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406 Engine Build...What do you think?

15K views 117 replies 11 participants last post by  lhmurphy 
#1 ·
I have a 509 casting, 2 bolt main block bored to 4.155. I'm using a Scat 9000 Series crank, 6 inch scat rods with ARP cap screws, ARP main studs, Probe forged -14cc reverse dish pistons, with blueprint cylinder heads that have 195cc intake runners and 2.02 int. and 1.60 exhaust valves....The cam is a roller thumper cam that has .513 and .498 lift, 227 and 241 duration at .05...also using comp retro fit roller lifters, trick flow 1.5 roller rockers, and Comp chromoly pushrods, Comp dual valve springs, 670 street avenger with 68 primaries and 74 secondaries, .35 pump shooter...What do you think of my setup??
 
#45 ·
I may check into that! Thanks man...the reason I really wasn't worried about compression is bc my friend basically ran flat top pistons with 64cc chambered heads with 2.02/1.6 and the same cam I have and he was at 36* all in by 3000 rpm, he used 93 octane and it never showed signs of detonation...and his 350 motor really idled awesome and ran great...I know he had .39 compressed thickness gaskets...I'm taking your deshrouding idea into consideration and will talk to my machinist and see if he thinks I should do it...I appreciate your info
 
#46 ·
Yeah-I have read the whole thread and just gotta say I hate it when O/P's ask a question or for help,then argue they have the answer already.Kind of dishonest in intent.

Sir you have burned through alot of guys good intentions trying to honestly help you with your "TEST".

Your loss....................................I'm out.
 
#52 · (Edited)
Intentions with a little bit of false information is why I'm pissed at this thread...I don't like it when I ask an opinion and someone goes on that the compression isn't what the kit builder says, especially when the kit builder makes a living doing so...it's disrespect towards me and the builder...and I'm sure it will run on pump gas ;) so don't tell me it won't! Lol
 
#51 ·
Ok well the guy who built my kit runs a profitable business doing so and if he says my kit is 10.3:1 and pump gas friendly, I'm going to take his word...and for one you have to be downright ignorant if you put a hole in a piston due to detonation
 
#50 · (Edited)
Bc the guy who sold me my kit said it will have 10.3 to one compression, and is pump gas friendly. And 2, a set up similar was made and it ran on pump gas and no one on here believes it which is irritating...so I dunno if that would bother you when you are just askin someone to check out your setup and that's why a post was made saying a motor has been running good and I meant my friends 350 with a very similar set up and not my build
 
#54 ·
Both are small blocks, same cam, he had flat tops with 4 valve reliefs with a 64cc chamber and he didn't have detonation issues...my 406 has reverse dome pistons that advertise 10.3:1 compression with a 64cc combustion chamber...and everyone on here seems too think this won't work
 
#61 ·
So your machinist has been in the game for what,30 yrs??.

Do you seriously think these guy in terms of engine building,it is their first rodeo??

How about guys on here that are machinists??. What,do just discount or ignore their advise because they are providing on this forum??.

Me??. Well let's see.I started messing with cars when I was 10 and I am 65 now........hummm how many yrs is that??.We have in our race operation been in business for about 40 yrs and 20 of it has been a very successful national win in 9.90 cars where last count/lost count involved 17 different cars.

So what I am about to say next is abit harsh but very true.Your running between us and your machinist and it's you that doesn't have clue that needs to listen to the advise given and learn.Big boy pants now if you own any........
 
#62 ·
I read the ad from the kit you bought on Ebay from Skip White. It does say it will have 10.3 compression ratio with 64cc heads. But to assemble the motor with the recommended amount of quench .035-.045 you would need to use a .015 head gasket. Nobody makes a .015 with a 4.165 bore for the 400 ci engine. The next available size is a .027 x 4.165 made by Cometic. With this gasket your quench will be .052 not ideal but will work. Your STATIC COMPRESSION RATIO will be 10.304 and your DYNAMIC EFFECTIVE COMPRESSION RATIO will be 9.051. This is too high to use pump gas. To use pump gas you need the DCR from 7.5-8.5. Here is an article that discusses Dynamic Compression Ratio. Dynamic CR
 
#65 ·
I think you bought stuff and asked for opinions after the fact; then got mad because someone you know built something similar and it worked. But the fact of the matter is, you don't know it will work till you do it yourself. When you get this thing accually running then you can let us know if we know what we are talking about. But then, I guess we would have to take your word for it that you didn't change anything (heads, pistons etc.). Cuase, you've never fibbed to us before... Post #57
 
#68 ·
See this proves you don't know for sure what you are talking about, because all you can argue for sure on is spelling of advice not advise and argueing over the fact that you asked for opinions not help.

This is what you posted.

And also mister this motor has been running pretty good for the last 3 years and I never hear any pinging...I just posted so I could see how accurate these forums are and if I would really wanna join...so that's why I posted this to see how many people would chime in about compression and say it wouldn't run 15 minutes or idle smooth...looks like my test is done:)

So you said it was "this motor." Not "my friends motor."

But in post #66 You said, "I never fibbed...the motor I talked about earlier was a friends 350 "
 
#69 · (Edited)
When you finish your engine and get it running let us know what octane gas you end up using. By chance if it does have any problems with detonation take a look at Crowers mechanical roller cams. Find one with the intake valve closing at 50* this will bring your DCR down to an 8.2. Get a real cam instead of that thumpr that is all sound and show and no go. Check out this cam since you have the compression to use it. http://www.crower.com/camshafts/chevy-262-400-power-beast-roller-cam-277r.html
 
#70 ·
When you finish your engine and get it running let us know what octane gas you end up using. By chance if it does have any problems with detonation take a look at Crowers mechanical roller cams. Find one with the intake valve closing at 50* this will bring your DCR down to an 8.2. Get a real cam instead of that thumpr that is all sound and show and no go. Check out this cam since you have the compression to use it. Camshafts | Connecting Rods | Roller Lifters | Rockers | Crankshafts | Pushrods | Clutches
I appreciate it man...and the thumper cam outdid 4 popular flat rapper cams made by comp if you can find the article but I wil look into your cam some
 
#72 ·
What do you mean you didn't. Those were direct quotes from your posts. I just coppied and pasted them to show you that did say it was your mortor not your friends.

So why did you join this forum?? To get opinions of your build? Or to prove that we don't know what we are talking about?
 
#80 ·
Ok well the kit is on eBay under 406 rotating assembly...unless u want me to make a video of the parts at the machine shop? This is gonna be so funny...type in 406 rotating assembly on eBay and click on the one that says 4.155 bore and -14cc...seller is white performance...
 
#84 · (Edited)
OK, after a good night's sleep, I'm not quite as grumpy as I was last night, so let us begin anew.

I googled the 14950-030 you posted and clicked on Skip White's ebay site. The following are some quotes from there.....

"These pistons are for use with 6.00" rods. The compression height is 1.140 -14cc DISH TOP WITH 2 VALVE RELIEFS. 4.155 BORE SIZE, RING GROOVE SIZE, 1/16 1/16 1/8 and will produce approx. 10.5:1 compression ratio on 64cc heads"

OK, so we have that info. Now, a little further down, this is written.....

"These pistons have 2 valve reliefs, and are considered a true REVERSE DOME top -15.2cc."

Hmmm, maybe it depends on who's doing the measuring, I don't know.

"Premium pump gas with an octane of 91-93 puts you on the thin edge of detonation."

Yeah, I'd agree with that. All it would take is a short cam like you plan to use to make 'er rattle.

Now, here Skip is saying 10.5:1, but just for the sake of argument, we'll use your 10.3:1 SCR to figure dynamic compression ratio. Dynamic compression ratio (DCR) takes into account the static compression ratio, the stroke, the rod length and the closing point of the intake valve. Compression cannot begin in the cylinder until the intake valve closes, so that is what determines the cylinder pressure, along with the static compression ratio. After many years of doing this stuff, I have found that the Keith Black calculator works well for me and I will generally use from 8.0:1 up to 8.50:1 dynamic compression ratio for use with pump gas. Some fellows will build a pump gas motor up to 9.0:1 DCR, but I prefer to stay on the conservative side of things. Of course, using a tight squish of 0.035" to 0.045" will go a long ways towards preventing detonation also.

So, anyway, using a 10.3:1 SCR, 6" rod length, 3.750" stroke and an intake closing point of 35.5 degrees ABDC @0.050" tappet lift for the 12-600-8 cam that you want to use, the calculator spits out a 9.05:1 dynamic compression ratio. Now, if we use the 10.5:1 figure that Skip published for these pistons, we would get a 9.22:1 DCR.

My suggestion would be to use more cam with your combination, one with an extended intake closing point to reduce cylinder pressure and the tendency to detonate. Staying with the Thumpr series that you like, the Comp 12-602-8....
12-602-8 - Thumpr
closes the intake valve at 43.5 degrees ABDC and would reduce the DCR to 8.78:1 if you use 10.5:1 in the calculator, or 8.62:1 if you use 10.3:1 in the calculator.

Oh, and by the way, please stop comparing your friend's 350 to your 400. You have an additional 50 cubic inches and that changes the combination. You can't compare apples to oranges.
 
#91 ·
Just remember that your static compression isn't that bad. You will have to run a large duration cam with some overlap. If you don't have the money to spend on a mechanical roller cam get a solid flat tappet like this Crower 00321. Chevrolet Mechanical Flat Tappet Camshaft - Camshafts. This will bring your DCR down to around 8.2 where you can run pump gas. Might even get away with 89 octane. Next time you purchase a kit don't trust the numbers in the ad they are trying to make a sale. Find a online calculator and find your static compression and dynamic compression ratio and then make a decision. It is always best to run a 9.5 static compression ratio with the gas sold today. That way it won't be a problem choosing a camshaft. BTW don't forget to use .027 thickness head gaskets not .039. Keep the quench as tight as possible.
 
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