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Author Topic:   Most compression
Dirt Roller

Total posts: 10
posted January 02, 2005 08:55 AM  
What are your opinions on the most compression you can run and still have a reliabe engine. The motor will have scat forged crank, h-beam rods, forged pistons, stock 350 block. Will also have 350 cfm carb. With higher compression should you use head and main studs.

Dirt Forum Champ
Total posts: 635
posted January 02, 2005 09:33 AM  
Studs are very advisable. As is using a splayed cap block built from a 2 bolt.

With a good balance job, LW parts (pay close attention to piston weight and use at least a 6" rod) I'd think it could live a long life at 13-14:1. With a 350cfm carb it's not going to be making the power it would with say a 850. That's in your favor. Make sure to use all 'HP' consumables. i.e. head gaskets, bearings, rings etc. Claimer type stuff won't cut it.

Dirt Forum Champ
Total posts: 635
posted January 02, 2005 09:36 AM  
Oh.. and don't bother gearing it for 7000 rpm. With a 350 carb it's going to start nosing over around 5800-6000 then drop like a rock shortly thereafter. Run the best flowing heads you can to crutch the small carb.

Running it to 6800 won't do anything but slow you down and wear it out faster.

Dirt Freak

Total posts: 205
posted January 02, 2005 11:53 AM  
Pay close attention to them on the main caps... I was at 13.8 to 1 but was spinning more rpm, but the need for the steel billet caps is a lesson learned for sure. Heed that advice..

unregistered Total posts: 205
posted January 02, 2005 05:35 PM           send a private message to goinrcn44h   Edit/Delete Message   Reply w/QuoteBBBBBB
Id save all those parts for a motor you can run a real carb on. Most of us running the 350 carb are getting by fine with stock cranks, stock rods. you cant make enough power to hurt much.

I dont know anyone around here though that can get a 355 to run at all with the 350 carb. Most of the tracks are halfs and tacky.

Dirt Forum Champ
Total posts: 578
posted January 02, 2005 05:49 PM  
i ran my 355 at 14.1 to 1 and it lasted 60 nights. we turned 6500 rpm. i had a stock crank, rods, and speed pro hypereutectic pistons. compression is the key to making a small carb motor run. remember to that 14 to 1 with a little carb is similar to 12 to 1 with a large carb.
if you are gonna spend money on good parts make them light weight!!


Dirt Newbie

Total posts: 4
posted January 06, 2005 05:11 PM  
what type of pistons are you running to get those comp. numbers? we have to run flat tops and a min. of 60 cc head and do not come close to those numbers.

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