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  #46 (permalink)  
Old 09-13-2012, 04:31 PM
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I just checked. The laws of physics has not changed since the last time you posted on this.

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  #47 (permalink)  
Old 09-13-2012, 04:50 PM
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Good luck with that set up. If you hit 300hp it would be doing unbeleiveable.
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  #48 (permalink)  
Old 09-13-2012, 05:03 PM
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anyone care to offer any actual help?
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  #49 (permalink)  
Old 09-13-2012, 06:07 PM
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Originally Posted by F-BIRD'88 View Post
I just checked. The laws of physics has not changed since the last time you posted on this.
Both of the OP's threads are merged here.

Pupvette, you have had 44 posts to your original thread, you shouldn't start another with the same problem.
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  #50 (permalink)  
Old 09-13-2012, 06:12 PM
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I posted a thread about trying to find out why the engine will not go above 4000rpm the issue of power loss maybe due to the fact that the motor won't go past 4000 but this issue was never addressed and/or posted about
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  #51 (permalink)  
Old 09-14-2012, 03:14 PM
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Originally Posted by Pupsvette76 View Post
anyone care to offer any actual help?

I've got to know the real detail; which includes part numbers and manufacturer if you don't have the specs. A turbo or any blown or laughing gas motor is not a simple accomplishment. It becomes a very large set of compromises the direction being set by the major use, an automatic transmission just adds to the difficulty because building the engine toward the high performance side then controlling it with gear selection makes the overall task a lot simpler.

I just finished an injected, turbo 911 for an owner with no cash flow problems, it took a year to build including extensive chassis, suspension and transmission work but the engine alone used up as much time as everything else and probably chewed up 80 thousand of the 100 thousand this cost him.

On the surface you have what I perceive as a mild cam in that it has a lot of duration and not a lot of lift, so what is called its Hydraulic Intensity appears fairly mild. But having the part number and maker or its opening and closing specs would be really helpful. Blown or juiced engines like a lot of exhaust duration and lift and for the ratio of the intake to exhaust valve size to be closer together than found in a normally aspirated engine. This is because there is more exhaust product to get rid of. This cam would appear to me to be very rampy that is long areas of slow and low lift chewing up lots of duration degrees. This just isn't good with a turbo, but again I need to know the events, I could be wrong on my assumptions.

The 624 head is kind of a do it all, but none too well head. It was found on 350's and 400s and had valve sizes that range from 1.72x1.5 in heavy duty trucks and industrial engines, to 1.94x 1.5 in average use 350s and did show up with 2.02 x 1.6 valves in some 350s and 400s. So when you say these have 1.94x1.5 is that by actual measurement? Supercharged and juiced engines like big valves and good porting. The blower does not overcome porting deficiencies, it just increases pressure not flow, remember gases like air and vaporized fuel are compressible so you can get a pressure change without a flow change.

The 1.5 rockers aren't doing you any favors with this moderate lift cam and lack of valve size (1.94/1.50- (especially exhaust) you're just not getting enough lift for the needed flows with these valves. This in particular backs up the exhaust to where the residual pressure in the cylinder is near the pressure coming off the compressor so the net effect of flow into the cylinder is much less than the pressure shown on the boost gauge. Again, flow and pressure are independent of each other where the flow of gasses is concerned. To a huge extent back pressure in the entire exhaust system is an issue. You need two gauges to really determine true boost pressure delivered to the cylinder as a function of CFM. One you probably have that measures intake pressure. The other gauge needs to read exhaust back pressure. To simplify, the difference between these two gauges of exhaust subtracted from intake is the Effective Pressure going into the cylinder. You will discover that with just 5 pounds of boost it's really easy to have no net gain over atmospheric as getting exhaust pressure under 5 psi takes a lot of attention to detail. This is one reason why guys tend toward higher blower pressure, but even this begets more exhaust pressure but there usually is some space here to mess with before the whole exhaust system has to be redesigned.

I can and will go on as I’m barely scratching this issue. Out of everything i've read (and I’m not negating the contributions of others at all) certainly cooling the intake charge for example is a good way to get around problems of cam timing, port and valve flows and exhaust pressure. But that works so much better when everything else is properly assembled and tuned.

I’m aiming at where I think your biggest problems are, but I’m leaving for a week of vacation and will be off line from this evening through the morning of the 24th.

Last edited by oldbogie; 09-14-2012 at 03:19 PM.
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  #52 (permalink)  
Old 09-14-2012, 05:05 PM
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If it wont rev up past 4kRPM:
1) running out of air due to turbo/intake air limitations
2)restricted exhaust
3)running out of fuel for any number of reasons
4)mechanical problem in valve train due to loss of valve control, usually a spring problem

I have a car in the shop with the first PP TBI system I have touched. The edit software is kinda clunky, and this car refuses to run the same for 5 minutes at a time. It also has the PP Fuel on Demand returnless pump setup.
I think that an A/F of les than about 12.0 is going to cost you horsepower, plus you cant count on the O2 to respond like a dedicated A/F gauge is capable of.
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  #53 (permalink)  
Old 09-22-2012, 10:12 AM
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old bogie you believe its a matter mostly of valve sizing not allowing air flow mainly the exhaust... i plan to remove the muffler i have on the car hopefully that will aid a little bit with exhaust pressure i do plan to put a better set of heads on the car a little later on.. i wanna know why it wont spin past 4800 even if i bring the rpm up slowly it wont spin higher
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  #54 (permalink)  
Old 09-22-2012, 02:30 PM
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not reading any of this, i say instead of the muffler remove the whole tailpipe. when meinekie first opened i had them do my first exhaust. they welded a new pipe right up to the old one with the old one extending into the new at an angle about three inches in!!! maybe you got something going on like that.. or maybe yer cams too far adanced, (or flat). hate to be dum but aint readin 4 pages. i can tell you this tho, with four pages on this subject you HAD to have somebody smart as hell tell you what to do!
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  #55 (permalink)  
Old 09-22-2012, 02:52 PM
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new build feels under powered

Pupsvette76, As you have been told the heads you have are poor flowing. I know you have to have 76cc chambers to keep your compression down. Look around and try to find a set of these heads cheap. 3973487-76cc, 1.94/1.5, 3973487X-76cc, 2.02/1.6, 3932441-76cc, 1.94/1.5. You can check with a machinist to see if the 1.94/1.5 valves can be upgraded to 2.02/1.6 without problems. Get a book on porting heads so you can do this yourself. Here is an article on head porting. Do-It-Yourself Small-Block Cylinder Head Porting - Tech Article - Chevy High Performance Magazine You can also get David Vizard's book, "How to Build and Modify Chevrolet Small-Block V-8 Cylinder Heads" You definitely need heads that breath and a large diameter (3") free flowing exhaust.
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  #56 (permalink)  
Old 09-22-2012, 03:17 PM
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Quote:
Originally Posted by Pupsvette76 View Post
Inside I all the nonsensical bickering I'm hearig to change the head... I looked at the world s/r torquer heads I believe they are 195cc int runners with 76cc chambers going back to my questio would u suggest using a thicker head gasket maybe copper in order to lower compression ratio so I can crank up the boost
I suggest you do some research on using copper head gaskets. To use the copper head gaskets the block has to be o-ringed. Check out this article on copper head gasket use. Engine Sealing: High Performance Head Gaskets: Engine Builder
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  #57 (permalink)  
Old 10-01-2012, 10:36 AM
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I have a friend at my local speed shop who can work me a deal on a set of afr heads I have to see if my valve reliefs on my pistons are big enough first because I believe these heads house a 2.05 int valve... I believe it's a 215cc runner and still a 76cc head
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  #58 (permalink)  
Old 10-01-2012, 02:47 PM
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Quote:
Originally Posted by Pupsvette76 View Post
i plan to remove the muffler i have on the car hopefully that will aid a little bit with exhaust pressure i do plan to put a better set of heads on the car a little later on.. i wanna know why it wont spin past 4800 even if i bring the rpm up slowly it wont spin higher
Not to contradict anyone but I believe something is going on besides the heads having 1.94" x 1.50" valves. A turbo- if done right- will work w/them. Not as well as it could w/bigger valves and/or better heads but it should pull hard to at least 6K rpm if not higher, regardless. By 6K rpm the boost may continue to rise but there will be a plateauing of the powerband due to the head restriction past that point.

How much boost are you seeing at 4800 rpm?

Is the engine smooth all the way up to where it stops accelerating or is it missing? Is there any popping through the carb or exhaust? What

Has TDC been verified? Not just by looking at the timing tab/damper line- but by actually setting #1 or #6 to TDC and see what the line/tab says? If it's off, the entire curve isn't what you think it is. Have you tried temporarily advancing the timing just to see if it revs higher? As long as the engine isn't under a load, there's no problem w/advancing it further than you would if you were driving the car.

Has the cam timing been verified? Compression test? Leak down? What do the plugs look like, color-wise? Fuel fresh? What octane?

What about putting a carb on it temporarily, just for testing? You might be under fueled. You've verified the TB is opening fully, right?

You didn't leave a grease rag in the intake, did you? Somewhere along the way you do need to disconnect the exhaust to be sure there's no excessive restriction there.
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  #59 (permalink)  
Old 10-07-2012, 07:37 PM
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thats the school of thought i was on... i can dial it up to 20 psi even before 4800 but i have dialed it down i never verified exact tdc its pretty smooth acceleration though ... never advanced it past 34 and i never thought to advance it past 34 just for idle no load no a bad idea... compression is ok and it runs on fresh 93 the only plugs i can use unfortunately are the accel shortys since i have extreme header clearance issues and the throttle is definitely oopen
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  #60 (permalink)  
Old 10-07-2012, 10:20 PM
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Quote:
Originally Posted by Pupsvette76 View Post
thats the school of thought i was on... i can dial it up to 20 psi even before 4800 but i have dialed it down i never verified exact tdc its pretty smooth acceleration though ... never advanced it past 34 and i never thought to advance it past 34 just for idle no load no a bad idea... compression is ok and it runs on fresh 93 the only plugs i can use unfortunately are the accel shortys since i have extreme header clearance issues and the throttle is definitely oopen
I'm not necessarily saying you need more than 34 degrees. What I AM saying is the timing marks- if not verified- might be making you think you have 34 degrees when you may not have that much.

The timing marks/TDC should be verified. A quick test for a lack of advance is to do as I said above- crank in some more timing to see if the situation improves. If it does, this might be pointing to an erroneous timing tab/damper line, or a problem w/the cam timing.
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