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Author Topic:   valve/piston clearance
hamer36
Dirt Maniac

Total posts: 196
posted April 10, 2005 06:59 AM  
I have a set of pro action 64cc heads on a motor and I'm thinking about going to the 50cc heads. Will the piston to valve clearance stay the same or will the pistons need work.I guess I'm asking if the chambers are built smaller or if the heads are planed at the factory to get the smaller chamber. I'd like to keep it short blocked as its pretty fresh. THX

hughes
Dirt Maniac

Total posts: 194
posted April 11, 2005 06:09 AM  
If you can run pop-ups, I would stick with the 64 cc, because you can't run pop-ups with the 50's. On a 350 you can get realisticly about 12.5:1 with the 50 cc and with the 64 cc you can pop it up to what ever you want. You would have to sink the valves to mill the 50 cc heads. I would save the money and get busy.

hamer36
Dirt Maniac

Total posts: 196
posted April 11, 2005 07:42 PM  
The motor is a 434 with flat tops and a roller cam.Heads are angle milled to 55cc. It should be a torque monster, but its a pooch. I have the 235 cc heads on it and I think the ports are too large since I've run the same cam number in a 406 (220cc heads) and it was a great motor.(blew it up last year, another couple weeks till its back together)I like to run 7200 max with a 400 but this 434 feels like it wants to be in the 8000 range.I thought I could increase the compression and port velocity with a different set.

leapinlizard
Dirt Freak

Total posts: 402
posted April 12, 2005 08:04 AM  
I don't see 230cc port's are to big for a 406. I've run that on a street driver for years. They will move up the RPM range though. My guess is it's probably over cammed. What can do you have?

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted April 12, 2005 08:10 AM  
230s are not too big for a 406 and most definetly not a 434.

What compression is this motor?
What compression was teh 406 you had?

hamer36
Dirt Maniac

Total posts: 196
posted April 12, 2005 03:22 PM  
The 406 was 13:1 and I'm guessing the 434 is about the same (flat tops with 55 cc chambers) 434 had a comp 263-266 @.050 and I've changed to a lunati 258-268 (Same as the 406). Beyond this, the difference is port size as both heads are the same brand. The 406 was so much better its hard to figure. We're going to throw gear at it this weekend to see how it behaves. I just hate to turn a long arm that many Rs.

Kromulous
Dirt Forum Champ
Total posts: 796
posted April 12, 2005 03:41 PM  
Gas or alcohol?

Those heads may be to big on gas, may...

The compression is in question, what gasket thickness, and how much was the piston in the hole? or was it zero decked?

I calculate the compression well up in the 14 to 1 range plus, but without the other info i dont know for sure.

Also that Lunati cam has alot of split in the duration, need to keep it a 6 to 8* max, plus its got alot of duration to run on alcohol if thats the case.

I think, think, that with this cam (Lunati) with the high duration and the bigger intake ports, you lost alot of port velocity, and torque. I would either crank it more, if you got good parts, or change the cam, smaller duration, and less split.

254* intake, and 260* exhaust @.050, same lift.

Your other cam doesnt have enough split, so...

Thats my thoughts anyway.

Krom.

Kromulous
Dirt Forum Champ
Total posts: 796
posted April 12, 2005 03:43 PM  
Also, for a really good opinion, go to 4m.net and post this in the power train section at the bottom.

PERFCONN, should give you a real good idea on whats going on with it, he is really helpfull over there and is highly skilled.

My opinions may be right, but i would like to see his thoughts myself.

hamer36
Dirt Maniac

Total posts: 196
posted April 12, 2005 07:45 PM  
head gasket Felpro 1004 about .041 thick .005 deck. Alcohol. What puzzels me is why one motor runs so well and the other doesn't. Yes I did degree both cams.

Kromulous
Dirt Forum Champ
Total posts: 796
posted April 12, 2005 09:04 PM  
I calculated (website) the compression at 14.6 to 1, so thats good.

230cc intake volume on alky, and 434 cubes is good as well. Maybe a little on the small side for a 434.

Only thing i could think of, is the cam. The jump in the runner size, and the more cubes must of moved the torque curve up in the RPM band.

You may try to crank on it, and see what happens, it may come to life, but i would hate to see you break something.

I think i would call, Lazer Cams, or Camcraft and look into buying a cam specific to you needs, and RPM range.


Kromulous
Dirt Forum Champ
Total posts: 796
posted April 12, 2005 09:05 PM  
Oh, what intake you got on it, and whats the valve sizes? Headers tube size as well.

rico 08
Dirt Forum Champ
Total posts: 1139
posted April 13, 2005 06:17 AM  
you said you hate to twist a long rod motor...
it's been my experience that the longer rod motors like more rpm over the short ones
just a thought

autoshop
Dirt Freak

Total posts: 298
posted April 13, 2005 09:19 AM  
it need a shorter duration cam unless your racing on a half miler. 252 at 050 intake 258 at 050 exhaust max.
lift somewhere 580 or 590

hamer36
Dirt Maniac

Total posts: 196
posted April 14, 2005 08:26 PM  
Headers are 1 3/4 into 1 7/8 same ones on the 406. Intake is edelbrock 2925. 2.08 intakes and 1.60 exhaust. If she comes to life with more R's, I may try the 220 runner heads on it. 64cc chambers; can't plane them because they're for the 406.

hamer36
Dirt Maniac

Total posts: 196
posted April 14, 2005 08:30 PM  
I thank you all for the input. I may try an even smaller cam when I refresh it(after 406 is done)

Kromulous
Dirt Forum Champ
Total posts: 796
posted April 15, 2005 08:41 AM  
One of my favorite cams is a Lunati, 50145 grind number. Its awesome, should work good for your application.


juliaferrell
Dirt Freak

Total posts: 370
posted April 15, 2005 11:40 AM  
What your experiencing is intake contamination. That cam won't work for the 434. If you could retard that cam 4 you would notice a slight difference probably. What are the intake and exhaust opening .050 numbers? Your killing cylinder fill with exhaust reversion. That's 14+:1 pulling LOTS more air than a 406 and doesn't require as long an intake event to work for you. That split is killing your engines torque and hp numbers.

Bill Hendren or Perfconn can give you advice as stated in the earlier post. They won't steer you wrong.

hamer36
Dirt Maniac

Total posts: 196
posted April 17, 2005 07:24 AM  
Thanks guys! What cam should I use in a 18* dart headed 406? Would the Lunati cam work in this motor or does the 18* change everything?

hamer36
Dirt Maniac

Total posts: 196
posted April 17, 2005 07:25 AM  
We did turn it up. It ran 7600 and was better, but not great. Good enough to break an axel though.

Kromulous
Dirt Forum Champ
Total posts: 796
posted April 17, 2005 09:09 AM  
18* degree heads, i dont know anything about, yet.

That Lunati i listed above is a great, alcohol burning 23* degree cam, good to about 7500 normally.

Contact the guy at Lazer cams, he has a website, and there is a cam recomendation thing on there, fill it out and send it in, he has good circle track cam expierence.

That or contact PERFCONN or Herndon Racing Engines, i think one posts on here, they may be able to help.

Broken axle, hmm mustbe makin some torque qith that monster. Doesnt sounds to bad.

hamer36
Dirt Maniac

Total posts: 196
posted April 17, 2005 09:16 AM  
Krom
I asked the cam question on 4m.net regarding the 434. Also asked about 18* cam in your question about heads. THX

Kromulous
Dirt Forum Champ
Total posts: 796
posted April 18, 2005 04:51 PM  
What rockers are you running 1.5 or 1.6's and rod length?

hamer36
Dirt Maniac

Total posts: 196
posted April 18, 2005 08:14 PM  
1.5 with 6" rods

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