How To Get 500+ More RPM, Without Changing Cam Options

[motorvated]

2.0 Liter Four. Doing a top end refresh and not planning on splitting the cases or changing the cam. Would stiffer valve springs and beefier pushrods get me there. I'm a little confused when looking at aftermarket springs, as the European Motorworks Single HD springs are rated at 135 psi seat pressure, and stock springs are rated at about 175 psi. Also thinking that chromoly pushrods set at zero clearance cold don't let the valves open fully when hot due to the lower expansion of the pushrod, plus they are a lot heavier than aluminum pushrods. So what can I use to get those elusive extra 500+ rpm? My old stock 1.8 floated valves up near 6,000, which wasn't bad, but I'd like a little more with the 2.0 liter. I'm racing the car in Vintage. Any suggestions.

[Dave_Darling]

Stiffer springs should get you there, but it won't help. Power drops off like a rock above 5000 RPM, so going up to 6K is pretty much a waste of time. The heads/cam/valves just don't breathe at that RPM.

Not sure what the deal is with the HD versus stock spring pressures listed, but I wouldn't be surprised if they were measured in a different way. (Such as spring relaxed for the one versus compressed to a specific height for the other.)

--DD

[wndsrfr]

Stiffer springs should get you there, but it won't help. Power drops off like a rock above 5000 RPM, so going up to 6K is pretty much a waste of time. The heads/cam/valves just don't breathe at that RPM.

Not sure what the deal is with the HD versus stock spring pressures listed, but I wouldn't be surprised if they were measured in a different way. (Such as spring relaxed for the one versus compressed to a specific height for the other.)

--DD

Dave's right on...the cam is going to dictate where your power is, but what you want to pay attention to is the torque curve--dyno your car then do a bit of choosing which size rear wheel/tire combination will gear you down or up depending on the track. You can also consider doing the transmission flip of 3rd & 5th and put in an "S" 4th to get AFKaSZ gearing--I love mine....

[GregAmy]

+3. Only value in more RPM witthout moving/improving the power curve (e.g., cams, valves, valvetrain timing) is if your ransaxle gearing *just* doesn't quite work for a particular track/corner/straight and you save time revving for a few seconds within a poor power band versus shifting to a better one.

Away from the track? No value, you're just revving into a range of significantly decreasing torque.

[rhodyguy]

You want to drive around at 6500rpm?

[motorvated]

Stiffer springs should get you there, but it won't help. Power drops off like a rock above 5000 RPM, so going up to 6K is pretty much a waste of time. The heads/cam/valves just don't breathe at that RPM.

Not sure what the deal is with the HD versus stock spring pressures listed, but I wouldn't be surprised if they were measured in a different way. (Such as spring relaxed for the one versus compressed to a specific height for the other.)

--DD

Dave's right on...the cam is going to dictate where your power is, but what you want to pay attention to is the torque curve--dyno your car then do a bit of choosing which size rear wheel/tire combination will gear you down or up depending on the track. You can also consider doing the transmission flip of 3rd & 5th and put in an "S" 4th to get AFKaSZ gearing--I love mine....

You guys are absolutely right. I guess if the torque drops off that dramatically from 5,000 rpm up, then the best shift point from one gear to the next is at the rpm in the shorter gear that corresponds to the same torque at the lower rpm of the longer gear that you're shifting into. Shift at too low an rpm and the torque in the longer gear is too low and you lose power. Also if you you hold the shorter gear to achieve too high a rpm, the torque in the shorter gear drops off too much before you shift and even though the rpm in the longer gear and the associated torque is higher, you've wasted too much time at too low a torque in the shorter gear and lost too much power there. I'd love to see a bunch of torque curves for the engine loaded up in all five standard gears.

[Mark Henry]

Heavier springs also take horsepower to run.

I agree the cam is over it torque curve at 5400-5600 rpm. The T4 has design limitations, The heavy pushrod valve train is a lot to be pushing around at high rpms.
The dual springs stops float when using high lift cams with aggressive ramps and a full balanced rotating assembly. Springs have a lot to do with cam choice, if you put dual springs on an otherwize stock motor you'd lose HP.

When I build a performance T4 I really don't give a shit about the final HP number, it's the torque curve I'm looking at.
Then you have to get that torque to the pavement.

[ConeDodger]

Stiffer springs should get you there, but it won't help. Power drops off like a rock above 5000 RPM, so going up to 6K is pretty much a waste of time. The heads/cam/valves just don't breathe at that RPM.

Not sure what the deal is with the HD versus stock spring pressures listed, but I wouldn't be surprised if they were measured in a different way. (Such as spring relaxed for the one versus compressed to a specific height for the other.)

--DD

Wrong Dave! If you go 500 rpm higher, you make more noise. If you do it enough, you make one final spectacular noise.

[tejon007]

Take a look at the whole picture...racing takes the right combinations of systems. Obviously, the motor and transmission are two important pieces, but there are other important things to consider like suspension, brakes, wheels, tires, etc.

It really makes sense to design a motor with the right camshaft for its intended use and how it works in your car and its setup. If you're really insistent on not changing the cam (BTW are you running carbs with a stock FI cam?), how about changing the rockers - ratio rockers? Roller rockers? (More$$ than a new cam)

Yes, it's a slippery slope, but if you're gonna tear the motor apart anyway, it's not that much $$$ to get the right cam, new lifters, gear, and a gasket set...right? Might plan on replacing the bearings too...full flow the oil pump, etc. A slippery slope.

Best wishes for your project!! (One of my projects is a Chalon also, but don't say it too loudly as not everyone appreciates their beauty)

[marksteinhilber]

Stiffer springs should get you there, but it won't help. Power drops off like a rock above 5000 RPM, so going up to 6K is pretty much a waste of time. The heads/cam/valves just don't breathe at that RPM.

Not sure what the deal is with the HD versus stock spring pressures listed, but I wouldn't be surprised if they were measured in a different way. (Such as spring relaxed for the one versus compressed to a specific height for the other.)

--DD

Dave's right on...the cam is going to dictate where your power is, but what you want to pay attention to is the torque curve--dyno your car then do a bit of choosing which size rear wheel/tire combination will gear you down or up depending on the track. You can also consider doing the transmission flip of 3rd & 5th and put in an "S" 4th to get AFKaSZ gearing--I love mine....

I agree that changing rear tire diameter can be an easier way to adjust gearing for a particular track. but tire sizes are pretty limited in 15 inch diameter and 195 or 205 sizes that fit on a narrow body. Also limited in tire compound that is DOT highway legal versus full on racing slicks that are track only and count against performance points.

[motorvated]

I'm running 235 50 15's Toyo Proxes on the rear with Chalon flares and I have upgraded to 911 suspension and brakes, so the car is set up nicely for the track. The 1.8 in it now is just underpowered. I picked up this 2.0 liter four and just now pulling it apart to see what it looks like inside. Don't know what cam or lifters are in it now, and it came with a set of 40IDFs not mounted on the motor. So I don't know if the motor had last been running carbs or FI. Not yet sure where I'm going with this motor, as I also have a Buick 215 V-8 conversion package that I might install if I choose to ditch Vintage and race with my regional SCCA. So I'll race this season with the 2.0 liter in Vintage and one or two SCCA events and see where I want to go after that.

So a couple of quick questions about the 2.0 liter. Can I remove the lifters from the top without splitting the cases, maybe by rotating the engine on the stand to get them to drop out or by somehow pulling them upwards and out? I need to determine if they are solid or hydraulic. And how much more difficult is it to split the cases once the P&Cs etc have been removed. Then can I replace the cam without disturbing the crank bearings.

[GregAmy]

I agree that changing rear tire diameter can be an easier way to adjust gearing for a particular track. but tire sizes are pretty limited in 15 inch diameter and 195 or 205 sizes that fit on a narrow body. Also limited in tire compound that is DOT highway legal versus full on racing slicks that are track only and count against performance points.

Keep in mind that changing tire size and/or final drive won't affect the engine characteristics and torque bands as you shift through the gears; you have to re-gear it to do that. Only thing tires will do is change the speeds you're going when that happens...

I'm having Chris at Tangerine building me up a 'box for the race car, tightening up the gear ratios so that I can avoid running past 6000-6500 and still shift to a solid torquey RPM range.

[Bleyseng]

I used to run up to 6500rpms for AXing.

HD valve springs(ie Hydro springs), Raby 9550 cam/lifters, chomemoly pushrods, Porsche swivelfeet adjusters and you are there with MPS adjusting...115/1120hp...

[Mark Henry]

So a couple of quick questions about the 2.0 liter. Can I remove the lifters from the top without splitting the cases, maybe by rotating the engine on the stand to get them to drop out or by somehow pulling them upwards and out? I need to determine if they are solid or hydraulic. And how much more difficult is it to split the cases once the P&Cs etc have been removed. Then can I replace the cam without disturbing the crank bearings.

Yes the lifters can be removed without splitting the case. Remove the PR tubes and you should be able to slide them out with your finger. Keep them in order if you plan to reuse them.

[Dave_Darling]

To remove the lifters, use a magnet. You'll have to remove the pushrod tubes and pushrods first, of course.

You cannot change the cam without completely tearing down the case. You might or might not be able to re-use the main bearings and such, but that just screams "false economy".

Splitting the case is pretty easy. Except for the first time or two, because everyone misses one or two of the through-bolts. Like the one hidden behind the flywheel. Or the lower one on the front of the motor that often gets caked over with gunk.

It the case doesn't come apart relatively easily, check for bolts you have missed. Because everyone does at some point.

--DD

[colingreene]

If you are going to race in vintage why would you not do the whole motor?
these cars are all 40 plus years old...

[Rand]

Just turbo it

[pvollma]

You guys are absolutely right. I guess if the torque drops off that dramatically from 5,000 rpm up, then the best shift point from one gear to the next is at the rpm in the shorter gear that corresponds to the same torque at the lower rpm of the longer gear that you're shifting into. Shift at too low an rpm and the torque in the longer gear is too low and you lose power. Also if you you hold the shorter gear to achieve too high a rpm, the torque in the shorter gear drops off too much before you shift and even though the rpm in the longer gear and the associated torque is higher, you've wasted too much time at too low a torque in the shorter gear and lost too much power there. I'd love to see a bunch of torque curves for the engine loaded up in all five standard gears.

Long ago I wrote a program to calculate shift points using tire size, gear ratios and torque curve:

Gear Chart Program

Stock gears and torque for a 75-76 2.0L are stored in the program. Read the "Help" page for instructions. It works best on a desktop browser vs. a smartphone.