In search of Torque.. lots of it

[sreidmx]

I am going to build a 400 for the wifes truck 92 k2500.. it has lazy gears(3.73 33 inch tire) so I am not delusional in what the engine sees for rpm.. figure towing 3rd at 55 its 2300-2600 depending on if the converters locked or not, and when the truck is in OD its cruising 2k around 70-80 so I need something that pulls low..and max will see maybee 4800 or 5k if I tweak the chip to allow it..

So.. my proposed combo is something like this.

400 .030 over
stock rods and crank with arp rod bolts
comp XE256H (per their recommendation)
Vortec heads
Edelbrock tbi vortec intake
some sort of roller rocker
9:5-1 or as close as I can get.
long tubes or try y headers.. It has shortys right now..

the only thing I am hem hawing about is the heads and intake. I can get dart iron eagles for $995 and they are thicker casting (better for heat) and have a better I/E ratio than any vortec head so the power is going to be better. I dont know what a set of vortec heads costs new with the intake.. I have to imaging 6-800?? plus the 300$ intake.. so I figure a swapmeet standard chevy intake and those darts it will be all the same pricewise..

Any opinions? suggestions?

 

[dyeager535]

I would stay away from the Vortecs if you can. It's not that they are bad heads (ok, they have pretty weak springs, pressed in studs, thin castings, and only clear about .45" lift, lol) but there is enough aftermarket stuff out there that unless you can get some Vortecs for a song, I think the aftermarket is the smart bet.

Someone has aluminum heads out now that are in the $800/pair range, and I *don't* think they are chinese pieces. I can't find anything in a quick search, but summit probably lists them, the ability to narrow down your search there is pretty darn good. Even if you had to get a carbed intake and TBI adapter for it, you'd probably be money ahead.

Oh, forgot, the Vortecs require self guiding rockers, so those are specific to the heads too. Roller rockers are cool and all, but in terms of necessity I'd say, meh. If you can afford them and want them, do it. If short on money, power "saved" by running them is inconsequential.

I'm running Hedman 62230's, these are the ones that seem to fit every one of these trucks out there. they are definitely not a full "long tube" like the 69830's that I replaced, however any before/after difference in felt power was not there. That was swapping over to single exhaust from dual at the same time as well.

Edit: These http://www.summitracing.com/parts/pmx-2171/overview/make/chevrolet or the blueprint engine ones are probably what I was thinking of. I'd certainly want to do some research and find external reviews on them, find out what components they are assembled with, where, etc.

 

[bigblock72]

I am going to build a 400 for the wifes truck 92 k2500.. it has lazy gears(3.73 33 inch tire) so I am not delusional in what the engine sees for rpm.. figure towing 3rd at 55 its 2300-2600 depending on if the converters locked or not, and when the truck is in OD its cruising 2k around 70-80 so I need something that pulls low..and max will see maybee 4800 or 5k if I tweak the chip to allow it..

So.. my proposed combo is something like this.

400 .030 over
stock rods and crank with arp rod bolts
comp XE256H (per their recommendation)
Vortec heads
Edelbrock tbi vortec intake
some sort of roller rocker
9:5-1 or as close as I can get.
long tubes or try y headers.. It has shortys right now..

the only thing I am hem hawing about is the heads and intake. I can get dart iron eagles for $995 and they are thicker casting (better for heat) and have a better I/E ratio than any vortec head so the power is going to be better. I dont know what a set of vortec heads costs new with the intake.. I have to imaging 6-800?? plus the 300$ intake.. so I figure a swapmeet standard chevy intake and those darts it will be all the same pricewise..

Any opinions? suggestions?

The 400 is a great option for making torque especially with some good cylinder heads. They have been my go to motor for 20 plus years and have served me well.

The Vortec heads work well as do the Iron Eagles, either is a good choice for this application.

If you don't need EGR then skip the TBI style intakes as they all suck. Better to make an adapter to a regular Permormer RPM intake. Don't worry fuel distribution isn't an issue if you build it right.

I would step up the cam a little for best results. I like the Summit 1102 for sub 9:1 motors and the 1103 for above 9:1 motors, the extra duration is needed to help keep the cylinder pressure in check so it doesn't ping and knock the rod bearings out. Most of the rpm guidelines on camshafts are for a 350 or smaller engine, subtract about 500 rpm for a 400. The larger displacement tames the idle a lot as well.

Long tube headers with at least 1 5/8" tubes will help a lot. Run 2 1/2" pipe and dual high flow cats into single large body magnaflow muffler (flowmaster will require 2 mufflers) and a single 3 or 3 1/2 tailpipe.

You will need to bump up the fuel pressure to the 350 injectors to about 22-24 psi (it works well regardless of what the internet know it alls say) and redo the PROM to get it to run right. Make sure you get a bored throttle body from E-bay as the stock throttle body is a huge restriction on a 400.

 

[sreidmx]

Most excellent responses! Thanks guys!
I have been talking to @folkenheath about this at length as well, I called Dart and Comp as well for options..
This is the revised combo
406
Dart 180 Iron Eagles 2.02/1.60
Dart recommended at least a .480 lift cam
stock crank and 5.7 inch rods most likely.

 

[bigblock72]

There is no need to put 5.700 rods in a mild use 400 like yours, save the money and hassle and run stock rods with ARP bolts.

Run stock replacement type pistons like H616cp30 with a 12.5 cc dish, 76 cc heads, .038" thick head gaskets and .015" deck height will give you 9.3:1 compression which I would consider max on an iron headed truck motor with 91 octane. A good cooling system will be a must with this combination to keep it out of detonation.

Keep the cam intake duration around 210 degrees @ .050, lobe center about 112 and the lift around .490" for the broadest and most usable torque.

 

[sreidmx]

Just outa curiosity why .050 quench?? I seriously do not get this?? Imho it needs to be tighter to fight detonation...

 

[dyeager535]

Just outa curiosity why .050 quench?? I seriously do not get this?? Imho it needs to be tighter to fight detonation...

I wondered as well, but I suspect that has to do with pushing the compression up. With dished pistons quench is pretty much out the window anyway, but if you already run ~9:1 with dished pistons and 76CC heads, probably not many ways around it.

You typically want flat top pistons, both dome and dish are hindrances to good flame propagation depending on head (when it comes to fast burn/Vortecs it is) and quench helps cool the charge, however adding 12.5CC to the chamber doesn't seem possible, largest I see on summit is 80CC.

But I'm listening!

 

[bigblock72]

Just outa curiosity why .050 quench?? I seriously do not get this?? Imho it needs to be tighter to fight detonation...

You could deck the block some more, .015" is generally where they come in at after the block has been decked and works out just fine. .040" is ideal but in the real world there is no real gain by losing .013" in this combination. Also keep in mind that dished pistons kill a lot of the quench. In fact I'd worry more about the compression ratio than splitting hairs on quench, on this combination you'll have to rely on a more modern combustion chamber design to speed up combustion for detonation prevention. Fortunately the TBI system is good enough that it will help keep everything happy as well, assuming it's tuned correctly. Keep in mind this engine is going to work hard pullling a lot of weight so excessive cylinder pressure is your enemy, especially with crappy 91 octane fuel. I've seen lots of guys build motors with over 9:1 but had perfect quench with a short duration cam for their pull rigs, tune the fuel injection for maximum power and go and rattle the pistons and rod bearings out of it in under 10k miles. Unfortunately you have to make some compromises to make it all work, but it will work well, it will have better most big blocks torque and fuel milage to boot.

You typically want flat top pistons, both dome and dish are hindrances to good flame propagation depending on head (when it comes to fast burn/Vortecs it is) however adding 12.5CC to the chamber doesn't seem possible, largest I see on summit is 80CC.

Again it's more about keeping the compression ratio where it needs to be than extracting every last bit of power. Going to a D shaped dish could be a good compromise for better quench and combustion efficiency, I'm not sure what cup sizes they come in and they are generally double or triple the cost of a regular dished piston.

 

[dyeager535]

And I would assume a partial dish piston would be pretty unlikely to have 12.5CC volume. ...would have to be pretty deep I'm thinking.

 

[sreidmx]

Thanks for the input, so as it sits I can get the head in a 72cc, the pistons Ill track down come in anywhere from 12.5 - 18cc it depends, I totally get the sentiment though regarding the compression ratio, that is actually the reason I was thinking 5.7 rod because it gives me a bit more wiggle room for piston choice, where the stock rod is limited to dome, flat top and dished, but not a lot as far as deeper dished pistons. Maybe I need to look at some other heads that are available in larger chamber size.. personally Id like to run a flat top for a little extra insurance against detonation and getting that thicker ring land.
I will also take a look at the D shaped dishes..

The other thought I had was just putting aluminum heads from jegs or summit.. I think that would help heat some but the engine guy mentioned the iron with a thicker deck added some well needed rigidity the aluminum heads and thinner iron didn't.

 

[bigblock72]

Thanks for the input, so as it sits I can get the head in a 72cc, the pistons Ill track down come in anywhere from 12.5 - 18cc it depends, I totally get the sentiment though regarding the compression ratio, that is actually the reason I was thinking 5.7 rod because it gives me a bit more wiggle room for piston choice, where the stock rod is limited to dome, flat top and dished, but not a lot as far as deeper dished pistons. Maybe I need to look at some other heads that are available in larger chamber size.. personally Id like to run a flat top for a little extra insurance against detonation and getting that thicker ring land.
I will also take a look at the D shaped dishes..

The other thought I had was just putting aluminum heads from jegs or summit.. I think that would help heat some but the engine guy mentioned the iron with a thicker deck added some well needed rigidity the aluminum heads and thinner iron didn't.

There isn't any ring land strength difference between a flat top and dished piston. Flat top pistons with 76cc heads puts the compression over 10:1. I don't know what your budget is for this engine build, so most of my recommendations are for stock type parts that will get you where you need to be. If you have extra money to go with 5.7 rods just make sure they are made for a 3.75 stroke to prevent any cam clearance issues. Frankly I'd rather see you go forged pistons on stock 400 rods than hyperuetectic pistons on 5.7 rods. Building engines gets real expensive in a big hurry so plan your build thoroughly.

Does your engine guy think you're building a nitrous or turbo motor? Cylinder head thickness is a non-issue at this power level, any quality head with a modern Vortec combustion chamber will do the job. If you can afford aluminum then use them, they will help with detonation.

 

[dyeager535]

So flat tops, 76CC heads will put you over 10:1. AL heads will take about a full point over iron heads in CR (and I'm sure that is based on other factors, I've heard that used as a general rule of thumb) so that would put the compression back into 87 octane range? I would assume good heads on a 400 would react the same as they do on the 350's...about 9.5:1 with vortecs and a good tune is possible on 87.

Perhaps the stars align at a ~10:1 ratio on AL heads that you can't do with irons? .040" quench, partial dished or flat tops, nothing real expensive?

 

[bigblock72]

So flat tops, 76CC heads will put you over 10:1. AL heads will take about a full point over iron heads in CR (and I'm sure that is based on other factors, I've heard that used as a general rule of thumb) so that would put the compression back into 87 octane range? I would assume good heads on a 400 would react the same as they do on the 350's...about 9.5:1 with vortecs and a good tune is possible on 87.

Perhaps the stars align at a ~10:1 ratio on AL heads that you can't do with irons? .040" quench, partial dished or flat tops, nothing real expensive?

The aluminum head rule of thumb seems to work in a car or lightly used truck application but is way optimistic in a heavily used, big-tired, high-geared, trailer towing application such as this. I would consider 9.5:1 the absolute max even with aluminum heads, and it will still need the right cam to keep it all in check. The reason being is the engine will be running at or near peak torque/peak cylinder pressure/peak cylinder temperature for much of it's life and will be on the verge of detonation for much of that time, there is only so much you can do with 91 octane especially with inconsistent 10-15% ethanol that a lot fuels have. When the truck is empty it should be okay on 87 octane. Always err on the conservative side to prevent broken pistons. Things only get worse on 100 plus degree days or when the crappy fuel starts leaving deposits on the pistons and combustion chambers. Ever wonder why the TBI 454s were less than 8:1? or the high GVW 350s only had 8:1? That's what you have to do to keep things alive when they're working at 100% for hour after hour. The newer stuff has the benefit of better combustion design and much better engine management that can tune each cylinder individually not to mention direct injection to deal with high compression and heavy loads.

I hate to sound like a broken record but I have had to fix a lot of the other guys ideas of what a tow rig's motor should be built like and it's not cheap nor fun, especially when a piston comes apart and destroys everything but one cylinder head. I have also had to try and tune high compression combinations to try and stop the nonstop pinging which only resulted in low power, glowing exhaust manifolds and overheating. Again it's no fun.

 

[sreidmx]

Oh trust me if I didn't know I am getting educated quick on the cost, I'm the type to build the issues out of it so there are no weak spots or at least they are reduced,
Let's backup a second here. For what I am doing I was thinking 9:1-9:5 is completely acceptable, the stock motor is 9:3-1. Still need to look around at other heads to see if there are larger chambers, worst case I'll give the heads to a friend to open the chamber up some, Or find the correct piston. As far as rods are concerned I'd prefer to avoid using a rod that requires the smaller base circle cam. And who knows maybe I need to look harder at piston choices for a stock length rod and forged piston combo.
At this point the budget is not set in stone, preferably the less I have to spend the better. I don't cut corners on this stuff it's not worth it in the long run.

 

[sreidmx]

The aluminum head rule of thumb seems to work in a car or lightly used truck application but is way optimistic in a heavily used, big-tired, high-geared, trailer towing application such as this. I would consider 9.5:1 the absolute max even with aluminum heads, and it will still need the right cam to keep it all in check. The reason being is the engine will be running at or near peak torque/peak cylinder pressure/peak cylinder temperature for much of it's life and will be on the verge of detonation for much of that time, there is only so much you can do with 91 octane especially with inconsistent 10-15% ethanol that a lot fuels have. When the truck is empty it should be okay on 87 octane. Always err on the conservative side to prevent broken pistons. Things only get worse on 100 plus degree days or when the crappy fuel starts leaving deposits on the pistons and combustion chambers. Ever wonder why the TBI 454s were less than 8:1? or the high GVW 350s only had 8:1? That's what you have to do to keep things alive when they're working at 100% for hour after hour. The newer stuff has the benefit of better combustion design and much better engine management that can tune each cylinder individually not to mention direct injection to deal with high compression and heavy loads.

I hate to sound like a broken record but I have had to fix a lot of the other guys ideas of what a tow rig's motor should be built like and it's not cheap nor fun, especially when a piston comes apart and destroys everything but one cylinder head. I have also had to try and tune high compression combinations to try and stop the nonstop pinging which only resulted in low power, glowing exhaust manifolds and overheating. Again it's no fun.

I agree on all fronts, you are right, but there is a huge variable here, the person driving the truck, this is my wife's rig, the most common thing this tows is a small two horse trailer. The max that could be with all her crap is 4-5k which it does no problem now.

And also this isn't my first rodeo building a motor for her tow truck either, the main issue I have here is the crappy gear and the ecu that doesn't like tight lsa's or any overlap. Both are ways to ditch some cylinder pressure.
We are very conservative when it comes to towing.. Never push the truck unless absolutely nessecary and good driving often defeats the need to do anything stupid.

Like I mentioned I probally will go to a megasquirt so I can run a wideband, egt and have better control of timing and fueling with much better resolution than the stock stuff..

 

[dyeager535]

Ever wonder why the TBI 454s were less than 8:1? or the high GVW 350s only had 8:1? That's what you have to do to keep things alive when they're working at 100% for hour after hour. The newer stuff has the benefit of better combustion design and much better engine management that can tune each cylinder individually not to mention direct injection

The L31's (Vortec 5.7 in trucks) were 9.4:1. The injection system was marginally better than TBI (that's being kind to the Vortec setups), no ability to tune specific cylinders. AFAIK there was no specific high GVW SBC at that point.

The L29's (Vortec 7400) were 8.75:1 apparently, Vortec chamber. L21's apparently used non-Vortec chambers and were also less compression. but I can find hardly anything on those.

Are either a good comparison to the 400? Piston diameter is just about in the middle of both, correct?

It seems to me that the Vortec chambers allowed GM fairly substantial increases in compression ratio, at least with the block architecture GM was using at those times.

If it can be done "cheaply", I don't see why one wouldn't go the safe route and keep compression on the low end. You really don't gain much from compression alone. That's really key, everything else is academic.

If one were to take all factors into account...quench, fueling, timing, cam, and cooling, I would expect that being a bit on the "high" side of compression is doable, especially if it's hard to get compression lower, easily/cheaply.

My 350 runs right around 9.4:1 with the Vortecs/87, and prior to getting timing and fueling right I was into the knock sensor nearly any time I was on the gas. Once I spent the time to get timing and fueling where the engine wanted it, there was no problem no matter the conditions I load it to. I'm certain however that if the temperature went over 220* or so and I was loaded down, I'd start to hear it. Of course when I put it together, I didn't know anything about quench.

I think a large issue is that many people don't take the entire vehicle as a system into account. The aftermarket certainly doesn't with their "computer friendly" BS. When considering heavy use at all times...something as simple as cooling efficiency can get you into trouble if the temp starts to climb and your cylinder temps are no longer where they need to be to prevent problems. And if you aren't going to spend the time to dial it all in, and make CERTAIN its good to go? I wouldn't chance it either. I can just imagine trying to pull a grade and having engine temp start to climb, and the only way to overcome the issue being to drive slower and slower.

 

[sreidmx]

I think I'm ditching this idea.. Seems like gearing it properly and swapping to an Ls is a wiser decision..

 

[dyeager535]

I think I'm ditching this idea.. Seems like gearing it properly and swapping to an Ls is a wiser decision..

The cost of building a "Gen1" motor properly is expensive enough that considering an LS instead often makes sense.

 

[sreidmx]

I agree. The other deal is I shouldn't try to bandaid it.. there are obviously issues with the way its setup now, so ill correct those before trying to "make" it better.

 

[Big Ray]

I'm going to put the 411 computer on my L31, only because I have a never run L31 I bought years ago...

Once it goes (if it does) it's LS all the way.