High compression 400

[jopes]

High meaning 13 ish to 1.

With compression that high would there be any down fall on the bearing life in the bottom end of the motor?

[79time]

would think you would have problems with the top end before bearing problems with the bottom!

[jopes]

I would think you would have problems with the top end before bearing problems with the bottom!


xplain please?

[jr78f150]

id say if you had problems it would be on the bottom end and bearing life would almost have to be shortened but have no idea how much. all the strain would be put on the crank and connecting rods is why i say that but i dont know anyone who has went that high on compression to get an idea from. he!!,do it and find out

[redmt79]

While the 400 has a very strong bottom end, I don't think there is any doubt about it being hard on the bearings. That will be a lot of stress on a long-throw crank.

You would also want the best head gaskets you can get. And the best starter.

[79time]

Second the good headgaskets.

I'm assuming you plan to accomplish the increased compression via a performance cam, and based upon the limited availability of performance parts I see the weakness on the top half though a spending some cash will help.

Would love to see the engine built though, what do you expect for performance numbers?

[jopes]

TIm has a chart on his site that lists a set of his pistons with 12.58:1 CR. I am sure getting to 13 from those pistons would not take very much.

What I would really like to do is a 434 stroker full roller with aussie heads. but...

what will most likely happen is a fresh block, unbored. Maybe even a new used set of rods and crank from the pull it yard. Bore the block and clean everything up. New pistons, and make it a full roller top end. Roller cam - lifters, and rockers. It will be with aussie heads like I have right now, as well as still running the SEFI thats on it right now, but maybe a bigger set of injectors because I am going to be running E85 with some trials I am going to be running on the old engine that I have right now.

[mrw]

Don, how is E85 going to work with that much compression? Wouldn't you be better off going with propane at that point?

[jopes]

E85 wants high compression. it has a high octane rating of 105 compared to straigh gasoline which at best is what 93 at the pumps if you can even find it. Anything more than that your looking for race fuel or alot of octane booster to get it up there.

Yes propane is a option. but I have already put on SEFI on my 400, so why switch to pane?

I am having problems finding the links right now, but I seen E85 really works best with the CR between 13-14. It is supposed to cool the intake charge when it is entering the cyclinder which is another reason it resists detonation.

[OX1]

I got a set of CHI's with a 60 cc chamber for my next build. Should be a hair over 12:1 with Tim's hypers made for aussies. I am running pane. Don't think I'll be running it enough to worry much about the bottom end bearings.

[jopes]

I got a set of CHI's with a 60 cc chamber for my next build. Should be a hair over 12:1 with Tim's hypers made for aussies. I am running pane. Don't think I'll be running it enough to worry much about the bottom end bearings.

thats also my idea. I only wheel it. Not legal to drive on the roads any more so why not have a little fun.

OX, post that up when you get it all done. Also what are the cam specs and all that good stuff your planning on?

[OX1]

thats also my idea. I only wheel it. Not legal to drive on the roads any more so why not have a little fun.

OX, post that up when you get it all done. Also what are the cam specs and all that good stuff your planning on?

It's going to be a long long time before that engine is done and running. I have whole new rig to build around it first. I am not looking for only low end as most are. I spent 2 grand on those heads and want to be able to get some power out of this thing when I want it. With 6.54 gears and the possiblity of a 5.4 ratio in the 205/black box combo, I'm not too worried about low end torque.

Some pics of the heads for now......

http://luxjo.supermotors.net/74%20ROCK%20CRAWLER/400/CHI%20HEADS/DCP04030.JPG
http://luxjo.supermotors.net/74%20ROCK%20CRAWLER/400/CHI%20HEADS/DCP04022.JPG
http://luxjo.supermotors.net/74%20ROCK%20CRAWLER/400/CHI%20HEADS/DCP04023.JPG
http://luxjo.supermotors.net/74%20ROCK%20CRAWLER/400/CHI%20HEADS/DCP04024.JPG

[OX1]

http://luxjo.supermotors.net/74%20ROCK%20CRAWLER/400/CHI%20HEADS/DCP04025.JPG
http://luxjo.supermotors.net/74%20ROCK%20CRAWLER/400/CHI%20HEADS/DCP04026.JPG
http://luxjo.supermotors.net/74%20ROCK%20CRAWLER/400/CHI%20HEADS/DCP04027.JPG
http://luxjo.supermotors.net/74%20ROCK%20CRAWLER/400/CHI%20HEADS/DCP04028.JPG

[OX1]

http://luxjo.supermotors.net/74%20ROCK%20CRAWLER/400/CHI%20HEADS/DCP04029.JPG

[mrw]

Did you or someone drop that head on it's corner? Lower left of that last picture looks like it needs dressing up . . .

[Johnny]

Yeah, but other than that, they sure are pretty...

[jopes]

Ox, Have you thought abotu making a 400 with SEFI on it?

[OX1]

Ox, Have you thought abotu making a 400 with SEFI on it?

Nope. Already have the pane setup. Getting "gas" is the only minor hassle. I've never stalled (not even upside down), and not had one, even minor, problem with it. Not saying you will have problems with EFI, but if you do (and many guys running it in the EB world do), then diagnosing can be a real PIA.

Anyway, we don't really have E-85 around here and those heads are not going to get low compression at this point without a piston that is as bad as the stock piston.

[OX1]

Did you or someone drop that head on it's corner? Lower left of that last picture looks like it needs dressing up . . .

I didn't notice when I looked over the heads, but it it does, it does.

[mrw]

Are those going in the MOG beast or a first gen?

[OX1]

Are those going in the MOG beast or a first gen?

in a 74, if/when..........

[jopes]

Nope. Already have the pane setup. Getting "gas" is the only minor hassle. I've never stalled (not even upside down), and not had one, even minor, problem with it. Not saying you will have problems with EFI, but if you do (and many guys running it in the EB world do), then diagnosing can be a real PIA.
.


I think alot of the EFI stuff that has reliability problems really has to do alot with the install from the person who put it all together. I really have very few sensors, and all except the ECM and harness are new parts. I don't have any worries about it.

besides if I do have a issue, there is plenty of EB's on the trail with SEFI I can barrow parts from. :D

[blythe_mechanic]

any time you build a performance engine you give up reliabilty, abit just be awary of that when you assemble the engine, i would recommend using the best parts you can afford and blue print and plasti gauge the bottom end when building, also like i did in my truck, use good hardware, i used the arp bolt kit, what you use is up to you , there are the best in my opion, also i would recommended a fluid dampiner and balancing the engine , mine is balanced to less the 2 tenths of a gram, and it will twist as tight as a small block,. if you can afford it get rid og the factory valve train its week and will not hold up to alot of high rpm, theaussie heads are a good choise too, 11.5~1 is a great rig engine and more and your talikng aot of bucks to make it stick together in the long haul

[unreng]

don...there's also the option of propane injection:

http://www.ls7.com.au/forum/showthread.php?t=96418&page=4 (http://www.ls7.com.au/forum/showthread.php?t=96418&page=4)

I've been researching some of the alternatives and it still looks to be rather expensive. :cash