Hi

As some of you know I have been having a motor built for me that has gone way beyond the expected time period. Now in addition to that it is not going to produce what were the original minimums established by me. Those minimums were an easy fit BB, able to turn 7000 RPM and produce 650 HP.

Now the final product will turn 7000 but the power falls short of expectations. For torque it makes 500@3200, 555@3750 and stays over 500 to 6000 and at 6750 is down to 445

For HP it is making 415@4000, 500@4750, 585@6250 then it starts to fall off and 570@ 6500 and holds that to 7000.

My question for those who have owned motors with this capability is how much does that shortage show up in the real world?

They are going to have some numbers run for me by monday on a custom cam from Bullet Cams and the guy that runs the numbers for them has said that with all that I have in heads, intake and cam etc that the absolute most I could get would be 600 HP.

What would some of you do? Take the motor the way it is or hope for better results with a different cam before making a decision

The motor is a marine 496 (a little stonger block) high quality everything but the cam seems a little off. However will I have to loose streetability to get the numbers I want and how much seat of pants and 1/4 mile difference is there between 585 and 650 HP. Is it a couple of tenths or more like a half a second plus

I have always respected the advice here and would really appreciate your input on my situation

Thanks

Doug

 

You can plug your numbers in here:
http://www.robrobinette.com/et.htm

Guessing 3450lbs and your numbers as flywheel hp -
585hp=11.09
650hp=10.71

 

I still think the numbers are low for what a 496 should make..but that said.....since it's holding onto power pretty good past peaK hp all the way to 7000 rpm....it WILL be a fun engine to drive. I hate one that dies off after making peak power.


You can easily run low 11's with that dude without pounding stuff too hard....and high 10's if you work it a little,


The heads are hanging in pretty well..so they should respond to some cam. Duration is where you will get more power. It's already peaking at 6200 or so...so a few more degrees will push it up to 6500-6700 and it will make more HP if it hangs in up there.

Just still have to decide on manners etc that you will be happy with.

BTW- what correction factors is he using on dyno? Is he going back to std?

 

Jim said

I agree Jim and something is wrong. Maybe the compression is just not what it is suppose to be but for me to go with the expense of a solid roller and shaft rockers in a street motor and then get Hyd roller performance will not work.

The motor should have been a 540 but still and as you said it is not putting out what the sum total of the parts should be putting out. It could be the head because no one checked the CC numbers and just took the word from Brodix to be accurate. A compression check only showed 155 and it should be getting 175. Heck the 427 I have now with the hyd roller and iron heads is 190 and it runs fine on 93.

If someone was standing by with the cash I would let the motor go and start over.

Anyway to sum it up I said no go ........... unfortunately the saga continues.

BTW thanks for the replies

Doug (shaking head in disbelief)

 

155 PSi with a 248* solid cam sure seems low. Do the pistons have a dome on them at all?

Don't give up yet....it's still a solid motor. It's survived dyno testing and tuning...so it's built OK....just something is wrong with combo. I'm really questioning that compression ratio.

Retarding the cam will lower cranking compression a little. He retarded it 2" I think...but from where? From say 106* to 108*? Or from 110 to 112*? It would help to know where it was to start with. Comp and just about everyone designs cams to be installed advanced.

Does he have a single plane intake you can try? Like just a basic Strip Dominator? We picked up a ton (30 RWHP) on a 540 going from a factory 427/425 style dual plane to a Strip Dominator...which is a pretty small intake. This was on a mild 9.5 compression hyd roller 540. Low speed power and driveability actually got better in that case.


JIM

 

I may be getting on the tail end of this discussion and there's some good advice that came your way. If on paper it's projected up to 650 ponies then the problem, hopefully, could be simple. Without being redundant there's two items you need to check out. Your roller cam and your intake. Case in point. Years ago I had a performance problem in spite of the fact that my Vette ran like a striped *** bass but only up to 5800 rpm and then I found after countless frustrating hours that my engine builder had forgotten to install a cam button! The difference was half a second quicker and finally getting my car in the high tens. Are you sure you have the right cam AND it's dialed in? And try another intake manifold for comparison. Your problem can be something very mundane. Best of luck, Raymond

 

Hi Jim

No the pistons have no dome at all and that bothered me enough before to ask why. However I was told that the math with everything involved would produce a overall 10.4 comp ratio. i had seen a mag article some time ago with the same cam and heads but the pistons in that motor were definitely domed. Maybe advancing the cam will have some benefit because I saw where Mark said he ran his at 4 degrees advanced with good results.

For awhile it seemed we were on the right track but problems with the water compression for the load on the dyno were making accurate conclusions impossible. Today a plastic valve was switched for a brass one and then the surging that seemed earlier to be a miss disappeared.

However no matter what and just as you said that compression is just to low.

Doug

 

What heads are you running?

What are the ccs?

What does the combustion chamber look like?

 

The heads are Brodix RR rectangular port with the CC option. I tried earlier to copy the flow numbers off their web page but I could not do it. However the cc is 119 and I opted for the cc option. The web page has the flow rates are up to 700 lift so at 660 I am well within the expected usage. I have heard of heads being worked on and coming out different then expected but from my standpoint I count on the info of others as to good or bad on things such as this.

Unless there is a malfunction with the comp gauge I think the problem has to do with that low #. Even though I am using a dual plane (IMO the best one out there) for testing purposes he has a 1" spacer mounted although that is to much height for the actual install.

There is suppose to be some hypothetical numbers for me on monday but I need to see why the comp# is so low before I even begin to consider anything else.

I asked for it to run on pump gas but I did not mean regular LOL.

Doug

 

With a flat top piston and 119cc heads your compression I get a compression ratio of 9:1 not 10.4:1.

 

That is about the level of performance it is generating. Plenty of torque but no HP.

 

I don't think it will matter what cam you go with, you will not see 650hp with flattop pistons.

Maybe if you went with Big Chief heads or something like them. But the cost involved is high.

 

Without real numbers on all the sizes its hard to figure the final compression ratio. If the valve notch is 3 cc's with a Felpro gasket and a .020" piston to deck you could really be at about 8.4:1.

Harry P.Hunter

 

I assumed that the block has been decked.

Most builders (that are trying to get horsepower) deck the block.


P.S. .6 is not as much as 1.4

 

You can't assume anything in this business!

Decking the block and the available horsepower are in no way connected.

An 8.5:1 compression ratio is still 8.5:1 whether you have a 9.800 deck or 10.200 deck.

Harry P.Hunter

 

Well , I think you have a big piece of the puzzle identified. I'm rough guessing 8.3-8.6 compression ratio at best. If you put a bigger cam in there it's really going to be a pooch.

You need about 2 more points of compression at least....11.0 wouldn't worry me any...and about 10-15 more degrees cam and you'll be a happy camper.

Sadly this is going to cost around $1000 in parts alone to accomplish. You need pistons, rings, cam at least. Did machine shop do all the calculations and parts ordering? At this point there is no way it's going to make the power you want without combo changes. I vote they give you your money back and sell that thing to someone else. Missing compression calculations like that is unforgivable for a professional machine shop. Plus it shows they don't build too many big blocks to think a flat top will ever get compression in an open chamber big block.

The Brodix heads really respond to some port work on exhaust side....but that ain't no problem on this deal yet.


Good luck.....keep us up to date. How much of your money does he have?


JIM

 

Hi Jim and others

I would rather you were wrong but logic and gut feeling tells me that you are right on the money.

Speaking of money and as far as them giving it back back I do not feel that returning it is an option even if it was his desire. He is one of the "Speedtalk" boys and I do not think he is dishonest by design but is robbing Peter to pay Paul. I have felt on the hook ever since I first gave him money down and I am getting a bad feeling that I am going to be looking for an attorney very soon.

As far as the components go I only picked the heads and intake although I did choose to go the internal balance route. All of the internal parts choices are his and I only picked the heads after he had pushed the 496 thing on me over my choice for a 540. It is more than just the 90% of the bill already paid but all the other stuff such as carb flywheel, clutch, headers, 5-speed, etc that I have picked up along the way.

He was always putting 540's down and spoke of them having tendencies to spin bearings. I have a feeling that the origin of the block is a contributing factor, like maybe he already had it or it came from a friend. I could be wrong about the block thing but it really does not matter. The 496 was just one of several bad choices he has made.

However now that it is push and shove time we will see if I made the one very critical bad choice of whom to work with.

Doug

 

Howdy

I went and saw the builder this morning and here is the latest

Going back through the order forms the rotating assembly is a (was) a "kit" from Eagle .30 over 489 piston/rod combo that comes to 496. The kit included SRP dome pistons and should be what is in the motor. However I have pictures of the pistons on a table prior to install and other than the dishes they are flat as a pancake. We also did a compression check this morning and it was exactly 150 so that confirms the flat top pistons in an open chamber head. He does the machine work and is the owner while the "other guy" does the assembly work. Other employees either work in the office or a rod reconditioning section but have no contact with building motors.

So he acknowledges the responsibility even though the screwup was with Eagle and he will do an immediate teardown and rebuild ASAP that centers around the parts. There will be a tad larger cam installed and he will do the exhaust ports in house. He also acknowledges the cam choice (although not terribly wrong) could have been better and that too is his bad.

So the bottom line is more time but He is being straight up and doing the right thing.

Doug

 

Well, that's GREAT to hear. I can't believe they used those pistons and didn't notice it on assy as an issue....but hey..at least it will be right now.

Do yourself a favor and go watch him measure deck height. Let's KNOW how far those pistons are down in the hole. Generally they end up .020+ DOWN. This of course affects compression and quench. For example..my motor has pistons .009 OUT of the hole above the block for a real nice tight quench area. Block might need some decking to get an acceptable number here.

I'd hold out to make sure you get new rings too.

As we said before....that cam isn't that bad....but you can use a lot more...so good news on him changing it too.

At least you get to look at bearings etc during teardown to verify that everything is healthy with it.

That's a funny comment about 540's spinning bearings. They use the exact same crank and rods that you just used to build the 496. They only have a bigger bore to get cubes. Mine is doing fine along with a gazzilion others.


Good luck...looks like it will all come together.

JIM

 

Sounds like he had a block that he needed to get rid of.