Looking for advice on sbc 400 build using 305 heads #416 w1.96 intake, 1.06 ex. Stock engine had 8.5 compression w/dish pistons, dont have original heads. Low milage engine w/standard bore, rods. I'm not sure how to calculate compression w/these 58cc heads. Planning to port match only. Using (real)old school Torker intake w/670 Holley Avenger, .488 lift Erson cam and headers. Hmm, maybe someone has idea's on how this combo might turn out? Compression ratio?

 

Download and install this

http://cochise.uia.net/pkelley2/dcrvb6.zip

 

Butt first, you gotta get all the right numbers.

Those 58cc heads, after they've had the bigger valves put in em, are going to be closer to 62cc by the time you relieve the chambers enough to where the bigger valves HELP instead of HURT. So don't forget to take that into account.



Here's the difference... doesn't make a difference that the valve is bigger, if all the stuff coming through it has to squeeze through that little crack around it where it almost rubs against the chamber "wall".

You need to know which dish your pistons have. Most likely it's 15cc but there were 3 possibilities in stock motors, and more than that in rebuilder pistons.

Then you gotta know your deck clearance; which is, how far "down in the hole" the pstons are at TDC. Odds are, if it's a factory short block, they miss the deck by about .025" - .030"; and if it's been rebuilt, they're about .020" farther down than that. Most people entirely leave that out, which is why you hear about 11:1 motors that run on pump gas. Simple... they're NOT 11:1, except in the owner's fantasies.

A "calculator" is only as good as the numbers you feed it. Garbage in, garbage out.

 

Yeh the short block is completly stock and original. I realize the chamber size in head is larger since the valves were put in, by how much I don't really know but I can see that the machinest had grinded out around the tight areas. I guess I'll have a better idea after it is built and a compression test is done. I am hoping for 9.5:1 or 10:1 roughly. 10:1 would be better w/cam I'm trying, I think. Thanks for the reply

 

Can't open this file from VETTEOZ, the set up file won't run. My computer is a dog, I hope my engine runs better than this computer.

 

Doubt you'll get that. Probably not much over 9.3 or so.

Re-think the cam & intake, if you actually care how it runs, and you're not just determined to scrape stuff off the garage floor and call it a motor. All of it is a giant mismatch or hopelessly obsolete. There's a reason nobody runs any of that stuff any more; and you can take it to the bank, it ISN'T because they're so tired of winning races all the time with it and just want to slow down. The carb too for that matter. Not much fun to spend a bunch of time and money building something and have it turn out to be a wimp... which that group of parts will certainly be.

Don't worry about what "calculator" to use. They're all THE SAME. Same as going to Office Max and looking at the shelf of calculators: 2 + 2 = 4 on any of em. Don't outsmart yourself over something that trivial. Concentrate on WHAT MATTERS, which is, getting the right numbers to plug in.

Compression test won't tell you diddly about the compression ratio. You need to measure the parts BEFORE assembly.

 

You saved it to your computer Ok but it won't open?

Prob need this program to open the .zip file
http://www.oldversion.com/download-W...15.5.9510.html

if you are running Win 95 or 98 select a earlier version of Winzip
http://www.oldversion.com/WinZip.html

 

Well O.K. then, I"ll work on figuring out the true compression before assembly. I'm guessing smaller cam might work better? I have an Air Gap intake laying on my garage floor with a Edlebrock 750 if needed. Just kidding, sort of. Yes I really don't know what combinations work on 400's. First one I've had, second engine assembly. It would be nice to get the RIGHT cam for this engine before I drop it in. Bolt on stuff is easy enough to change anytime, after I have more money.

 

You need to slow down and do some research before you start throwing things together.

With high compression ratios you want and NEED larger cams. Larger cams will bleed off that compression to bring it down to a safer dynamic ratio. Really you're supposed to make your static compression complement your cam, not the other way around, but you seem to be hellbent on using 305 heads which are probably going to lead to an astronomical compression ratio so you need all the help you can get.

You need to

1. Determine usage for this engine. What kind of power are you wanting to make? How practical do you need it to be? There are tradeoffs.

2. Pick heads and cam that can support your proposed power level.

3. Aim for a static compression ratio that compliments your head/cam combination

4. Get an intake that will compliment your head/cam combination.

You dont just say "I have a 400 block, and I have 305 heads, lets put them together and bolt on whatever fits that sounds good".

 

Trying to download program now, looks like 4 hours. Yeh I live in the dark age's w/dial up, being in the Cascade Mountain Range. Just a poor country boy. Thanks

 

Yes I need help. I am going to try to research/determine compression ratio tomorrow. The heads I had built for a 350 but the 400 fell in my lap as a short block in great condition. I only know what I read from other people. I am not wanting a daily driver. Just want to have a little fun on weekends. I have read the head/block combo works well. I based the cam from the usable rpm range advertised that I wanted to stay within, although I only guessed the compression would be close to 10:1. Tight budget and limited knowledge hinder's this project. Thats why I am here asking for advice from people who know how to build a moderate hp engine utilizing as much of what I already have when reasonable. Is 425 hp unreasonable? I appreciate the responses!

 

Sorry ,
Try this earlier much smaller size version for faster download.
http://www.oldversion.com/download-WinZip-5.0.html

May not work with Win 7