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Let the Clutch Out
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Discussion Starter #1
Okay as some of you may know my old mans 406 SBC didn't perform to his expactations. So We are thinking of pulling it out and tearing it down due to some info we found out. We found that His Deck Height is still stock on his Dart SHP block 9.025 so this is got to be hurting his Compression and hurting power. How much I don't know but his Rotating Assembly is this
Light wieght 3.75 Stroke Crank
6.00 rods
4.155 bore 1.125 Compression Hieght dome volume -5.4cc so it should be about 11.4 to one guessing these pistons were forged with a 9.000 deck hieght in mind.

Also Wondering if the valves are unshrouded or not Dart Pro 1 215's . We are just not sure of what his engine guy did the only thing we are positive of is the car isn't making good steam (runs 11.50 @115 @ 3300+lbs) the cam is degreed and installed straight up but who knows we'll see when we get it apart.

So what do you think this thing is loosing HP wise ? I know with the Formula my Friend has we are coming up with about 9 3/4 to one Compression from the Cranking Compression numbers.
 

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Okay as some of you may know my old mans 406 SBC didn't perform to his expactations. So We are thinking of pulling it out and tearing it down due to some info we found out. We found that His Deck Height is still stock on his Dart SHP block 9.025 so this is got to be hurting his Compression and hurting power. How much I don't know but his Rotating Assembly is this
Light wieght 3.75 Stroke Crank
6.00 rods
4.155 bore 1.125 Compression Hieght dome volume -5.4cc so it should be about 11.4 to one guessing these pistons were forged with a 9.000 deck hieght in mind.

Also Wondering if the valves are unshrouded or not Dart Pro 1 215's . We are just not sure of what his engine guy did the only thing we are positive of is the car isn't making good steam (runs 11.50 @115 @ 3300+lbs) the cam is degreed and installed straight up but who knows we'll see when we get it apart.

So what do you think this thing is loosing HP wise ? I know with the Formula my Friend has we are coming up with about 9 3/4 to one Compression from the Cranking Compression numbers.
deck block or go to thinner head gasket.. might try advance cam 2 to 4*
 

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advancing the cam should definitely help..smaller head gasket or even shaving the heads a little is not always a bad idea either..its better to have a smaller dome with a smaller chamber rather than a huge dome piston with a big chamber..flame front travels better with smaller dome and smaller dome is lighter
 

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Let the Clutch Out
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Discussion Starter #4 (Edited)
deck block or go to thinner head gasket.. might try advance cam 2 to 4*
We Plan on deck height going to 9.00 the pistons are Wiesco's and I know on a Old Set I had For My Old 388 SBC the Ppistons were "Designed" with a 8.998 Deck Height to get Said Compression with XXcc Heads, So I hope my Dads is close I'd like to get the thing to at least a true 11 to 1 and his Cam is a Comp Roller X292R so its a Street Cam but He at least took the Timing cover off to see if or where it was degreed. Now it sits on Straight up . I was just wondering a Guess a HP loss with the piston obviously being a Flat top and obviously being down in the whole I just wonder how Much all of that affected the HP just compression alone is bad but it can't be Buring Clean so to speak?
 

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Behind Enemy Lines In Ca.
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"I just wonder how Much all of that affected the HP just compression alone is bad but it can't be Buring Clean so to speak?"

Probably quite a bit. I am sure your quench is not good either.
 

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Let the Clutch Out
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Discussion Starter #6
"I just wonder how Much all of that affected the HP just compression alone is bad but it can't be Buring Clean so to speak?"

Probably quite a bit. I am sure your quench is not good either.
I know the Super Victor Intake is hurting this Combo a Bit also but it seems Like the more I hear what his Engine Guy didn't do the more I understand why its only making about 425 hp this is a street Engine and has belt driven WP/fan and Alt. but :confused:
 

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I know I am the only one saying this but zero decking the block I do not believe it worth much HP. I used to think that it was critical and I know it "helps" but it will not make or break an engine. I ran 2 stock blocks one decked and the other not decked same top end (switched from one block to the other). It ran the same ET and MPH.
If you are tearing it down anyway then you might as well deck it but I would not tear it down just to deck the block.
 

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I don't know what formula you're using to work out CR from compression test. Does it take into account cam size. I have changed cams and seen 20psi difference in compression test. Even advancing or retarding cam will make a difference to cranking pressure.
One thing I got caught on a couple of yrs ago was I changed heads and cam on 377sbc. It would have been hard pressed to be making 450hp when I was expecting 500+. I pulled engine, checked cam timing etc and couldn't find anything. Ran it again and it was the same. I had 36*total timing in and had advanced it more looking for the hp.
I happened to be talking to another guy about it, he suggested taking timing out and said the heads I was using had a good chamber shape and didn't need as much timing. I started taking timing out and away it went, quicker every time I took more out. Ended up at 28* total and picked up 1/2 sec in 1/8th mile.
 

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The best way to know what your compression is to actually poor it and figure it out , it's the only way you will know for sure instead of going off of what mfg's claim their stuff is .
 

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Well... this engine needs about 75 hp minimum to meet expectations right? Maybe 100....?

Something is sure off... I don't think giving it a couple points of compression is going to bring that power to the table...

Have you cut the filter and things like that? Something is in left field.
 

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X2 ^^^^^^
It's like anything else, it's the combo of things that make it work.
Compression is worth a few HP(10-15hp) But, no way 75-100hp! Somethings not happy, you need to look at the whole engine and go from there. IMO you will be wasting time and money just adding a few points of compression. Might be the right direction to help it out, but not the fix all. good luck



T-flow
 

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We Plan on deck height going to 9.00 the pistons are Wiesco's and I know on a Old Set I had For My Old 388 SBC the Ppistons were "Designed" with a 8.998 Deck Height to get Said Compression with XXcc Heads, So I hope my Dads is close I'd like to get the thing to at least a true 11 to 1 and his Cam is a Comp Roller X292R so its a Street Cam but He at least took the Timing cover off to see if or where it was degreed. Now it sits on Straight up . I was just wondering a Guess a HP loss with the piston obviously being a Flat top and obviously being down in the whole I just wonder how Much all of that affected the HP just compression alone is bad but it can't be Buring Clean so to speak?
Did you take a degree wheel and actually check where the cam is installed? just because it's installed straight up with the timing set, doesnt mean the cam is actually straight up. most cams will have a 4* advance ground into them.

You really need to list many more engine specs to determine where power is to be gained.
 

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Lets lists the knowns, which will support the power desired...

Pro1-215's will support 500+
406 CID will support 500+ in street trim.
Intake manifold will supprt 500+ unported
The carburetor will support 500+
Even 9.5:1 should support 500 hp within this combination

The cam is an unknown to me.... I have no idea on the specs.

Right now this engine is barely making over 1.0 Hp/CID........ and that makes no sense.
 

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Did you do a leak down test to see if or where there might be a problem.Did the rings seal,is the valve job not sealing ? You could have all of the cam and compression in the world,if the rings aren't sealing properly you will never make power.
I have that same head on a flat top 408,makes barely 12.5 to 1,with a Bowtie intake,950 Quick Fuel and a Ultradyne 680/660 267/271 109 solid roller built around a stock 509 casting block that made 650.
 

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Whats in it for a tune?

If a motor is this unhappy the tune ( timing, jet, plug #)will have to be way off and the plug will show it. So whats the plug look like?
 
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