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Old 08-09-2010, 12:38 AM
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GM Goodwrench motor build up...Seeking advice

I came across a good deal on a GM Goodwrench 350 motor. It was totally free so I can't possibly complain about the price. I'd like to utilize as much as it's freeness as possible and at the same time attempt to transform it into a motor that is capable of a high 11 second pass in an 86 Monte Carlo SS. I hear that the stock TH2004r tranny is quite capable but that the 7.5 rear end is a weak link.

For now the tranny and rear end are part of the 2nd and 3rd phase of the project. I'm wanting to plan and build the motor in phase 1 of the project.

So here I am...

I've read the Chevy High Performance Magizine articles a series of 8 of them that outlined a plan to put together this otherwise anemic motor which they baselined @ 240 hp and through a series of trials of various cams, intakes, heads, and headers/exhausts they were capable of increasing the numbers to 400+bhp and a torque reading of something like 415 ft-lb. I thought that was pretty good but wasn't sure if those numbers were enough to get my 86 Monte SS down the track in less than 12 seconds or not.

Anybody have any personal knowledge as to which head/cam/intake set up can produce as good or better numbers than listed here and still keep the motor fairly streetable with good low-midrange power capabilities. With the stock internals I don't imagine I'm going to want to spin it much over 6200-6500 rpm I wouldn't think. Maybe those rpms are too high. I admit. I'm fairly new to the GM side of things and really have only a basic limited knowledge of it all.


What do you guys think so far as a good head/cam/intake/carb setup. to get the most power yet still be streetable with the GM Goodwrench bottom end?


Roach

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Old 08-09-2010, 06:16 AM
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Unless you're gonna upgrade the pistons, I wouldn't plan on turning it over 5500 rpm very often. A set of true flat top hypereutectics would be a good inexpensive way to go. Guessing at about 3600 lbs, and about 350 rwhp, (400~425 flywheel hp), puts you at 12.60s. A motor like that would be able to easily take a 100 shot of nitrous, which would take you solidly into the 11s. Even 350 flywheel hp will probably grenade the stock rear, so you might want to concentrate on that first.
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Old 08-09-2010, 08:06 AM
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The only way to get all what you want is to supercharge it.
Its the cheapest route to that required power level. (11 sec et`s)

Fully max effort port the crate motor heads.
Weiand 177cid supercharger 2.33:1 pulley drive ratio.
(7`bottom 3`top)

Lunati 401A3LUN cam lunati 73943 springs.
750-850 holley carb.
long tube headers
3500 stall converter 4.10 gears.
The th2004r and 7.5 rear are fine with upgrades.
Use an Auburn posi and Moser axles.
lower control arm relocation brackets and air lift air bags + 9x27 et streets
for traction.

Use 110 octane race gas when using the high boost for 11 sec et`s
in your Monte Carlo
Reduce the boost (pulley ratio) for street use on pump gas. (6`bottom 3top pulley for street)`
Detonation must be avoided to let this motor live.
It will if and only if you get your head around that.
That means 110 octane for high boost at the track.

Last edited by F-BIRD'88; 08-09-2010 at 08:14 AM.
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Old 08-09-2010, 09:21 AM
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I'd shoot for 12s, it seems a lot simpler and more streetable for cruise night and such, but still packing quite a punch!

Regardless I'd grenade the weak stock rearend for the fun of it before upgrading. I don't think they're worth anything, and they're worth the same to the scrap metal guys working or grenaded. Just post pics. Gotta love duability testing bad factory parts.
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Old 08-09-2010, 09:59 AM
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i would not say that the 2004R is capable of handling 450+tq with out upgrading it, same with the 7.5 rear, but to be honest i dont know if i would spend the money on the 7.5 rear to upgrade it because it will still be the weakest link. i agree with some of the others that a mid 12 would be a little more realistic with that short block as i wouldn't want to turn it past 5500-5700 and i'm not sure that i would put any kind of forced induction on this motor without completly rebuilding it, these motors are notorious for inferior quality
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Old 08-09-2010, 11:26 AM
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Quote:
Originally Posted by roach4047
I came across a good deal on a GM Goodwrench 350 motor. It was totally free so I can't possibly complain about the price. I'd like to utilize as much as it's freeness as possible and at the same time attempt to transform it into a motor that is capable of a high 11 second pass in an 86 Monte Carlo SS. I hear that the stock TH2004r tranny is quite capable but that the 7.5 rear end is a weak link.

For now the tranny and rear end are part of the 2nd and 3rd phase of the project. I'm wanting to plan and build the motor in phase 1 of the project.

So here I am...

I've read the Chevy High Performance Magizine articles a series of 8 of them that outlined a plan to put together this otherwise anemic motor which they baselined @ 240 hp and through a series of trials of various cams, intakes, heads, and headers/exhausts they were capable of increasing the numbers to 400+bhp and a torque reading of something like 415 ft-lb. I thought that was pretty good but wasn't sure if those numbers were enough to get my 86 Monte SS down the track in less than 12 seconds or not.

Anybody have any personal knowledge as to which head/cam/intake set up can produce as good or better numbers than listed here and still keep the motor fairly streetable with good low-midrange power capabilities. With the stock internals I don't imagine I'm going to want to spin it much over 6200-6500 rpm I wouldn't think. Maybe those rpms are too high. I admit. I'm fairly new to the GM side of things and really have only a basic limited knowledge of it all.


What do you guys think so far as a good head/cam/intake/carb setup. to get the most power yet still be streetable with the GM Goodwrench bottom end?


Roach

The CHP article is a very good series of what can be done with the Goodwrench engine without going into the rotating assembly. One has to remember that as the power level and RPMs go up, component life expectancy goes down, pretty much geometrically. Which is to say using the original crank, rods, and pistons that when you double the power output and RPM the life of parts goes down to the square root of the original designed life expectancy.

Where the average rodder has an apparent gain on that is that often doubling the power doesn't require doubling the RPM. So you don't feel the full impact of the equation. However, the life of the parts goes down rather remarkably and sometimes suddenly.

That said, you can take a Goodwrench bottom end to 6 thousand plus a little, but the this stuff, especially the rods and pistons are working right on their design limit.

The CHP article never does optimize the power result as they never address the bottom end. This goes not only for the rotating dynamics but also combustion characteristics. When you get up into the 6 thousand RPM range you should really start thinking better rods and pistons. The latter, pistons, also gets into better combustion and detonation resistance. While CHP used the Vortec head which has a lot of bang for the buck in the performance it delivers, they never replaced the circular dish factory piston. These leave a lot to be desired in power output as they as a result of their design cannot optimize squish and quench which probably leaves another 30-40 horsepower on the table. Replacing these pistons with a D dish type so the far side of the chamber has a much closer closing between the piston crown surface and the head's step. this feature lets you push the compression higher without having to up octane of the fuel, which if you're already at 91-93 octane there is no solution save track racing fuel available. So optimizing the squish quench will let you get away with more compression which offers several other opportunities of which are simply use the higher compression, or give up some of it to hold a higher dynamic ratio against a longer duration cam.

My street building experience shows that doing the piston change on the Goodwrench block will dyno at 400 hp with as little as the Comp 262 cam. This cam can be used to hold up the bottom end torque which works better to launch a heavy car with high gears as is rather typical of a heated up daily commuter car where you don't want a cam that drives you to a high stall converter and don't want so much noise from a high winding motor that you can't hear the stereo.

As for getting the Monte into the 12 second bracket that's going to take more along the lines of 500 horse, stiffer gears, and some weight redistribution and reduction. My S-15 when the 350 was young could get under 13 with a similar engine as I describe, a modified 4L60E and 3.08 gears. But the truck weighs under 2800 pounds, has some serious weight redistribution and lots of suspension work.

The 200R4 tranny is not up to 400 horse without a lot of very expensive specialty parts. The way a V8 loads the tranny with lots of torque suddenly is very different from the way a turbo V6 does. So V8 conversions on stock 200R4s eat up them pretty quickly. The 7.5 is a weak link for sure, it can be crutched with putting in a posi, using a girdle in place of the sheet metal cover and running something like Lucas Shock Proof diff oil in there. But the 7.5 will always be on the edge. There isn't a cheap solution to this. The rear ends the Buick Grand National Turbo and the 442 Olds will bolt in, there isn't anything bigger that just bolts in. Rear ends are getting to be an expensive problem as most of the good 8.2s and 8.5s are gone from the wrecking yards.

Bogie
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Old 08-09-2010, 02:36 PM
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Thanks for all the reply's. You guys really know your stuff. It seems like the more questions I get answers to the more questions I then come up with due to not having considered certain things. A number of you have answered questions already that I didn't even know I had just yet....hahaha .

My mind is pulled in a number of different directions so far as how to go about building up this motor. My latest thoughts are should I build it or should I sell it off and then use that money to help pay for a good stroker kit???


How much money do you guys think I could reasonably expect to get from selling the crate motor on Craigs list or Ebay?

If I did sell the crate motor then which foundation/block should I then consider to achieve my goals of building an 11 second motor?


Anybody know of a source that sells GM parts @ 10% over costs+ shipping or better? I've got the hook up when it comes to Ford parts but not on GM stuff.

Should I decide to go the route of a stroker motor I would like to assemble it myself to help save on costs. Which stroker kit can I use for my goals and still remain a fairly economical budget?

Ideas?

Roach
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Old 08-09-2010, 04:11 PM
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If you want to sell it off, then build a 454 based BBC to go 11's in this car..
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Old 08-09-2010, 09:44 PM
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How much would it likely sell for??


Roach
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Old 08-09-2010, 10:08 PM
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Scoggin Dickey sells new for $1500 bucks. I would guess you can get around $800 bucks IF you have the receipt from whoever got it to prove it's what you say it is. Less if you don't have. You can get whatever somebody is willing to pay for it.
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Old 08-09-2010, 11:54 PM
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After some more thought. I've been wondering what would be an ideal stroker motor utilizing this particular block?

383? or something else?

Roach
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Old 08-10-2010, 02:33 AM
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Quote:
Originally Posted by my87Z
i would not say that the 2004R is capable of handling 450+tq with out upgrading it, same with the 7.5 rear, but to be honest i dont know if i would spend the money on the 7.5 rear to upgrade it because it will still be the weakest link. i agree with some of the others that a mid 12 would be a little more realistic with that short block as i wouldn't want to turn it past 5500-5700 and i'm not sure that i would put any kind of forced induction on this motor without completly rebuilding it, these motors are notorious for inferior quality
These engines are built in Mexico. These do have some quality issues just because they are built so cheaply. I just have a newer 1 piece rear main seal block that I got for free as well. I'm completely rebuilding mine from the bottom up but using the stock crank/rod with 2 bolt mains. I've also bored the block .060" over. You can build an 11-12 sec. motor MANY ways. Just do some research and learn the numbers. Even if you build a motor with some help and guidance and don't bother caring why or how it's making the power, the motor/car will never last. I say this because if you want to be drag racing this car, that is a lot of abuse. The car and engine will need a lot of maintenance and continual tuning. You really need to know your stuff to keep it functional even after it's built. Do some good research of some of the information you have received and read and figure out the how and why. You will be so much better off. I don't want this to be taken the wrong way. Just giving you the harsh reality of this kind of hobby.
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Old 08-10-2010, 09:48 AM
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Originally Posted by oldbogie
The 7.5 is a weak link for sure, it can be crutched with putting in a posi, using a girdle in place of the sheet metal cover and running something like Lucas Shock Proof diff oil in there. But the 7.5 will always be on the edge. There isn't a cheap solution to this. The rear ends the Buick Grand National Turbo and the 442 Olds will bolt in, there isn't anything bigger that just bolts in. Rear ends are getting to be an expensive problem as most of the good 8.2s and 8.5s are gone from the wrecking yards.
For a while the hot ticket for them was to get a take out Torsen posi from SLP (they used to sell them for $89), gears, stud kit, solid pinion spacer and a reenforcing cover, which worked OK on the street but regular, hard launches at the track would still break them.

Most of the good axles of any type are gone from the JY at this point, and if you're going to go the jy route the best bet is to grab something from a full size truck and shorten it (occasionally you'll still find a good ford 8.8 also), but between that and the fact that aftermarket axles haven't gotten that much more expensive (they seem to be going up in price less than inflation), it's almost a no brainer that if you're going to seriously beat on a car just go aftermarket.

WRT to the goodwrench 350... depending on the year that it was made and what it was intended to be a replacement for what you have might be significantly different. For the most part they got larger chamber heads and compressions in the 8.5-8.9:1 range, most got decent bottom ends, at least as durable as the 350 bottom end used in the trucks at that time were, usually a little better. I don't know why you would limit it to 5500, over the years I've seen a few of them regularly spun up to 6500 or so without any issues, and in general, depending on what you're starting with either boost it or drop some smaller chamber heads on it bumping compression a point or so, and run a bigger cam, headers, intake...
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Old 08-10-2010, 01:07 PM
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The reason I say 5500 is cast pistons, in a 350, they will only go to 6500, or above, just so many times, before the stress gets to them. They were designed with a 5500 rpm redline from the factory, and it's pretty safe to go there with them pretty regularly in a healthy motor. Sure some will go much higher, but not for long.
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Old 08-10-2010, 01:37 PM
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Quote:
Originally Posted by roach4047
After some more thought. I've been wondering what would be an ideal stroker motor utilizing this particular block?

383? or something else?

Roach
Yes, you could build a 383, but in my opinion it's not necessary. A well-built 350 could definitely turn out an 11 second 1/4 mile. It will need to be able to turn at high rpms though. You'll need a steel crank, steel rods, forged aluminum or hypereutectic pistons, high flowing aluminum heads with small chambers, and a fuller roller valve train to start. You should also consider using nitrous and/or forced induction to really bump up power output. If you go the forced induction rout you will steel need forged crank and rods also.
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