Author Topic: esr370 stoker piston hitting dome (Read 4410 times)

mea350r · « **on:** September 02, 2013, 11:34:54 AM »

Why is this happening? I just bought this motor. It is a 78.00 mm bore has not been started. When I put head on it will lock at top of stroke. With head laying on loose it will lift head when I crank it over.

Pumashine · « **Reply #1 on:** September 02, 2013, 11:45:11 AM »

Whole stroker motor? The head can be cut to match. A quick fix is to use a 2mm spacer plate. But was the cylinder ported for a stroked crank?

derby · « **Reply #2 on:** September 02, 2013, 11:52:57 AM »

On a esr 370 the piston sticks up above the deck. You must have the wrong dome.
Also check the spacer plate just to be sure.

4mm stroke uses a .190 spacer
5mm stroke uses a .250 spacer

mea350r · « **Reply #3 on:** September 02, 2013, 11:54:01 AM »

Whole stroker motor...it has a spacer plate already on it. Do I add another plate???

derby · « **Reply #4 on:** September 02, 2013, 11:55:21 AM »

No, no extra plate needed what stroke is the motor?

Just eyeballing that looks like you have exactly what the 370 should have sticking out. Take a pick of the dome. Also any numbers on the dome?

mea350r · « **Reply #5 on:** September 02, 2013, 12:00:33 PM »

I'm not sure if it is a 4 or a 5 but I can measure plate to see what size it is.

mea350r · « **Reply #6 on:** September 02, 2013, 12:20:10 PM »

Piston rises above head 1 mm. .25 spacer

mea350r · « **Reply #7 on:** September 02, 2013, 12:23:49 PM »

Dome. 76dt7655r

Pumashine · « **Reply #8 on:** September 02, 2013, 12:42:34 PM »

So you have a 78mm bore and a 76mm dome ? Derby will know. The dome has a good step in it. Maybe you just need a 78mm dome? If you measure the diameter of the piston and compare with the diameter of the step cut in the dome you will know if it is going to hit.

derby · « **Reply #9 on:** September 02, 2013, 12:59:40 PM »

You have a 5mm stroke. I can tell just by looking at the spacer. Pumashine is right if those are the numbers on your dome you have the wrong dome.

The dome you have is for a 330cc with 4mm stroker crank.
76 stroke (4mm stroke), dome top, 76mm bore,55r is a low end race gas dome.

You will need a new dome from esr. You could probably have someone cut the dome you have but the cost would be as much as a brand new dome.

mea350r · « **Reply #10 on:** September 02, 2013, 01:09:35 PM »

Hey thanks a lot I appreciate your help. I will order a new dome tomorrow.
Is there a chance this is a 330 cylinder bored to 78 mm? It is on last bore

C-Leigh Racing · « **Reply #11 on:** September 02, 2013, 04:23:32 PM »

Quote from: mea350r;10774

Hey thanks a lot I appreciate your help. I will order a new dome tomorrow.
Is there a chance this is a 330 cylinder bored to 78 mm? It is on last bore

If it is a 330 bored out to 78mm, you'll find out when you bolt the head on & run it, because the sleeve will be so thin between the bore & the inner edge of the o ring groove, small pieces will chip off.
Take a pic of the top of the cylinder with the inner o ring removed so we can see how thick the sleeve is between the bore & o ring groove.
Neil

The Phantom · « **Reply #12 on:** September 02, 2013, 08:03:31 PM »

Quote from: derby;10750

On a esr 370 the piston sticks up above the deck. You must have the wrong dome.
Also check the spacer plate just to be sure.

4mm stroke uses a .190 spacer
5mm stroke uses a .250 spacer

I have the 350pv 4mm stroker and I use the .250 spacer. piston is above the deck about 1.125mm[ATTACH=CONFIG]1705[/ATTACH]

derby · « **Reply #13 on:** September 02, 2013, 09:09:17 PM »

Phantom you can setup a motor many different ways. But to get the deck height like yours with a 4mm stroke the cylinder had to have been modified or you are using a different rod. Show a pic back away viewing the piston where it is and the cylinder bolted down with gaskets and .250 spacer.