cautionary tale (my engine upgrade experience)


New Member
hi everyone. i've just finished up an engine upgrade, and it hasn't turned out the way i had hoped, so i thought i'd share it with everyone in hopes that it can save someone time/money/grief. :(

so - i've got a 1966 amphicar. it ran very well, with an original 1146 engine with only about 7,000 original miles on the car/engine. numbers all match and all that.

the problem was, it was slow and was kind of dangerous on the freeway because it was so slow.

i wanted to do a nice upgrade to get it to go freeway speeds (about 70 mph up a particular incline on our local freeway system which is on the way to a lake.)

so i did my research and found that a popular engine used by spitfire race car guys is the 1300 "small journaled" engine. they are rare - most 1300s have the "large crankshaft" and don't run quite as well/fast/good as the small ones.

after a ton of work, i found one, and had it shipped to me.

i sent it to a local machine shop to get rebuilt. the instructions were to put a mild performance cam, increase the compression ratio to 10:1 and balance the crankshaft and flywheel.

i also got a fries clutch system, a pierce manifold and a weber carburetor.

i had to fabricate a custom exhaust pipe to make it all fit.

here's what it all looks like:

NeTQFMU.jpg'd it work out?

well, first off - i picked the wrong machine shop. they were horrible. horrible horrible horrible. it took 6 months of nagging and begging and pleading to get it done, and then when it was done, the head leaked, they used the wrong gasket, the valves were all messed up, pushrods wrong size, etc etc etc. total nightmare.

but, i got that all worked out.

next, the carburetor caused a lot of trouble. wrong sized idler jets, wrong sized main jets. i got that all worked out.

the throttle linkage is wonky - still haven't quite got it worked out, but it's "good enough" for now.

timing was very tricky, but i got that all worked out.

so, now that things seem to be worked out - how is it?

it's pretty slow. seems like it has about the same power as the old engine.

it doesn't really wind up very fast and there isn't much torque (i've been told that the 1300, especially the small crankshaft one, has weak torque.)

i haven't taken it on the freeway yet - just some main roads, and there's no way it'll go 70. it seems to cruise at 45mph in third gear okay, but 4th gear feels like an overdrive instead of a real gear.

so there you have it. my "racer 1300" motor swap pretty much failed.

not sure where to go from here. i'm considering going down the rabbit hole and trying again with a 1500 spitfire engine.

anyway, hopefully this sad tale is useful to the community. :)


Amphicar Forum Admin
Staff member
Thanks for the update.

My amphicar has the original engine which was rebuilt a few years back. I am absolutely convinced that it is significantly slower after the rebuild. I could get it crusing at 70 on the highway before, now it runs out of steam before it ever gets there.

I did consider a Weber carb, have a new one sitting on the shelf. I was concerned about the hassles of linkage, jetting, etc. based on your experience I will probably leave it alone.

I have driven / rode in a couple of 1500 powered cars. Definitely more power there.


Active Member

Wow, the results of your story couldn't be more different than what my two converted 67 Amphicars can do. Both cars will easily cruise at 70 with plenty of room under the gas pedal and have top speeds of about 87 MPH. I routinely drive the cars on California freeways. I did these conversions over 10 years ago and the cars still run just fine. When I had 1147's in the cars they were slugs on the freeways and could barely reach 70 MPH. In California that makes you something of a rolling road block and I didn't like it at all. Now they deal with minor road pitch variations easily, will climb a 6% grade in forth at about 50 MPH and I only have to drop to third on 7 percent and higher grades. Luckily I don't run into those too often because that puts the cars at about 43 MPH at the highest RPM that I choose to rev the engines. I'm told these engines can rev quite a bit higher but I don't like pushing them that hard.

You are right about the conversion not being a total drop in but it sounds like you did most everything right. It sounds like the rebuilder was the main problem.

First, I believe all small crank 1296 engines came with flat top pistons and have a 9 to 1 compression ratio. Boosting it up to 10 would mean shaving something. I wouldn't recommend that. Triumph had some odd engines with 8.5 to 1 compression and I believe you can tell those by the cupped pistons though I've never actually seen anything but photos of them.

I've played with many cams and find no difference at all between them. Displacement is everything.

Yes, you need a custom tailpipe and a weird muffler and it appears you have both of those.

Yes, the engines run better with a one size larger main jet. No big trick to install.

Timing is nothing special, lthough if you actually did manage to increase the compression ratio you might have trouble getting the engine to run without ping even on premium gas. Octane booster anyone? I use Pertronix modules and my cars have been converted to negative ground. Never a problem.

The 1500 (1493) engine is a stroked version of the 1296. The longer stroke certainly give you more torque at the stop light but these engines have rather poor lubrication and the Red Line of the 1500's is so low that many people warned me against going that way if I wanted to run at over 65 MPH. That finished the idea for me, coupled with many stories of overheating problems with 1500's.

1300 small crank engines do NOT have low torque. Large crank versions have the same torque and stroke but with a more massive crankshaft. That makes the engines moving parts heavier and less responsive to quick speed changes.

I found upgrading the engines to make an almost day and night change in the performance of these cars. They are much more enjoyable to drive than with the 1147 engines.

NOTE: I just noticed that you installed a fuel filter at the engine end of the fuel line. I once did that too and had nothing but problems. For some reason, which I don't understand, if you want to add a filter install it at the gas tank end of the line or between the fuel pump and carb. Strangely, this could account for a lot or ALL of your performance issues. It sure did for me. I remember thinking adding a filter would be a nice thing to do for the car but after weeks of problems an old mechanic told me you just can't locate the filter there. I pulled it out and all the problems went away. Pull that filter out and try your engine again.

I'll try to post a few photos of my engine installations as soon as I can figure out how to get them off of my new, fancy computer.

John Friese
67 White
67 Red
Santa Barbara CA
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New Member

thanks for sharing your experience. i'm not sure what the difference is between my setup and yours, but it sounds like yours is working out better than mine!

i'll test the compression this weekend and see if i have any problems with any of the cylinders. i'll also add the pertronix ignitor and see if that helps (i have one, just haven't installed it yet.)

btw, i use 100 low lead gasoline, so the 10:1 compression ratio isn't a problem.

i just took it out again this evening and first and second gear are okay - but when i put it in 3rd gear, it's like all the power disappears and i'm sitting there at 40 mph and acceleration is weak from there.

maybe the small journal has just too little torque for the amphicar 3rd and 4th gear ratios?

tell me more about the fuel filter - i don't see how that could have any affect on the performance. very strange sounding.


Amphicar Expert
Chuck Chuck had a hot cam in his.....I took it out and put std one back in and away he went,,, Night and day difference,
All my cars have rebuilt(By me) 1147's.. All timed etc the very same.. My green car is a dog compared to all the rest.. hmm.
My orange Fiberglass car is the fastest,of the line and to speed.
All cars have fuel filters under tank, Elc. fuel pump auxl, insulated fuel lines.

Turn props on when on highway for turbo trust!!! (not)
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Active Member
I can't really explain why the fuel filter location would be a problem but it sure killed the performance of my car until I pulled it out again. This was several years ago and I really didn't understand it back then. I had chased the performance ghost for weeks though and I was tired of trying to figure it out. I believe I moved the filter to under the gas tank and it worked fine though I'm not sure I just didn't dump the whole idea of the extra filter. Years later I added an electric fuel pump under the tank and it came with its own filter. I use an under dash switch to run that pump a few seconds refilling the float bowel of the carb if the car has been sitting a long time. I used to spray starting fluid into the air intake hose but that was a bit of a pain too. The electric pump also adds a backup to the mechanical pump in case it should fail. Works perfectly.

Here are a few photos of that engine compartment.


Weber air intake adapted back to accept the Amphicar air cleaner. Lucas alternator, oil catch can hoses to keep air filter cleaner


Oil catch can, coolant recovery tank and alternator showing. Also once tried aluminum radiator but not worth the price.


Throttle linkage is mainly original parts with a custom mounting plate for the L arm and a fancy link made from "all thread" and brass tubing with fancy swivels. The pull cable is standard Amphicar but I move the cable hole further out on the front muffler bracket to keep good alignment. The intake adapter does a good imitation of the old flash suppressor.

John Friese
67 White
67 Red
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Active Member

Reread my previous response, the small journal of your engine has NOTHING to do with torque.
Get that filter removed and try the engine again.



New Member
okay, i'll try removing the filter and report back.

EDIT: just tried it out. no change for me. 2nd gear peaks at about 26mph, and 3rd gear is a very weak slow climb from there.

but wow - what a beautiful looking engine compartment you've got there! :cool:

a couple of questions:

1 - why do you plug the vacuum advance on your carb?

2 - where did you get the adapter for the air filter so the original amphicar one can fit on?
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Active Member
Sorry to hear that didn't do any good. I was pretty sure that was a problem for you. It definitely was for me. Since it didn't work I'm afraid the blame must fall back onto the rebuilder. A compression test will tell more.

The Pierce/Weber instructions says to not connect that hose.

The adapter came from Carbs Unlimited (800-994-CARB). Part number 99010.600. You'll need to make up a small bracket to hold it down. I used some aluminum channel held down by metric hardware. See photos.


Old photos of home made hold down clamp for air cleaner. (Use Locktite and a jam nut on that center bolt)


Just another detail photo of the linkage system. This time in my Red car.

You used the term freeway in your posting. That's generally used in California. If you get around Santa Barbara I'll let you drive one of my cars so you can see how a 1296 should run.

John Friese
67 White
67 Red
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New Member
i grew up in california, but i live in utah now - so, i'll have to take a rain check on the ride, but thanks! :)

could you tell me how fast you go in 2nd gear? i was doing some tests today on mine, and it looks like i get to about 26 mph in 2nd gear before the power goes flat. then shifting into 3rd and accelerating - it just seems to have no guts at all.

i don't have anything else to compare it to, so i'm just curious what you are able to get to in 2nd gear.

btw, the one thing that seems to be working well is your clutch system. thanks for that. :D


Active Member

I have a tach on each car but that shift out of second I just do by ear. I start off my cars in second gear unless pulling out of the water or climbing an unusually steep driveway. I never find the engines to lose power because of RPM in any gear. I think they would climb right up to "valve float" speed and I wouldn't want to do that. The shift point I notice most is the one I run into when a mountain road goes from 6 to a 7% grade. I enter the 6% to 7% transition part at about 50 MPH. I know I'm entering the 7% part because of a road sign and the fact that the car slows down. I usually let it drift down to about 32 MPH and then shift into third gear. As you know that drop into third is quite a big one. The car easily accelerates again up to about 43 MPH and around 4300 RPM. It would certainly go higher but it's screaming pretty good at that speed and the 7% grade is over a mile long so I just settle around that speed. Bye the way, with my tires 4300 RPM is about 65 MPH in forth. The wind noise at that speed somewhat blocks the engine noise so I don't pay any attention to it, unlike when the car is going slower.

For what it's worth, I once left Santa Barbara at 4:30 AM to drive to San Diego and did the entire run through the Orange county freeways at between 82 and 85 MPH. I believe it was that trip when I ran it up to 87 MPH. I don't remember the tach readings very well but I think it was around 6000 RPM. I know somebody should be able to compute that but I'm too lazy right now.

Check your timing with a light. These engines can do really strange things if the timing is way off.

I'm glad you're enjoying my clutch system at least. They work well an have been quite bullet proof over the 10+ years I've been selling them.


John Friese
67 White
67 Red
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Midwest Amphicar

Worlds Largest Amphicar Destination
I think the engine is too tight. A true possibility with a bad builder. Pistons expand with heat and will be dog slow if tight. Improper cam bearings. Improper torque on rods. Do not forget valve lash. Also with mods you should have dual valve springs. I met more bad builders then good.


New Member
i fixed it!

turns out that i did not install the two manifold studs that the 1300 engine requires that the 1147 engine does not require.

that's a subtle difference between the two engines that a missed like a dummy. :confused:

after those studs were put in and i was able to fully seal the intake, everything hopped up great! very peppy and 70 mph is no problem!

i'm going swimming next week!
Bottom line here if you want to upgrade your 1147 to get more power is.....Keep the 1147 and get a Weber/peirce intake and carb, or toss the 1147 and get a 1300 with a weber peirce? Stay away from the hot running 1500? My 1147only has a couple thousand miles on a rebuild and runs great but it has no power and that solex always makes my garage smell like gas! Lastly, where do I get the Weber / Peirce setup? Thanks


New Member
canitfloat - i'm not sure what the "right" answer is.

the 1147 might be able to get a bit of a boost w/ a pierce/weber setup, but what worked for me, and what has worked for a few others is getting a 1300 and run a weber and a pierce manifold. you can't both of those here:

as far as the 1500 goes, i'm actually thinking about getting one just to try it out. some say it has problems, but there are different ways to mitigate those. everything is a trade off.

but just a general warning - once you start down this rabbit hole, it's pretty messy and takes a lot of patience and work, but then again, we are amphicar owners, so i'm not sure how much sense we all have anyway... :)