to a carbed motor....

For my circle track car I'm limited to stock manifolds/carb/pump premium, however I can use a combination of milling/decking/thinner gasket to get my compression as high as 11.5. How far can I push the compression before I start running into detonation with pump gas? I'm thinking near 10.5 but I haven't given it a shot yet... anyone have some experience?

thanks!

[rcaineguy]

I don't have any personal experience with carb'd 2.2's, but I do know that back on the mid-80's Direct Connection came up with one of their 'recipes' for producing 180 HP on a 2.2 Dodge. Don't know how much is applicable given the rules you have or whether the old part numbers are still available but I can provide a reprint of the old article I have:

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HOW TO BUILD A 180-HP STREET ENGINE
So you want to build one up the old-fashioned way, without nitrous, a turbo, or supercharger... here's how.
Start with DC's big-valve ported head and mill as necessary to obtain 10.2-1 compression- the same as a Shelby production motor. This will work with 92-octane pump gas because the Chrysler 2.2 has a better combustion chamber design than most competitive wedge-type engines. Race gas would allow 11.5-1 or even higher compression, yeilding in excess of 200 HP.
If using a manual trans, the 288-degree duration/.528-inch mechanical cam is recommended; automatics should use the milder 276-degree/.493 cam. If you do not want to install mechanical lifters, Engle has a whole series of big hydraulic cams that produce almost as much horsepower. With any of these cams, special valvesprings and retainers are required, as is (if not already so equipped) the forged DC rocker arm. Use the 1 3/4 x 2 1/2 inch headers, the appropriate DC off-road ignition computer, and dual 45mm side-draft Weber carbs.
Assuming the short-block is in good shape, there's no need to dive in and rebuild the motor. However, if it's time for a rebuild, bore it .050 and use the good DC forged lightweight pistons, rings, and bearings. Install DC rods, or rework the production rods and add DC nuts and bolts. Hone the block with DC's honing plate.
Result: 180 streetable hp- enough to tame the Mustang or put the Camaro on the I-rocks.

180-HP ENGINE/MAJOR PARTS LIST
part No. description
P4349649 45MM Weber side-draft carb. (2 needed)
P4349566 side-draft intake manifold with linkage, 45mm carbs
P4349660 race-ported cylinder head assembly complete w 44mm intake/36.8 mm exhaust, race valvesprings,and retainers.
P4286466 Header, high-output, for 1981-86 L-body
P4286779 Mechanical camshaft (288 adv. duration, 72 deg. overlap, .528-inch lift, 108 deg. centerline) recommended for manual trans.
P4286778 Mechanical camshaft (276 adv. duration, 56 deg. overlap, .493-inch lift, 110 deg. centerline) recommended for automatic trans.
P4349445 Mechanical lash adjuster kit (8 required)
P4120962 High-performance computer 1978-82 models
P4286543 High-performance computer 1983 models
P4349263 High-performance computer (non-turbo or FI) 1984 models
P4349741 High-performance computer (non-turbo or FI) 1985-86 models
P4349147 Sintered-iron cam followers (8 required)
OPTIONAL, IF REBUILDING ENGINE
P4349260 .050-inch lightweight race piston (4 required)
P4349148 Race piston ring set
P4120850 Connecting rod, magnafluxed and shot-peened, w/ high strength nuts and bolts. (4 required)
P4286787 Honing Plate
P4120964 Tri-metal main bearings, positions 1,2,4,5 (4 required)
P4120965 Tri-metal main bearing, position 3
P4120966 Tri-metal rod bearings (4 required)

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That's the context of the article I have. It doesn't say what kind of torque the package produced or provide any sort of dyno-graph. Like I said, I don't know how much would apply to your situation but at least it should answer your question about compression ratio. You say stock manifolds, does that mean exhaust manifolds too? What about cams? Even if they have rules on cams do they have the ability to even check that?

[Vanquizor]

Sadly very little there the rules allow.... I will be using the ecu and milling for compression though. Looks like I may have the motor in for the last race this year so I'll post how it does...

[89acclaim]

Is it going to be a 2.5 or a 2.2?

[Moof]

My friend matt built up a 2.2 crabed in his 86 charger. 11:1 compression, bored .020 over, ported head / intake / exhaust, 1mm oversized valves, cam (unsure of specs). Last weekend, he converted it to 5-spd. He can hang with the Z24's now.

[Vigo]

thats cool, probly in the 15s then.

[ACR Turtle]

Quote:

Originally Posted by Vanquizor Just curious if anyone's really putting the boots to a carbed motor.... For my circle track car I'm limited to stock manifolds/carb/pump premium, however I can use a combination of milling/decking/thinner gasket to get my compression as high as 11.5. How far can I push the compression before I start running into detonation with pump gas? I'm thinking near 10.5 but I haven't given it a shot yet... anyone have some experience? thanks!

General rule of thumb for V-8's is you can run roughly a point more compression with an aluminum head than you can with an iron head, due to the heat exchange rate. So should be similar for your application.
The mini stocks are interesting to watch. My neighbor has one and his car is fairly illegal but damn that things fast. For example he was telling me that he hsa to run a stock flywheel but the rules don't say how much it has to weigh so he mills it to the minimum surface thickness then mills the backside down as well. Also somehow they had two sets of pressure plate fingers mounted on top one another for extra pressure. But there isn't much cable life. I've learned in round track racing its only cheating if you get caught. Because if your not doing it the guy in the winners circle is.

[tmef]

You can run into a problem when you do excessive milling. The timing belt becomes too long. Mopar made a timing belt that was one tooth shorter to compensate for this, but I don't know if they are still available. Is there a claim on the motors in the class you are running?

[hukedonfonix]

you should be able to run 11.x compression on pump gas if you put a cold thermo (160) in and a little more agressive cam fights detonation a littel and would really help in your circle track case... my friend's dad did just that

[flight704]

i am building a dodge dakota with a 2.5l fwd motor in it. I have twin weber 45 dcoe carbs in a blow through mode. not completed yet ,,, but as it stands now i have 9.5 comp pistons and will run 15 psi boost,, max allowed on the webers ,, i will throw up some posts when it is rolling and i get it to the dyno and find out what it will do. ive been told repeatedly it wont work but i am not deterred lol

[shelbypage]

I run a FF/S NHRA Stock rampage,by the NHRA rules the the block is milled to +.015 (piston above deck) and the head is @48cc This is for the 2.2 h.o. motor. This will give you about 11.8 to1 comp. You have to have the oversize cam belt tensioner to make up for all the milling but the motor makes about 160hp. Thats with stock carb,manifold,and a Reed stock class cam(320@.430lift) This motor combo should work great in a mini stocker as well. It has run a best time of 14.80@97mph.

[Berlinwall5985]

yeah....I have a friend whose dad has a 1984 shelby charger with a completely built 2.2L HO carb motor that dynoed at 212 whp. He's had it for years and to my knowledge, he runs in the 13's. It's mostly a track car. He's actually selling the thing for $4000 I think if anyone's interested. He's the service manager mechanic for Mopar at Darcars Dodge in MD.

[Una]

I took the Shelby HO engine in my '83 Shelby Charger, and tossed on a swirl head, which is supposed to raise the compression .5.. Also put a roller cam on that engine, along with a turbo intake manifold (no turbo tho). That car really gets up a boogies. Also gets 40mpg on the freeway.