yep!! thats alot marky!! its really cool of you look for those flags[img]i/expressions/face-icon-small-wink.gif[/img]

thanks
kc

 

Fred and iron how do you guys know what comp you had? Did you find out what the ACTUAL comp is or is that what the piston was rated or a mechanic told you etc. This makes a large difference.

I currently have an 11.2:1 Ross piston but the actuall comp is 12.6:1 and previously there was a JE 10.8:1 that was around 9:1 actual.

So you have to know the actual compression and theres two ways to do it. The more accurate way is the measure the cc's of fluid (normally oil is used) that it takes to fill the cyl with the engine assembled. The other is really close but much easier as its a mathamatical formula thats loaded into a computer program (much easeir for us in a rush or not wanting a mess etc).

Personally I have not had the problems that some have, but I have noticed a loss of power and an increasing oil leak that is either in the head gasket or head cover gasket etc and will be starting a thread on this when I tear it down for inspection and some other new mods soon.

I have also known of people running higher comp with no problems at all and running stk studs etc but then there are others who have stories like fred. There has to be reasons for this and I have heard all kinds of things from the better known engine builders from actuall comp being well above what was expected to improper torqing of the various bolts and studs and everything in between.

There have also been opinions on the different rev kits being responsible for a lot of the problems as the internals of this engine were not designed for running at those rpms and once you increase the loads on the internals of the engine with all the other mods it just pushes things beyond the limits. Problems with the rod and rod bearing have also been reported etc.

I am of the opinion that its a combination of things that cause these problems. Sure a overly expensive larger stud would help and it does but also requires some machine work and can get expensive. There is a cooling issue with this engine even in mildly modded examples and once you go to the levels that many of us do this becomes a problem. Heat not only robs power but causes all kinds of additional stress on the engine by causing everything to expand, and the more heat the more expansion. To a point this is good as it allows many parts to perform better like how the piston and cyl will seal well etc but push it and every thing starts to become ugly.

Actually the most prevelant problem I know of with higher comp engines is blowing out the head gaskets. This is from many obvious and some not so obvious things that happen but most all of them are corrected with either proper torqing and re-torqing the bolts and studs and or using a gasket that is designd for higher comp applications. Cometic has a gasket that they suggest be used when comp is 13:1 or above and it has a round metal ring that cant blow out etc. So there are ways to avoid some problems.

Fred I am very curious to what you had or have on that engine that may have contributed to your problems.

 

Remeber even a bone stock 400ex from the factory is different from one another mabey you got a Monday morning Quad.

 

I did research it - no problem. Same as the DS - except with a 14:1 - no problem there either. I am watching it, and folks can buy them if they want, I was willing to roll the dice on it after talking with 3 race mechanics. If people are scared, they should buy the big head bolts. Its not a problem for me, but at the same time I recognize its a personal decision that everyone should make on thier own. Three months and counting .....

 

IRONROD,
If you don't mind me asking how much did that edelbrock set you back. I plan on doing something very similar once I get my yearly bonus. Thanks
James

 

440EX026,

It's 13:1 because thats what JE rated it for on the 400EX, and Duncan Racing tested it at using the method you mentioned. I don't take any one persons advice on what they say, I do the research and find the documentation to support the compression rating.

My only concern now is overheating. Even though I am using a HP4 semi-synthetic, I am looking at the largest capacity cooling oil tank I can find and right now thats the ACE oil tank. When the funds are in, thats next on the shopping list.

Marky

 

The Edelbrock 38MM "Doug Eichner" Carburetor (pre-tuned) with thumb cable for $493.95. I didnt pay that. The best deal I know of is $474.99, but I didnt pay that either. I got a deal cuz I test the stuff.

 

Yep.....I was thinking it was going to be around $500.00. So how do you like it?
Thanks
James

 

I ran a 14:1 comp ratio (I cc's the head and everything to find out) it was ok on head studs, but I did have a head gasket blow once. I fixed it, milled the head a little and its was fine. I had a custom wleded up combustion chamber, decked the head, and shaved from the cyl as well. It wa sa flat top piston making that comp ratio.
Marky, Use the 4stroke tech oil cooler, its the way to go. It droips oil temps alot more than a bigger tank, feeds cool oil right to the valve train, and adds 1/2 quart capacity.

 

Its the best carb I've run on any motor ever. I'm not sure how well it works on other quads, but for the 440EX its awesome.