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Author Topic:   first time here
elvislomas
Member
posted December 28, 2002 12:30 AM
hello I just got a computer and this is the first site I,ve found ,seems very cool.I bought a used car last year and ran 6 of 9 races with a tired 305 and had a blast. Now that I got the basics down I want more power and hope to be able to throttle steer it this year. I,ve bought a '68 4 bolt builder and am having it boiled now. My car is a 72 ventura and I race at a small track in Hayden Colorado. My question is what pistons should i buy and how do I pick a cam(hydraulic only).I am limited to a 2barrel w/500 cfm and there is a mysterious claimer rule that I don't understand except that it's supposed to limit cheating. I want at least a year (9 races) before any tear down as reliability is more important than outright power. The heads have intakes that are just under 2 inches and I plan to use the 4 barrel intake with the adapter plate I fabbed for the 305 to neck it down for the 2 barrel carb. Any help or input would be appreciated.

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KPLugnut
Member
posted December 28, 2002 07:52 AM
Welcome to the incredible world of racing, Elvis, and also to the best dirt track racing site on the planet! (OK, so I'm a bit biased LOL).
First, your pistons won't be able to be chosen until the machinist boring the block is able to decide where the cylinders will clean up at. If the thing has never been rebuilt, usually .030" over stock diameter will be sufficient. At that point, you need to decide how much you can afford to spend. One can buy pistons for $50/set and anywhere on up to nearly $1000/set, so really it all depends on what the entire engine package, rules, and power goals ask for.
My suggestion would be to hook up with a good machine shop, give them as much info as you can about where you're going to race, what the car weighs, rpm goals, as well as your budget and they should be able to assist you in building a dependable engine.
Now, as for your carb rules, you mentioned a "500cfm" carb...does that mean ONLY the Holley 4412 2bbl carb, or ANY 500cfm carb?
Regardless, for ease of tuning, versatility, and dependability, I'd recommend the 4412 2bbl. There is power to be gained thru proper tuning, maintenance, and beginning with a well-built blueprinted carb doesn't hurt either.
You mentioned a homemade spacer/adapter....airflow management from carb to intake is very important in tuning the torque curve of a motor, too. If there are no rules other than perhaps a thickness limit to how tall the spacer can be, then there is power to be gained there as well.
In your intake, the quadrajet intake is a good start, but we'd recommend using the older style ones without the EGR valve setup. Their runners are balanced better.
In the heads, a good 3 angle valve job (at least) by a knowledgeable machinist, as well as setting up the valvetrain (stem heights, spring pressures, etc) is of utmost importance. Angle milling the heads helps, too, along with decking the block to leave the pistons not more than .005" down in the hole.
Cam choice is a long subject as well. A lot depends on your rpm needs, rules of course, and probably the most important thing to remember is that bigger is not always better. Keep in mind, tho, if you ask 100 other racers, you're likely to get about 90 different answers as to "what cam is best". Learn from it, and then with the help of experts you can pick a cam that will easily serve your needs.
I can't stress enough the value of the enourmous amount of knowledge you just tapped into by becoming a dirt forum member, and I recommend hanging out here as much as possible, read all you can, and ask questions every step of the way. The huge numbers of great people here are priceless.

And if there's anything we can do to help you to the front, just ask.

Dayton Umholtz, owner
Kinetic Performance http://www.kineticperformance.net


racer17j
Member
posted December 28, 2002 12:16 PM
welcome to the forum first i'll give the the basic concept of the claim it's not to stop cheaters it's to scare guys from building a $6000 motor that they can lose if claimed for less then it cost to buy a junk yardmotor and a re ring kit. as for what parts to use get a good set of pistons for around 100 or so if you ever go on ebay i just bought a set of hyperutectric pistons with rings and bearings for 115 plus shipping.if you use good parts ie.clevite 77 bearings i've seen guys run 40 nites on a motor if they keep up with oil changes before they refresh it. as for a cam do you have any limits other than it has to be hydrolic if not i can suggest a couple grinds that work real good for us over the years. as for throttle streering this type of car i'm thinking that maybe you want the rear end to be a little more free you can do this lots of ways with stagger and air pressure stuff like that it's mostly set up not motor and we all can help you with that any more questins don't be afraid to ask this is a great site and you'll learn something new everyday


elvislomas
Member
posted December 29, 2002 03:10 PM
quote:
Originally posted by KPLugnut:
Welcome to the incredible world of racing, Elvis, and also to the best dirt track racing site on the planet! (OK, so I'm a bit biased LOL).
First, your pistons won't be able to be chosen until the machinist boring the block is able to decide where the cylinders will clean up at. If the thing has never been rebuilt, usually .030" over stock diameter will be sufficient. At that point, you need to decide how much you can afford to spend. One can buy pistons for $50/set and anywhere on up to nearly $1000/set, so really it all depends on what the entire engine package, rules, and power goals ask for.
My suggestion would be to hook up with a good machine shop, give them as much info as you can about where you're going to race, what the car weighs, rpm goals, as well as your budget and they should be able to assist you in building a dependable engine.
Now, as for your carb rules, you mentioned a "500cfm" carb...does that mean ONLY the Holley 4412 2bbl carb, or ANY 500cfm carb?
Regardless, for ease of tuning, versatility, and dependability, I'd recommend the 4412 2bbl. There is power to be gained thru proper tuning, maintenance, and beginning with a well-built blueprinted carb doesn't hurt either.
You mentioned a homemade spacer/adapter....airflow management from carb to intake is very important in tuning the torque curve of a motor, too. If there are no rules other than perhaps a thickness limit to how tall the spacer can be, then there is power to be gained there as well.
In your intake, the quadrajet intake is a good start, but we'd recommend using the older style ones without the EGR valve setup. Their runners are balanced better.
In the heads, a good 3 angle valve job (at least) by a knowledgeable machinist, as well as setting up the valvetrain (stem heights, spring pressures, etc) is of utmost importance. Angle milling the heads helps, too, along with decking the block to leave the pistons not more than .005" down in the hole.
Cam choice is a long subject as well. A lot depends on your rpm needs, rules of course, and probably the most important thing to remember is that bigger is not always better. Keep in mind, tho, if you ask 100 other racers, you're likely to get about 90 different answers as to "what cam is best". Learn from it, and then with the help of experts you can pick a cam that will easily serve your needs.
I can't stress enough the value of the enourmous amount of knowledge you just tapped into by becoming a dirt forum member, and I recommend hanging out here as much as possible, read all you can, and ask questions every step of the way. The huge numbers of great people here are priceless.

And if there's anything we can do to help you to the front, just ask.

Dayton Umholtz, owner
Kinetic Performance http://www.kineticperformance.net



Wow this is so cool. Thanks for all the info.As far as the motor goes, I disassembled it myself and the bores were in good shape with very little ridge. The pistons came out easily. My machinist thought that it would be fine with just a hone. The pistons are stock and appear to be about 8 to 1's nothing special. The crank is forged and also in good shape according to the shop.I took your advise and just asked the shop to recomend stuff, He said flat top 9 to 1's with a little decking will be ok.He said about 100 bucks will buy a good set.
As far as the carb goes there is no specific rule other than 500 cfm. The carb I got came off a 50 year old chevy ranch truck that was trashed. I got a generic rebuild kit and replaced needle,seat ,float and gaskets. The main jet is stock and ran a good mixture with the 305 (plugs looked ok after each race but victim to blow by on the old mill), the track is at 7000 feet A.S.L.. I would like to find a replacement and will shop for the 4412 and start again with jetting.
There is no height restriction so I have stacked up an impressive array of crap to fit a round peg in a square hole and add about 1.5 inches of rise as I've heard its good in general to give the intake some room but would like a tighter rig than mine, any suggestions on adapters?
The cam choice is going to be decided after we buy pistons and get all the details to a shop in Denver that will custom grind one for about 80$. Sounds cheap to me but I trust the shop as they are very involved with the local track.
One more question comes to mind, how will I break the motor in? I live in the mountains and can go to a spot to idle it where the lack of mufflers won't be a problem but I couldn't drive it around legally. Should I buy an old beater and stuff it in there first? Would this be worth the lisencing and plumbing etc.?
Thanks for all your help. Elvis
Ok me again. I sent an e-mail to you and it was undeliverable so i attached this to yours and am sending it back. Is this the right way to respond?


hesseracing
Member
posted January 01, 2003 10:14 PM
elvis, welcome and now you are ruined for life, you have found the world of racing. no drug like it anywhere. as far as breaking in the motor talk to the shop where you are getting the work done as well as the cam maker and find out how long they want you to run the motor and at what rpm's to break in the cam. usually 20-60 minutes at various rpm's. after that take it racing. the break in is to seat everything after that run it like you stole it. if its built right and the oil/filter are changed regularly you should get a couple years from it before you need to tear it down and check rings and bearing. i run 25+ races a season with a 383 pushing 500+ hp and usually get 2 seasons with taking good care of the motor and changing the oil/filter every other week. good luck and enjoy


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