No top end

[Lowered and Louvered]

Hi Folks, I just rebuilt m10 motor, high top piano pistons, stock cam, 38 38. Machinist told me don’t advance the timing to much and use the best pump gas I can find, I have no top end, very torquey at low rpm. I at about 12 advanced. Any thoughts?
 

 

[Greg Mierz]

12 * advance where and when? total in even with big top e12 pistons should be 33-36. Get a good timing light and check.

 

[kbmb02]

9 hours ago, Lowered and Louvered said:

Hi Folks, I just rebuilt m10 motor, high top piano pistons, stock cam, 38 38. Machinist told me don’t advance the timing to much and use the best pump gas I can find, I have no top end, very torquey at low rpm. I at about 12 advanced. Any thoughts?

 

What RPM are you seeking for strong top end? (your stock camshaft is a limiting factor). -KB

[Lorin]

Are you talking about cam timing or ignition timing?

 

12 degrees total ignition timing is not enough. I’ve had some M10 engines that couldn’t take more than 30 degrees without pinging on pump gas, I would start in that neighborhood. 

[TobyB]

Where does it stop pulling?

 

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[Hans]

Who installed the head? Check that cam tdc notch and crank tdc line up.

[Son of Marty]

All good advise, also check that your linkage is allowing that the throttle plates to go all the way to wot. 

[AustrianVespaGuy]

With a stock cam and 9.5:1 pistons you're probably safe up to 40 degrees BTDC on even midgrade 89/91 pump gas. . .

[Greg Mierz]

As a reference my 9:5/1 piano tops, schrick 284 big six copy cam(think 292 with 304 lift) 45dcoe 15/16's and I can run 34-35* and still run regular under 80* air or so, check throttle and timing .

 

[Overdraft]

It's amazing what I learn in reading these posts.  What a community!

[Hans]

On 3/2/2022 at 3:10 PM, AustrianVespaGuy said:

With a stock cam and 9.5:1 pistons you're probably safe up to 40 degrees BTDC on even midgrade 89/91 pump gas. . .

I think that's pushing it a bit for the street. The ti distributor gave 39 deg if memory serves, but that was when Germany had leaded 98. I was told 33 with dcoes as a starting point with ti pistons.

[Hans]

Did you see my post on tdc above?