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Old 01-16-2005, 04:27 PM
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modified dirt car motor

Need some help my friend runs a modified race car! He bought a 400 chevy short block they call it a 377 new to me but its bored 30 over,6 inch eagle i beam rods,manley forged dome pistons no numbers dont know how to tell,was told probly are.150 dome on them.GM crank number 1182 is that a 350 crank? balanced rotating assembly four bolt mains arp bolts. dont know what bearings it has.this completely fresh but bought at racers auction.He was running a 355 so this is new to us. It runs on 3/8 mile track 3 speed manual with 543 gears.What cam do we need? What will max rpm be on this engine? This car runs on alcohol so what compression do we need? We have a set of double hump heads port and polished 64cc i think will these work ok on this motor? Hes also got some 601 castings 50cc not sure what they are.Need help any will be appreciated thanks.
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Old 01-16-2005, 06:30 PM
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A 377 is generally a 400 with a 350 crank in it. Lots of piston surface area and the rpms of a 350. The Camel heads will work if you have to run stock castings. The 601 heads are 305 castings.
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Old 01-16-2005, 08:27 PM
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if you check the ebay motor stores you should be able to find a cam or what ever else you need veryly cheap.i've dealt with racers outlet quite a bit and kevin will treat you right.a found another store there that sold predator cams.you can have them make the cam you want if you like.i bounced all over the ebay motor stores and found alot of parts that i wouldn't be afraid to buy.doesn't always have to be name brand to serve its purpose.you shouldn't ever have to look for a gear with the 377.their always in the power band.

if you check the ebay motor stores you should be able to find a cam or what ever else you need veryly cheap.i've dealt with racers outlet quite a bit and kevin will treat you right.a found another store there that sold predator cams.you can have them make the cam you want if you like.i bounced all over the ebay motor stores and found alot of parts that i wouldn't be afraid to buy.doesn't always have to be name brand to serve its purpose.you shouldn't ever have to look for a gear with the 377.their always in the power band.

if you check the ebay motor stores you should be able to find a cam or what ever else you need veryly cheap.i've dealt with racers outlet quite a bit and kevin will treat you right.a found another store there that sold predator cams.you can have them make the cam you want if you like.i bounced all over the ebay motor stores and found alot of parts that i wouldn't be afraid to buy.doesn't always have to be name brand to serve its purpose.you shouldn't ever have to look for a gear with the 377.their always in the power band.

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Old 01-16-2005, 09:22 PM
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Do not run the 601 heads, they are some of the worst performance castings for SBCs, the Double Humps are twice the head. Do you have those casting #'s? Also can you check intake CC's?

With alcohol your max compression is limited to about 15:1..with 14:1 being a good # to shoot for.

As far as cam selection look for a solid with 255-265* of duration @.050" and about .550-570" lift.

Your max RPM should be 7500 but trying to keep it below that(7200 ideal). The 377 has a monster bore and a short stroke, they rev easy so keep an eye on it.


This is of course with open rules. You may need to check on max compression and lift allowed for your series.
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Old 01-16-2005, 09:45 PM
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You say that 15 to 1 is max compression with alc. U mean the association limits this? Just wondering.
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Old 01-16-2005, 09:53 PM
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Sorry, i don't know what the rules are, I have just read and heard that 15.5:1 is the max with alcohol, no personal experience.

As far as the rules go in his particular series it could be 12.5:1 compression ratio max and 480" max lift. I'm not sure of his series...just how I'd build the motor if it was mine(13.5:1 compression, solid cam with 106* of lobe sep with around 550-560"lift and 255-260*of duration@.050" using the ported double humps). Somebody else may have a different combo.
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Old 01-16-2005, 10:44 PM
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Thks for the response. Alc likes high comp and 16 to 18 to 1 is ideal for it in a n/a application. An engine with that compression is a lot easier to make repeat and more responsive to fuel system changes. Look at a blown engine, the running compression on alc is around 26 to 1.
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Old 01-17-2005, 04:07 AM
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377 cubes

Thanks guys for your help .
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Old 01-17-2005, 07:38 AM
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Double Hump heads are going to make you car a slug. You need a port size at least twice that size with Alky. If you have enough money go with Brodix Track 1 for 23 degree stuff or the 11x head. If you don't then go with Dart Iron eagle 49 cc. Min. port volume of 215 prefer 230. Turn it 7500. If your a two holer, then it be all used up by 7200. It'll be smooth on the gas though.
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Old 01-17-2005, 05:53 PM
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Hey johnsongrass1 will it be beter to run it on race gas or alcohol? also he dont want to spend money on new heads. What kind of horsepower do think this thing will put out?
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Old 01-17-2005, 08:54 PM
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Without new heads.....nothing that impressive. I would doubt you could squeeze much over 400. With good heads and all the other stuff mentioned on this thread, you can about double that number. All about combo, and old heads are not part of a high HP combo.

Course, you did not mention your goal power output that I saw.

Chris
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Old 01-17-2005, 09:36 PM
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We have a set of double hump heads port and polished 64cc i think will these work ok on this. ---quote.
-------------------------------------------------
The double hump heads can be made to work, but it's going to really depend on how well they are ported. If they are modified to deliver 250 CFM, they'll work.

The smaller runner volume of the double hump heads is going to be a hinderance as you will need double the amount of fuel with a given amount of air with alcohol fuel compared to gas.

I think you could make them work, but it will not be optimum.

You'll need to angle mill the heads IMOP to get the chambers down to the low 50s in size, and I would want 14.5:1 on alky.

The 601 head is not too bad for small cubic inch engines in certain situations. I use them in 305 Sprint Car engines.

However, their small combustion chamber is a total mismatch for the large 4.125 bore size of the 400 block. Their airflow capabilities are are not matched to large cubic inch engines anyway.

Do all you can, with what you have, where you are.........
Now!
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Old 01-18-2005, 04:29 AM
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Thanks for the ideas and help.
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Old 01-18-2005, 09:53 AM
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I use the sealer on the bottom half and locktight on the upper portion.

As far as ring seal with studs, If you have plated the bore than yes the studs will changethe bore roudness slightly but if you are using cheap rings with a standed bore than you have nothing to worry about. Cast iron rings are very forgiving with out of shape bores.
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Old 01-18-2005, 08:23 PM
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Well far as horsepower not realy sure what his goal is im a bracket racer and im just helping him out on the car.Hes new to this and the car had a 355 claimer motor in it not sure what horsepower that would be. The motor was fresh when he bought the car ,the lack of him checking water before race and running it hot until he blowed it up was the downfall. I drag race on saturday nights and was not at track with him. If we use the double hump haeds would it be beter to use race gas instead of alky,and what compression should we not exceed in doing that.The short block is internaly balanced as far as we can tell the crank has been drilled in spots what kind of harmonic balancer do we need or does it matter? thanks john
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