Torque & HP Open Discussion

Alan, what has gotten into you? You can still ski, plenty of "golden" years to do all that engine stuff.

M3Fan wrote: Although the riser area is a bit restrictive doesn't the length of the restriction become a factor as well? For example, an automotive header may be less restrictive at the collector but then you've got 2" exhaust going all the way back to the rear of the car with twists and turns, cats, mufflers, resonators, etc. With a lot of these boats you've just got 10 feet or so of 3" hose and nothing else to restrict flow after the riser.

While flow of the exhaust system is one concern another major factor that will not be overcome with stock manifolds is that they are considered a Non Tuned design meaning no pulse or suction waves are produced so there is absolutely no scavenging effects to help evacuate exhaust gases from the cylinder. You would need to get into a header/collector design and I don't believe even the hiteks fall into this catagory as they are not long enough. So restriction may not be as big a detriment as overall design.

Let's not forget about the water in those 3" pipes and the effect it may have as well.

Although the riser area is a bit restrictive doesn't the length of the restriction become a factor as well? For example, an automotive header may be less restrictive at the collector but then you've got 2" exhaust going all the way back to the rear of the car with twists and turns, cats, mufflers, resonators, etc. With a lot of these boats you've just got 10 feet or so of 3" hose and nothing else to restrict flow after the riser.

Alan
I pulled the manifolds out of the barn last night. Need to remove the risers and throw them in the trunk. We have a 20 in cut off saw at work for sectioning aircraft parts during engineering investagations. Maybe over the weekend I'll come in and cut them up.

Waterdog wrote: Alan I'll get those exhaust manifolds out of the barn & put them in my work car. I'll cut 1 if I like it I'll cut the other the same and ship it to you. Probably just the inboard half to cut down on weight. Could you donate the cost of shipping to the club ( CCFan)?

That will work Andy, do you have a bandsaw at your disposal? I wasn't really looking forward to tackling this with just a sawzall.

81nautique wrote: GottaSki, I'll play around with that in the next few days but I'm sure I'll have some questions so stay tuned.

most excellent. look forward to it.

Likely those heads will like more cam lift than you are used to seeing. Most windsors reach deminishing returns above .45", but it appears the canted valves really open up and get away from the cyllinder wall from .45" on up and the flow continues to climb in earnest.

Alan
I've been holding on to a set of cracked exhaust manifolds, to cut open. Would you cut it front to back, thru the center of the pipe plug holes on each end ? Just wondering what would be "best".

AFR185/RHS180 flow comparison

Mark,

Here are some graphs for engine both current and with the mods you mentioned, I also added one with the RHS heads I'm going to use. Without having the exact cam specs what I did was put together a stock 351 and then make your changes to it like CR and intake. There are no provisions in the program for marine exhaust so the reports I will email you are going to show stock exhaust with mufflers but the only other selections are open headers. All of the models so far have used the same exhaust options. There are no provisions in the program to add the underdrive pulleys.

MM's 351 as it is currently, 9.7CR,stock cam, 1.7 rockers, stealth:


MM's 351 with the AFR185,10.5 CR, .470 cam, 1.7 rockers, stealth:


MM's 351 with the RHS180,10.5CR, .470 cam, 1.7 rockers, stealth:


This one is a side by side:


If you want anything changed just let me know, you might want to really take a good look at the RHS180 heads. I found that out of the box they flow better than the AFR and are less expensive although you'ld have to decide iron over aluminum.

I think the real answer to your question is will a cam and head change add 75-100hp and it appears that it will. Better install some grab rails in that machine.

[QUOTE=81nautique] Matt, Here's a graph based on your specs. Some of the input is guesswork but I think it's fairly close. Seems to match up pretty closely to a gt40 280 hp motor. Do you have flow data on the heads? Shoot me your email address and I'll send you a pdf of the report, if you want to change anything just let me know.

[/QUOTE

I tryed 3 inch headers but there was not much difference! I think stock manifolds has much torque and that is what you need.

MaddMarxx wrote: Alan..Do you think you could run that program on my motor with what i have now plus the upgrades I am going to add soon, I think the CR is close to 9.75 now, its has 30 over with flat tops, 1.7 rockers, block is decked with a wiend stelth intake, with stock heads now but i am going to add a set of alum AFR 185s, and a cam with around 470 lift and a holly 715 cfm and a set of edelbrock manifolds and alum under drive pullys with a fluid dampner, my Brother has been telling me the heads and cam could add 75 to 100HP, I would like to see if your program agrees...thank you.

Mark, are you saying you have 9.7:1 CR now or after the head change? Your stock heads probably have 65CC Chambers and the AFR185 will have 58CC. If thats the case it's going to push your 9.7 CR to 10.5:1 which the aluminum heads will like better than iron. You're going to be in the same situation as me with those big valves and will need to check for piston to valve clearance before bolting everything up.

Do you have more detail on the cam? What I really need to do this right is the following info from the cam card:

intake valve open=_____
intake valve closed=_____
exhaust valve open=______
exhaust valve closed=_____
specify if the above is at seat to seat or .o50 timing.

Advertised duration and/or .050 duration(just specify which it is.)

Those numbers are as important as the lift for the program to work.

If you don't have actual cam info I'll substitute data from a few known cams like mine or trbenj's. Later AA

Mark,

I can run one based on assumed CR but we could get a better report if you have all the details on the pistons and cam. Later today I'll post all the detailed info required to do a proper test but in the meantime we'll use some assumed numbers.


Crazy busy day today so if I don't get to you til tomorrow hang in there I didn't forget you.

Interesting thing to me is "the worlds fastest Mustang" my quotes,is that he's running basically stock exhausts with just some port matching.Maybe that accounts for why H&M's sound different.I would guess that the PCM's were not built for performance but for a way to get the exhaust out of the boat,fishing or skiing it didn't matter. Hiteks and to a lesser extent the H&M's I would guess,were made with performance 1st. I have to go now,I have to start locking my boat up

Matt, Here's a graph based on your specs. Some of the input is guesswork but I think it's fairly close. Seems to match up pretty closely to a gt40 280 hp motor. Do you have flow data on the heads? Shoot me your email address and I'll send you a pdf of the report, if you want to change anything just let me know.

Lastly I will be the first to admit that I am a rookie engine tuner, I've never felt experinced enough to interpret a plug chop confidently. Fully knowing my shortcomings there I am making an adapter that will sit between the manifold and the riser that will accept an air/fuel sensor. I've purchased an digital meter that will monitor A/F ratio at any rpm range and load so I can fully tune the engine in the spring. There's a good chance without it I will never get the engine tuned to perform near it's potential anyway. This will be a temporary meter so once dialed in it will be removed and I plan to make it available for anyone with PCM manifolds to borrow if they like.