Will cam play nice

[eoseitz01]

Hi everyone. I'm working on my first engine build and managed to break a time sprocket bolt off in my cam. Luckily I have a new cam and was wondering if it would be a good match.

I have an 1981 LT9 block bored .30 over with a pair of 202 camel hump heads. I have stock length hardened steel push rods and 1.6 comp cam roller rockers. The head gasket is an advance auto felpro blue strip gasket. I'm not sure on the thickness. The lifters are most like stock. I don't have details on those. The Pistons appear to be flat top.

The cam I'm wanting to put in is an Erson e110421.
The specs are below.
SBC Performance hydraulic cam
-296*, 228*@0.50, .472 lift High Flow 1H

Would this be compatible with my build? I'm wanting to run pump gas and I'm concerned I may not be able to with this cam.

Thanks.




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[Hib Halverson]

LT9 was an early 80s, 5.7L truck engine with heavy-duty emissions.

My guess is the CR is quite low so...yeah, you can run pump gas maybe even regular fuel.

That engine with the cam you're using, the likely low CR and the big-valve heads is probably going to be a slug. What intake manifold are you using?

 

[eoseitz01]

I went from the stock 76cc heads to a 64 cc 202 head. I've got an edelbrock performer intake and 700 performer 4 barrel carb.


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[kpic]

As the engine was bored +.03 what pistons did you install?

 

[eoseitz01]

Idk. I bought the block that way.


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[eoseitz01]

I know the are 30 over by the .30 stamped on top. They are flat top. Other than that I don't know anything about them.


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[Tom Bryant]

I see a few "it depends" here. You need to know the deck height, volume of the 2 or 4 valve reliefs in the piston head and the compressed thickness of the head gasket to figure static CR. Also were the heads milled to true up the surface which will reduce the chamber volume below 64cc? With the flat top pistons and the 64cc heads you should be in the 9.75 to 10.5 CR range.

With the iron heads it looks like you are well on your way to a premium fuel only engine if you are lucky. You might be able to run E85 (it's higher octane) with the Stabil Ethanol protection additive. I don't know. I've never tried it. Your cam has a 108 degree lobe separation and calls for higher compression. The narrower lobe separation increases overlap which bleeds off combustion pressure. Thus the need for a higher compression ratio. You should call Erson but I'd think the 10.5cr might be in the low end range for this cam. They may suggest a better option for the parts combo you have.

Tom