305 Racesaver sprint piston scuffing issue

[Carnut1]

Intersting thread, Do you have flow info on each intake port within the cylinder head and intake manifold? It would be intersting to see if this cylinder is getting more or less air than the others. Thanks Charlie.

[victorymachine]

As induction Apprentice suggested I bolted the head to the block and measured the cylinders from the bottom. Looking back at my build sheet, #2 and #8 piston and cylinder bores were within one tenth of each other at assembly. I checked them all, but payed close attention to these two since they should be virtually the same. #2 cylinder is now a few tenths bigger than #8 cylinder. That might be from the #2 piston rubbing out a little clearance during the scuffing. The bottom line #2 is not tighter than the other bores nor did it have any weird distortion...

My guess is that the engine was not properly warmed up and the piston ran out of clearance from expanding quicker than the block.

I think Cogburn has it correct, the straps on the plugs is blue with #2 strap spreading some heat into the threads/base and the porcelin on #6 is glazed. Looks like heat/lean to me , I also agree the nozzels have to checked .

I think sometimes pictures can be deceiving. As previously admitted I'm no methanol expert, but the plugs look fine to me. Here are a couple pictures after I cleaned them up with a paper towel. they had a small amount of carbon/oil residue on them. Correct me if I'm wrong.

#2 plug:

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#6 plug:

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-what have you done about this bypass hole?

-what do you have for a water pump?----what type of pump & belt drive system?----what rpm ratio to crank?

-what do you use for hoses to and from the radiator?

-how high is the water fill cap compared to the top of the valve covers?

-how is the water out of the injectors plumbed back to the radiator?

-where is the radiator?

-what & who's fuel injection nozzle number/sizes are you using?

The bypass hole is plugged at the water pump face of the block.

The water pump is a stewart race pump. Factory holes are plugged at the front of the block and output from the pump is rerouted to the center of the sides of the block. I believe the water pump is turning half the crank speed.

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Radiator is in the standard location at the front of the sprint car..lol..
Hot water is returned to the radiator from four individual hoses at each corner of the intake manifold, effectively at each end of each head. Each hose has it's own bung in the top tank of the radiator. Fill cap is in the top tank of the radiator and is roughly even with the valve cover tops. The return hoses have to run slightly uphill to the radiator.
I'm curious Bill, watcha thinkin,?

Intersting thread, Do you have flow info on each intake port within the cylinder head and intake manifold? It would be intersting to see if this cylinder is getting more or less air than the others. Thanks Charlie.

No I don't. But we plan to pressure up the intake and be sure there are no cracks in the #2 intake tract..

We are gonna flow the nozzles/injection system sometime today or tomorrow, I'll let you guys know if we find anything. Thanks again everyone.

[allencr267]

Front engine mount plate's torque and/or too long bolt into the waterjacket pushing on that cylinder?
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'bearings look fine, with the exception of the pieces of piston skirt that ran through them from the scuffing.' Not filtering?

[Adger Smith]

Next time you put it in the Sprinter swap the locations of the return hose for # 2 cylinder on the tank.
Just a thought... the bung could be in a location where it is getting closed off by water flow pressure in the radiator, constant flow or a burp back situation.
You might want to put some air bleeds on the intake outlets. Could be developing an air lock around the # 2 cylinder or in the return hose.
I'm of the opinion there is a quirk in the water flow/system, not something done in machine work if there is no fuel distribution problem.

[Adger Smith]

Another thought... does the block have a torque bar/limiter attached to the Rt side original motor mount pads?
If it does it could cause distortion of the cylinder wall.
Hey, tell us what the tie wire on the two head bolts on the rt side is all about?
Sure does have the deck lowered on that block. After market block?

[pamotorman]

tech inspector seal ???

[victorymachine]

Another thought... does the block have a torque bar/limiter attached to the Rt side original motor mount pads?
If it does it could cause distortion of the cylinder wall.
Hey, tell us what the tie wire on the two head bolts on the rt side is all about?
Sure does have the deck lowered on that block. After market block?

Nothing is bolted to the side of the block. The motor is held in the chassis by a plate bolted to the bellhousing surface and a small plate at the front bolted to the holes on both sides of the timing cover.

Pamotorman got it, the tie wire is a seal. Racesaver 305's are inspected and sealed before competition.

The block is a production 305. The deck is a normal production height(not drastically cut). The bosses on the water pump are really beefy. Maybe that or the angle of the pictures make it look short...

Saw your other post and will give that some consideration.

Thanks for the replys guys!

[Geoff2]

I would still be looking at oversized piston/undersized bore.....

[user-23911]

You mean piston to bore clearance?
That piston is all messed up now but the other 7 should be measured for skirt collapse and clearance.

To me, that one just got too hot because it was too lean ...pre ignition.

[gmrocket]

looks like fuel wash to me. i dont see any discoloring on the piston from lean/heat

and the piston top looks to clean for that much running,,looks like fuel going right through it. i think your first clue was not being able to get heat in the motor. #2 could be the richest of the bunch and when you leaned the others, #2 when to just less rich?

a simple eg temp probe would have shown you something.

[houser45]

I don't see any tuning issue fro the top of the piston, Its a clearance problem or a clearance problem due to a cooling issue. I am not sure why you filled the block at all, A racesaver will only put out around 450 hp. It doesent need filled and that's less cooling and more weight added to the engine. We don't fill our 535 hp 305's here either. That extra water helps keep oil temps down. I would look at the water jackets in that block real close. You also should pay no attention to water temps to get fuel correct either. read plugs and look at exhaust ports if your not going to dyno it.

[houser45]

And I will say I agree with Cogburns post

[In-Tech]

I'll throw an opinion based on the soot in the exhaust that somewhere in the tune it is WAY fat and washing and burning oil.

[victorymachine]

I don't see any tuning issue fro the top of the piston, Its a clearance problem or a clearance problem due to a cooling issue. I am not sure why you filled the block at all, A racesaver will only put out around 450 hp. It doesent need filled and that's less cooling and more weight added to the engine. We don't fill our 535 hp 305's here either. That extra water helps keep oil temps down. I would look at the water jackets in that block real close. You also should pay no attention to water temps to get fuel correct either. read plugs and look at exhaust ports if your not going to dyno it.

Thank you for taking the time to post.
I have to respectfully disagree about the block filler. I think when you factor in the weight of the water the filler displaces, it really doesn't add much if any extra weight to the wet, ready to race engine. My thinking is it helps to stabilize the bores. We use good oil and change it often, so a little extra oil temp shouldn't be an issue in my opinion either. We can agree to disagree.

Also, for the record, water temps were not the only thing we were watching to tune the engine! Although I didn't previously mention it specifically, I was looking at the plugs after each pill change as well.

You mention looking at the water jackets real close. What specifically should I be looking at? As previously mentioned, they were thoroughly cleaned with acid before filling and are still squeeky clean...

I'll throw an opinion based on the soot in the exhaust that somewhere in the tune it is WAY fat and washing and burning oil.

You are exacty right about the burning oil. However, that picture was from the engine after 3 seasons of racing before tear down when it came to my shop for the freshen/rebuild.


It was Sunday afternoon, before we were able to try and flow the injectors/injection and we didn't have the right fittings to do so. We will try and get that done late this week. Thanks again to all who have replied.

[jac mac]

You are exacty right about the burning oil. However, that picture was from the engine after 3 seasons of racing before tear down when it came to my shop for the freshen/rebuild.

If that pic of exhaust was taken after three seasons and assuming the engine had not been scuffing pistons on every meeting for those past three seasons a review of any changes by owner or previous engine builder prior to the first scuffing incident might be in order. Sometimes its quite revealing to talk with previous engine builders! I take it that the #2 plug is broken in the pic above.