[Firebob]

Ok so apparently the Edel round port heads(295cfm@600) have large enough ports to slow down velocity and kill off some of my low end on my 400. The concensus seems to be that the bigger ports require higher cubic inches.
Now I'm wondering if I would experience the same scenario if these same heads were bolted on a .030over 455? Seems like no matter what engine they would go on the smaller ports of my Dport 16s would always offer higher velocity A/F charge as opposed to the larger ports of the bigger round ports.

Opinions?

[gtofreek]

The D-ports will always have more velocity because the ports are so small. That doesn't mean it won't run good with bigger ports.

What are you looking for from your engine?

215 cc's is not big enough to cause a problem with a 400, or for sure a 455. As far as killing off low end torque, I wouldn't worry about that either. The 400 I built with Eddy round ports made ridiculous torque at just 2300-2500 RPM. A 455 would love them.

You can make a lot more power with the E-heads. If you want to make more than 450 HP, go with the E-heads. Iron d-ports will take a lot of money and time to make power equal to bolt on E-heads.

[Firebob]

I would love to hear the specs you used on the 400 with round ports because mine ran great with the Dports and then after switching over to the Edels it just doesn't have that kick low down that it used to. It still runs good but just not down around 1500-3000 like before.

[Steve C.]

""Many feel the 215cc intake port of our Performer RPM is too large for the street, but we've found that the long connecting rod and big crankshaft throw associated with the Pontiac V-8 tend to make them less sensitive to port volume. The RPM is a great head for street engines, and I pushed for a large intake port when developing the Performer D-port-one much like that used in our Performer RPM."



Read more: http://www.highperformancepontiac.co...#ixzz3BzX7BT4p



.

[grandville455]

Did the comp ratio change? How much total timing are u running now compared to the 16's? Eldys like more timing usually. What about jetting? Ports being bigger may want more fuel also. Don't give up, just keep tuning it!

[gtofreek]

Originally Posted by Firebob

I would love to hear the specs you used on the 400 with round ports because mine ran great with the Dports and then after switching over to the Edels it just doesn't have that kick low down that it used to. It still runs good but just not down around 1500-3000 like before.

Here is a link to a thread on that engine. I could not find the thread I started here on it. Don't know what happened to it.

http://pontiaczone.com/forum/showthread.php?t=19759

One thing you can do to help increase intake velocity is to use a cam lobe with a fast opening ramp. This quick opening will help start the velocity in the port more so than a slow lobe.

[steve25]

If you want to a simple yet accurate comparison it would go like this between a apples to apples 400 to 455 CID swap.
The optimum crank angle in a 400 is 74.2 degrees, in a 455 the angle is 72.4 degrees, that's a 1% difference.

A 455 is a 13.5 % larger motor than a 400 there for the total Intake port velocity gain in the 455 is 14.5%.
This also means that that a 455 will make its peak torque at 14.5% less rpm than a 400 given the same size and flowing heads.

This is also born out in practice by a stock high compression 400 making peak torque at 3200 rpm and 1970 high compression 455 coming in at some 2780 rpm!

If a stock iron 156 CC intake port runner on a 400 feels real good in the throttle response department and you exchange out a set of let's say Kaufman D port heads at 182 CCs than you will drop 16% of the port velocity out of the motor if the airflow numbers where the same, this translates right into a 16 % reduction in torque and also raising the rpm point of peak torque by that same 16%!
This assuming that the stock heads where providing all the air flow needs of the motor in regards to how it was Camed and it rpm range.

Now that stock high compression 400 is making it peak torque numbers at 3700 rpm, if these 182 CC heads are then put on the 455 you would basically end up with the same peak torque rpm of the stock headed 400!

Now if you want to ask yourself what can we do to the 400 to keep the same throttle response feel and torque range than all that's needed is to pass 16% more air through that 16% larger 182 CC port and we are right back at square one, well almost!

The controlling issue in this apples to apples test is is that any given motor needs to be at a minimum rpm to have a need for a given amount of airflow.

This means that if let's say the 400 motor can only use 180 cfm of air at 2500 rpm, but your chosen heads are sized to pass 200 cfm than you have right there a 19% reduction in throttle response!

In a race motor with a 4K or greater stall converter this drop off in torque means nothing, but on a street motor it does, and the reduction in torque also means a slower to rev motor until that torque number get to what it was stock, so let's hear the arguments against what I have posted folks as I am sure it will happen, but if it does let's have facts, not crap like I can tell by the seat of my pants that I have not dropped bottom end torque and throttle response when I went to 215. CC heads from stockers on my whatever CID motor!

[Firebob]

Yes the CR did change. While it was out I had the block decked to .005. The head chambers are basically the same, so the CR went from 9.7 to 10.1. Also the cam was changed from 226/226FT to a 230/230 hyd roller(both at 110LSA). Also changed was RA exh mans to Doug's round port headers.
Timing is the same at 36* all in @2200. No jet changes. I'm tuning carb with a wideband and it's already got bigger jets in(75primaries) than anyone else says should be in there but these run the best.

Steve, I'm going to have to re-read your post to try and sort it out. The intake lobe profile is a bit rounder(faster) than a linear lift(more lift@.100) and I've got 1.65s on the intakes.

If I can make this configuration run as well with the round ports as it did with the Dport16s I'll keep it. If I have to go back to the Dports and try and cam it up to raise the torque band and get back some of the low end I might consider it. If I can get the best of both worlds out of building the 455 and end up with a win/win then that might be the way I will go. Just wish I knew for sure it would be worth the trouble before I spend that much more dough on it.

[b-man]

Originally Posted by Firebob

Yes the CR did change. While it was out I had the block decked to .005. The head chambers are basically the same, so the CR went from 9.7 to 10.1. Also the cam was changed from 226/226FT to a 230/230 hyd roller(both at 110LSA). Also changed was RA exh mans to Doug's round port headers.
Timing is the same at 36* all in @2200. No jet changes. I'm tuning carb with a wideband and it's already got bigger jets in(75primaries) than anyone else says should be in there but these run the best.

Steve, I'm going to have to re-read your post to try and sort it out. The intake lobe profile is a bit rounder(faster) than a linear lift(more lift@.100) and I've got 1.65s on the intakes.

If I can make this configuration run as well with the round ports as it did with the Dport16s I'll keep it. If I have to go back to the Dports and try and cam it up to raise the torque band and get back some of the low end I might consider it. If I can get the best of both worlds out of building the 455 and end up with a win/win then that might be the way I will go. Just wish I knew for sure it would be worth the trouble before I spend that much more dough on it.

When swapping from iron heads to aluminum you really need to bump the compression up by 3/4 to 1 full point, due to the superior heat rejection of the aluminum heads. Loss of heat = loss of power. This is one reason why you some lost low-end.

If you didn't have the chambers on the E-heads cc'd then you may have even lower compression than you think, the 72cc E-heads commonly come in at 75ccs.

Chances are good that the E-heads will like some more timing advance, about 40 degrees total may be needed.

[steve25]

B man, if you look at a Otto cycle efficiency chart you will see that even a FULL point of compression change from 10 to 1 up to 11 to 1 only makes for a 1.7% change in overall power levels, so by far the greatest change is still in regards to port velocity!
This efficiency rate of change is regardless if the head is iron or aluminum!

A change from 8 to 1 up to 9 to 1 makes for a tad larger 3% change in power! but still on 400 hp motor this only buys you 12 more HP! Nothing to sneeze at, but nothing monumental!

[Skip Fix]

Look at many many other motors head intake port sizes and 215 for a 400 , or for sure 455 is fairly common. Heck many aftermarket heads of 215 cc are made just for stroker 383-400 SBCs. They do generally measure 75cc as Bart said, and need 38-40 degrees of timing.

Here is AFRs 190cc for 2000+rpm in 350-400 motors
http://www.airflowresearch.com/index.php?cPath=24_29
210s 3000+ rpm
http://www.airflowresearch.com/index.php?cPath=24_33

5.7 LS1 motors have a 210 cc head

As Paul said
"215 cc's is not big enough to cause a problem with a 400, or for sure a 455. As far as killing off low end torque, I wouldn't worry about that either. The 400 I built with Eddy round ports made ridiculous torque at just 2300-2500 RPM. A 455 would love them. "
4.8-5.3L 200cc
6.0 210 and GM uses them in trucks that need low end torque.

Compression, timing and cam add a bunch more variables.

[PunchT37]

Hell, even GM 4.8 and 5.3L engines have 200cc runners. I know they`re fuel injected but,...


A 4.8L is only 294 CID.

Head specs;


706 & 852 & 862
Head: 1999+ LR4 4.8-liter Truck
1999+ LM4 / LM7 5.3-liter Truck

Material:Aluminum
Part Number: 12559852, 12561706 ,12559862

Combustion chamber Volume:61.15cc
Compression Ratio:9.5:1
Intake port Volume:200cc
Exhaust Port Volume:70cc
Intake valve Diameter:1.89-inches
Exhaust valve Diameter:1.55-inches

[PunchT37]

Originally Posted by Firebob

Yes the CR did change. While it was out I had the block decked to .005. The head chambers are basically the same, so the CR went from 9.7 to 10.1. Also the cam was changed from 226/226FT to a 230/230 hyd roller(both at 110LSA). Also changed was RA exh mans to Doug's round port headers.
Timing is the same at 36* all in @2200. No jet changes. I'm tuning carb with a wideband and it's already got bigger jets in(75primaries) than anyone else says should be in there but these run the best.

Steve, I'm going to have to re-read your post to try and sort it out. The intake lobe profile is a bit rounder(faster) than a linear lift(more lift@.100) and I've got 1.65s on the intakes.

If I can make this configuration run as well with the round ports as it did with the Dport16s I'll keep it. If I have to go back to the Dports and try and cam it up to raise the torque band and get back some of the low end I might consider it. If I can get the best of both worlds out of building the 455 and end up with a win/win then that might be the way I will go. Just wish I knew for sure it would be worth the trouble before I spend that much more dough on it.

So, you got a 400 with a HR 230/230 cam and 1 7/8 headers. What`s the rest of the cam specs, intake, carb, gear and car weight? Auto trans? Converter?

[Stan Weiss]

Originally Posted by PunchT37

Hell, even GM 4.8 and 5.3L engines have 200cc runners. I know they`re fuel injected but,...


A 4.8L is only 294 CID.

Head specs;


706 & 852 & 862
Head: 1999+ LR4 4.8-liter Truck
1999+ LM4 / LM7 5.3-liter Truck

Material:Aluminum
Part Number: 12559852, 12561706 ,12559862

Combustion chamber Volume:61.15cc
Compression Ratio:9.5:1
Intake port Volume:200cc
Exhaust Port Volume:70cc
Intake valve Diameter:1.89-inches
Exhaust valve Diameter:1.55-inches

That is because that are will to run some rear end gear ratio lower than a 2.73:1 and turn some RPM's.

Also what is the intake valve size for that port volume?

Stan

[Stan Weiss]

Originally Posted by PunchT37

So, you got a 400 with a HR 230/230 cam and 1 7/8 headers. What`s the rest of the cam specs, intake, carb, gear and car weight? Auto trans? Converter?

Isn't that tube a little large?

Stan

[PunchT37]

Originally Posted by Stan Weiss

Isn't that tube a little large?

Stan

In some apps., yes. IMO

[Firebob]

Well the RPs have been altered slightly (not by me) I would think so I can't say what volume the ports carry. Since they, reportedly, flow more than an out of the box set I have to believe they may be a bit more than the 215cc advertised(probably not much though). So from what you guys say I maybe need to look elsewhere for tweaks and adjustments to sort things out.
Where would I add more timing? Initial or more mechanical?
I'm sure there is a much better cam choice than the one I have. It just happened to be the one I had so I put it in. This CID and head arrangement might very well wake right up with the right choice of cam. That may be where a lot of my issue could be resolved. I'm tempted to pull the hyd roller and start trying out solid FT cams till I find the right combo. They are a lot cheaper to experiment with.

[steve25]

In regards to SB Chevy heads and some others they have a intake runner that is greater in length that the Pontiac intake runner!

These days a good head for a 500 to 550 HP 400 CID SB Chevy that will buzz to 7000 rpm or a tad more is a 200 CC runner, but the port choke / minimum port area of the Chevy 200 CC head is near the same as a 185 CC runner in a Pontiac head due to the runner length difference!

So once again it's not a apples to apples comparison!

A very common 383 SB Chevy build has been shown time after time to work best with a 180 CC head for a 475 HP street strip car.

Just keep in mind that as a motor gets up to high and higher rpm's that any given amount of airflow has less and less time to get from the air filter on top the carb down into the combustion chamber.

A larger amount of near stalled air at the back side of a intake valve at the cams over lap period does not do crap for making VE numbers above 100%, but if you reduce that amount of air some and then pass it down the intake tract faster you have VE numbers above 100% at a very usable rpm, not up at 7500 rpm!

Just ask yourself how is it that super stock Pontiac drag cars in the mid to late 80s where running into the 9s with iron heads that where allowed only a valve job that differed from stock, not drop 1 of porting was allowed!
So how did they run these 1/4 mike times without big airflow numbers folks?
I will give you a hint, it wasn't with slow moving air thru overly large intake passages!

Yes it's true that a motor that has limited intake airflow due to high velocity will have the HP curve nosing over faster that if it had more airflow to use, but like I posted before if the average TQ and HP numbers are better in the rpm range the motor was built for, so will the performance be better!

[Firebob]

Not sure if the Doug's are 1 7/8" or 1 3/4".
All I know is 230/230 HR on a 110LSA and the lobe design for the intake has slightly more lift early. Didn't get a cam card.
The carb is a 800qjet withe the choke plate removed and build to the second recipe in Cliff's book only with a little more bypass air and 75 jets. Intake is an RPM that's been port matched to the heads a sized to the bigger ram air gaskets.
Rear gear is 3.23 and Trans is M20 wide ratio. Car is heavy at 3900lbs.
The valves are 2.11/1.77(changed from the 1.66).

[PunchT37]

They`re gonna be 1 7/8 or 2 inch for round ports. 1 3/4 are d-ports. So, 1 7/8.

Would be nice to know the seat timing on that cam. Did you degree it around 106 degrees? Base ign. timing at 12 to 14 degrees? Faster cruve, all in at 2500 or less?