lets look at this example

grumpyvette

grumpyvette

Administrator
Staff member
71chevy said:
I have had several attempts at building a motor but just cannot seems to understand what components to match. I had a local builder put a 383 together for my 71 chevy truck in hopes that I would have better luck. It sounds really good at an idle but the street performance is not that great. I have restored everything on the truck except for the motor and interior so I am good at a lot of things mechanically but I am not getting the idea of matching stroke, compression, cam, heads, intake, carb and ignition. I just want a decent sounding lope that can smoke the tires whenever I am at city street speeds.

Here is what I have
350 block bored .30 over
400 stock crank
5.7 rods
forged flat top 4 valve relief piston
Patriot performance 190cc aluminum heads
Roller rockers 1.6
Edelbrock Air Gap RPM intake
Quick Fuel Q-750 carb
Summit HEI distributor
Elgin Hydraulic cam 1011P
350 Turbo tranny
2300 - 2500 Stall converter
3:08 gears

I had it dyno'd and it had 300hp and 302 tq at rear wheels so it isn't a huge dud but it doesn't perform well on street.

I was going to start with 3:73 gears and maybe a TCI 3000-3400 stall. If that didn't help maybe putting a carb like 670 street avenger and maybe an MSD distributor with 6al and blaster coil. If that didn't help I was going to research putting afr 190 or 195 heads on it and possibly a retro fit hydraulic roller cam.

Any suggestions of where to start would be great...hopefully its not a complete rebuild.

Thanks for your time
Mike
Click to expand...


ok lets look at that combo and see whats not going to match well and why its not working as you expect.

Elgin, Hydraulic Flat Tappet Camshaft, Chev SB
Chev SB
Lift: .490/.490
Duration: 300/308
Duration @ .050": 232/234
Lobe Separation: 108 LC
Rough idle. Upper end power, 3500-6500.

you stated you had
2300 - 2500 Stall converter
3:08 gears,
you also say you have Patriot performance 190cc aluminum heads, when i look for 190cc Patriot performance 190cc aluminum heads
i see 185cc, and 195cc come up and 64cc and 72cc combustion chamber sizes

http://www.jegs.com/i/Patriot-Performan ... 0/10002/-1

http://www.summitracing.com/parts/PAR-2171/

ProMaxx Performance#723-2180 comes up as Patriot performance 190cc aluminum heads on jegs
190cc Aluminum Cylinder Heads
Small Block Chevy
2.02''/1.60'' Valves
190cc Intake Runner
64cc Combustion Chamber
Angle Plug
Assembled
theres nothing wrong with the cam used or heads but that cam, will not work in that application with that gearing and converter stall speed, your compression is a bit high for typical pump octane gas,especially if you have the 64cc combustion chamber heads and assuming you have a standard block that has not been deck milled and your quench is nearly correct you should have a head gasket in the .020--to-.024 thick range which puts the static compression some place in the 10.5-11:1 range
camcomp.jpg

because of the compression ratio you really can,t drop back to a lower duration cam easily so going to a 3300 stall converter and 3.73;1 rear gear would help allow your engine to operate in the cams intended power band, you did not mention headers, and exhaust, youll need a low restriction exhaust and headers to get that combo to breath, Id also point out that swapping to a 200r4 over drive transmission would help a great deal once you swap to the high stall speed and 3.73:1 rear gearing so I would plan on swapping to a 200r4 rather than buying a high stall converter for the th350
transmission-dimensionsf.gif
 
Excellent information

Here is a link to the heads I have but it looks like you found the information
http://www.summitracing.com/parts/par-2181

I do have headers and 1 1/2" exhaust all the way out the back (short bed truck) with turbo style muffler.

That is interesting how the SCR helps define the recommended cam duration along with the power range. I always run 91 fuel but every once in a while I stop by my local airport and mix aviation and 91 fuel 1/2 & 1/2...it does run better.

Do you think the quick fuel Q series 750 is too big for the motor or it enough just need to get motor into operating range?

With the dyno showing rwhp at 300hp and 302 tq ... would you suggest a different cam, heads or ignition to get the HP and TQ up while still being able to run the A/C on the street? Is it possible to make just a couple changes to get closer to the 500hp & tq range?

I will go ahead and get the TCI 241001 converter and 3:73 gears because it seems like I will need to stick with a cam that will need the converter and gears due to SCR.

Thanks for the information
 
i would look for more lift while i'm at it, with a 2.02 intake valve you could afford to max out your spring capacity and still be selling yourself short on lift. to test the theory you could inexpensively add a set of 1.6 rockers and once you realize theres power ther, leave the rockers and get a cam with more lift. i also think according to grumpy's LSA table that your LSA is too loose and you should be in the market for something like a 106 LSA or tighter and atleast 55 degrees of overlap with a good tuned exhaust.

also i see you have some sort of exhaust work but it says 1 and 1/2" exhaust. that must be a typo of some sort. what kind of manifolds are you running? long tubes? cast irons? theres plenty of threads linking to calculators here from wallace racing that can help you choose a primary header diameter, and length along with a collector length and diameter, based on your horsepower/rpm goals and your cam events. by the way welcome to the forum and have fun hot rodding!
 
Yes I am running Long tube headers 1 1/2" primary tubes and 3" collector. I have 2" exhaust from header collector out the back of the truck with a basic turbo muffler. Should I consider upgrading exhaust for better flow?
I already have 1.6 roller rockers installed. I'm still reading and trying to wrap my head around the whole cam LSA numbers and what that actually does in correlation to duration and lift. By looking at Grumpy's table my cam power range should be starting between 2800 - 3200 area and I'm coming in a little high at 3500. Looks like going from an LSA of 108 to 106 would lower the intended power band but would it lessen the vacuum and have less choppy idle? I know duration comes in to play with those figures and I'm not sure exactly how to tell what cam would be the best to get the most street power, with a wide torque/hp power band, with a nice choppy idle and has a good vacuum. Would a retro fit type roller cam be better...any cam suggestions would be appreciated.
I am putting 3:73 gears in it next week knowing that the 3.08 is not something good for the street. I like the idea of not buying a higher stall for TH350 and just saving money for a 2004r but I will have to save for that one. If I could find the same type of tire burning results between 0-45 mph with a cam change that might be a little cheaper right now. I would still want the 2004r for the OD capabilities.

Thanks again for your input!
 
71chevy said:
Yes I am running Long tube headers 1 1/2" primary tubes and 3" collector. I have 2" exhaust from header collector out the back of the truck with a basic turbo muffler. Should I consider upgrading exhaust for better flow?
I already have 1.6 roller rockers installed. I'm still reading and trying to wrap my head around the whole cam LSA numbers and what that actually does in correlation to duration and lift. By looking at Grumpy's table my cam power range should be starting between 2800 - 3200 area and I'm coming in a little high at 3500. Looks like going from an LSA of 108 to 106 would lower the intended power band but would it lessen the vacuum and have less choppy idle?
it would tend to lower the power curve VERY SLIGHTLY but IT WOULD ALSO TEND TO LOWER VACUUM AND INCREASE THE CHOPPY IDLE
I know duration comes in to play with those figures and I'm not sure exactly how to tell what cam would be the best to get the most street power, with a wide torque/hp power band, with a nice choppy idle and has a good vacuum.
THOSE ARE BOTH CAUSED IN PART BY OPPOSITE CHANGES, CHOPPY IDLE TENDS TO BE FROM INCREASED DURATION AND TIGHT LSA, good Vacuum FROM LOW DURATION AND WIDE LSA Would a retro fit type roller cam be better...any cam suggestions would be appreciated.
I am putting 3:73 gears in it next week knowing that the 3.08 is not something good for the street. I like the idea of not buying a higher stall for TH350 and just saving money for a 2004r but I will have to save for that one. If I could find the same type of tire burning results between 0-45 mph with a cam change that might be a little cheaper right now. I would still want the 2004r for the OD capabilities.

Thanks again for your input!
Click to expand...
 
I found my dyno sheet...It looks like my peak rear wheel TQ is 335 @ 4200 rpm and peak rear wheel HP is 295 @ 5000 rpm.
Just to keep the truck street friendly what would the expected tire movement rpm be with a 3300 stall with the hp/tq figures of my truck with 3.73 gears?
At this point stall converters for the 200r4 are expensive and just wanting to make sure and choose the right one.
I don't want to rev the rpms up to 2500 before the truck starts moving while cruising town.
Do I need to consider a cam change to get a lower stall speed or would a 2700 - 3000 stall work good with my power band?
 
one of the most common myths about high stall torque converters , is that the car won,t move under part throttle until near the rated stall speed is reached by the engine, think about that a second, then think about how your current car reacts to part throttle and realize your stock converters stall speed is probably 600-700rpm higher that the rpm that effectively moves your car at part throttle.
the first thing youll want to do is test your current converters stall speed and find out what your currently dealing with, so you have a few facts and a start point!

viewtopic.php?f=71&t=1715
 
I will definitely read through the entire stall converter link and also call a few manufacturers like you suggested.
I have been reading through tons of your posts each night trying to figure out how to get the right combo...btw you have a lot of excellent documentation. My problem is bouncing the info off someone so I can apply and understand the info.
I have had 3 various stall torque converters that I was able to move under part throttle but the stall speeds were always 2400 - 2800 in SBC. I had a BBC with a 3000-3400 stall and it just slipped a little at low RPM's but would jump right up to stall when I hit the throttle. The one bad experience was the 327 with 3400 stall and it didn't move until 2500 rpms. I have always wondered what was so different and never wanted to repeat that scenario.
When I tested my current stall speed it started spinning tire at 2400 but it starts moving with no brakes at 1000 rpm.

I have been looking through cams that would potentially give me a wider power band with duration @.50 around 233.
I found this Crower roller cam that was mentioned in another post in 2006 that has a very wide power band.

http://www.crower.com/camshafts/chevy/c ... 11985.html

After initially reading through a lot of posts it just seemed like my current cam has a high rpm narrow power window that might not work in my favor.
But with the correct gear ratio and stall converter my current cam may also work great without any cam change.
 
Id point out that the quality of the manufacture of the high stall converter varies a great deal between manufacturers and Ive seen a 3300rpm stall converter in a big block car that had very little slip at part throttle over about 1600 rpm, and a similar 3200 rpm rated stall converter that barely moved the car until you had the engine over 2200rpm, so ask around before buying any brand.
theres bound to be other good sources but these guys seem to have good converters, or put a different way, its the brand Id buy if i was currently looking for a new converter and had the cash to buy one

http://www.converter.com/vigilante.htm
 
71chevy said:
I have been looking through cams that would potentially give me a wider power band with duration @.50 around 233.
I found this Crower roller cam that was mentioned in another post in 2006 that has a very wide power band.

http://www.crower.com/camshafts/chevy/c ... 11985.html
Click to expand...

Don't know how much this might help you, but it can't hurt. That's the same camshaft I used in my 400 cu*in SBC. The engine idles at 900-1000 RPM. The carburetor is a Speed Demon, 750 CFM. I have a 200-4R trans and 3.73:1 rear gear ratio. I'm using a torque converter rated at 2800 RPM stall speed, purchased from CK Performance.

12” STREET AND STRIP LOCK UP CONVERTER #24RC/SS
http://www.ckperformance.com/resources/ ... RTERS.html

The one place where we differ considerably is weight, the TBucket only weighs about 1800 lbs.

Some videos where you can hear how it idles and performs.

http://youtu.be/pxDt3mLaBdk
http://youtu.be/F4w8YlTA4MI

 
You must log in or register to reply here.
Back
Top