Inliners International Forums General Discussion Engines 292 refresh

The 292 in my 84 Chevy K20 is starting to use a little oil and blow by. It still runs really well and has even compression numbers. Anyways, I am wanting to rebuild a 250 mercruiser head I have waiting around to be used. I am thinking new guides and stainless valves, possibly mill down for a compression bump. I use my truck is a daily driver and tows a boat and 23 ft. travel trailer from time to time. I do have a big exhaust manifold and 2 barrel carb on it but that's the limit of hot rod goodies. Anyways, what would you guys do to the head to make it bullet proof and ready to work. My truck runs 3000 rpm at 65 for a 80 mile round trip daily. Thanks for any ideas

I would install larger valves, 1.85" intake 1.6" exhaust.
Or at least 1.6" exhaust valves installed.

Mill down head because the replacement head gasket will be thicker than the original head gasket. A better aftermarket towing type camshaft will improve it as well.

MBHD

These are just small block chevy valves yea? Also what is a good number to peel the head down? .030 to much? As far as the cam goes, I had not thought about changing it. Is there a cam that will give me more torque down low then stock? When I get the head done, I was thinking about using some heavy duty springs like the Z28 style.

Yes, you just use SBC valves.

You could mill it .040.

Camshaft, something like this but for a 292: http://www.summitracing.com/parts/cca-61-232-4/overview/

Installing to stiffer springs would be a good idea & Comp Cams says you need new springs with the cam I posted.

MBHD

If you are going to install a new camshaft & springs, I would get the .100" longer valves.

MBHD

All cams require a specific valve spring installed height, open and closed pressure specific for the cams lift. A Z28 valve spring is only for use with a Z28 camshaft which is solid lift, and requires more pressure than any hydraulic camshaft will ever need, so you need to use the correct valve spring for the cam you are using or you can wipe a lobe off of the cam.

A stock SBC valve is shorter than a stock Chevy 6 valve, so I would use a .100 longer SBC like Hank said.

I will start looking around for the .100 valves. Seems the z28 springs on the small blocks were only 15 pounds more then regular truck springs. (95#) Installed on the small block. Been awhile since I used them. But as I recall they worked well on mild cams. I know Im working on a 6. I can take a look at what comp wants for springs as well. Is this cam even worth installing from a power point. My motor is pretty choked off with the factory intake.

Anything you can do will help the power up to a point, but even with a stock intake, you aren't going to be choking it out by any means.

I was doing a little reading about the lump port mod. They showed a open chamber head being cut for a 1.94 valve and it looked like the chamber was cut back for shrouding reasons. Is this a needed step or a race mod searching for every ounce of power? Also, Im not in a huge rush to get this head done so I may as well do it proper. Would the lumps be of good use in a truck application ? Also will these large valves and such have a major impact on fuel mileage? And last but not, Guides. Normal iron guides or those bronze liners. Is one better then the other?

Yes, the 1.94" valve gets close to the chamber wall & should do some chamber wall relief.

I recommended 1.85" valve because you do not need to do any relieving of the chamber walls, mileage or torque should not suffer.
Also, because you did not seem to want to make much power over what you currently have, & seem to be hesitant on wanting to change the camshaft.

Going to a 1.94" valve will cause mileage drop, less low end torque
I would not add lumps unless you are wanting to go into a different direction from what you originally wanted out of your current engine.

Meaning, do you want to make more power & suffer a bit in the mileage department, less low end torque, throttle response?

Bronze guides are better.

MBHD

Ok thanks, just kinda learning as I go here. Im just hesitant to make huge changes as my truck is not only daily driver it gets crazy good mileage. Believe it or not 18 mpg, I know I know, I have checked dozen times. So to stay on track, 1.84 valves +.100 bronze guided, surfaced - .040. I will give the cam a shot you mentioned as mine has many miles on it. I was looking at the 250 head today. I pulled the valves to kinda look for cracks. Anyways, there is a small area surrounding the exhaust valve seat. I think its where they hardened the head for unleaded gas. It surrounds the seat by about 1/8. Will I need to cut the head for a new exhaust seat or just open it up for the 1.6 and blend it?

If it has surface hardening, it is usually not that deep, guessing .020"?

So, if that is the case, I would install shallow seats for the 1.60" exhaust valves, blend it, minor bowl clean up & help (port) on the short turn radius.
Shallow seats, just to be safe & not hit into a water jacket.

MBHD

May I ask what kind and size 2bbl carb are you running? Thanks. Jay 6155

Its a motocraft/autolite 2100 off of a 66 mustang 289. It has been adapted to the stock intake with a adapter from Mr. Gasket. If I remember right it has 1.18 casted on it. I read some place that its rated at 320 cfm. Came stock with #50 jets, played around a bit and settled on size 48. I tried 46 jets but it had ever so slight of a lean surge doing around 70 mph so richened up a hair. This carb runs 100% better then the rottenchester I took off. Gas mileage and power went up quite a bit.

Thanks for letting me know. There is no way that a 1bbl can feed almost 300 cubic inches of engine! Autolite2100 carbs are on of the best IMHO. Have you considered a different intake manifold? CNC Dude on this board is in process of making a 2bbl manifold that would be a nice addition to your truck. Jay 6155

O yeah, ever hear of the flying toilet?

http://i732.photobucket.com/albums/ww328/Bossofu/024.jpg

MBHD

Wow! Now. That's a 1bbl! Jay6155

Made from a real barrel?