Looking for advice on the engine: swap or rebuild?

[yurakud]

Hello,

I recently purchased a Roadster. This is my first one so there is a lot to learn for me. It's a 1968 (originally 1600) but previous owner swapped 2000 into it. It starts right up and idles well. Can't test on the road as the car is not road worthy at all. I'm exploring my options and looking for recommendations. On one hand I'd like to swap SR20DET into it, already found couple of potential units, or should I just rebuild the U20, add solex carbs and maybe swap in 5-speed transmission instead of 4-speed?

Thank you.

[Gregs672000]

Welcome to the Family! Tons of experience here to help you decide. It really depends on your goals, skills and budget. A U20 is a unique engine that was never used in any other vehicle, makes excellent power (especially for its time), is very reliable and well suited to the car. There are a few things you can do to improve output, from fairly simple (de-smog, improved ignition/distributor, cams, induction, exhaust) to more intensive (port work, higher compression, crank-fired or fully programmable ignition, EFI). I've had my car for over 36 years, and the engine is at the higher end of development while still being a very happy, easy to drive street car. It's making somewhere between 140-150whp (final timing and dyno power pull pending) with a strong, flat torque curve above 3000rpm... that may not sound like a ton of power but the car weighs 2100lbs or so, and it's more than enough for me. I don't think you'll get too much more out of a street U20, and that is with some fairly "rare/expensive to get today" parts (like the Solex manifold). If the U20 needs a rebuild you can review various vendor sites to determine a parts budget, then talk to machine shops etc if you're going to do the work. U20 parts are not cheap, nor is finding a good machine shop easy these days. I'm not sure I'd like 300hp, but if your goals are high power the SR20DET is likely the best way to go, and all the mods are very well sorted out here and elsewhere. You would step into EFI, requiring computers, GOOD wiring (very important), a high pressure fuel system, etc.

The other things to consider is what else will need to be done to the car itself to make it enjoyable. 300hp is fine in a stockish car if you want to light up a single rear wheel and put yourself in a ditch when it overpowers a suspension not prepared for it... you'll want a limited slip (RX7 or aftermarket), decent springs and the highly recommended Bilstein shocks ($$). Car needs to stop too, and brakes are not cheap either!

With a well running U20, I'd start with getting the car going down the road safely, repairing any worn out suspension, brakes and 50+ years of use/abuse THEN consider upgrades. A stock, well running U20 will certainly put a smile on your face. If you're used to big power doing long burn outs... that's not this car. These cars are for dancing on twisty roads while loving the convertible car experience, and having envious folks stop you to admire the car or tell you of their experience with one and why they wish they had one now.

Hope this helps... regardless, HAVE FUN!

[redroadster]

You ,As a newb to these ,I feel the need to mention a safety concern with all 311s
The steering shaft or death spear as some who had intimate knowledge of it, way back when , it was known to come flying at the driver thru the outer metal case and into one's chest
A factory well secured horn pad was a big help
It is/was a collapsible steering shaft ....but after a few yrs the siezed up , there were quite a few that died from this and in only a seemingly lite to medium hit ....something to consider in beefing up the engine for you know ,...speeding

[Alvin]

What is your budget?
What is your timeline?

Get it roadworthy with the current engine/trans and drive it a few thousand miles before even considering an engine swap, of any kind.

[jhayden]

Get it roadworthy with the current engine/trans and drive it a few thousand miles before even considering an engine swap, of any kind.

+1

You have a U20 that currently "starts right up and idles well?" If it also does that when warm with no timing chain rattle, you already have a powerplant that numerous members of this forum would covet. Brakes then fine tune with current carbys.

Jon

[theunz]

I think Greg gave great advice. You would have to spend stupid money on an engine swap if you want to run with modern cars, and then you still have 50+ year old driving dynamics. The stock U20 is a lot of fun and the five grand or so for the Solex’s and B cam hardly seems worth 15 HP. I enjoy mine for what is is, vintage sports car, and that’s the way I want to keep it.

[vorpal]

I have plans for an engine swap for my 67.5 1600 but that is well after I put a year or so on it in current stock form and fix all the problems that inevitably arise. Just got it road certified yesterday after years of fixits and part replacement.

[david premo]

FYI you can just the B cam in the engine and then you get the 150 HP, the cam makes the horse power not the carbs. If run SU’s with the B cam they run fantastic and even know of a C cam in an SU U-20 that the guy is very happy with. The carburetors just mix fuel and air, the big advantage the Mikuni Solex’s bring is much quicker acceleration of corners and improved drivability pretty much at all RPM’s. I think for now you should just get the car sorted out and enjoy it until you can assess what is best for what you want from the experience.
Dave

[yurakud]

Thank you everyone for great advices, especially Greg ! Exactly what I was looking for. I thing I just got excited of the idea of SR20 swap, the "coolness" of it, but wasn't sure how feasible it would be for me. Especially since I want to get it road worthy asap because I want to start enjoying driving the car.

[Gregs672000]

My pleasure! Do avail yourself of the info on the U20 as there are some important things to do to it... most important to shim the upper chain tensioner (see the tech wiki). The tensioner is oil fed/pressurized and at start up/no oil pressure it allows the chain to strike the "L" of the chain guide just under the cam gear. This allows it to fatigue the metal which then breaks off and destroys your engine in a fraction of a second. Shimming the tensioner keeps the chain tighter under all conditions. Remove your valve/cam cover and inspect it. Also, the big nuts on the cover are NOT reefed down on... tighten to snug to seat/seal the rubber gasket with moderate finger pressure on your ratchet. The big nuts suggest a lot of tightening torque but you will fracture the cover by reefing down on them! With experience you will get a feel for it. Over time the rubber gasket gets hard and won't seal as well, and more torque won't fix it... replace if needed with a new rubbery one if it's leaking down the sides of the head. They last a long time. I clean the metal really well and oil free, then add a little gasket maker to the cover's edge then install the gasket over that so it adheres to the cover. This keeps it ON the cover when you remove the cover from a hot engine... Otherwise they can slip off... irritating! You can also read up on smogged vs de-smogged engines, distributors and initial timing... also very important this is or has been done right.
Let the adventure begin!

[fj20spl311]

Spend your time and money getting it to a good driver, i.e. brakes and electrical systems. put some mile on the car before you decide on the engine and/or transmission.

[SLOroadster]

A U20 is a very solid engine. It does have its weaknesses, but so does every other engine out there. Its a simple engine, that looks complex, but really isn't. It makes enough power to be a lot of fun. It will tell you when its unhappy, if you choose not to listen then its not the engines fault. The upper timing chain does stretch, you can do a few things to keep it happy however. If, down the road you want more power it can make more power and still be pretty bulletproof. Heck, mine will turn 8000 RPM with no ill effects. Yep, I've done a few things on mine, but I'm still running stock rods and pistons. I've made a couple ill advised attempts on the track to blow it up, and its failed to do so. (A good thing)

Give it a chance. You might be surprised.

Will

[yurakud]

A U20 is a very solid engine. It does have its weaknesses, but so does every other engine out there. Its a simple engine, that looks complex, but really isn't. It makes enough power to be a lot of fun. It will tell you when its unhappy, if you choose not to listen then its not the engines fault. The upper timing chain does stretch, you can do a few things to keep it happy however. If, down the road you want more power it can make more power and still be pretty bulletproof. Heck, mine will turn 8000 RPM with no ill effects. Yep, I've done a few things on mine, but I'm still running stock rods and pistons. I've made a couple ill advised attempts on the track to blow it up, and its failed to do so. (A good thing)

Give it a chance. You might be surprised.

Will

Thank you!

[Gregs672000]

Just to clarify to a person new to the U20, simply swapping in a "B" cam or similar (higher duration and more lift) will NOT get you to 150hp (that was at the crank with no accessories attached and running optimally tuned 44mm Solex Carbs). The engine will still make very good power, but your ability to tune it will be limited. SU carbs are great and very flexible, but cannot flow the same air as a Mikuni style side draft or have the more precise tuning offered by incremental jet size changes. Similarly, the adapted later nissan EI distributor is a great upgrade but it does not allow you to adjust ignition timing anywhere in the curve like a 123 distributor or a crank-fired ignition, and research/dyno work has shown even a couple of degrees of timing can make a significant change to power output at certain rpm while hurting output elsewhere. I'm NOT putting myself out as an expert here, though I've been down all these roads progressively over the years and have seen the pros and cons of the various modifications I've tried. There are many very knowledgeable folks here who can provide good advice and guidance. For me, it's been my hobby, a great friend and an outlet for tinkering and learning!

The goal of the car is to be FUN, and that does not mean it has to have tons and tons of power! Regardless of how the car is equipped, there's just something about them that puts a smile on your face. 38 years and I've never fallen out of love... enjoy!