Your Pinto Compression Ratio?

[Snapperpaul]

I have researched myself into a corner and now need some "Real World" data.

What cam and compression ratio are you running?

Who needs super unleaded with what compression ratio and cam?

With this data i can get a Matrix going of compression, cam and Octane, then i will have a better idea of of where to start with my engine.

[Guest SEgan]

Hope you don't mind me adding to this thread Paul as I am also interested in the points you have raised. I have read the chapter in Des Hamill's book but would like real world experience, also in addition whats best?

 

High compression ratio with less advance to stop knocking OR

Lower compression ratio with maximum advance (36ish degrees)

 

Modern engines seem to run higher compression ratios on standard fuel AND have much better shaped combustion chambers, (Zetec 2.0 10.2:1). If the timing can be accurately controlled (Mega Jolt?) then surely up to 10.2:1 on standard petrol should be ok.

 

Also how much of a difference does it make?

 

Views??

 

Sean

[Guest mower man]

Hi do not know what comp my 2 .1 is but it is very sensitive to ign timing ,seems to run on normal fuel ok but seems alittle more responsive on super head is std except for .75mm skim piston is at deck hieght, head gasket is Elring compressed to 1mm . mowerman all comments welcomed

[Snapperpaul]

Mowerman your compression ratio will be around 10.3 to 1 which is the boarder line between 95 and 97 octane.

I will do the proper maths on your configuration when i get to work.

If you go Megajolt you could have 2 maps which can be switched on the fly for different octane's

[Snapperpaul]

SEgan , i have the problem that the head i have has 40cc chambers and on a 2.1 bottom end gives a bit more static compression than i want but the cams require more compression to work properly.

And this is where the dilemma is, i can modify the compression ratio with the different thicknesses of Cometic Multi Layer gaskets available from about 10.3 to 11.2.

 

The Pinto like compression and i will be using valve lubricant such as Millars (the head is an old but well modified leaded one) so i may as well use one with octane booster.

Do i use 95 + booster ( prudent as you can get 95 anywhere) 97 and booster (11.1 should be no problem) then which of the cams do i set the engine up for (285, 305, 312)?

I am erring on 10.5 to 1 and the 305 cam.

 

I would always build to the best compression ratio for the fuel as the Pinto like compression

10.2 should be fine but the cams like more, on a standard engine you can use a Felpro gasket and try it out then swap to a standard gasket if it pinks, for me the Adjusa gasket that crushes to 1mm does not help and they dont do a standard gasket for a 93mm bore so its Cometic MLS for me and they are £100 a throw.

 

Pistons are good for 10.5 to 1 so that should be my limit but then we get back to actual chamber pressure which is less than static due to the inlet valve closing fully after BDC but then volumetric efficiency rises as the revs go to peak torque, then my head explodes.

 

So i am now asking for what compression ratio and cam you have with what fuel the engine is happy with.

[Guest SEgan]

Hi Paul

 

I see your 'problem' and at £100 per head gasket it is a decision you want to get right first time

 

I was running a 300 deg cam with the standard static compression, the cam was great at the high end but gutless on pickup due to the valve overlap. I am currently re-building my engine after failure of big-ends following a day out at Barston with a low oil level . While I have it all in bits I have decided to take 60 thou off the head to bring the compression up to 10.2 with a standard gasket, with the option of a thin one if I want to go futher

 

With a compression ratio of 10.2:1, I am tempted to stick the standard injection cam in to bring the rev range down and thus less likely to destroy the bottom end. Has anyone run a higher compression ratio with the standard cam?

 

My 300 degree cam is an FR1 it gives about 10% more lift with the extra duration, I think 10.2 is quite conservative for a 300 but we will see.

 

Sean

[Guest mower man]

Thanks for the info I got a similar reading from my portable oxy powered computer using such parameters as luck and pure guesswork!! Would realy like to see your figs .By the way the computer is a permanently attached to my shoulders but gets frozen quite easily by having falling down water poured into its front loading port????!!!*&^%$£ Best wishes and regards mowerman

[Guest old_timbo]

My Pinto has a standard carb. 2.0l bottom end, standard head gasket with a flowed 2.0l injection head, flowed and matched inlet manifold, weber 32/34 dmtl carb, Piper 285 cam. I modified a standard Bosch dissy to go fully advanced at 3500 rpm. Using Shell V-Power I got max power on the rolling road at 5800 rpm 32 deg advance (which gives 8 deg at idle). Was told max power was 148bhp at flywheel, but think its probably in the 130's in reality. Cammy tick over at 900rpm, good of low down grunt. On ordinary unleaded runs noticably worse - less low down torque, less willing to rev. so normally use V-Power. Also good on Murco and Essso Super Unleaded, pants on BP Ultimate.

 

Tim

[Guest combatsapph]

2.1 Pinto, Piper OHC134 high torque cam, 10.7:1 compression - runs on normal unleaded.

 

Super unleaded gave me no extra power - max torque @ WOT is achieved @ 36 deg on my Pinto - super unleaded let me run up to 40 deg but by then torque was dropping off noticeably.