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Saturday Night Racer >> RACE TECH >> SPORT MOD ENGINE ????????
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Message started by CaliforniaKid14B on 08/16/11 at 12:16pm

Title: SPORT MOD ENGINE ????????
Post by CaliforniaKid14B on 08/16/11 at 12:16pm

Took my sport mod out to chow speedway, did fine didnt run hot or have any problems. only issue i was having is at top speed down the stright away it dont seem to run as smooth any idea? its not falling on it face just kinda of sputtering

this is what im running for motor
350 bored 60 over stock pistong rods and crank stock 76cc 441 heads. victor jr intake holley 4412 crab 76 jets, stock hei distributor timing advance is at 34 degree, jr motorsport camshaft 531 542 lift

was thinking i might have to much advance for a stock motor would that cause any problems?

might try newer plugs and wires and see what happens any tips would be greatly aprreacted

Title: Re: SPORT MOD ENGINE ????????
Post by streetstockracer on 08/16/11 at 12:59pm

Not enough compression for intake manifold and camshaft. Try an intake with less plenum volume. Need more compression for that combination. Your static compression is probably 8-8.5:1 depending on piston style, deck height and head gasket volume.

Title: Re: SPORT MOD ENGINE ????????
Post by ka_jd7and1 on 08/16/11 at 1:35pm

What RPM are you turning? Might be starving for fuel?

Title: Re: SPORT MOD ENGINE ????????
Post by Missle Motorsports on 08/16/11 at 1:48pm

Didn't yer Battery Die @ the End of the Race?
Might of been not enough Voltage to Fire in the upper RPMs?
The Sportsman 2V Intake I still think would work well with your SetUp

Title: Re: SPORT MOD ENGINE ????????
Post by RACEGLASS on 08/16/11 at 2:41pm

What sprark plugs are you running? Have you taken a plug reading...this might be a good plae to start looking.

Title: Re: SPORT MOD ENGINE ????????
Post by racer41x on 08/16/11 at 7:57pm

I ran 355 stock pistons,stock rods and crank,194 double hump heads,Victor Jr ,4412,chevy high energy Dist and a crower 351 cam. Set the timing at 38 degree and the engine turned about 7000 at Chowchilla and 6800-7100. Jets where around 74-76. I ran it in a 3200lbs. streeter. I think you are not using enough timing,try 38 degree.

Title: Re: SPORT MOD ENGINE ????????
Post by Rodney on 08/16/11 at 8:49pm

streetstockracer wrote on 08/16/11 at 12:59pm:

What he said. Your cylinders are not making enough "suck" to get a proper signal to the carb with that intake/cam. Find one of those generic dual plane intakes and you should be more gooder. More advance shouldn't hurt but remember, it's a more of a crutch than a cure. Moving the cam forward to the next area code is would help a little but is just another crutch.

In the big picture, you might consider shopping for some tighter chamber head castings. Hope this helps.

Edit. I mis read your post. Everybody has given good advice, but if it's laying over on the top check the fuel pressure.

Title: Re: SPORT MOD ENGINE ????????
Post by DaveBauerSS6 on 08/16/11 at 10:44pm

If the tuneup and the mechanics are right you can run a tunnel ram and 2 carbs. The intake will not fix it.

Make sure the jetting is correct and the timing components are good. I run about 78 to 80 jets, try going up 2 sizes. Lean jetting/ power valve problems can make the motor run sour at the top end. Modules can go bad. Next check your valve springs, if the problem is always at the same RPM its a hint there are weak ones. Borrow a hand spring checker, and check them on the car. If you are not sure of their history, throw them away.
Then put on the tunnel ram. ;D

Title: Re: SPORT MOD ENGINE ????????
Post by sj_valley_dave on 08/17/11 at 10:59am

Hey Dave...Those are big jets for a 4412...IMO...When we got our gauge legal 4412 from Willy's, it had 73's in it after their dyno pulls, with the adjusted altitude and plug reading we went down to 72's and stayed there pretty much. This was a 14:1 360, Dart head, 254*/605 lift solid at 8000 rpm. Wlly's said that the 4412 will only flow so much air and don't use is carb as a crutch when I told him that we had 78's in the old 4412...He got offened, we listened to him and by far the best 4412 we ever ran!

Title: Re: SPORT MOD ENGINE ????????
Post by bb49mod on 08/17/11 at 12:21pm

We also run hei. They like a lot of voltage. If your battery was dead, that will cause it to not run good on the top end. Also the stock module is not good enough for racing. DUI (performance distributors) has a stealth module that looks just like a stock one that will work great. Remember---voltage. The more voltage you put in the more fire you get from the hei. Call DUI and talk to their tech department---1(901)396-5782. They are in Georgia, so call early from Lost Banjos.

Title: Re: SPORT MOD ENGINE ????????
Post by DaveBauerSS6 on 08/17/11 at 7:46pm

Dave... you are right and VDL runs 73 out of the box, but remember these are modified, the emulsion tubes are changed and they massage the channels and boosters. Ive found The standard unmodified 4412 runs good at 78 jets.

49mod...right on the voltage and the stock module limitations.
Recent experience on the DUI.... one blown motor due to the pickup confusing cylinders 7 and 8. One sour running motor due to the pegs that hold the advance weights coming loose. Both returned to DUI and confirmed. Sorry that performance is out of my budget.

Title: Re: SPORT MOD ENGINE ????????
Post by CaliforniaKid14B on 08/17/11 at 9:12pm

Well my BATTERY was dead towards the end of the race so that could be big part in it, didnt run it as hard in the heats when battery was good charged so couldnt say excatly if that the problem.

TIMING well at 36 degree the car will hardly start with igniton on have to leave igniton off crank it over and hold to the floor then flick igniton on only way it will start unless u get lucky with the ignition on and hold it to the floor and it cranks and fires

All the RPMs i turned was 6000 to 6100 in the main event but still dont believe i had it to the floor.

going to find another fix not changing intake after i bought this new vic jr.

im using stock head gasket that come in the kit, this is a stock block never been decked that i know of

so if i found some 305 head or some nice double humps would the cure my compression problem my the intake work better??????????????????

my PISTONS are what ever a stock rebuilder would put in a motor with stock 350 crank, NEW ROD MAIN AND CAM BEARINGS AND NEW RINGS my heads are a 76 cc 441 want to say 194 might be 202 head with BRAND NEW 600 lift spring just installed.

SPARK PLUGS are a bosch well havent took a reading after racing it but took out #1 so i could put it on top dead center and plug was pretty dirty but that could of been caused by not letting the car run long enough and fire long enough to clean the plugs never got it warm

JETTING i have to check they might be 78 jets, this crab im using came off last years motor which was a 355 stock piston stock hyd cam cast 2 barrel intake same heads im using now same crank, i might look into cleaning the carb cause it did sit for 7 or 8 months covered in the shop and all i did was put gas to it and fired right up.

DISTRIBUTOR it is completely stock brand new stock module, last year i was using a msd box that was used as the module for the distributor i have now MSD box brund out so had to go back to stock module

BILL we have other guys running stock distributor in our class with stock modules i believe the 1 and the 72 spot mod is running stock hei with no problems might just be my nuts is junk LOL low budget racing at it best lol

COME TO THINK OF IT WHEN I TOOK MY TEST DRIVE DOWN THE ROAD WHEN I HELD IT AT 6000 RPM I HAD A SPUTTER ALSO BUT THE BATTERY WASNT FULLY CHARGED BUT IT WOULD RE FIRE THE MOTOR UNLIKE AFTER MY MAIN EVENT.

Title: Re: SPORT MOD ENGINE ????????
Post by DaveBauerSS6 on 08/17/11 at 11:00pm

Dave... I opened a new VDL 4412 and a off the shelf 4412 and measured the power valve fuel ports. I don't remember the exact numbers, but the VDL was opened larger than stock. Hence the smaller main jets. I think the idea was to make a better transition from the main to power valve circuits. I wrote the numbers down somewhere, but without the info on the booster and emulsion tubes its only info.

FYI... my new VDL 7448 350 cfm carb for the IMCA stock car has 83 jets! VDL says thats what is needed for that carb..

Title: Re: SPORT MOD ENGINE ????????
Post by Missle Motorsports on 08/18/11 at 1:15am

Nick, is that Cam you are using a Hydrualic or Solid?

Title: Re: SPORT MOD ENGINE ????????
Post by CaliforniaKid14B on 08/18/11 at 11:56am

it JR MOTORSPORTS PRC 108 CAM SOLID CAM

Title: Re: SPORT MOD ENGINE ????????
Post by formercrewguy on 08/19/11 at 6:54pm

Like Old School 6 is always telling me......concerning voltage......."sh!t .in..........sh!t out " lol.

Title: Re: SPORT MOD ENGINE ????????
Post by Bap33 on 08/20/11 at 10:03am

You may already know most of this, I'm just tossing out my best help.

Voltage is more important when using an OEM style HEI than when using a spark box (6al) type ingnition. Battery must be healthy.

I run an OEM style HEI. I run 0 size cables all the way from the battery to the starter. The NEG cable directly to the outer starter/block mount bolt, the POS on the solenoid as normal. I do it this way because having the ground just bolt to the chassis means the engine ground for the dist is in the motor mounting system. Paint, mud, rust, oil, and lots of other stuff can disrupt a good grounding surface. So, by using the bolt on the block you ground the block directly, and the HEI housing is grounded by the hold-down clamp. Make sure the clamp mount is clean and do not paint the clamp. Chrome looks good, and in this case works better. Also, make sure your in-line disconnect is the right size for the job. The SUMMIT or SPEEDWAY offered race parts are perfect.
Will this fix your issue? No idea. But, if you do your power supply like this, when you push the starter button you are getting every drop the battery can offer. I have had good luck with this system.

It is still possible that the sputter was not due to a lack of battery if it went on for a while and did not change or get worse as the race went on, and only happened at WOT durring high RPM. Poor voltage "should" show itself under heavy load, and that "should" be under acceleration, or, if the battery was fading, the issue "should" have been worse as time went by, but I'm just guessing.

I wasn't there to hear it, or see it, so these are flat guesses for possible issues for high-end sputter that is constant with RPM and throttle position are:
Cell pick-up not in the bottom/rear corner.
Fuel line sucking air/sucking shut between cell and pump.
Fuel cell vent not working.
Fuel pump has debris in it/not working correctly.
Fuel filter debris.
Air cleaner/air flow restricted
Debris in fuel bowl.
Metering plate ports/air vents plugged
Throttle shaft vacuum leak.
Tight valve lash
Loose valve lash
sloppy timing chain
cam walk due to no button on a solid cam
Bad valve spring(s)
Bad plug wire(s)

Another issue is possible timing/dist issues. Bad timing can cause a consistant flutter. If you are using an OEM harmonic balancer, you must be sure that the timing mark is correct and that the outter ring has not moved. If you see more rubber bulging out fore or aft, then it may have moved(rotated) and that makes it pretty tuff to time correctly with a light. Be sure the timing mark is correct. Make sure the timing tab is correct too. I know these are basic, but it they are not correct, you can't be sure of timing. I run a 355 on gas at 33*-35* .... and I use two steps colder than stock performance plugs and 8mm wires. All off an OEM style HEI, and spin 7,000 rpm without issue.

I run the timing advance plate locked at full advance. I do this to avoid over-advance and timing bounce. I wire the starter direct and the ignition on a switch. This really is needed for starting a full advanced car, but also helps start a hot car, makes setting valves a little easier, stuff like that. I would suggest running the plate locked, pinned, at full advance. Fill the hole that is left from removing the air/vac can with some blue RTV. Just a blob and let it set up, install the cap and that little plug should be good for keeping out debris. You MUST cover the dist when pressure washing if you do not seal the cap properly. I cover mine with a heavy plastic bag from the nut-bolt supply place. Big, shallow, tuff, free. Perfect.

Anyways, that's my $0.02

The sizing and design of the intake/carb/cam/ and such is very important, but it has been my experience that those issue are where you find power, response, and drivability more so than a sputter in a lower powered engine running down a short straightaway. A flat cam, bad valve springs, sloppy timing chain and stuff like that are more likely than a bad air signal at the carb due to poor plenum/runner volume/valve opening in this application. But, that too is just my best guess.

Good luck