Compression ratio for 2056, While i am at it Options

[worn]

Pulled the motor after several years of service from the 2056 build. Two problems have plagued me. The reason i pulled the engine was to seal persistent oil leaks. I am going after the oil pump and some gaskets and seals. The second problem has always been cylinder head temps. They are kinda high. I built the motor to have a 9.0:1 compression ratio, which works in my cast iron block, water cooled TR6. On further consideration, that may be a tad high. Especially after a few hours of highway driving in the summer.
The internet has lots of calculators to do the math. I can get or may already have cylinder shims. What ought it to be? The goal is dependable gobbling of miles with some increased power due a 2056. Suggested ratios? Guess i should have asked this question some time ago.
Thanks folks. You are great.

[falcor75]

I'm running 10,3:1 in my 78x96 engine so if everything else in yours is up to par it should be ok. At cruise my CHT's sit around 150-160° C (300-320F)

[76-914]

@McMark might be the person to ask. He's built several of them. (IMG:style_emoticons/default/beerchug.gif)

[yeahmag]

The engine is a combo. We would need to know what cam, heads and headwork, and exhaust you are running.

[worn]

The engine is a combo. We would need to know what cam, heads and headwork, and exhaust you are running.

I am running a cam from webcam described as using the "Raby grind". The exhausts are backdated from 1976 to a 1974 era SSI exhaust. I am using the stock EFI and I tweaked the MPS. I want to keep the fuel injection. #3 cylinder head plug has reached 400° F on uphills in the summer (when everything isn't frozen solid here).

[yeahmag]

I'm guessing that's a Webcam #73 variant for DJet. I would say that 8.0:1 to 8.5:1 would be more appropriate, but I'm not an expert on that cam. So, next you need to consider timing and AFR. What are those set to?

[worn]

I'm guessing that's a Webcam #73 variant for DJet. I would say that 8.0:1 to 8.5:1 would be more appropriate, but I'm not an expert on that cam. So, next you need to consider timing and AFR. What are those set to?

Timing is set stock. If i run much leaner than 10:1 the engine runs hot. However the engine gives better performance around 13:1 or even leaner. Yes, the cam is a 73 plus 2.5 degrees as i recall. Have to look at the card to be sure.

[yeahmag]

John Connolly of aircooled.net (who I trust) recommends 7.8-8:1 on that cam. I’d guess that’s a smoking gun assuming everything else is good.

[worn]

John Connolly of aircooled.net (who I trust) recommends 7.8-8:1 on that cam. I’d guess that’s a smoking gun assuming everything else is good.

Thanks! I guess i should look at my collection of spacers.

[porschetub]

I'm guessing that's a Webcam #73 variant for DJet. I would say that 8.0:1 to 8.5:1 would be more appropriate, but I'm not an expert on that cam. So, next you need to consider timing and AFR. What are those set to?

Timing is set stock. If i run much leaner than 10:1 the engine runs hot. However the engine gives better performance around 13:1 or even leaner. Yes, the cam is a 73 plus 2.5 degrees as i recall. Have to look at the card to be sure.

What is your stock timing?,with that comp maybe a dial back a touch,just saying,cheers.

[Mark Henry]

Web #73 cam a 8.5 CR is about the max, make sure to check both sides. You can stack base shims, 3 max.

Big engines, oversize intake/exhaust, large duration (overlap) carb cams (or aftermarket FI) are the ones that can run higher CR.

[rbzymek]

So I will be receiving my SCAT 2056 long block in a couple weeks. I requested a Web 73 cam and 8.5:1 CR. They did the build with new type 2 heads and 42x38 valves. This will allow me to re-use my tin and intake system. The exhaust valves will be sodium filled, with SS 2.0L heat exchangers. I plan to use my L-Jet FI from the 1.8 that I am rebuilding. After reading this thread I am wondering if I will have temperature issues. I do have a taco plate temp gauge but it only has a red zone, no numerics. I also have a wide band AFR meter for tuning. The engine is ready to ship at this point. Any suggestions or things to look out for? Better temp gauge? How hot is too hot? Thanks in advance.

[rbzymek]

Make that 40x33 valves.

[worn]

Web #73 cam a 8.5 CR is about the max, make sure to check both sides. You can stack base shims, 3 max.

Big engines, oversize intake/exhaust, large duration (overlap) carb cams (or aftermarket FI) are the ones that can run higher CR.

Thanks. I probably should mill thespigots, but don’t want to split the case. Deck heights on one side are about 0.010 different between sides. Is it ok to use shims under the cylinders to even things up? Have to re-read the Wilson book again.

[worn]

Make that 40x33 valves.

Hope that you are very happy about the way the car moves. I was on the highway with the ‘72 3.2 conversion. Big smile just emerged and stayed there. Sunny day, and i am driving the car of my dreams.

[rick 918-S]

Carb cam. The overlap is likely causing a pulse in the intake thumping the maps. Not ideal. I would install a FI cam, leave the compression as is, add a lightened flywheel, and tune the injection with a exhaust sniffer if you can get the air fuel ratio right at cruising speed the engine should run cooler.

[Mark Henry]

Web #73 is a stock FI duration cam with a hair more lift.

[rick 918-S]

Web #73 is a stock FI duration cam with a hair more lift.

Cooling flaps working then? Compression alone will not cause a hot condition that cannot be solved.

[Bleyseng]

Make that 40x33 valves.

Why such small valves?