Hey everyone.

I'm in the middle of re-biulding an engine that was pulled from an '89 F-450 Super Duty, a 460. This engine is going to be swapped into my 1977 Lincoln Mark V.

I'm in the middle of a re-biuld of the new engine (which is TPI of course). The stock pistons are 8.5:1, and i'm looking to get slightly higher compression pistons (the stock pistons were shot, a couple of them had chunks burned out of them), probably around 9:1. I'm going to be ordering a master re-biuld from PAW (Preformance Automotive Warehouse). The price difference between the stock cast pistons (8.5:1) and the 9.2:1 hypereutectic Keith Black pistons is around $200.

Now, this engine will be running most of the time on 87 octane, so biggest question is will i still be able to run 87 octane on a 9.2:1 compression on a 460. I'll probably be getting a diablo chip with programs for 87 and 93 octane, becasue the car will more often then not be my daily driver. The 93 octane program would only be used when takeing it to the track.

Also, how much power will i really gain going from 8.5:1 to 9.2:1? This engine will be in a '77 Lincoln Mark V, a 5,200lb tank of a car (), so the car is NEVER going to be 'fast'. I just like to have some power. The engine is going to have a aftermarket camshaft and some other minor tweeks for power, and i'm just wondering if the higher compression will be worth the $200 more.

Thanks for your opinions.

 

When you up the compression ratio you will get more power. You may or may not be able to run 87 octane with the 9.2:1 ratio. My guess is it will not run on 87 without some serious pinging. Since gas is so expensive now anyway, why not pay for premium gas. Regular is not cheap anymore.

 

Yeah, i know i'll get more power, i'm just wondering exactly how much power i'm actually going to get. Is it worth the $200 more?


As for pinging, i've been told that i'm on the bleeding edge of being able to run 87. In the winter i'd probably be okay (f$cking chicago winters) as the colder temps will keep it reasonable, but in the summer i might need mid-grade, and i'm just trying to figure out if the added costs of the pistons and gas is worth the extra power.

 

It is impossible to know how much power you will get. There are too many variables. However, my point was that regular is not cheap anymore and that it isn't that much more for premium. Here in Florida regular is about $2.00 a gallon. What is another .20 cents per gallon? I think it is worth it.

 

With an aftermarket cam, 9.2:1 should be no problem at all, even on 87 octane. I presume you are mod'ing a computer to match the car and motor? Just have the chip set for the gas you plan to run, with (if possible) an alternate burn set for the higher octane if you want. If you go to KB's website, they have a calculator there to figure your actual compression ratio with the cam, combustion chamber, etc.

 

Hey Breeze, thanks for the reply. Yes, i'm probably going to get a 3-stage diablo delta chip custom-programed for an 87 octane and a 93 octane program.

I looked at that calculator on KB's site, and unfortunetly it askes for a lot of info that i don't know (gasket thickness and whatnot). I'm also still trying to figure out what size my heads are. I'm useing the stock heads on the engine (again, a 460 off an '89 F-450), and most places ask for the head size (in cc i guess?) when i order pistons. Any idea how to find that?

 

92-95cc heads in that era. With the KB pistons, you should be in the 8.5-9.5 range. Roughly 8:1 (corrected) is the max CR with Iron heads and Pump fuel (premium). There are other factors that come into play, but usually arent an issue unless you are building to the extreme in CR, Cam, etc. We have 2 460s at the shop running 9 and 9.5:1 respectively. One with a Performer cam and the other (9.5) with a Comp Cams 4x4 Extreme cam, both run pump 87 all day long with no problems at all. My 429CJ powered 1990 F250 has a advertised CR of 11.26:1, corrected to 8.1:1, and with the aluminum heads, we are aiming to have it run all day long on midgrade.

Try this calculator here http://kb-silvolite.com/calc.php?action=comp2 to give you a general idea (all it needs is advertised CR, rod length (6.605), stroke (3.85) and cam closing), and if you havent read it, this is a very good piece on compression ratios http://kb-silvolite.com/news.php?act...c1223bb1e28c1f

 

Thanks again for the reply breeze. I'm still not COMPEATLY clear on one thing. I put in what i belive to be the right number for my cam (the catloug is pretty unclear, and i'm also damn inexperianced), but i put in 262 for the cam closeing. Does that sound about right for a cam rated for lots of low-end with power between 1500-4000rpm?

*edit* Oh yes, and the calculator put out something like 5.1. does that sound right?

 

Not really... 262 would be the duration of the cam. What cam are you looking at using? Using a Comp Cams Magnum 270 (intake closes at 61, add 15 = 76) you get 6.8:1 corrected, which would run very comfortably on 87

 

Hey Breeze. Okay, i'm not sure the number that i'm looking for here then . . . It's an SSI cam kit, specs as follows (maybe something is just named differently?)

Duration @ 0.050 lift . . . . . . . 204-214
Duration advertized . . . . . . . . int 262 exh 272
gross valve lift . . . . . . . . . . . int .484 exh .510
Deg. Lobe Cen (WTF?) . . . . . . 112

That's all the manual gives me. Can you make heads or tails of that?

 

What you need are the opening and closing events on the intake. It will be on the cam card with the cam, but usually not in the manual. You will need to call and get them. The numbers are given in degrees. (IE, Opens at 26, closes at 56 or such) the closing number is what you need to compute your corrected CR. A quick cam tutorial.... aim to keep the numbers as low as you can (26/56 for example instead of 32/62) as the lower numbers will make for a more responsive motor. A higher set of numbers will give more top-end power, but will usually result in a less streetable motor, plus a 460 is not designed to turn 6-7000 RPM, and being in a 77 Lincoln, you are going to want all the bottom end oomph you can get with that heavy of a vehicle. Also, I would suggest using a Comp (my preferance) or Crane over the "house brand" cams from PAW, just a personal preferance there, as the price differance between the two (comp and house brand) is very minimal and Comp has an excellent tech line. Another thought.... the price of a kit with pistons and all from Summit Racing or PAW, minus the camshaft, plus a comp cams (or crane) is going to be very close to the cost of the kit with the house cam. A comp cams Extreme energy 262 (cam grind xe262h p/n 34-238-4) would be very close to what you are looking at in the house brand, and will run 87 pump with your application and 9-9.5:1 pistons.

Comp Cams tech help line 1-800-999-0853

 

Okay, i was able to get ahold of PAW and ask them about the cam opening and closeings, this is what they gave me:

@0.050 lift:
intkae open 5 BTDC
Exaust open 44 BBDC
Intake close 29 ABDC
exaust close 10 ATDC

Plugging those numbers into that calculator thing, even with the STOCK 8.5:1 pistons, it still gives an actual compression ratio of 8.159!

Is there something wrong here?

 

*bumpity bump bump*

 

What gear ratio is in this, I also assume that it will have a C-6 automatic in it?

When you did it did you add 15 degrees to the intake closing figure? If not you need to which would make it 44 not 29.

Using your numbers I get a effective compression ratio of 7.88:1 which will run on unleaded although you might need premium.

I ran the KB 137 in my 460, with 92cc heads they were 10.3:1 comp. ratio. First I had a Edelbrock performer cam in it a it pinged terribly even on 91 with octane boost in it. Then I switched to a Comp Cams X-treme 4x4 cam and it ran great on 89 octane and it started getting significantly better mileage. The truck weighed 7000 lbs. It would be a great car motor.


Here is the specs on my cam
PART NUMBER34-235-4 
ENGINE FORD 429-460
GRIND # FF X4 262H-11
DESCRIPTION STAGE I
INT EXH
VALVE ADJUSTMENT HYD HYD0
GROSS VALVE LIFT .514 .524
DURATION AT
.006 TAPPET LIFT 262 270
VALVE TIMING OPEN CLOSE
AT .006 INT 24 58
EXH 70 20

THESE SPECS ARE FOR CAM INSTALLED
AT 107 INT C/L
INT EXH
DUR AT .050 218 226
LOBE LIFT .2970 .3030
LOBE SEPARATION 111.0 INT MASTER ID 5432
ADVANCE 4 EXH MASTER ID 5414
RECOMMENDED CC VALVE SPRINGS 926-16

With that cam and my 10.3:1 comp my effective comp was only 7.64 with the edelbrock cam it was like 9 something so it made a big difference.

As someone else said I would stick to a Comp or Crane cam not some off brand. I personally prefer the Comp Cams, and like said earlier they (Comp) has a extremely helpful tech line.

 

Thanks for the post, brian.

The stock rear gears in this car were 2.73, but due to the OD in the new tranny i'm changeing them to 3.25. The transmission is going to be an E40D (i got the engine and trans from the same truck, '89 F-450 Super Duty).

I did not, however, add the 15 to the intake close. That does bring it down to a more reasonable 7.714 actual compression useing 8.5:1 pistons. Plugging in 9.2:1 pistons gives me 8.341, though, and with an iron block and iron heads, i'd probably ping it to death on 87 i would think.

Thanks for the tip on that cam, PAW carries it. It's about $70 more then their house brand cam, though. : \ You think i would be able to use the 9.2:1 pistons with it, though? I'd kinda like to, haveing hyper-whatevered pistons would make me feel better about maybe adding nitros to it in the future sometime.

You wouldn't happen to have the opening and closeing events for it?