Score! GRM is awesome, and that sign is classic.
Score! GRM is awesome, and that sign is classic.
oldeskewltoy wrote: think noddaz needs some "sponsor" space on the LTDI checked the Melling cam specs exhaust side has more duration and more lift... wondering if the added amount "fixes" exhaust flow/flaw issues????? intake is 282 duration.... what is stock?
I found these supposedly "stock" 460 cam specs.
Looks very close to the "Cobra Jet" cam. Yes, exhaust timing is a bit longer to deal with the poor-flowing ports. The plan is to grind off the smog pump "bumps" and smooth out around the valve castings, too, on the exhaust side.
Did some work on the piston side of the equation recently...pics and write-up will be forthcoming!
This may turn out to be the best Lemons engine the Tunachuckers have ever had.
Although the rear end was supposed to be the best one of those, and... well...
PISTON MATH
In order to determine static compression ratio (SCR) for the engine, we need to know a few things:
For the D3 heads, we're using 94cc as a set chamber volume. Eventually the heads will get cc'd, but until then 94cc is a good average of the production range for these heads (93 to 95 cc)
Stock 460 pistons (supposedly) come in 3 different flavors:
Carburated: 22cc dish volume, 1.760 compression height (CH) Early FI: 7cc dish volume, 1.760 CH Late FI: 15cc dish volume, 1.770 CH
The reason I wrote "supposedly" we'll get back to....
The stock head gasket that came off this engine measured 0.050" thick. The thinnest aftermarket 460 gasket gives a 0.027" compressed thickness. So that's what we'll be using.
After cleaning off the top of one of the stock pistons, and the deck surface, a feeler gauge inserted behind a steel straightedge (with that piston at TDC) showed 0.024" deck clearance.
The wrist pin on the piston measured 1.040" in diameter. Taking half that (.520) and subtracting from the distance from the top of the piston to the bottom of the wrist pin gives the CH of the stock piston.
But...wait a minute...
All the data I could find on "stock" carbureted pistons showed a 1.760 CH. These pistons measured 1.770". And these have the deeper dish (0.250 deep) which was only on the carbureted pistons, so they couldn't have been swapped already. (Also, this engine only has 30,000 miles on it, it came out of a little-used RV).
So...what's going on? I measured and re-measured and checked my calculations and kept getting 1.770". Problem is, if we go to the Early FI pistons like we plan, that helps a bit with compression (due to a shallower piston dish valve cutout area) but doesn't help with quench. Even with the thinnest head gasket we'll only manage about 0.061" quench (since advertised CH is 1.760). We wanted to be in the low 40's. If we go with later FI pistons that keeps the quench at 0.051" (due to advertised 1.770 CH) but SCR will drop a bit due to slightly deeper piston dish/ valve cutouts.
We're basically stuck looking at these piston options to stay within budget. There's some cheap flat top A/M pistons, but the advertised CH is 1.752" so they won't help compression and will hurt quench. Every other piston option is not LeMons-budget friendly.
I guess it's possible I'm missing something and the "actual" CH is slightly higher than advertised, in which case the early FI pistons may still give 0.010" better quench and bring up SCR. Some browsing through various forums seems to show the early FI are generally recommended for budget performance builds.
This may be one of those times to stop thinking, and just buy the stupid pistons.
I am a little confused, but I think I get the idea.
It sounds like you need to take .020" off the deck. I would not recommend a 4" grinder, but you can probably manage to make this happen at work.
don't cut anything until you have the pistons you intend on using......
we could "throw" all kinds of things at you... (caliper poor, specs wrong, etc) but you will only know when you have another set of slugs....
Could the RV engine use a piston designed for it???
tuna55 wrote: I am a little confused, but I think I get the idea. It sounds like you need to take .020" off the deck. I would not recommend a 4" grinder, but you can probably manage to make this happen at work.
Yes, decking the block could be a way to do this. Conceivably the block could be decked without even swapping pistons (saving $$$).
Two problems though:
1) Would decking the block require removing all the rotating components from the block- crank, pistons, etc? Or could it be done with all this in place?
2) If the block were decked, the heads would sit lower relative to the manifold, so the intake manifold would need to be cut as well. There's all sorts of geometry that comes into play here, the 'V' angle, etc. Not as simple as just taking 0.020" off each deck height and calling it good.
In reply to volvoclearinghouse:
I've never done it, but my understanding is that small amounts of decking are totaly cool with leaving everything flat since gaskets and through holes allow for certain misalignment.
I don't know what the limits of this are in real life.
But I also agree that everything OST said above. Your equipment (no offense) is totally capable of being off 0.010".
The worst part is that you would probably need new pushrods.
At 0.010 off it could easily be manufacturing error (did you try measuring both sides?, multiple pistons?), or cheap digital calipers that shouldn't really be trusted for anything serious. Mic it or at least get the dial/vernier caliper out.
Possibly a good test would to buy ONE "early FI" piston and compare it to the piston that's in there. I can find a cheap one for about $30 and then I'll know what I'm up against without buying a whole set.
I don't deny that my measurement tools may not be the greatest, but at the very least it was extremely repeatable, and would go back to 0.000 +/- 0.0005 every time. Also, the wrist pin measured 1.040" diameter, which is EXACTLY what the OEM spec is. Which makes me think the caliper is reading correctly.
@ tuna55:
Yeah, I don't know how much I can "fudge" and not need to fuss with machining the intake. I mean, the stock HG were 0.050" compressed, and I'm already talking about going to a 0.027" gasket, so there's another 0.023" of misalignment right there. Would another 20 off the block matter? And to the other question, does the crank need to be removed for decking?
It just occured to me that I could test fit the engine together by bolting the head directly to the block without a gasket- this would simulate decking the block 0.027, and tell me if it'll all work before cutting metal.
Again, tuna, you're right, at some point it'll start to matter for pushrod length, too. How much slack can hydraulic lifters account for?
EDIT: since the BBF uses pedestal-mounted rockers, the easiest thing to do would be simply to shim them to account for thinner gaskets & a decked block.
volvoclearinghouse wrote: Again, tuna, you're right, at some point it'll start to matter for pushrod length, too. How much slack can hydraulic lifters account for?
It depends on the valvetrain. I am not remembering the way the big Fords work.
volvoclearinghouse wrote: It just occured to me that I could test fit the engine together by bolting the head directly to the block without a gasket- this would simulate decking the block 0.027, and tell me if it'll all work before cutting metal.
I like this idea. I'll bet the manifold bolts up with minimal fuss. The worst may be drilling out one or two bolt holes and matching the ports if it shows misalignment.
Just think of the weight savings for .020" off of that big deck surface!
http://www.fordmuscleforums.com/all-ford-techboard/490129-how-properly-shim-pedestal-mount-rocker-arms.html
Well, assemble it without gaskets and do that!
volvoclearinghouse wrote: And to the other question, does the crank need to be removed for decking?
you should strip the entire block......
remember you are going to run new pistons... which mean new rings... which mean you will need to hone the cylinders at the very least.... so yes... you will need to remove the crank
oldeskewltoy wrote:volvoclearinghouse wrote: And to the other question, does the crank need to be removed for decking?you should strip the entire block...... remember you are going to run new pistons... which mean new rings... which mean you will need to hone the cylinders at the very least.... so yes... you will need to remove the crank
I know a guy who totally honed the cylinders without removing the crank
--->this guy<---
tuna55 wrote:oldeskewltoy wrote:I know a guy who totally honed the cylinders without removing the crank --->this guy<---volvoclearinghouse wrote: And to the other question, does the crank need to be removed for decking?you should strip the entire block...... remember you are going to run new pistons... which mean new rings... which mean you will need to hone the cylinders at the very least.... so yes... you will need to remove the crank
Is that so? PM incoming..
I just realized you can back calculate the compression height from deck height, stroke, rod length and deck clearance, I get 1.768, the .002 can easily be accounted for by your straight edge of questionable strightness or being slightly off TDC.
In reply to BrokenYugo:
Correct, assuming the parameters you quote are to the Ford OEM parameters.
The straightedge is potentially of questionable straightness, though I tried various portions of it and kept finding the 0.024 feeler was the best fit. So, if it's un-straight, it's consistently un-straight. 
oldeskewltoy wrote:volvoclearinghouse wrote: And to the other question, does the crank need to be removed for decking?you should strip the entire block...... remember you are going to run new pistons... which mean new rings... which mean you will need to hone the cylinders at the very least.... so yes... you will need to remove the crank
Since the engine's on a stand, I could just rotate it upside-down when honing, so the debris falls on the ground and not into the crank area.
You can do many things.... but I've found that short cuts tend to backfire... Not all the time... but when they do, you end up doing things a second time... and usually for additional cost. An engine being used in competition (even low cost racing), is going to find the flaws...
It isn't hard to dis-assemble the rest. Be careful, mark each bearing as to its location, and bag them. Then you can hone and clean completely leaving no residue. Once the block is clean and dry re-assemble, and check clearances with Plastigage. If clearances are good.... re-assemble the bottom end with assembly lube
In reply to volvoclearinghouse: Please be reasonably scientific about what you intend to do.. Porting exhaust ports tends to be a waste if you have to use the cast iron manifold.. The problem is not so much restriction or lack of flow (remember the exhaust only needs 80% of the flow of the intake because the piston is pushing the exhaust out when the exhaust valve is open). Camshaft design can accommodate some deficiency. The problem is that ports right next to each other may be 90 to 270 degrees apart and depending on where the outlet is and exhaust pulses can "stack up"
As to camshaft design you should have a baseline of what sort of time you spend at whatever RPM you are running at.. Let's assume 80% of the time you are at between 4000 and 5500. That is the only thing that matters.. how much power/Torque do you gain(or lose) at those RPM? You will quickly find out the real power gainers all gain power at RPM you won't use or will only be at for 2 or 3% of the time!!! and spending money for a new cam and lifters won't really gain you much on the track.. There are plenty of those Engine analyzer programs around that will tell you what you wind up with. You spend about a 1/2 hour plugging your specs into it (or changing something similar to your specs) and now you can see what the compression gain will yield or what the exhaust port work will yield. How much whatever camshaft you are thinking about using will yield,.... whatever
If you really want to be obsessive it is possible to calculate any possible lap time changes..
frenchyd wrote: In reply to volvoclearinghouse: Please be reasonably scientific about what you intend to do.. Porting exhaust ports tends to be a waste if you have to use the cast iron manifold..
We plan on using headers. Also, it's a good learning experience, since I've never really ported anything before.
frenchyd wrote: The problem is not so much restriction or lack of flow (remember the exhaust only needs 80% of the flow of the intake because the piston is pushing the exhaust out when the exhaust valve is open). Camshaft design can accommodate some deficiency. The problem is that ports right next to each other may be 90 to 270 degrees apart and depending on where the outlet is and exhaust pulses can "stack up"
I understand that's generally why cast log exhaust manifolds suck. Hence headers.
frenchyd wrote: As to camshaft design you should have a baseline of what sort of time you spend at whatever RPM you are running at.. Let's assume 80% of the time you are at between 4000 and 5500. That is the only thing that matters.. how much power/Torque do you gain(or lose) at those RPM? You will quickly find out the real power gainers all gain power at RPM you won't use or will only be at for 2 or 3% of the time!!! and spending money for a new cam and lifters won't really gain you much on the track..
That's too scientific for us. We don't use any fancy data acquisition or anything like that. I know from driving the car that we tend to run above 2000 RPM basically everywhere on the track, and touch 4200 or so at a couple of places. With a 3.25 gear, which we plan to swap to from the current 3.00, we might touch 4500 RPM. Most of the time on track is spent between 3000 and 4000 RPM, I'd estimate.
We're also not really spending much money. So far we have $200 into the engine 'core' and a case of not-very-expensive beer into performance parts.
We also kinda need to build a new engine, anyway, since the old one's getting tired. So we might as well put some effort and thought into it.
frenchyd wrote: There are plenty of those Engine analyzer programs around that will tell you what you wind up with. You spend about a 1/2 hour plugging your specs into it (or changing something similar to your specs) and now you can see what the compression gain will yield or what the exhaust port work will yield. How much whatever camshaft you are thinking about using will yield,.... whatever
I did just that. I think I mentioned somewhere earlier that the combo we want to run should net us around 300 HP in the 3000-4500 RPM range, and 450 lb-ft of torque in the 2000-4000 RPM range.
frenchyd wrote: If you really want to be obsessive it is possible to calculate any possible lap time changes..
Again, we don't use any telemetry, and lap times recorded vary a lot due to driver differences, track conditions, and whether a Fiat spat all of it's engine oil across Turn 14. It's more about having a bit more loud available under the pedal, a little more mash-you-against-the-cheap-race-seat thrust, and a bit bigger grin as the Miatae and E30 disappear in the panoramic mirror.
volvoclearinghouse wrote: Again, we don't use any telemetry, and lap times recorded vary a lot due to driver differences, track conditions, and whether a Fiat spat all of it's engine oil across Turn 14. It's more about having a bit more loud available under the pedal, a little more mash-you-against-the-cheap-race-seat thrust, and a bit bigger grin as the Miatae and E30 disappear in the panoramic mirror.
This, this is the epitome of the Grassroots Spirit. Keep it up!
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