bogging coming out of corners

J

jk68mod

Member
I am running a sportsman with a 355SBC, MSD 6AL, Blaster2 coil, Dart heads, HEI dist changed over for the MSD(no module, coil not in cap), 500CFM Carb, and 6.83 gear.

I looked at the tach Sat. in the corner to see what the Low RPM was and it was around 4200(when I looked right about the time I got on the gas). the cam is from 3200-7200 range.

I have changed to 3 different Carbs, changed and checked the timing chain/gears, tried some different timing settings.

Now for the problem:

the engine is laying down/ bogging at corner exit and I only get 6600 RPM flat footing it. Everyone else is leaving me at corner exit!!!!!

any suggestions?

Thanks
Jerry


P.S. I race at MCS
 
Sounds like heads or intake might be too big, air/fuel is losing velocity after the carb. Or maybe poor choice of cam? Talk to one of the good motor builders around and see what combos they'd recommend. When we ran Sportsman there we ran a 6.50 gear and a 350ci most of the time and didnt have a power issue (ours was usually handling). With those heavy cars you want a torquer not a rapper. If you over cam it like a mod thats 1000lbs lighter than you, it will never pull hard out of the corners.
 
Which darts the original or the platinum series. What compression ratio, duration of cam @ .050, and what is the intake centerline the cam is degreed to?
 
specs

about 12:1, original Darts 200cc 2.02intake valves, 108lobe sep on cam. timing chain is straight up. I just wonder if the cam is the problem! Any suggestions on a cam?
 
Definitely the cam should be using something about 250-252 duration intake, 106 lobe separation, degreed to 100-102. The 108 lobe separation is taking out the peak torque which that motor is short of in the first place. You could advance it 4 degrees and loosen the lash .002-.003 that might help some.
 
Yep its the cam. Those are good heads (not too big). Got to find one that is for a heavy car and gives plenty of torque.
Cant give suggestion but if you call any cam manufacturer they will tell you what you need. I use Lunati, but have used Howards and CompCams too and Howards is about the cheapest, If your looking to save money. But any one of them if you call them will get you where you need.
 
Jerry,

I was listening to you on the front strait the best I could and did hear a bit of … errrr… blubbering :rolleyes: (is that a word :rolleyes: :eek:) as you rolled on the gas and stayed all the way down the straight. That could be any number of things but I’m think Racing 68 might be on the right track with the degree the cam is installed at.

Question, did you use my phenolic spacer when you tried my carb? … Or did you use the same one you had been using?

My cam recommendation for flat tappet stuff I’ve found that the Elgin 1090 cam if far and away the best choice. You WILL have to degree it on installation the grind always seemed to be 3 degrees off. Um, sorry that means buying another new timing chain that’s degree-able.


Thanks,
Bryan

Trace... Is it me or is the number of number 68's in this post corn-fusing you? :eek: LOL it is me. ;)
 
findings

the first thing I found was that when I aligned the timing marks on the timing gears, I put on the balancer and timing tab, and the 0 on the tab is at 10 on the balancer. So this means I was timing it to 36 by the 0 on the balancer and that really turns out to be only 26.

I went ahead and checked the degree on the cam and it is off 1 degree from where it is supposed to be.

Thanks for the help I will try this weekend and see where it leaves me.
 
i dont know about all this motor stuff. i would check your float level, make sure you dont have a fuel line clogged, try looking at your fuel pressure gauge in the corner rather than the tach one lap, might tell you something. i would check simpler stuff before tearing the motor down.
 
just because the marks are aligned does not mean the engine is at top dead center. you must use a degree wheel and piston stop to check that.
 
Racing 68 said:
just because the marks are aligned does not mean the engine is at top dead center. you must use a degree wheel and piston stop to check that.
Click to expand...

He was using a degree wheel on the balancer when he discovered this... He just failed to type it out.
 
sat night

OK here it is... I ran hot laps and the car was ok but a little hard to start. So, I backed the timing off about 5degrees and went out for the heat. THE DARN THING BOGGED AGAIN!!!! So I put the timing back and ran the feature. The engine didn't bog, I went from 10th to 4th with one yellow. But, it was 245degrees when I pulled off the track. Also not hard cranking either now.


Any suggestions?

Thanks for all of your help also!!

Jerry
 
The hard cranking could be a number of issues besided timing. Low battery..bad chassis ground even a starter can cause this. Distributor with advance working full bore all the time will also do this. I would have the distributor checked for advance operation. Take it to a shop have it spun and see what its doing. You can put a light on it...rev it up and kind of see what the advance does. But ive learned if in doubt....have it spun. Its inexpensive and 9 times out of 10 people find out a problem thats there and they didnt even know it. May not be the cause of the bog...but something that needs changed for better performance
 
Try phasing the distributor and locking it out. This will put your timing at full advance and ought to let it come off the corners alot better. While you have your distributor out, make sure you don't have any more then .015"-.020" end play on your Disrtibutor shaft. That will help make your timing more stable at an idle and through out the RPMs.;)

Didn't wade through all the responses so if you already have it locked out, sorry.

Don

WCRE
 
After changing your cam timing you may need to change your carb jetting also, may contribute to your higher coolant temp.
 
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