Chevy 400 sb conversion questions

[FJKai]

Due to the amount of 40 conversions, I thought I'd ask up in the 40 section. I'm in the middle of a chevy 400 sb conversion into my 60 using the Mark's adapter and the stock manual 4 speed. 400 wasn't my first choice based upon the somewhat "standard complaint" about cooling issues. But, it was a great deal, hard to pass up, and a close friend of mine who is a die hard chevy guy, swears by the 400 and says he will never mess with a 350 again (he is a pre-runner guy in San Diego and says he and all his buddies run them with no probs). So, based upon this, I'm going with the 400. The 400 came out of a friend's pick-up who used it as a daily driver for about 5 years with no heating problems. I was hoping to hear from both sides on this, by sides I mean guys who've run em' with no probs, and the guys that had/have problems and how they fixed them (hopefully fixed them). I'm keeping my fingers crossed, but I'm also ready to upgrade the radiator, pusher fans, maybe even the mythical "high flow" water pump if I have too. Anyways, some real life experience would be appreciated. Thanks ahead of time. Oh yeah, I've done a search or two on this and not a whole lot comes up, at least by my search words.

 

[ajfriz]

Did it come with an automatic? I have heard some pretty bad stories about auto 400s put behind a standard tranny. I know you can do it if everything is ballanced. You might want to check into that.

 

[FJKai]

Engine came out of a 76' impala. I would assume it was probably an automatic based upon that. We are going to put a balanced 168 tooth fly wheel on it of course.

 

[largenfirm]

Engine came out of a 76' impala. I would assume it was probably an automatic based upon that. We are going to put a balanced 168 tooth fly wheel on it of course.

My understanding is that *there* is where the ugly comes in! I've overheard that the 400/flywheel combination must be rebalanced if they're not a matched set. Problem comes up in that the 400/auto ring gear (whatever it is called) are balanced at the factory, as are the 400/flywheel.

A balanced flywheel by itself is insufficient.

Never been there, never done that, just overheard some guys BSing about it one day at NAPA, don't know how it would be done, even.

FWIW

Kirk

 

[FJKai]

Hmmm. Then what does that mean? Heavy vibrations? Once again, what does that mean overall? I'm not a true motorhead per say, but I do understand the basics of motors and can turn wrenches and figure it out, but in terms of technical functions what are we talking about here? How does this relate to cooling problems? Please forgive me on this one, this is the first time anyone has mentioned this issue. Ouch, now I'm really getting nervous.

 

[largenfirm]

Has nothing to do with cooling problems, but the gist was that a shade-tree swap like this would result in heavy engine vibration under acceleration, with at least one of the conversation participants feeling it would be enough to damage the engine.

I believe I saw somewhere that the crankshaft can be spin-balanced with the flywheel to get past the problem. A quick websearch might be in order...

http://chevyhiperformance.com/techarticles/4402/

And a pretty good explanation, here

http://yarchive.net/metal/flywheel_balance.html

Kirk

 

[pygpen]

sb400's are externally balanced, make sure you have the right harmonic balancer and flywheel/flex plate for the 400 and you will be good.
I had a 400 in my GMC for years and never had cooling problems. In a 60 you should be able to put enough radiator in it to cool it sufficiently. Don't worry, have fun.
PMK

 

[Corbet]

sb400's are externally balanced, make sure you have the right harmonic balancer and flywheel/flex plate for the 400 and you will be good.
I had a 400 in my GMC for years and never had cooling problems. In a 60 you should be able to put enough radiator in it to cool it sufficiently. Don't worry, have fun.
PMK

I agree, my stroker 383 has a 400 crank. I had to get a special fly wheel and balancer as it too is externally balanced. You should be fine there.

Cooling, get an AL radiator, high flow water pump, and thermostat. Make sure you have good air flow with what ever fan you use.

 

[FJKai]

Found out chevy only has one 168 tooth flywheel made for sb 400's from 1969 to 1980 and I can easily order and get one, so balancing isn't going to be as big of a problem as I originally thought (stock harmonic balancer is still on). So I'm back to my original concern which is of course cooling. I appreciate all the comments. I'm kind of bummed out to find out that the sb 400 was/ is rated at only about 175 hp. Seems like it should be at least 200+, but that's what the specs I saw said. I guess it's still better than the stock 2F and eventually I'll rebuild it down the road and have it make a lot more, but in stock, 4 barrel form, only 175 hp. Kind of takes the thrill out of the whole conversion thing, I think I was better off not knowing. lol Thanks again for the comments guys.

 

[pygpen]

Go back to being in denial, like everyone still running an F motor......
PMK

 

[Brian in Oregon]

Google Chevy 400 Steam Holes

The issue with the 400 Chevy is whether the block and heads have the steam holes and whether they line up. The cylinders are siamesed due to their large diameter and these steam holes are important (and not needed on the smaller displacement blocks). Click the Google link for more information.

That your friend had no cooling issues is a pretty good indication he probably has the steam holes, they line up, he has proper head gaskets, and they're not plugged with rust and debris.

I'm not going to touch the balance issue other than to say it's easier to balance an engine prior to installation than to have to pull it out, balance it, and reinstall it. You can also "freshen" it with new rings, bearings, gaskets, cam, lifters, timing chain, cam bearings and oil pump after hot tanking it nice and clean and deglazing the cylinder walls. While not a true rebuild, it has had five years running time on it and I'd think it would be worthwhile. At least it would give peace of mind as you would definitely be able to inspect everything thoroughly.

 

[FJKai]

There we go. Now that's what I was hoping for. Thanks for the info and links Brian, and everyone else that's thrown out their 2 cents.

 

[dgangle]

BTDT, except in previous 75/07 FJ40 I owned. As others have said they are externally balanced. Get the right harmonic balancer and flywheel. I had to buy mine from GM as I could find none used. I had a 350 in it before and replaced it with the 400 with the 350 flywheel/clutch. Man, did that sombeach vibrate. Duh.

Cooling, ditto to all said. I will say that I ran a stock 3-core I6 rad with no shroud and a GM clutch fan for years. It ran hot, upwards of 260F at times plowing wet/heavy snow or driving at highway speeds with the plow on or at highway speeds in the heat of the summer. Yea it was hot but that engine made soooo much more torque than the 350 it was silly. It had plenty to spare. Second and fourth gears were all you needed with 4:11's and 33's.

Done right, anything can work.

 

[FJKai]

Well at least one thing got cleared up, use a chevy sb 400 flywheel and harmonic balancer. Other than that, it seems that the pros and cons for the sb 400 is a pretty close 50/ 50 split, which gives me hope, or a 50% chance of having minimal problems. The good thing going for me is that I know the engine source and it ran with no heating problems (granted it was a chevy truck radiator in a chevy truck with lot of room). I'll just continue on and see how my luck, or lack of, pans out. Thanks to everyone again for their input.

 

[Sculpin74]

Stock internals only need the factory issue 400 flywheel and harmonic balancer.
Regular maintainance (flushing) is the key to keeping the steam holes clear.

175 hp? I'm thinking thats just numbers on a page and doesn't really say much for the difference you feel in the seat of your pants!
Add a good exhaust and a dual plane intake to the mix and you'll think that number magicly doubled! Add a cam swap to the mix and it most likely WILL be doubled!
Even STOCK they work very well...like a built up 350!

They can run a little hotter, but the only one we ever had problems with was swapped into a little import car for...midnight racing, and the rad was barely adequate for the job, not to mention that engine earned its keep. LoL

 

[FJKai]

Well we finally got the 400 in and fired it up. So far I have yet to see the temp run hotter that 180 degrees. Of course I'm mindful that it is still winter here in SW Oregon, but it was a bit warmer than it has been, probably in the 60's when I first ran it, but idling in the driveway with the hood shut for 15+ mins it still stayed at the 180 mark. I'll be keeping my fingers crossed until our summer 100+ temps are reached, but so far I think I'm off to a good start. The timing is still off pretty bad and will be fine tuned this weekend, but so far I'm happy. Once again, thanks to all that gave their 2 cents and experiences. Oh yeah, the Marks adapter worked pretty killer and was cake in terms of easy install, but the motor mounts still needed to be "modified a bit" in our case. I guess we'll see how well everything holds up in due time though.