improving flow for the 3FE’s top end (1 Viewer)
- Thread starter RockDoc
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Keep it up RocDoc,
Can you explain more about the throttle body modification? Why did you choose to do it and what advantages you hope to gain?
Can you explain more about the throttle body modification? Why did you choose to do it and what advantages you hope to gain?
- Thread starter
- #143
Randy (Iaintscared1969) would be able to speak to it better, but...
Diameter has increased from 70mm to 74mm, which means a 12% bump in cross-sectional area (slightly bigger bump in functional area when you consider that area goes up as the square of the radius while the area hampered by the throttle plate and shaft go up linear with the increase in radius). This means greater flow/less restriction at full throttle, and should mean that flow ramps up quicker with rotation of the plate (which may lead to the snappier response I've heard mentioned with this upgrade).
The TB is something I've heard others mention from their 3FE upgrades (ones Randy has had a hand in, Overhanger's, Moby's, Pappy's done it on a 22RE, not sure about his 2FE) as helping when balanced with other upgrades for breathing such as a longer duration cam and head work. A bit of info here: https://forum.ih8mud.com/60-series-wagons/40908-big-bore-throttle-body.html
Diameter has increased from 70mm to 74mm, which means a 12% bump in cross-sectional area (slightly bigger bump in functional area when you consider that area goes up as the square of the radius while the area hampered by the throttle plate and shaft go up linear with the increase in radius). This means greater flow/less restriction at full throttle, and should mean that flow ramps up quicker with rotation of the plate (which may lead to the snappier response I've heard mentioned with this upgrade).
The TB is something I've heard others mention from their 3FE upgrades (ones Randy has had a hand in, Overhanger's, Moby's, Pappy's done it on a 22RE, not sure about his 2FE) as helping when balanced with other upgrades for breathing such as a longer duration cam and head work. A bit of info here: https://forum.ih8mud.com/60-series-wagons/40908-big-bore-throttle-body.html
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- Thread starter
- #144
Edit, I just realized that I wrote down the wrong intake closure angle for the 2F here, and calculated wrong. Corrections in red where needed 
Some geometry fun from early this morning.
I've been playing around with the dynamic compression ratio, which is the idea that a true measure of the compression in the engine takes in the timing of intake valve closure. If the cam timing is changed (i.e. longer duration), you change the effective compression ratio (i.e. drop), and that's why engines that use long duration can run higher static compression ratios. This is detailed in Dalton's book, and is used to help decide a safe compression ratio to run with an "upped" cam. By keeping the dynamic compression in line with what is seen with the stock chamber volume and cam timing, you stay in a safe zone despite monkeying with both of these parameters.
So looking at the Fs, here are three diagrams that I used to figure out the swept volume of each configuration from the point of intake valve closure on the compression stroke. All is done to scale, with the 3FE having a stroke of 95 mm and a center to center connecting rod length of 148 mm, and the 2F having a stroke of 101.6 mm and a rod length of 190.5 mm. Intake valve closure is 48* ABDC for the 3FE, 43*(53*) ABDC for the stock 2F, and 59* ABDC for the Delta regrind posted up by Dave-T in the first camshaft link in post 1.
So, from the effective sweep for each configuration, the following has been put together. I've assumed that the late 2F (2F with world market 3F head) has a stock compression ratio of 8.3:1 (posted by Jim elsewhere). You might notice I am calculating for the 2FE now.
Piston area 69.4 cm2
Stock 3FE comp: 8.1:1
Squish vol: 92.84
Swept vol: 659.17
Total vol: 752.01
Stock head CC vol: ~77
Stock effective sweep: 83.5mm
Effective swept vol: 579.2 cc
Dynamic compression: 7.24:1
Stock late 2F comp: 8.3:1
Squish vol: 96.53
Swept vol: 705.1
Total vol: 801.63
Stock effective sweep: [STRIKE]91.1mm[/STRIKE] (85.4mm)
Effective swept vol: [STRIKE]632.2 cc[/STRIKE] (592.7cc)
Dynamic compression: [STRIKE]7.55:1[/STRIKE] (7.14:1)
2FE with Delta cam (59* ABDC intake close)
effective sweep: 82.1
effective swept vol: 569.8
for effective compression of [STRIKE]7.55, squish vol: 87.0 cc[/STRIKE]
for dynamic compression of 7.14, squish vol: 92.8 cc, 77 cc chamber volume, 8.6:1 static compression
for dynamic compression of 7.24, squish vol: 91.3 cc, 75.5 cc chamber volume, 8.7:1 static compression
[STRIKE]CC vol: 71.2 cc
static compression: 9.1:1[/STRIKE]
So it looks like with a longer duration cam, [STRIKE]9.1:1[/STRIKE] 8.6:1 should be pretty safe on the 2FE. If someone can let me know what is a safe static compression to run with the stock cam, I can push the numbers a bit further (although static compression of [STRIKE]9.1:1[/STRIKE] 8.6:1 sounds pretty high already).
Oh yah, I also have 5 of the intake ports all done up like shown for #5 in pics above. So when I have a chance, I'll run them all with the flow bench and compare them to #2 (the un-modified standard).
Some geometry fun from early this morning.
I've been playing around with the dynamic compression ratio, which is the idea that a true measure of the compression in the engine takes in the timing of intake valve closure. If the cam timing is changed (i.e. longer duration), you change the effective compression ratio (i.e. drop), and that's why engines that use long duration can run higher static compression ratios. This is detailed in Dalton's book, and is used to help decide a safe compression ratio to run with an "upped" cam. By keeping the dynamic compression in line with what is seen with the stock chamber volume and cam timing, you stay in a safe zone despite monkeying with both of these parameters.
So looking at the Fs, here are three diagrams that I used to figure out the swept volume of each configuration from the point of intake valve closure on the compression stroke. All is done to scale, with the 3FE having a stroke of 95 mm and a center to center connecting rod length of 148 mm, and the 2F having a stroke of 101.6 mm and a rod length of 190.5 mm. Intake valve closure is 48* ABDC for the 3FE, 43*(53*) ABDC for the stock 2F, and 59* ABDC for the Delta regrind posted up by Dave-T in the first camshaft link in post 1.
So, from the effective sweep for each configuration, the following has been put together. I've assumed that the late 2F (2F with world market 3F head) has a stock compression ratio of 8.3:1 (posted by Jim elsewhere). You might notice I am calculating for the 2FE now.
Piston area 69.4 cm2
Stock 3FE comp: 8.1:1
Squish vol: 92.84
Swept vol: 659.17
Total vol: 752.01
Stock head CC vol: ~77
Stock effective sweep: 83.5mm
Effective swept vol: 579.2 cc
Dynamic compression: 7.24:1
Stock late 2F comp: 8.3:1
Squish vol: 96.53
Swept vol: 705.1
Total vol: 801.63
Stock effective sweep: [STRIKE]91.1mm[/STRIKE] (85.4mm)
Effective swept vol: [STRIKE]632.2 cc[/STRIKE] (592.7cc)
Dynamic compression: [STRIKE]7.55:1[/STRIKE] (7.14:1)
2FE with Delta cam (59* ABDC intake close)
effective sweep: 82.1
effective swept vol: 569.8
for effective compression of [STRIKE]7.55, squish vol: 87.0 cc[/STRIKE]
for dynamic compression of 7.14, squish vol: 92.8 cc, 77 cc chamber volume, 8.6:1 static compression
for dynamic compression of 7.24, squish vol: 91.3 cc, 75.5 cc chamber volume, 8.7:1 static compression
[STRIKE]CC vol: 71.2 cc
static compression: 9.1:1[/STRIKE]
So it looks like with a longer duration cam, [STRIKE]9.1:1[/STRIKE] 8.6:1 should be pretty safe on the 2FE. If someone can let me know what is a safe static compression to run with the stock cam, I can push the numbers a bit further (although static compression of [STRIKE]9.1:1[/STRIKE] 8.6:1 sounds pretty high already).
Oh yah, I also have 5 of the intake ports all done up like shown for #5 in pics above. So when I have a chance, I'll run them all with the flow bench and compare them to #2 (the un-modified standard).
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New to the Cruiser game but still play with drag cars. Very cool thread. Tons of power in the heads. You should see if you can find a junk head then you can experiment. Lay back the short side radius and get some more out of the bowls. Find where you can get the flow #'s up on the junk heads. Than have at it. Here's where the can of worms opens. Now you can change cams to take advantage of your increased head flow. Fun stuff. Enjoy matt
. Lay back the short side radius and get some more out of the bowls. Find where you can get the flow #'s up on the junk heads. Than have at it. Here's where the can of worms opens. Now you can change cams to take advantage of your increased head flow. Fun stuff. Enjoy matt
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As a data point, a desmogged 4.5L 2F that is currently my DD has a DCR of 7.8 and it detonates on 87 octane junk gas. Runs quiet on 91 octane.
Apparently the stock DCR of 7.55 is pretty close to the limit. The SCR was bumped up to make up for the increased EGR flow on the 79-later 2F in the USA. If building a big-inch engine without EGR, be careful not to get too far from the stock DCR.
Apparently the stock DCR of 7.55 is pretty close to the limit. The SCR was bumped up to make up for the increased EGR flow on the 79-later 2F in the USA. If building a big-inch engine without EGR, be careful not to get too far from the stock DCR.
- Thread starter
- #147
So considering that the engine will be desmogged, do you think a DCR of 7.55 is all fine and good? or would it be advisable to drop it a touch just for safety's sake? In principal I don't mind running mid-grade, but I suppose that would be a hassle in some situations.
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There are plenty of desmogged 81-87 2F's that don't rattle running on junk gas at the 7.55DCR.
Keep in mind that your improved pumping efficiency and better 3FE intake manifold will add ram tuning to the 7.55 number, so it could be prudent to build a little lower than 7.55, knowing that if that last little bit of performance is needed, the head could come back off and have 1mm knocked off to get the CR up higher.
Keep in mind that your improved pumping efficiency and better 3FE intake manifold will add ram tuning to the 7.55 number, so it could be prudent to build a little lower than 7.55, knowing that if that last little bit of performance is needed, the head could come back off and have 1mm knocked off to get the CR up higher.
- Thread starter
- #149
Got the last intake port up to match the other 5, and started on the exhaust ports. Not doing much to the exhaust side. Just cleaned up the transition between the cast and machined surfaces and narrowed down the guide boss a touch (but definitely NOT the guide itself on the exhaust side). Started in to polishing the exhaust ports, but I'll need to track down something better to use as the die grinder goes through the air too fast for polishing and I don't have a decent buff for the dremel. I think I have an electric die grinder in the garage somewhere, just need to find it. 
That will leave cutting anti-reversal ratchets into the ports and polishing the chambers, then the head will be ready to take in to have the valves done and I'll start putting in more attention to the intake setup and exhaust manifolds.
That will leave cutting anti-reversal ratchets into the ports and polishing the chambers, then the head will be ready to take in to have the valves done and I'll start putting in more attention to the intake setup and exhaust manifolds.
- Thread starter
- #150
A couple pics from polishing up the chambers. So far they are done to 150 grit, if I have the patience, I'll go at them with some 1000 grit to make them as smooth as possible. I don't want to remove too much material and alter the shape of the chambers, but I have removed most of the beaded texture from the casting surface.
Short of a thermal barrier coating, polishing the chamber surface should yield the lowest heat transfer from the combustion gasses into the head. Smoothing the surface lowers the area across which heat can be transfered, not sure if there will be some benefit from reflection too. Lowering the heat transfer keeps the energy in the gasses where it will do work, and out of the cooling system. The smooth surface should also help to combat carbon build-up and possibly detonation?
Short of a thermal barrier coating, polishing the chamber surface should yield the lowest heat transfer from the combustion gasses into the head. Smoothing the surface lowers the area across which heat can be transfered, not sure if there will be some benefit from reflection too. Lowering the heat transfer keeps the energy in the gasses where it will do work, and out of the cooling system. The smooth surface should also help to combat carbon build-up and possibly detonation?
I was paying attention when this page started and now I feel overwhelmed reading through the last half.
PabloCruise
SILVER Star
Good work Doc!
- Thread starter
- #153
Some pics of current state. Everything is done in preparation for going to the machinist except the anti-reversion features, which I'm pondering on/starting now.
Chambers and exhaust ports are polished up pretty decent... fine grinding stone to take out the casting texture -> several fining grades of sandpaper (to 1000 grit) -> a polishing buff with Autosol cream polish.
The intake ports have been left unpolished, as there isn't the thermal benefit, and a polished surface is supposed to be worse for wet flow.
exhaust ports:
intake ports:
starting to play with an anti-reversion feature at the exhaust mating surface:
Chambers and exhaust ports are polished up pretty decent... fine grinding stone to take out the casting texture -> several fining grades of sandpaper (to 1000 grit) -> a polishing buff with Autosol cream polish.
The intake ports have been left unpolished, as there isn't the thermal benefit, and a polished surface is supposed to be worse for wet flow.
exhaust ports:
intake ports:
starting to play with an anti-reversion feature at the exhaust mating surface:
- Thread starter
- #154
Here's a better picture of the channels cut around the exhaust ports.
Combined with splaying out the openings on the manifolds (seen started below) those channels should give a fairly decent anti-reversion effect to keep exhaust flow/positive pressure from making it's way back to the chamber. This anti-reversion helps to combat the poor low RPM performance that often comes with improving high RPM performance through a longer duration cam. Somewhat similar features put into the intake tract are supposed to similarly help low RPM performance as you improve flow. The theory for both of these is shown back in post 104.
I also have the cam in hand now, it's a slightly broken-in MAF RV grind, apparently the engine it was in suffered from a terminal oil system fault within a couple K miles of rebuild. Thanks Dan
Combined with splaying out the openings on the manifolds (seen started below) those channels should give a fairly decent anti-reversion effect to keep exhaust flow/positive pressure from making it's way back to the chamber. This anti-reversion helps to combat the poor low RPM performance that often comes with improving high RPM performance through a longer duration cam. Somewhat similar features put into the intake tract are supposed to similarly help low RPM performance as you improve flow. The theory for both of these is shown back in post 104.
I also have the cam in hand now, it's a slightly broken-in MAF RV grind, apparently the engine it was in suffered from a terminal oil system fault within a couple K miles of rebuild. Thanks Dan
ntsqd
technerd
Were it me I'd first blend and massage the upper 1/2-2/3 of the port perimeter and test the flow when bolted on a head. The exhaust gasses will be coming out mostly on the roof of the exhaust port so opening up the bottom of the ports doesn't offer near the gains that opening up the tops will, and stands to hurt low flow velocities from too much cross sectional area.
Certainly try to blend the bottoms in, but don't take them all the way down, keep the port floor radius as large as possible.
Certainly try to blend the bottoms in, but don't take them all the way down, keep the port floor radius as large as possible.
PabloCruise
SILVER Star
I'm not port-matching or significantly opening things up, I'm going for this:
Help! Can anyone 'splain to me wtf I am supposed to be seeing in this?
- Thread starter
- #158
You can look at post 104 for more. The diagram you've quoted shows a cross section through the exhaust manifold/header (on the left) and head (on the right). By opening up the manifold/header opening at the contact, and cutting a channel around the port on the head, you make an interface that is flows well in the correct direction, and poorly in the opposite direction.
This might help, taken out of Vizard's book showing aftermarket anti-reversion headers:
This might help, taken out of Vizard's book showing aftermarket anti-reversion headers:
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PabloCruise
SILVER Star
Wow! Very cool!
I notice they make a coment about cross-over pipes being used between headers. Is that a valid statement that the cross-over can increase low-end torque and mileage w/ A.R. features?
Are you going to use the factory 3FE exhaust manifolds?
If yes, will you use a cross-over pipe to connect the two banks?
I notice they make a coment about cross-over pipes being used between headers. Is that a valid statement that the cross-over can increase low-end torque and mileage w/ A.R. features?
Are you going to use the factory 3FE exhaust manifolds?
If yes, will you use a cross-over pipe to connect the two banks?
- Thread starter
- #160
Those are the stock manifolds (post 154). My exhaust is currently a 2 in 1 out muffler with no cats, I expect I'll stick with that. It shouldn't need a cross-over since the 2 backs of cylinders come together at the muffler. I'm not sure off the top of my head if the benefit of a cross over on a dual exhaust v8 comes from an inherent need to balance between the 2 banks, or because the exhaust pulses aren't rhythmic in each bank. I should have a look back through the chevrolet inline six-cylinder power manual (Leo Santucci) and see what's said in there about exhaust.....
*edit* No discussion of, or photos of, the use of cross-over pipes with inline six dual exhausts systems in Santucci's book. Anywhere there is a photo of a complete system, it consists of dual 3-1 headers ending shortly after the collector pipes.
*edit* No discussion of, or photos of, the use of cross-over pipes with inline six dual exhausts systems in Santucci's book. Anywhere there is a photo of a complete system, it consists of dual 3-1 headers ending shortly after the collector pipes.
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