IMCA motor

[jay]

Hey Guys ,,,I haven't been her for a while ...And no we didn't race the big block last year .... I am thinking of building a smallblock mopar this year for IMCA...Want to use the 48degree R3 block and 48degree W2 heads...About a 264 at 50 roller cam...Billet crank....and ross 13-1 pistons on 6.250 billet rods ..... running around 7500 rpms....the question is big bore short stroke ,,versess smaller bore ,longer stroke....need to know all about the oiling problems a cures...will oil through the push rods but not sure where to get them.....Any ideas will help....I know 340 King is in about the same class ,,,,,,,Thanks guys

[Rich33]

Wow...That's a lot of motor for a modified class (I'm guessing you mean modified). There's still the claim. And, don't be too sure that the Chebby guys wont claim you if you start walking away from them!

[sanborn]

The bore/stroke really depends on the type tracks you will race on. Tacky tracks like a moderate bore/ longer stroke, slick tracks like a larger bore/ short stroke. The R and R3 block will take a bore as large as 4.180" quite nicely(Note, the R1 will only go to 4.100" safely). Billet cranks are readily available between 3.25" to 3.80". Suggest you contact Bryant since they do practically all the Mopar cranks.

For oiling up to 7500, just clean up all passages in the block, especially the cap/block match. I would suggest slotting the main bearings for better rod oiling. The pushrods are available for CV products in practically any length. You will need something close to 7.40" depending on deck height. The roller lifters are available from CompCams in .904" diameter. While at it I would buy the offset intake lifters to give a better pushrod angle with W2 heads.

For heads, use the new style W2. I have heard the closed chamber don't work as well as the open chamber. I understand there is a slight spark plug location difference and the closed chamber requires more ignition advance to produce max power. Maybe someone here has first hand experience, I don't. My experience with the new style open chamber head taught me that the smallest dome possible to achieve your desired CR is best, flat top is better and a dish piston produces the best HP but that requires a very small combustion chamber.

For Headers, the W2 doesn't like small, start with 1 3/4" tubes and you may need 1 7/8" for good power to 7500.

The W2 flows great on the intake side, good but not great on the exhaust side. I don't think you will need that much roller cam, suggest you start at about 256 @ .050 on the intake and about 260 @ .050" on the exhaust. Lift in the low .600" range will be fine.

You are talking about a lot of money for a IMCA engine that can be claimed for almost nothing. Are you sure you want to spend that much- sure is risky. I don't think UMP engines can be claimed. Don't really know for sure.

[340king]

Jay, I would be hard pressed to say that I am in the same class. The money that you are contemplating spending is about what I have in three engines assembled right now.

The first observation I have is that you would have to be running on asphalt to hook well enough to use even part of the power you will be making.

If you go with the combination of parts that you have sugeested, 600+ hp and/or more than 500 ftlbs of torque are not out of the question, depending on the head flow numbers.

What size track and type of surface are you planning to run?

[Rich33]

UMP modified claim is $550 plus engine exchange.

I know that most of the modified guys here (chebbies) get nervous when they put anything beyond a set of OEM double humps on their engine, let alone consider going to an aftermarket block. And, then you've got the problem hooking up like 340King was talking about.

One thing that you might have going for you is that there are not nearly as many claims in IMCA out west as their are in the central regions. We only had one claim last year in this area...Rumor had it the guy was running an engine out of a Winston West car. They were making it work and winning races, but Grandpa (who finances the operation) made the driver refuse the claim. Now they can't race IMCA again until they pay the fine.

[jay]

More info for you ,,,will be running dirt tracks from 1/4 mile to 1/2 mile ,,,The engine I was thinking of building was for special event ,(outlaw events) ,,,however it may be to much engine,,,was thinking of a 4.15 bore ,3.45 stroke engine ,,home track gets evey slick by feature time ,,,would consider stock block motor ,if anyone knows what will work well,,,OH yea I am talking modified class,,the stock crank is what bothers me though,,,for the RPMs I want to use,,maybe this will help the thinking for every one,,,Thank...........340king knows we ran a 450 cu. in. big block for years in a stock class and were the fastest thing on the track,,well on the straights that is LOL...Hope to hear from you ........Jay

[340king]

I have basically had four different engine combinations in my car. They were two different variations of 340's and 360's. The following is my opinion on how they worked and how they were built.

First engine was old reliable, 340. I ran this engine in my street stock for about 4 nights, pulled it out and ran it 50,000 trouble free miles on the street, put it in my modified with a cam change and ran 20 nights and finally broke a piston. It was a stock dimension engine except for the cam. It was a little shy on compression, but I tried to run methanol anyway. Once I found and fixed all the spark leaks, it ran flawlessly.

This engine was killer on 1/2 mile dry slick tracks. It had a real broad torque band and would pull easily on slippery tracks. I never had it in a good car, so it may have been better than I thought.

The second engine was a KB pistoned 360, fashioned after a friends engine. It had stock heads Victor 340 intake and a good cam. It had ignition problems for the first 15 or so nights. It would not run over 6,400 rpm regardless of the gearing or track size. Then MSD rescued my effort and this little engine really rocked. It was a handfull on dry slick, but if you could pedal it, you could fly. It now happily resides in a '70 Duster drag car running 11.65 quarters.

I then built a second 340, it had mildly ported 273 commando heads. Unfortunately, the heads were too mild and this was a 9:1 engine. The two created an engine that pulled ok, but never was a real threat. It didn't help that the cam that is in it was for around 12:1 compression. I ran this engine on the street for about 20,000 miles. It is going into a '79 short box step side truck this summer, pulling a 4 speed (factory).

Then, I built a second 360. This one had Ross pistons, W-2 heads, M-1 intake, internally balanced crank and other goodies. It was dynoed at 500 hp at 6,000 rpm on gas. I ran it for about 10 shows. Then while attempting to fix the rear main seal leak, I discovered the crank was broken. You are correct to worry about the stock crank. The engine showed some promise, but I only ran it in a good car for about 5 shows.

I then built the third 340, the Purple Headed Monster. It was the second generation of ported 273 heads. They flowed over 185 cfm @.300" lift. This was with 1.94" valves. I really liked driving with this engine. When the traction was good, it was untouchable on dry slick track. It was 11:1 compression, flat top pistoned, .040 over bored. It ran real good until the heads cracked, one on both the inside and outside, the other just on the inside. It had a M1 intake, Reed tight lash cam and polished rods.

I have since rebuilt the Purple Headed Monster using the new W-2 closed chamber heads. We have spec engines that can't be claimed and that is what this one is now.

I also rebuilt the internally balanced 360, using 360 HS heads. It is in the car now and hasn't been track tested other than the practice track. I nearly wore out a set of McCreary's playing up there this year.

If I were to contemplate running down south, I think I would try to run a mid compression 340 or 360 with the 360 HS heads. Ported of course. The 340 cranks are good up to around the 550 hp range, then you need to find both a block and crank setup.

[Jesse Lackman]

Hi all,

We had a 400 hp @5300 360 (SAE J1349 correction) in a 120" IMCA Mod here in ND. As you can imagine the rear percentage was very high. When we went to the "good" 445 @6200 hp 360 the hp overpowered the tires in spite of the high rear percentage in a 2800# car. The driver did not like this engine. Too much power he said. (He is a Ford man what do you expect!) Here are pictures of this car in testing;





The above car is retired and this is what we are working on now;



The new car should have a similar power to weight ratio than the old one with the Super-Magnum 3.9LV-6 (not running yet). With a stock non magnum 3.9 it was about one second off race lap times in testing last fall.

The trouble is the IMCA Mod tire. It is hard to hook up and too much hp will just fry it. Then it's even worse!

------------------
Jesse Lackman<A HREF="http://www.revsearch.com" TARGET=_blank>

Revsearch Engine Dyno</A>

[This message has been edited by Jesse Lackman (edited January 11, 2001).]

[Racedude_5]

2800Lb? Most of the cars here in west ky are in the 2200lb range. We had good luck on dry slick tracks running imca with a stock stroke .030 340. I won my first feature with this and won by a full straight way over the field.

[340king]

Racedude, your car weighs almost the same as mine. Only question is whether that is with or without the driver. My car weighs 2160 with about 3 gallons of gas. I am forced to race at 2,500 lbs because of Wissota rules. This requires a lot of ballast and is a pain to get exactly where you want to match the track conditions.

I have never driven the car in competition form without the weight. I would really like to run some IMCA events in the future, its just that they are so far away. The car was originally an IMCA car. It came from Enid, OK. The current owner of the design is Dirtworks. The car I have was the basis for their current coil spring cars. They just cheapened it up and changed some of the really neat things on it.

[speedway]

I am currently building a super modified with the R-3 Block although we are using Brodix B-1 Heads,( these are the spec heads for our class) I am utilizing a 4.125" bore with a 3.335" stroke. This will be a Sonny Bryant model that i got from stanton. Manly 6.30" rods and J & E pistons with little or no dome. We are using an Ultradyne 259/264 cam at .656" lift with roller lifters.Oiling through the pushrods requires a hole be drilled into the oil galley from the lifter bore which is very easily accomplished. we also opened up the main oil galley from the side from .250 to .275" for better main oiling.The system will utilize dry sump oiling, a magneto ignition, and our class requires a 4412 two barrel that will sit on a M-1 Manifold.We are expecting about 500 HP. form this combo as this is what we used to get with our chevy. This will mate to a 2000lb car on a 1/2 mile banked oval, the results are awesome. 140 mph on the straights and 100plus in the turns. See www.cam 360.com for a picture of these awesome racecars.