Rebuilding the 350 finally

[silverscottsk10]

Looking at rebuild kits from summit, I'm reusing my heads, crank, and block, the heads are stock, the block is standard bore,
Looking for a little better cam, with a little more grunt
More or less looking for two main kits to rebuild the 350
Around 600$ total
Also will be needing new harmonic balancer, and will be looking at arp hardware
Anything I'm missing?



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[Jarhead79]

Check out these guys
http://www.northernautoparts.com/

 

[silverscottsk10]

I'm stoopid
I can rebuild engines and combines but I've got no clue between forged and hypereutectic pistons
I'm looking at the bottom kit

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[HotRodPC]

Looking at rebuild kits from summit, I'm reusing my heads, crank, and block, the heads are stock, the block is standard bore,
Looking for a little better cam, with a little more grunt
More or less looking for two main kits to rebuild the 350
Around 600$ total
Also will be needing new harmonic balancer, and will be looking at arp hardware
Anything I'm missing?



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You still got some splaining to do as far as intent. Are just re ringing or boring? Have you had the block mic'ed yet? Are you going to do that before you decide? If replacing pistons, you going with dish or flat tops?

Using the same rods?

Same crank? Going to have it turned? Mic'ed? Maybe just a polish?


Lots of unknown here as what advice or suggestions to give.

 

[silverscottsk10]

Stock as possible, honing block, std bore as far as cast # goes, re-ring if possible, stock heads so unsure of pistons, autosupply has cranks included so possibly going that route


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[HotRodPC]

So then you should be able to get off pretty cheap. If you're not boring the block, no need to buy pistons. Pistons nornally don't wear, the rings do.

Is there any reason to magnaflux the block? Or hot tank it? Are you having the cam bearings replaced too? Any rods knocking currently?

Maybe you can get by with just a re ring and valve job. New timing gears, oil pump and gaskets. Pick a RV grind cam and lifters from Summit and call it good.

I'd try to find someone who knows a little about mic'ing the bores and crank journals though. Also keep in mind, re ring jobs don't last as long as a full reman but last plenty of time. The current condition of the bores and crank journals will usually determine how long they last.

 

[silverscottsk10]

So then you should be able to get off pretty cheap. If you're not boring the block, no need to buy pistons. Pistons nornally don't wear, the rings do.

Is there any reason to magnaflux the block? Or hot tank it? Are you having the cam bearings replaced too? Any rods knocking currently?

Maybe you can get by with just a re ring and valve job. New timing gears, oil pump and gaskets. Pick a RV grind cam and lifters from Summit and call it good.

I'd try to find someone who knows a little about mic'ing the bores and crank journals though. Also keep in mind, re ring jobs don't last as long as a full reman but last plenty of time. The current condition of the bores and crank journals will usually determine how long they last.

I know about mic'ing, I just don't have any bore gauges or mics
It's a fairly new block
I just don't know how it was ran before I got it
And then I ran it pretty hard
Just never built my own engine from scratch, I've built them, but were never performance, I can't find one of the engine building books around at any of my auto stores
Lift and duration has to do with cam lobe and lobe length iirc


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[HotRodPC]

You're not really building a performance engine are you? Basically just an overstock cam? You're not going to crazy with the cam I'd hope. I figured you're looking for an RV type grind? If it's a newer block then it may just need a re ring and bearing with a valve job. But that all depends on what you mean by newer block. How about wear? How hard someone drove it doesn't matter near as much as how well was it maintained. Driving them hard doesn't bother me a bit. Not changing oil or letting them overheat does bother me.

Just got Amazon.com and order a book. I've seen one as low as $7.

 

[silverscottsk10]

You're not really building a performance engine are you? Basically just an overstock cam? You're not going to crazy with the cam I'd hope. I figured you're looking for an RV type grind? If it's a newer block then it may just need a re ring and bearing with a valve job. But that all depends on what you mean by newer block. How about wear? How hard someone drove it doesn't matter near as much as how well was it maintained. Driving them hard doesn't bother me a bit. Not changing oil or letting them overheat does bother me.

Just got Amazon.com and order a book. I've seen one as low as $7.

Not reallyhigh performance but it needs more torque with the 3.42 gears, it's days of long trips are over, and again there's no info on the engine prior to when I got it, I changed it every 3k with filter and did run hot once when fan belt broke
If you was going to build a slightly more than stock engine what valve springs and cam would you run?
I'm not against getting a bigger torque converter but I'd like to keep mine since it's stock but brand new


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[rich weyand]

A note on cams I have posted in the past to queries like this.

================

A word on cams for you.

12-230-2 will work fine. With dual-plane and long-tube headers, 290hp/420lbft. Lift is .432/.444. RPM range is 600-4600.

12-235-2 will wind a bit tighter. With dual-plane and long-tube headers, 290hp/415lbft. Lift is .421/.451. RPM range is 1000-5200.

12-300-4 is what I am running. With dual-plane and long-tube headers, 275hp/420lbft. Lift is .390/.390. RPM range is 600-4600.

So all of these are in the same ball park. 12-230-2 has the same hp and torque as the 12-235-2, but will run out of pull at 4600 rpm. 12-235-2 will match that, and pull to 5200, which is a better fit with stock shift points. 12-300-4 gives up some hp on top, matches the torque in the bottom, but keeps the stock .390/.390 lift, which is easier on the valve train (and cam lobes). That's why I picked the 12-300-4, for engine lifetime sake, since they are so similar in performance.

All three cams will work with stock lifters and springs. Note: NEW stock lifters and springs.

For the 12-230-2 and 12-300-4, you should replace one weight in the TH350 governor with the next bigger weight to bring the stock shift points down 500 RPM. The stock fly-weights in the governor on CKs is .0625 thick, 14 grams. Replace just one of them with a .080 thick, 16 grams. Use the stock springs. If it's a stick, then you will time the shifts yourself, so no worries.

The stock cam is an old cam design. In an ideal world, valves would be open or shut, with no in-between. That would maximize flow while giving you an earlier intake closing for more dynamic compression and a later exhaust opening for longer pressure on the exhaust stroke. Unfortunately, we can't do that -- cams are ramped. You can tell how long the ramps are by subtracting the .050 duration from the advertised duration.

The stock cam has ramps in the mid- 70-degree range. All three Comp Cams have modern computer-aided designs with ramps in the mid- 40-degree range. That's 30 degrees less dead space in both the intake and exhaust cycles. The difference that makes in the ability to tune the other cam parameters cannot be overstated.

I think you will be very happy with whichever of those three cams you pick. Not a bad choice among them, really.

=====================

A note about lope. Everybody thinks they want it, but what it means is that the engine doesn't want to run at 700 rpm. So how much torque do you think you're going to get at 1000, or 1500? An engine that's going to generate torque at low rpm is going to LIKE running at low rpm, so it will idle really smooth.

The way they get launches at the drag strips out of engines with a lot of lope is to run high-rpm lockup torque converters so they can wind the engine up to where the hp is. High-rpm torque converters are great for the drags, but a PITA to drive around on the street, and they're hard on transmissions.

 

[silverscottsk10]

A note on cams I have posted in the past to queries like this.

================

A word on cams for you.

12-230-2 will work fine. With dual-plane and long-tube headers, 290hp/420lbft. Lift is .432/.444. RPM range is 600-4600.

12-235-2 will wind a bit tighter. With dual-plane and long-tube headers, 290hp/415lbft. Lift is .421/.451. RPM range is 1000-5200.

12-300-4 is what I am running. With dual-plane and long-tube headers, 275hp/420lbft. Lift is .390/.390. RPM range is 600-4600.

So all of these are in the same ball park. 12-230-2 has the same hp and torque as the 12-235-2, but will run out of pull at 4600 rpm. 12-235-2 will match that, and pull to 5200, which is a better fit with stock shift points. 12-300-4 gives up some hp on top, matches the torque in the bottom, but keeps the stock .390/.390 lift, which is easier on the valve train (and cam lobes). That's why I picked the 12-300-4, for engine lifetime sake, since they are so similar in performance.

All three cams will work with stock lifters and springs. Note: NEW stock lifters and springs.

For the 12-230-2 and 12-300-4, you should replace one weight in the TH350 governor with the next bigger weight to bring the stock shift points down 500 RPM. The stock fly-weights in the governor on CKs is .0625 thick, 14 grams. Replace just one of them with a .080 thick, 16 grams. Use the stock springs. If it's a stick, then you will time the shifts yourself, so no worries.

The stock cam is an old cam design. In an ideal world, valves would be open or shut, with no in-between. That would maximize flow while giving you an earlier intake closing for more dynamic compression and a later exhaust opening for longer pressure on the exhaust stroke. Unfortunately, we can't do that -- cams are ramped. You can tell how long the ramps are by subtracting the .050 duration from the advertised duration.

The stock cam has ramps in the mid- 70-degree range. All three Comp Cams have modern computer-aided designs with ramps in the mid- 40-degree range. That's 30 degrees less dead space in both the intake and exhaust cycles. The difference that makes in the ability to tune the other cam parameters cannot be overstated.

I think you will be very happy with whichever of those three cams you pick. Not a bad choice among them, really.

=====================

A note about lope. Everybody thinks they want it, but what it means is that the engine doesn't want to run at 700 rpm. So how much torque do you think you're going to get at 1000, or 1500? An engine that's going to generate torque at low rpm is going to LIKE running at low rpm, so it will idle really smooth.

The way they get launches at the drag strips out of engines with a lot of lope is to run high-rpm lockup torque converters so they can wind the engine up to where the hp is. High-rpm torque converters are great for the drags, but a PITA to drive around on the street, and they're hard on transmissions.

I've read about the 12-300-4, comp cam is the producer correct? but while it is apart I'd like a little bigger lift, nothing thumpy but something that you can just barely hear, also I'm running a th400 if that makes a difference. Never been in one but my guess is it's a heavier version of the 350


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[rich weyand]

Comp Cams produces all three of the above.

Usually when someone says bigger for a cam, they mean duration, not lift. That will make the idle rougher. Next step up in duration from the 12-235-2 is the 12-339-3. From the 12-230-2, you could go up to the 12-234-2 or the 12-238-2. Above that and you will need to go to a higher-rpm lock on the torque converter not to bog from a stop.

My understanding is that the TH400 is basically a HD TH350. Higher transmitted torque limit. The most torque the General ever bolted up to the TH350 was 410 lbft.

 

[silverscottsk10]

Comp Cams produces all three of the above.

Usually when someone says bigger for a cam, they mean duration, not lift. That will make the idle rougher. Next step up in duration from the 12-235-2 is the 12-339-3. From the 12-230-2, you could go up to the 12-234-2 or the 12-238-2. Above that and you will need to go to a higher-rpm lock on the torque converter not to bog from a stop.

My understanding is that the TH400 is basically a HD TH350. Higher transmitted torque limit. The most torque the General ever bolted up to the TH350 was 410 lbft.

I'm not against running a bigger stall at all, but if I could get around it I was gonna try lol
And "general"?
Say I'm wanting 320-350hp
What would your build consist of?
I don't have the cash to replace heads but seeing as they are fairly new along with the block I'd at least like 300hp
I figure having heads polished and a better compression ratio would be a start


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[rich weyand]

Horsepower is the wrong metric. You race horsepower, you drive torque.

Horsepower is the correct target for racing, because you are going to keep the engine RPM up in the 5000 rpm area, in the middle of the fat part of the horsepower, for the whole race. When you drive, you spend 99+% of the time in the 1000-3000 rpm range. The peak of the horsepower curve at 5000 rpm doesn't matter, the torque from 1000-3000 does.

Back in the before times, when I got my driver's license, the LS-6 Chevelle and Hemi Cuda were the big machines. They were both de-rated on the spec sheets to keep insurance rates down. The LS-6 in particular made over 500 horsepower. In contrast, the Buick GSX only had 360 hp, but it had 510 lbft of torque. The guys with the LS-6 and the Hemi Cuda left him alone, because he would blow their doors off in the 1/8 mile. That car was insane. 1/4-mile they would win, when they could keep their rpms up in the range longer, but on the street, that thing had the hole shot from hell.

OK, that said, here's a chart, in order of more horsepower and less torque and higher lift and longer duration and rattier idle and higher rpm before the engine comes into the torque curve.

Assume dual-plane manifold and headers, stock everything else. Note 12-239-3, not 12-339-3 (typo, sorry). HP is at 4500, torque is at 2500 for all. These are all torquer cams. You can get more horsepower, but it'll be a windup toy and have the hole shot of a three-speed bicycle unless you put like a 2500 rpm stall torque converter on it, which is hard on transmissions. Higher lift numbers are harder on the valvetrain, and will generally involve other-than-stock springs. The last four require at least a bit higher rpm than stock torque converter.
12-300-4 275hp 420lbft Lift is .390/.390 RPM range is 600-4600
12-230-2 290hp 420lbft Lift is .432/.444 RPM range is 600-4600
12-235-2 290hp 415lbft Lift is .421/.451 RPM range is 1000-5200
12-234-2 303hp 415lbft Lift is .447/.454 RPM range is 1000-5200
12-238-2 307hp 406lbft Lift is .462/.469 RPM range is 1300-5600
12-239-3 307hp 406lbft Lift is .462/.480 RPM range is 1300-5600
12-242-2 316hp 396lbft Lift is .477/.480 RPM range is 1600-5800
12-246-3 325hp(@5000) 385lbft Lift is .490/.490 RPM range is 1800-6000

BTW, I went for the first one on the list. Couldn't be happier.

 

[silverscottsk10]

Horsepower is the wrong metric. You race horsepower, you drive torque.

Horsepower is the correct target for racing, because you are going to keep the engine RPM up in the 5000 rpm area, in the middle of the fat part of the horsepower, for the whole race. When you drive, you spend 99+% of the time in the 1000-3000 rpm range. The peak of the horsepower curve at 5000 rpm doesn't matter, the torque from 1000-3000 does.

Back in the before times, when I got my driver's license, the LS-6 Chevelle and Hemi Cuda were the big machines. They were both de-rated on the spec sheets to keep insurance rates down. The LS-6 in particular made over 500 horsepower. In contrast, the Buick GSX only had 360 hp, but it had 510 lbft of torque. The guys with the LS-6 and the Hemi Cuda left him alone, because he would blow their doors off in the 1/8 mile. That car was insane. 1/4-mile they would win, when they could keep their rpms up in the range longer, but on the street, that thing had the hole shot from hell.

OK, that said, here's a chart, in order of more horsepower and less torque and higher lift and longer duration and rattier idle and higher rpm before the engine comes into the torque curve.

Assume dual-plane manifold and headers, stock everything else. Note 12-239-3, not 12-339-3 (typo, sorry). HP is at 4500, torque is at 2500 for all. These are all torquer cams. You can get more horsepower, but it'll be a windup toy and have the hole shot of a three-speed bicycle unless you put like a 2500 rpm stall torque converter on it, which is hard on transmissions. Higher lift numbers are harder on the valvetrain, and will generally involve other-than-stock springs. The last four require at least a bit higher rpm than stock torque converter.
12-300-4 275hp 420lbft Lift is .390/.390 RPM range is 600-4600
12-230-2 290hp 420lbft Lift is .432/.444 RPM range is 600-4600
12-235-2 290hp 415lbft Lift is .421/.451 RPM range is 1000-5200
12-234-2 303hp 415lbft Lift is .447/.454 RPM range is 1000-5200
12-238-2 307hp 406lbft Lift is .462/.469 RPM range is 1300-5600
12-239-3 307hp 406lbft Lift is .462/.480 RPM range is 1300-5600
12-242-2 316hp 396lbft Lift is .477/.480 RPM range is 1600-5800
12-246-3 325hp(@5000) 385lbft Lift is .490/.490 RPM range is 1800-6000

BTW, I went for the first one on the list. Couldn't be happier.

Thank you, I've never had any of this explained before in a way I could grasp it,
Now say I want 500ftlb of torque, I would need to bore the engine or stroke to have more displacement to run a better cam to get that number correct?
This won't be my daily driver, that said it will be driven when it's being driven, I tend to have a heavy foot, with a budget of 1000$ what would you say is the best "bang for buck"


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