The Stovebolt Site Forums The Shop Area Engine Shop 848 Head Tweaking

I have an 848 head on my 57 235 now. Runs great however, I always want more Power. I found another head in good shape and was wondering what the best modifications are to do to the extra head. Porting, polishing & bigger valves? What should I do to it to get the best possible performance?

I miss all the old school mechanics that used to hang out here...where ya at guys? :p

Shipwright,
They all went to check their you know whats!


Stuart.

The two biggest improvements to the head are polishing and milling. There's not enough room in them to do much on the valve size. Best thing to do for milling is to establish you valve clearance before milling so you don't have to sink the valves, which will reduce your flow.

Do you have copies of the old speed manuals? "How to Hop up Chevrolet & GMC 6-cylinder" by Huntington, and "Chevrolet/GMC Speed Manual" by Bill Fisher AKA California Bill are full of great ideas.

Nothing beats cubic inches, have you considered a 261? For best possible performance bolt it onto a 261 block. Seems like you only had a single 1BBL carb when I viewed your bolt. You can weld up the chamber area for increased compression. There are a lot of pistons to choose from as well. A supercharger would look good on your truck if you can find one.

When you say there are alot of pistons to choose from...can you lead me in the right direction?
I posted in another forum that I was told that Corvette or Cadillac pistons with domed tops would give the 9:1 compression I'mm looking for. Another old rodder said that there is not enough clearance for anything but a flat head stock piston.
Can you clear the confussion up?
-jeff

All ya have to do is take a 235/261 head and take a look at the very poor combustion chamber design.It's hard to do any improvements without a flow equipment or a lot of past experience,no one on this site past or present has that experience.According to Patrick Dykes,you can spend a lot of money and time reworking the head and not end up much better than a stock head.Leo Sanducci ,before he raced 292's,ran 235 and 261's,he says the same for a street engine.
They used to make wierd domed pistons for 235's to raise compression,not available anymore.Using flat top pistons,milling the block as necessary for zero deck height,mill the head about .060 that,watch the intake valve to piston clearance,and wind up with 9-1 actual compression.This is more or less the maxiumum compression these engines will tolerate on the current pump gas.
The so called Caddy piston conversion requires some expensive and possible suspect crank machining to get more cubic inches,but your still dealing with the poor head design.
You can spend thousands of bucks on these engines and wind up with 200 or so hp.
If ya want real HP in a vintage engine,the 302 GMC is the way to go.The same money spent will give 250 HP at reasonable rpm on the GMC.
I had a great running 261 in my 37 Chevy pu,replaced it with a GMC 302 in the same state of tune,the difference in power is really noticable.That's my opinion from actual experience building these old lumps.

It should be fairly straight forward to get 9:1 on a 235 rebuild using the 848 head. Head was run across the grinder to straighten up, inserts, new stainless 1.5 valves. Bore it .060 with flattop Bagger pistons from Patrick. Howard's M4H 3/4 solid lifter cam set at .012 and .014. When compression checked recently it was 160 across the board thats 9:1.

Thanks guys. Those 302s are hard to come by these days. Maybe I should just be satisfied with what I have now.

Tony,

[QUOTE no one on this site past or present has that experience [/QUOTE]

How do you know this. :rolleyes:


Stuart.

Stuart, Tony's number is 107, senior member, has heard and done most of the things that folks ask about,, in my opinion, if Tony gives me advice, I can take it to the bank..........Fred

Joker,

My bank account is closed!


Stuart.