overheating race car - stumped!

[cbuczesk]

I didn't have time for a baseline after I built the engine. The head has new seats and guides and the valve springs were tested. I adjusted the valves last week before the race. I checked the head bolts and they were tight.

I think what appeared to be a lean condition on the front 3 plugs was actually the blown head gasket. I'll pull it this week and check it for straightness. It's going to be a busy couple weeks. I also have to pull the transmission and fix a broken roll pin on 3rd gear. The joys of owning a race car! Thanks for all the help guys!

Chuck

[LeonV]

At 6500 RPM's the thing that usually goes wrong is a valve starts floating.

Do you have any corroborating data or calculations to even remotely prove this, or is the statement pure conjecture?

[madkaw]

Wade,

Are you serious?

"Here at ClassicZ , we don't have magic bullets" -

--ummm, I hope you aren't speaking on my behalf with such a pompous statement.

So I guess your car never sees redline for fear of floating valves?

[Pomorza]

Chuck

Could you be kind enough to keep us posted on what you find, maybe post some pictures. I would really like to see that cause of that overheating if it is actually the HG. As for redlines, all cars have them and they vary depending on too many factors to list. I personally don't like approaching them - I have a hard limiter at 6500 - but I've seen Z's hit 8k before without an issue. It all depends.

Thanks

Jan

[cbuczesk]

Jan,

I'll post pics when I get back out to the garage. Tue-Thu nights are filled with softball playoffs, volleyball, groceries, mowing, etc. I'm off Friday so I'll work on it then and post some pictures. I'm curious to see the head gasket too.

Chuck

[gnosez]

So our 300 hp L28 with the 44mm carbs, pistons and other nice bits from the original BSR 240 running at 13:1 CR on 110 fuel ran hot from day one.

The 240 did real well at the VRG event last year taking 1st, 2nd (overheating on the last lap), and DNF (first lap overheated).

We changed out radiators, hoses, timing, a new head gasket, reconfigured the cooling system, replaced the BSR E31 head, etc.

Little bubbles became much bigger bubbles once the throttle was blipped. Current thought is a small cylinder wall crack.

Since the only thing that didn't get changed was the block and we started to get bubbles at idle and then big bubbles at WOT.

We figured cracked block.

Out came the engine and all the usable stuff (8-gal custom oil pan, diesel water pump and custom front cover, a real BSR valve cover, the huey tranny oil cooler

[cbuczesk]

Wow. I sure hope I don't have a cracked block. I had the radiator cap off while the engine ran so I could see if the coolant was flowing through the radiator. It was. I didn't notice any bubbles though. I'm anxious to get the head off this Friday.

Chuck

[cbuczesk]

I pulled the head today. Everything looks good. I was hoping to see something that didn't look right. I have another E31 head that I just picked up from the machine shop. I think I'll put it on the block and get the old head pressure checked. What do you guys think?

Chuck

[Pomorza]

Hmm that interesting

How do the valves look on the head? Any of them burned (really lean)? How did the pistons look?

Jan

[cbuczesk]

Valves and pistons look fine...everything looks fine. #1 and #2 are a little lighter in color than #3-6 but everything looks good.

Chuck

[madkaw]

HG fire rings all look solid, no blow by anywhere?

On my HG , it showed up more as a discoloration of the fire ring.

[madkaw]

Valves and pistons look fine...everything looks fine. #1 and #2 are a little lighter in color than #3-6 but everything looks good.

Chuck

Lighter as in cleaner then the other pistons?