got a buddy who had a 413 rebuilt by a third party shop and he asked me to help diagnose some driveability issues. The thing has no power... I mean it feels like a stock slant six under acceleration. My diagnosis is the engine builder put the wrong pistons in it and it has very low compression, just thought I'd post here and see if y'all agree with me. Some clues:

- the big one is the static compression test showing about 95-100 PSI across the board.... pretty much tells the story as far as I'm concerned but I checked other stuff below as well

- It runs and idles very smooth and doesn't run hot no matter what you do to it. Verified no vacuum leaks. Starts instantly, no issues with anything like that other than severe lack of power

-the spark plugs are a nice golden brown like they should be, so I feel confident the carb is tuned pretty well

-I played with the timing and ran it all the way up to 30° BTDC (!!!!) but the thing only ran better this way (!!!!) Never could get even a trace of spark knock under load.

- as a check of the above point, I verified timing mark on balancer is correct and showing TDC of #1

- tried swapping known-good carb and distributor just to be sure, same results.

- doesn't burn oil or anything like that so we have some confidence the builder did all the machine work correctly, including the confidence of previous positive experience with this builder


....so add all that up and I'm thinking it has low compression pistons installed by mistake. I recall reading one time about the 413 having a car and a truck piston and you had to be careful about which one you ordered so I'm thinking the builder made this mistake. Would the clues I've described support this? They put 516 heads on this engine, so if it did have the truck pistons with the closed chamber heads, what would we guess the CR to be?

Compression sounds low, but it should still outrun a 6 cyl. By "30 degrees timing" do you mean with full advance? I'd set total timing to 34 or so with the vacuum advance disconnected and see if that makes a difference.

I think you have answered you own question with what you have done. There is one other possibility and that is the cam wasn't degreed and it's installed in the retarded position.

....no I mean 30° initial

Acted the same with two different known good distributors.

I asked him about the cam gear and whether it was installed straight up, he said he thought it was a standard gear with just one set of keyways so I discounted that possibility. Only other possibility I considered was if the gear or cam was mis-machined somehow but that seems highly unlikely.

Anyone know what the deal is with the 413 truck pistons? I told him to get with the engine builder and find out what the paperwork says, part numbers, whatever, but the suspense is killing me so I thought I'd post about it here.

purrs like a kitten and yet is completely gutless.

The crank gear will have the extra slots not the cam gear.

Had someone degree the cam in a 440 years ago and it was a dog.Ran smooth but had no power.Turns out he degreed the cam wrong.On the exhaust valve I believe.Set it where it was supposed to be and what a difference.
I would pull the timing cover and degree it to be sure.It could be way off due to the grinding of the cam also.
You can advance it 2-4 degrees if you are worried about low compression while you are there.

I've had several 413 industrial engines that I put 516 and 915 heads on. They ran very well and were far from dogs. I'm willing to bet a steak dinner that the problem is either the cam timing or the cam itself. I had a simular problem 15 years ago. Bought a Erison 292 cam for a 383, it made no power at all, as in a moped would out run it. Turned out that the allingment pin was in the wrong spot. That's when I learned the value of having a cam degreed.

My guess is the cam is in wrong! maybe even marks are not lined up!

update- I was right (this is my "told you so" moment )

They pulled the heads and found some deep dish pistons. I wish they had taken a measurement of how far down in the hole it was, just to satisfy my curiosity, but oh well... Anyway, after sufficient prompting the truth came out. According to the story the parts supply warehouse could not find the correct 413 .030 pistons for a car as specified in their catalog but they had some 413 .030 pistons for a truck on the shelf, so the parts picker guy figured "same thing, right?" Eh, not so much. According to the book this piston yields a 7:1 compression ratio with closed chamber heads, so with the 346 heads they had on it I'm impressed that it ran at all.

Hope this helps serve as a cautionary tale to anyone pondering the rebuild of a 413.... be careful what parts they try to sell to you.

Perfect excuse to install a turbo charger.... or two.

Kevin

lol we talked about that (or a supercharger) but it's a very nice restoration of a convertible and power adders were a bit outside the scope of the project, so they pulled the engine and found what is supposed to be the correct pistons for it. This time they will be measuring things as they go instead of taking the parts guy's word for it