2.0 Pinto w/ 45s & GTS1 Cam

[westcort]

Long time forum lurker here... figured I'd contribute something, ask a couple questions & share my last dyno run.

Modifications are:

2.0 Pinto
Ported Head with oversize inlet valves (I forget the size)
Head has been skimmed a bit, but not a lot. I forget how much exactly hence the CR is not known. I believe it's around 10:1 or so.
Kent GTS1 camshaft w/ vernier pulley, matching Kent valve springs
Twin 45 DCOEs - 62mm trumpets, 36mm chokes, 140 mains, 155 Air correctors, F16 Emulsions, 55f9 idles, 4.5 Auxiliary Venturi, 40 Pump Exhaust Valve, 45 Pump Jet, 2.00 Needle Valve
Standard fuel pump w/ Malpassi fuel reg set to just under 3psi
4-2-1 headers into 2 1/4" exhaust
Burton Electronic distributor w/ matching coil, 30 degrees timing all in
Running 98 octane fuel

Run 1 was done before run 2 where I'd added the vernier, re-timed the cam and swapped out the points dizzy for the electronic one.

119hp @ wheels, 116 ft/lbs @ wheels
163hp @ fly & 159 ft/lbs @ fly (estimated)

Keen to hear some thoughts from those more experienced engine builders/tuners here about anything that stands out from the graph and specs, room for improvement, or any comments in general. Would like to know the best place to get the next 10-15hp from. I know this is very difficult to say without knowing CR as it's likely where the gains would lie, so maybe taking a head off and working that out is the next step.

Questions:
I'm curious about my 140 mains and 155 air correctors, it seems like most engines with similar specs I've seen have bigger mains and airs. From my understanding the bigger your mains, the bigger your airs need to be, and vice versa. Would I be able to go up in mains and also airs to potentially make more peak power, or is there more to it than this. The tuner said we were on the verge in his mind of needing to go to 145 mains, but he didn't have any comments on the airs too.

I'm also curious about peak power being just over 5500rpm, I'd have thought it'd be higher up the rev range around 6500 given the camshaft. What keeps it sitting at 5500rpm? Choke size in the carbs? Would 38mm chokes make slightly more power at the expense of the mid range?

I'm also chasing a clean progression between the idle and mains circuits. I have 55F8s originally but changed to FF59s with better results. The 55F9s are great when the engine is cold, but once it warms up it runs worse, even after adjusting the mixture screws. Considering going to 60F8s to see if that makes things better or worse. Right now there's a stutter at around 2500rpm if you're moving at a moderate speed in first gear, and it can splutter a bit between gear shifts. Once the car is warmed up and I'm sitting in traffic for example, this is where the progression seems to be worse. Will the engine be running richer once it's hot?

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[Graham]

some thoughts, give the jet sizes the power and torque figures look rather optomistic to me, as does power given the power peaks at such low rpm.

in this case i would say small airs in relation to mains means its not working well at high rpm, which it isnt. it may be the 140mains are actually too small and being masked by the equilly small airs.
A switch to 38mm chokes may extend the top end performance, and will definatly require bigger mains and airs.
From my finding the burton distributor wont have enough advance at high rpm, not that your engien is exactly doing high rpm
the engine wont run richer hot, but it will prefer a leaner mixture.
cam manufactures tend to quote the maximum extremes at which a cam will work. look at my recent cam test for some more ideas http://www.turbosport.co.uk/showthre...RALLY+CAM+TEST

[katana]

I'm no dyno expert but I'd say the dyno calibration is way out - no drive train should 'loose' 50% of generated power - i'd say 20% would be a lot!
Was this just a power run or a proper tuning session? If the latter, the operator needs some more schooling cause that certainly isn't optimal.

[mariors2000]

It's lost 40hp in drive train how did you get 50% lost or am I missing something

[westcort]

Thanks for the reply Graham. I just realised I posted the same dyno page twice, here's the second page with the graph and AFR details as well which may provide more clues perhaps.



To reply to your points Graham, do you mean that it is because of the small airs in relation to mains, this could be the reason it's not performing well at high RPM? Or this combination of jets is required due it not performing well at high RPM because of another reason (flow of head perhaps)?

Given the specs of the engine, what size air and main jets would you usually start with? Originally we started with 145 mains but it ran too rich so dropped to 140, but I'm wondering if the 145's were too rich because the 155 airs were too small in relation, and really we should've gone bigger airs first to see if the 145's would work.

Regarding the dizzy, it's only got between 10-12 static advance, so can go plenty more all in if required, but after experimenting with more total advance (34-36) the engine actually produced less power. We found that where it sits now is actually the sweet spot (30ish degrees).

Thanks for sharing the other thread, having a read through that now. Just want to also say thanks for the countless hours you put into sharing your dyno work too. I've watched nearly all your youtube vids and they are a huge wealth of knowledge which helps enthusiasts like myself a lot who live in parts of the world where it's hard to come by this kind of knowledge. If you set up a Patreon or something similar would happily buy you a few pints. Cheers

[Graham]

i just meant its not performing that well at high rpm, you are correct theres a good chance it was rich on the 145's because the airs are so small, the effect isnt dramtic but airs will have some effect on the mixture at lower rpm.

assuming a sensible engine spec my go to starting main size for 45's is 145 and i'd probably pair that with a 170ish air, sometimes the air size just depends on what size i have thats not already in another set of carbs

re timing, i have found a few engines which only want 28 odd degrees around 3500rpm, but @5,000 plus want as much as 33/34. im told that the magnetic trigger in the burton system tends to retard at high rpm, although i havnt actually measured it

[Miniliteman]

My 2 cents: GTS1 is ultimate road cam you will need a very good flowing head to get the full out of this cam.
Looking at the figures the 140 main jet and approx. 115 bhp at the wheels (graph) sounds compatible to me. What isn't is the approx. 162 bhp at the flywheel. It would be more like 135 bhp. Think there is a miscalculation in the flywheel bhp figure. Maybe it is one of the settings used. Looking at the rpm and mph of the max power listing (5727 rpm and 88 mph) that doesn't match the test gear setting of the software (3.000 and 1.000) .

Suggest you try 145 main jet, a 170 air jet and 55F6 for idle.

[katana]

It's lost 40hp in drive train how did you get 50% lost or am I missing something

118hp / 2 (50%) = 59hp + 118hp = 177hp . . . . .ok 15 off but I only glanced at the figures and thought 118 read 110 which would have made it 110 + 55 - 165 !
118hp x 0.4 (40%) = 47.2hp + 118hp = 165.2 so closer to 40%, so apologies but its still a lot!

[Forest_rallying]

When you say standard fuel pump, do you mean the the mechanical one on the side of the block? If that’s the case then it needs replacing with something like a Facet.

I was hoping that Graham might have tested the GTS1 cam as it’s specification would suit a Rally cam with its very high lift and short duration. The Dyno sheet says it’s a std cam, was that a mistake? Your guess for the compression ratio sounds a bit hit and miss for my liking, maybe a compression test might give you some idea on cylinder pressures. It’s difficult to say much about your head regarding the big inlet valves and porting without seeing photos of it. I have known of badly done heads producing very little more power than std.

I think the 160bhp is a tad optimistic, Miniliteman is correct with about 135 to 140 @ the flywheel. I don’t think going to 38mm chokes is going to make a blind bit of difference to the power of your engine, it could even make some of you running issues worse.

[Miniliteman]

The Dyno sheet says it’s a std cam, was that a mistake?

To be honest when I first saw the jetting and the rearwheel hp I thought that can't be a GTS1. Looking at it again and also at the lambda-graph it could well be a std cam.

[mariors2000]

Puma race engine says about 17% drive train losses and dyno on this forum dirk said similar results also I think 20% is fair what do you guys on hear think cheers mario

[Miniliteman]

118hp / 2 (50%) = 59hp + 118hp = 177hp . . . . .ok 15 off but I only glanced at the figures and thought 118 read 110 which would have made it 110 + 55 - 165 !
118hp x 0.4 (40%) = 47.2hp + 118hp = 165.2 so closer to 40%, so apologies but its still a lot!

That's not how to calculate it. Using approx. values of 120 bhp at the wheels and 160 bhp at the crank for simplicity the drivetrain losses are (160 - 120) / 160 = 25% .

If you look at the dyno graphs and numbers posted you can see a calculated drivetrain efficiency of 76,5% or 23,5% loss.

[westcort]

Hey Fellas, thanks for the replies and thoughts. Miniliteman you are on the money with the drivetrain losses in your post above, that's how it was explained to me by the dyno owner and the math checks out.

Forest_rallying - Yep it's the standard mechanical pump correct. Given AFR ratios are fine across the rev range, I'd have thought standard fuel pump is doing it's job. Curious to hear your thoughts on this?
The dyno sheet comments where it says "Std,Cam,Weber 45DOCE, Mobil 98" the 'Std' is referring to the bottom end which is standard, the cam is 100% for sure a GTS1 as I installed it myself along with matching followers and springs from Burtons.
The question around 38mm chokes wasn't to necessarily chase more power, it was more so a question around the location of the peak power. I was curious if 38mm chokes would move peak power further up the range to circa 6500RPM. More just from an understanding of where the peak power is located in the curve and what effects this.

Outside of the progression issue the engine runs great. Might pull the head off for a look when summer comes to get more concrete info, but will try the suggest 145/170/55F6 jets too

Here's a photo of the jewelry box incase anyone's interested

[westcort]

Side note: I thought on equal scaled graphs, Pintos only produced more HP than Torque once you hit 150hp?

[Forest_rallying]

My 2 cents: GTS1 is ultimate road cam you will need a very good flowing head to get the full out of this cam.
Looking at the figures the 140 main jet and approx. 115 bhp at the wheels (graph) sounds compatible to me. What isn't is the approx. 162 bhp at the flywheel. It would be more like 135 bhp. Think there is a miscalculation in the flywheel bhp figure. Maybe it is one of the settings used. Looking at the rpm and mph of the max power listing (5727 rpm and 88 mph) that doesn't match the test gear setting of the software (3.000 and 1.000) .

Suggest you try 145 main jet, a 170 air jet and 55F6 for idle.

Hey Fellas, thanks for the replies and thoughts. Miniliteman you are on the money with the drivetrain losses in your post above, that's how it was explained to me by the dyno owner and the math checks out.

Forest_rallying - Yep it's the standard mechanical pump correct. Given AFR ratios are fine across the rev range, I'd have thought standard fuel pump is doing it's job. Curious to hear your thoughts on this?
The dyno sheet comments where it says "Std,Cam,Weber 45DOCE, Mobil 98" the 'Std' is referring to the bottom end which is standard, the cam is 100% for sure a GTS1 as I installed it myself along with matching followers and springs from Burtons.
The question around 38mm chokes wasn't to necessarily chase more power, it was more so a question around the location of the peak power. I was curious if 38mm chokes would move peak power further up the range to circa 6500RPM. More just from an understanding of where the peak power is located in the curve and what effects this.

Outside of the progression issue the engine runs great. Might pull the head off for a look when summer comes to get more concrete info, but will try the suggest 145/170/55F6 jets too

Here's a photo of the jewelry box incase anyone's interested

Attachment 88674

I had problems with a NA Cosworth engine with Hot air at stage starts on Rallies, the filter king was in exactly in the same place as yours. The hot air from the radiator fan was hitting the filter causing it to get warm and the fuel was evaporating. I moved the filter and the problem was cured. I would still bin the mechanical fuel pump, they have no place feeding a pair of 45’s.

[Graham]

The question around 38mm chokes wasn't to necessarily chase more power, it was more so a question around the location of the peak power. I was curious if 38mm chokes would move peak power further up the range to circa 6500RPM. More just from an understanding of where the peak power is located in the curve and what effects this.

38chokes are only likely to move peak power up the rev range if they are holding the engine back, to a point the worse the head the more likely bigger chokes will help. a head which works really well will get away with more restrictive carburation. you just have to look at a lotus/ford twincam, on 40mm carbs they can make power that a pinto can only dream of on the same size carb

[Forest_rallying]

38chokes are only likely to move peak power up the rev range if they are holding the engine back, to a point the worse the head the more likely bigger chokes will help. a head which works really well will get away with more restrictive carburation. you just have to look at a lotus/ford twincam, on 40mm carbs they can make power that a pinto can only dream of on the same size carb

I think there are other issues with the engine that’s making it produce maximum power at such low RPM. It’s characteristics are similar to a Sig Erson 134 cam.

[westcort]

I had problems with a NA Cosworth engine with Hot air at stage starts on Rallies, the filter king was in exactly in the same place as yours. The hot air from the radiator fan was hitting the filter causing it to get warm and the fuel was evaporating. I moved the filter and the problem was cured. I would still bin the mechanical fuel pump, they have no place feeding a pair of 45’s.

Great pick up mate, I wonder if that's the cause of my 'progression' issues. As mentioned earlier the issues only arise once it heats up in traffic or been stationary. Sounds similar to your stage starts. Easy enough to investigate and test if it makes any difference, will give that a shot.

I'll get the head off for a look once summer comes around and share the findings. Given everything else about the engine is either new or of known/confirmed specs, if there are issues it'll be there. Maybe the port work is garbage and it's not flowing enough, or maybe the CR isn't high enough for the cam, or both, we'll see.

[mariors2000]

Have you got flow numbers for cylinder head did you get it flowtested

[Tpau]

Uncle Tony had a long talk about bore taper (wonder if that’s spelled correctly)
He described a case where if the bores are worn bigger on the middle the engine will still give decent power and compression at low rpm but not giving good power at the top.
The theory was that the rings would not keep the seal to do the bore as rpm increased

So when checking the head check your bores as well
/T

[Forest_rallying]

Great pick up mate, I wonder if that's the cause of my 'progression' issues. As mentioned earlier the issues only arise once it heats up in traffic or been stationary. Sounds similar to your stage starts. Easy enough to investigate and test if it makes any difference, will give that a shot.

I'll get the head off for a look once summer comes around and share the findings. Given everything else about the engine is either new or of known/confirmed specs, if there are issues it'll be there. Maybe the port work is garbage and it's not flowing enough, or maybe the CR isn't high enough for the cam, or both, we'll see.

Don’t forget to fit a decent electric fuel pump whilst you’re at it.

Also don’t forget to calculate deck height and head gasket volume when working out your compression ratio.

[Graham]

Great pick up mate, I wonder if that's the cause of my 'progression' issues. As mentioned earlier the issues only arise once it heats up in traffic or been stationary. Sounds similar to your stage starts. Easy enough to investigate and test if it makes any difference, will give that a shot.

I'll get the head off for a look once summer comes around and share the findings. Given everything else about the engine is either new or of known/confirmed specs, if there are issues it'll be there. Maybe the port work is garbage and it's not flowing enough, or maybe the CR isn't high enough for the cam, or both, we'll see.

ignition timing doesnt suggest CR is too low for cam

[Forest_rallying]

As a matter of interest Westcort, how much have you had to machine the head for the valve spring platforms and what springs are you using? The Kent GTS1 cam has an advertised valve lift of a whopping 13.65mm (537 thou) for the inlets, a lot of lift for what they are selling as a fast Road cam.

[Miniliteman]

ignition timing doesnt suggest CR is too low for cam

From the info I gather it runs best with 30 degrees all out (best power). That doesn't suggest that CR is too low for me.

[Graham]

From the info I gather it runs best with 30 degrees all out (best power). That doesn't suggest that CR is too low for me.

thats what i said!

[Miniliteman]

thats what i said!

I need glasses

[westcort]

As a matter of interest Westcort, how much have you had to machine the head for the valve spring platforms and what springs are you using? The Kent GTS1 cam has an advertised valve lift of a whopping 13.65mm (537 thou) for the inlets, a lot of lift for what they are selling as a fast Road cam.

I haven't machined the head at all for the valve spring platforms mate, and I used "VALVE SPRING SOHC PINTO/ESSEX COMPETITION SINGLE FT415" as suggested from Burton Power when I asked.

Which electric fuel pump is the best for this application mate? What does everyone go with. And do you still run the fuel pressure regulator if the electric pump puts out a low enough psi?

Mariors2000 - No head flow figures, but if I get more work done this summer I'll get some

Tpau - Yep that'll be the plan once the head it off, fair shout

[Graham]

I haven't machined the head at all for the valve spring platforms mate, and I used "VALVE SPRING SOHC PINTO/ESSEX COMPETITION SINGLE FT415" as suggested from Burton Power when I asked.

Which electric fuel pump is the best for this application mate? What does everyone go with. And do you still run the fuel pressure regulator if the electric pump puts out a low enough psi?

Mariors2000 - No head flow figures, but if I get more work done this summer I'll get some

Tpau - Yep that'll be the plan once the head it off, fair shout

i will be somewhat at odds with some here, but a good standard pump will supply 145bhp no problem, in fact it will even go a bit more in short bursts.

any electric pump man enough to supply your fueling requirements really needs a regulator

[Forest_rallying]

i will be somewhat at odds with some here, but a good standard pump will supply 145bhp no problem, in fact it will even go a bit more in short bursts.

any electric pump man enough to supply your fueling requirements really needs a regulator

That’s strange Graham, I am sure I read in one your posts from many years ago that the standard mechanical pump was inadequate for that purpose, maybe I am going senile! I have yet to see a decent competition engine of all specifications with the std fuel pump, we even had electrical twin SU’s on a 1558 Twink.

[Graham]

That’s strange Graham, I am sure I read in one your posts from many years ago that the standard mechanical pump was inadequate for that purpose, maybe I am going senile! I have yet to see a decent competition engine of all specifications with the std fuel pump, we even had electrical twin SU’s on a 1558 Twink.

back in the day it was proven a standard pump runs out of puff around 145bhp, assuming its a good one.

now i have a slightly different take on the subject. it depends how you look at it, a standard pump will go past 145bhp ive proved it on the dyno, BUT ive also proved around 150bhp it cant keep up with a continuous demand

[alladdin]

I have yet to see a decent competition engine of all specifications with the std fuel pump,.

exactly most pinto that fit your description are over 145
plus theres the " must have" mindset and possibly a reliability factor due to twin pumps ?

modern new pumps may of course be better or worse than originals i have no idea personally

[Miniliteman]

The blueprinted 2 litre GP1 Pinto with a quoted 165 bhp had a mechanical pump.

[Forest_rallying]

The blueprinted 2 litre GP1 Pinto with a quoted 165 bhp had a mechanical pump.

Maybe that’s so, but you are talking of a brand new fuel pump there and even one that might be
slightly modified knowing what the Group 1 Regs were like, not one that’s possibly over 45 years old and has been to the Moon and back regarding mileage. I think for what a new Facet pump costs it’s a no Brainer to fit one considering the problems Westcort is having, another possible problem’s then eliminated.

[Forest_rallying]

[QUOTE=westcort;3782045]I haven't machined the head at all for the valve spring platforms mate, and I used "VALVE SPRING SOHC PINTO/ESSEX COMPETITION SINGLE FT415" as suggested from Burton Power

I would be checking your cylinder head geometry when you get the head off and asking why a cam of that lift hasn’t needed the spring platforms machining for one. Are the Burton single springs of a thin coil wire, is there one less coil than a conventional spring or have they just gone soft like a Biro spring. I bought a single set of Newman springs with an order, the wire was so thin you wouldn’t even want them in the base of your armchair. We have all heard of engines hitting the brick wall because of faulty valve springs. The other thing to check is that you are getting somewhere near the advertised valve lift of the cam model.

[westcort]

So summer is here and as planned the engine is out of the mk2.

We're on a mission to see what I can do to squeeze more juice out of the motor and see if I can figure out / remedy why it makes peak power at a low RPM.

First stop was measuring the camshaft:

The GTS1 has 8.2mm of cam lift according to the Kent cams specs and I can confirm it's more or less correct, maybe 0.1mm short
On the Kent cams website valve lift is 13.65mm Inlet/13.28mm Exhaust and on the burton power website it's Valve Lift: 0.504" inlet/0.492" exhaust. 0.504" is 12.8mm so I'm not sure why there is discrepancy between the two websites but the important part is what the head has and it's ~12.8mm. So confirmed the cam is delivering the desired lift (if we take Burtons figures as correct).

This leads me to believe the Inlet valves are the correct length as the geometry looks good and I believe I'm getting the advertised lift. I haven't pulled them yet but will update on that when it's done. The inlet valves are 44.5mm and exhaust valves are standard. I've gone ahead and bought the 45.7mm 882T valves from REC and will be getting the seats cut to suit and these installed. I know for sure these are standard length, so regardless of what's revealed with the current valves, my geometry should be good moving forward.

The head has a thickness of 93.8mm which I believe is 1mm or 40thou skimmed? The pistons are standard 0.5mm below the deck height and the head gasket came to a crushed thickness of ~1.3mm. At a guess I'd say my compression is below 10:1? Which isn't high enough for the cam no doubt. I imagine this is where I'm losing my power if my assumptions are correct.

I haven't measured the bores as that's out of my league, will leave that to the machine shop, and it's hard to see the full extent of the port work until the valves are out, but it looks like there hasn't been a lot done. Someone has tried to match their carb manifold to the head though by the looks of things and done a terrible job (pics below).. so will get then seen to.

My plan moving forward is this:

Drop the head off to get the new valves fitted.
Get the port work inspected and improved where needed.
Deck the block to bring the pistons flush, and get the bores measured and checked. (I'm hoping to avoid going oversize but will if needed)
Measured the combustion chambers to bring all equal and then plane the head to reach 10.5:1 compression ratio.
Running a felpro 1mm head gasket, so I'll have 1mm of squish.
Run in new rings if required for 200km then back on the dyno to hopefully see a better looking graph.

One other interesting find was that there was no O-ring for my oil spray bar. Not sure what happened to it, whether it perished or what. Can someone shed light on what material it's made from? There just seemed like some kind of what seemed like piece of swarf there... But the camshaft looks good so I'm assuming oil was still getting to it fine so the spray bar must have somehow been sealed?

[Graham]

spray bar o ring is black rubber/viton or similar, i dont always even fit them, so much oil comes through the cam tower it wont effect camshaft lubrication.

[Forest_rallying]

It’s winter here in the Uk and we have approximately 10 inches of Snow this morning which arrived overnight.

I noticed the cam lift that Kent advertised the GTS1 at and thought it was very high lift for a fast Road cam, so I would think the Burton advertised lift to be the correct one.

There’s plenty of good information about head porting somewhere on this forum to help you out and yes the inlet ports look a bit of a mess and need tidying, it looks like someone’s been trying to replicate an injection port.

I don’t think you’re far off the mark with the rest of your mods, although I wouldn’t have bothered going for the Group 2 size valves if your Group1 valves are in good condition. Keep us all informed on your progress.

[alladdin]

could well be an almost standard head going on whats visible.

[alladdin]

we have approximately 10 inches of Snow this morning which arrived overnight..

drizzle here in wales

[Forest_rallying]

drizzle here in wales

Grizedale stages had to be abandoned yesterday morning due to deep snow, with some people stuck in the Forest overnight.