Sport Mod Engine

[chrysler300le]

I'm just starting my first year racing and doing a partnership with another guy on a IMCA Sport Mod. Right now were running chevelle stub with Chevy power. I would like to eventually run Mopar engine. How would you guys recommend building an engine to be legal in the Sport Mod class? I have several 360 blocks and 596 heads. I have one Magnum block. What cam, pistons and other block mods do you recommend?

[340king]

I perused the IMCA Southern Sport Mod rules. I assume you are under the southern rules.

If so, you need to build an engine much like the one they outlawed for us in the Wissota Super Stock. The only exception would be the camshaft. The trick to these rules is getting the vacuum requirement and the compression number balanced. It takes the right cam and the right compression ratio.

The engine we built used Magnum heads for a closed chamber. It made getting the compression with a flat top piston easy. Then we used a flat top pistoned 360 crate block for the bottom end. The intake is a no-brainer, use the Edelbrock #2915 Victor 340 intake, like this one. http://motors.shop.ebay.com/__?_from...ctor+340&_nd1=

I would consider either an AFB, AVS or thermoquad carb. If you can find the one year of thermoquad, I think it is an 850 cfm unit. I haven't ran one, but I think it could be done.

When it comes right down to it. I don't think HP is going to that big of a deal however. I would focus more on the chassis and not as much on the ultimate output of the engine. I think you will be able to blow the tires off pretty much all the time with the 2 bbl carb in the feature.

[chrysler300le]

Oh I forgot to mention I'm Northern Sport mod. Slightly different rules. I figured the advantages would be in the handling of the car and not the engine. But I wouldn't mind running Mopar.

[bmoddan]

We run unsanctioned up here but our motor package is the same as IMCA. As far as motors goes it all depends on what level you need to be at for the competition. Here at our home track their are some $6000 to $8000 chevy engines running around so we have a fairly well built 360 in car atm. Working on a 340 for later this year. Anyhow I would start with a stock crank, a set of Eagle rods and some hypereutectic pistons. Mind that we have found with the older heads that it can sometimes be difficult to get down to 9 to 1, especially if the block has been zero decked. We take our valves to 2.02/1.60 for better flow, but we also turn upwards of 7k plus. Cam is a Lunati stick that I can give you the number of if you PM me. Hughes ground us a very nice cam that ran great in the lower rpm range for a more "stock" engine. Get yourself a set of adjustable rocker arms. We have never had much luck running hydraulic cams in racecars but that is just us. Go right to the IMCA approved intake. The thing seems to flow better than the cast iron manifolds we tried and the weight savings is a big added bonus for scaling reasons.

[clarkj]

Dan,
I was worried about keeping my compression down for my USRA hobby stock motor...you pretty much affirmed my worries I guess. I have a zero decked flat top 360 with J heads, so I am in that same boat you mentioned. I was figuring on getting Cometic to make me some thicker head gaskets. Is that what you had to do?

[B-Mod Dad]

We needed to lower ours in a hurry last year as we had in comp.checked at our shop and we were 9.4! Double stacked 2 stock head gaskets and took a chance that they would hold. Never had a problem. No water leaks and no compression leaks. We also have had to take one set of heads and take out the 2.02's and put in 1.94's to help lower the compression. Heads can really vary. We have them from 69 cc to 73 cc. Suppose it depends on how much
they have been decked and if it has had seats replaced. We run chevy valves in all our motors as they are lighter and smaller stem. also can get with undercut stems for better flow. We are trying the beehive springs this year for the first time, but we can't run them next year as we are going to be IMCA Sportmod up here next year. Supposed to lighten the valve train the same as running titanium valves. We will see. We put in the oil crossover tube under the intake for better left side oiling on the valvetrain and also run a 1" hose from the back of the pass. side valvecover down to the driverside of the oil pan to get the excess oil back into the pan. we run the 8 qt. Kevco pan. If you have any more questions let myself or BMod Dan (my son) know. We will try to help out a fellow Mopar racer as much as possible. PS: we build our own engines except for machine shop work.

Dave

[chrysler300le]

how long are chevy valves verses Mopar valves?

[B-Mod Dad]

We run .100 over chevy valves to get the right spring height. Kind of depends how far your valves are sunk into the head. Just have to put 1 in and measure the spring height. Also depends if your springs need to be 1.750 or 1.800.

Dave

[340king]

After looking over these rules, I still think the intake is a good idea. Obviously, you will have to adapt it down to the 2 bbl carb. I would use the Holley 4412 carb also.

The engine that we had would be a great starting pad for this build. You would have to change pistons and cam. Otherwise it would be race ready. At least IMCA seems to have come common sense with the rules.

[chrysler300le]

Has anyone raced Magnum blocks or heads? How will the tech inspector react when it doesn't have rocker shafts since mopars are suppose to have rocker shafts.

[clarkj]

Thanks B-mod dad/dan! I will be building my own, too..other than whatever machine work gets done. I figure I will cc my heads, see what I have, and have Cometic make me some head gaskets. Just wish they weren't so proud of them. I plan on doing those same oiling mods that you have done, too. I am not planning to change valves on this set of heads, but I might have to check out those Chev valves next time around. I sure wish we could run a 4412 Holley in our class. I have a Rochester now, but I am afraid I will get some grief over it. Do you guys ever plan on trying to hit Oskaloosa this summer? Be sure to let me know if you do, I would love to come check out the car.

[340king]

300e, we ran Magnum heads on the 360 that I talked about with shaft rockers. I had a rocker stand built to support the shaft. It bolted down to the rocker pedestals on the Magnum heads. My design was adapted from the original design by a guy from OKC. Let's see, I think his name was Sam Neer (sp).

I asked the governing body if it would be OK. They said they didn't see any problem with it since the Chevy boys mill, drill, tap and run guide plates on the Chevy heads. This was simply a way to run stock rocker arms. After about 3.5 years of running this combination and a couple of tear downs, they changed their minds. We started to dominate. That was all it took.

So whatever you do, get it in writing that it can be done. Once you start to dominate and Chevy boys start to complain, they will forget what they told you. At least, that is what happened to me.

[mopar mad]

strange how that happens huh

[AVENGER29]

Magnum heads is the way to go, we ran southern sport mods from the early days on, we were very competitive with magnum heads...
Avenger

[chrysler300le]

Has anyone ever ran a 318 on dirt track? To me its just a baby 340. With an overbore its not that much short on cubes and using 340 or 360 heads it should run nearly as good. I believe Cageman said on another thread he doesn't care much for the 360 and I've heard from a few others that the 340 is better on circle track then the 360. Whats everyone's opinion on that?

[B-Mod Dad]

The jury is still out as far as we are concerned. Just finished the 340 last Sunday morning and is still sitting on the stand. We open 2 weeks from Fri. and are starting out with the 360 that we won 5 features with last year. Will probably run it 2 weeks and then put in the 340. Will post reports as we go along. Will be interested to see how much difference there is in weight between the 2 complete motors. Will set on the electronic scales when we switch the 2. Hope is that the 340 will get us off the corner better and especially on starts and restarts. the 360 takes awhile to get wound up compared to the lightweight Chebbies.

Dave

P.S.: The crank weighs 6 lb less alone then the 360.

[chrysler300le]

Yea I would be very interested in the results of this. My guess is there is no more then 25lbs difference between the 2 but I could be wrong.

[mopar29mod]

I never ran a 340 in anything but agree that it probly rev's faster being shorter stroke but in trade it seems that you really don't need the big RPM with the 360, some other mopar folks I talked with don't run the RPM's that the chevy guys do. I did run a 318 in a pure stock and also in my street car. I love'em they just run forever and are pretty tolerant of about anything you can put in them. On the street nobody ever believed I had a 318.

[AVENGER29]

we always rev less than the chebies guys, we normally ran 400/500 rpm less at least and we usually geared 20/30 points less than they did, if they were running 6.25, we would be geared 5.95
Avenger

ps dont have much experience with 340's, we were alway after cubic inches, always built our 360's to max rule of 370.....and the fact that we did have a lot of 340 stuff kicking around

[bmoddan]

I agree with ya Avenger. We run a 5.83 on our short 3/8 home track compared to the chevy guys running a 6.50 or 6.20. We might be at a disadvanage on the longer tracks with the 340 but we run several stop n' go type tracks around here and hoping the lighter 340 will gives a better jump up off the bottom of the track.

[AVENGER29]

would'nt mind playing with some 340 stuff, but most of that stuff is hard to come by, 360's were very plentiful and we always made plenty of power, reliable and not too expensive.

Once Brit gets comfortable and starts chasing it down, we are going to be under power, the chevy guys here are on the crazy side, with as much nascar chevy stuff floating around some of the motors are on the verge of being cup motors, for us to go buy 340 stuff, doesnt make sence, better to inherit some old Nascar stuff,
some friends at RPM and we do Kahne some favors, hope they return it like they claim they will, inherit a complete or a couple of complete assemblies.....rebuilt to suit our needs and go really fast....if Brit adapts to full size cars like she has done on everything else, she will be damn fast....the kid can flat out drive a kart....need to translate that into a 600hp mod and then maybe late model asphalt....
Avenger

[340king]

I like the 340's for two reasons. The first and most important to me is feel. I can sense and so can any good driver, the first hint of losing traction. They just feel different under your right foot than a 360.

Secondly, I like the less fickle part of gearing and camming of the 340. They don't like being bogged out of a corner any more than any other race engine, but they don't snap the tire loose all of a sudden and leave you slide ways coming up off the corner as easily. This is just my humble opinion.

The 360's need to have a more conservative cam than a similarly prepped 340 to get off the corner and starts as quickly. I don't know why that is. In the super stock car, the 340 with a 2° longer intake duration cam pulled harder than the closed chambered 360. On paper the 360 actually needed more cam. I went conservative since I had experienced the soft 360 starts.

After 2 years of running the 360 super engine, the owner bought another one to run when the big 360 was being freshened one year. It had a "special grind" hydraulic cam in it. It ran much better off the line on starts. We tore that engine down and found it had a puny little Comp Magnum cam in it. So we took 6° off the intake duration and opened up the lobe separation another 2°. Then the big 360 was a rocket all the time after that. It was a real eye opener.

This old junk 340 I have has always ran better than it should. It is just a happy engine. It will probably pop the cork now that I have said that.

[Dauer 33]

I bought a 340 short block for 100 $ that just needs a light hone and a piston that is going to b my next motor for my hobby stock might even let the ol man try it in his sport mod, I would expect with the shorter stroke I should be able to turn it harder that the 360 and the gm stuff.

[thesandman23]

We just bought a Harris car and we have some questions on where to buy a mopar crate engine that has knowledge on the B-Mod class.

Any help would be great!

[john briggs]

We just built a mag head motor and we are running the stock magnum rocker arm set up on a hyd cam (we have a vacuum rule). I bought some push rods that are 7.600 long and run the AMC lifters. We are turning this engine 6800 every night and its fast! Top three car if we can catch some luck...
the problem with the mag heads is the small chamber, might give you a fit trying to get it down to 9-1...Engine seems to be a good combo so far, no issues that I can really complain about other than having to run some funky looking valve covers.

[john briggs]

My take on the 340 - 360 question is I like the 360 better. It pulls harder and I have just started getting into the newer blocks and the magnum rods/piston combos are much lighter than the old 340-360 rods. I just balanced and new engine and it took less metal to bring into neutral than the older 360 cranks. Also, I like the oil fixes that they incorperated in the new blocks and I belive that makes my life better in the long run.
Im building a "crate engine" for a friend that is going to bonniville this aug andI will tell you that the crate engine idea is not a bad one, but the thing has not enought heat cycles on it for me!

I think you would do better by finding an engine out of a pickup with 100000 on it and start with a good bore and crank clean up.

I like these aftermarket magnum heads. I am running a set of the EQ heads that Ii bought last winter from Clearwater Cylinder heads in clearwater florida.
Talked to them last week and the are the ones selling heads to hughes! So I guess Ive found the importer. the RHS heads look great and I think they are comming from the same foundry as the EQ's.
I built this last engine for $2200 from start to finish and its runing up front in a fast damn class.
These are just my thoughts...