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Author Topic:   First Practice/questions
racing33A
Dirt Forum Racer

Total posts: 97
posted April 11, 2004 09:10 AM  
We just had our practice weekend and I must say I am a little disappointed.The car seemedto work good and the engine went pretty well, but I could not get past 5500rpm.That is my question.Why only 5500rpm. I run a 3spd manual in second gear(1.89)with a 3.73 rear gear on a 3/8 mile medium banked track.If I did my math correctly that should be close to a 704 final drive ratio.Last year I ran a 6.28 and also could only get to 5500rpm(max),so I do not think it is a gear thing.
The engine is a 360ci(chevy),flat top speed pro hypers(coated),rochester 2bbl card, stock steel intake,k-n air cleaner,.600 lift springs,416 heads(305),new valves which are one better than stock,midwest #8 camshaft installed straight up, stock rods with bolts, scat crankshaft,locked distrib with a msd pick up coil.
Why cant I get it to up past 5500rpm at the track.Is it the camshaft, is it the heads.I could really use some help on this one.
Thanks to all who reply with thier thoughts and ideas.
racing33A

19J
Dirt Freak

Total posts: 370
posted April 11, 2004 11:04 AM  
Where on the stretch does it hit 5500? You could be running out of carb. If the carb isnt built enough for that engine then thats all it will push. The next thing could be your ignition system. It dont sound like your cam but i guess you never know.

racing33A
Dirt Forum Racer

Total posts: 97
posted April 11, 2004 11:38 AM  
it is hitting the 5500rpm at the end of the straight, right as I lift for the corner.I just am baffled by the fact that even with the deeper gear it is still only hitting 5500.
racing33A

racer17j
Dirt Forum Champ
Total posts: 5390
posted April 11, 2004 02:32 PM  
i run prettmuch the same size track and every thig thatyou are describind only thind differernt isweruna 410 gear and right arround 7000 rs sounds like your notenough gear

------------------
U LIFT U LOOSE

racing33A
Dirt Forum Racer

Total posts: 97
posted April 11, 2004 06:13 PM  
racer17j,
It has a msd module and accel super coil,both are about 2 yrs old though.Could a weak battery do this?I do run an alt, but sometimes it gets a little run down before it start up.
Joe Taylor,I am already at a 704.If that aint deep enough then i do not care to see what is.
Keep it coming.I really appriciate it.
racing33A

bigcityracer
Dirt Freak

Total posts: 431
posted April 11, 2004 08:50 PM  
What is your timing set at??
May have a faulty module!
Have you replaced cap and wires lately?
May need to install fuel pressure gauge, it may be dropping off at high R's!!
Have you done a compression check on all cylinders?

eaton89
Dirt Freak

Total posts: 268
posted April 11, 2004 08:56 PM  
I'm not familiar with that head but have had a 305 head do exactly that to me before. Pulled really well tell it got up in the rpms and about 5600 RPM it would quit pulling. What size vales are in them.

racer17j
Dirt Forum Champ
Total posts: 5390
posted April 11, 2004 09:29 PM  
bigcityracer,
1.module and coil are 2yrs old
2.cap,wires,and plugs are new
3.comp is at 170 to 180 on the gauge
4.new stock fuel pump
racing33A

Flatlander
Dirt Freak

Total posts: 355
posted April 11, 2004 09:47 PM  
gotta beleive it's the heads anywhere over about a 688 is a lot of gear for a 3/8 I'd say not enough flow less air =less HP JMO

Raz_900
Dirt Forum Champ
Total posts: 635
posted April 12, 2004 12:48 PM  
I had a pair of 601 heads (same as your 416s) with 1.94/1.6 on a 355 and it would turn 6000-6200 without much trouble. Although I can run a 4bbl and Performer intake.

What rpm is it at coming out of the turn? The cam isn't going to pull had until about 3500-4000.

Does it accelerate at all? The heads shouldn't limit a 360 CID motor to 5500. The stock intake isn't helping things either, but shouldn't stop it at 5500. What about exhaust? Stock manifolds? Pipe Size? What 2bbl? A stock 'small' 2bbl is going to make it hard to get many revs.

racing33A
Dirt Forum Racer

Total posts: 97
posted April 12, 2004 03:37 PM  
Raz,
The heads I have are stock valve size.The carb has been worked on a little bit,but is still a basicly stock rochester 2bbl.My corner revs were about 3000-3500rpm coming out.Yes it did accelerate and hit 5500 right at the end of the straight.The exhaust manifolds are log type that have been opened up a bit.The pipes are 2''o.d(rules)that go back past the driver and end before the axle.
racing33A

bigcityracer
Dirt Freak

Total posts: 431
posted April 12, 2004 05:03 PM  
I beleive the rest about the heads maybe causing the problem. Try running the shortest tires you have with a little more than usual air pressure, if that doesn't bring more R's look to porting and polishing the heads. If that's not allowed swap with 350 heads. You may need to kick in more compression with the 350 heads. All other equipment sounds good for what you need. GOOD LUCK

maniac motors
Dirt Maniac

Total posts: 128
posted April 13, 2004 06:09 PM  
what are you running for ign timing and jets in the carb i run track thats 1/2 mile (on concrete outside wall) with 3.42 gears and saginaw 1.68 2nd gear turned 5850 all year long.dont let anyone tell you the 416 heads are junk i run them for compression (compression = power just the smalll valves make it lower in the rpms dont try over 6000 or your wasting it get the car handling good and free in with good bite off and use the torque to pull away off corners. i run 36 degrees no vac advance and 72 jets
hope this helps also the 416's you have are they rebuilt with a good set of springs or just new springs? a good 3 angle valve job will work wonders for you. Scott Fowler
10x racing



Raz_900
Dirt Forum Champ
Total posts: 635
posted April 13, 2004 10:25 PM  
Personally, I think the cams too big. If you're only getting 3000ish rpm out of the turn, the cam's below it's intended power range and the motor's a slug. By the time you get to 4000-4500 where it's really working, there isn't enough straightaway left to really get going. Midwest is smoking sumthing if they thing that cam will pull at 2700 rpm. Plus, your heads and intake will never let you get to 6800-7000 rpm which is the max recommended (and what you should aim for using that cam)

You could try running the cam to the loose side of the lash spec, maybe even a few thou higher than the highest spec. Anything to make it smaller. If you want to stick with a solid cam, I'd recommend something in the 230-240@.050" intake range. Comp Cams has quite a few in that range that would work MILES better than what you have. Unfortunately you have a engine system (carb, intake, heads, manifolds, cam) that aren't balanced and this is what'll happen. The 2" pipes, stock intake and exhaust manifolds and 2 bbl carb are all working against what the cam wants.

Get a cam with a 6000-6200 rpm peak and you'll be surprised. You'll probably have to back off the gear a bit once the things has some b@lls coming outta the turn.

Good luck.

Oh.. and if you run an Alt., it should eliminate anything with a weak battery or low voltage to the ignition. You could try a different module, but sure sounds like a mismatched cam to me.

racing33A
Dirt Forum Racer

Total posts: 97
posted April 13, 2004 10:42 PM  
To The forum,
Thanks again for all the help.I believe I will try the cam change first.If that doesnt do it then the heads are next.
racing33A

racing33A
Dirt Forum Racer

Total posts: 97
posted April 18, 2004 12:15 PM  
Just got back from the first race of the season and now I am happy. First off let me say thank you to all who helped me out with my rpm problem. Now the update on what I found that was not helping me at all.When my car was built 2yrs ago it was outfitted with a rubber fuel line from front to back.We secured it up to the frame rail with those rubber adel clamps, but what we did not notice was that the clamps had pinched the fuel line almost flat in 4 seperate spots.We all know if you aint getting fuel,you aint going anywhere.I replaced the fuel line and came up with better attaching ideas.After that the car got so much more fuel that I had to jet down from a 72 to a 68.We also double checked the timing and found it to be way to far advanced(cheap --s timing light).The reults of fixing just that stuff was an increase of 1000rpms.We did not win but we came from 16th to 8th through heavy traffic and we were closing on the front pack when time ran out and the flag dropped.
Thanks again to all the awesome people on this forum.
racing33A

    

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