301 poly conversion to hemi-build options ?

[oldngood]

What can be done with the Chrysler 301 poly, to convert it to hemi- I realize the hemi parts are bolt on- but has anyone done this, and is it worthwhile ? I am trying to make a decision if these 301's are worth saving or not.

[George]

If you like a Hemi that "never was". The main thing is the pistons Poly pistons have offset valve reliefs, Hemis are across from each other. Generaly not interchangable, but Leo's book said sometimes Chr did interchange the pistons, if guess if a low lift cam was being used. You would probably need to talk to Bob Walker at Hot Heads about custom pistons.

[George]

There is/was a class at Bonnieville that a converted 301 was perfect for, so at least some were converted. I've asked on various Forums if anyone knows if they adjusted the cylendar walls down for the 301, or if it's just an underbored 331. If someone was to have one of them sonic checked...

[oldngood]

you hit the nail there, while there's a lot more info on these early Hemis now, with Tex Smith, etc. books- there is also a lot of grey area, and unknowns- that other makes of engine have scienced out thoroughly- the info gap isn't filled yet with early hemi

such as- what is cylinder wall thickness of all the early poly and hemi engines, and max overbore ? this can be logged easily with a sonic tester

next- what are intake/exhaust port volumes in cc for heads ? There is scant flow information on these early heads, I'd like to know what the early small-port 331 heads flowed, because if they really flow terrible numbers, and can't be improved much, why bother with them- then I can make educated decisions and spend money where it belongs on a buildup-rather than guess and speculate and waste time/money

example: I read a nailhead buildup on the net, where they ported heads to gain 5-8 cfm per side- IMHO that's a waste of time.

using common sense, it looks to me as if the early 331's can be ported out, and larger valves installed, to get them near the later 354/392 heads in port volume, and make the early 331 heads useable ? There looks like a lot of material between intake ports and manifold bolt holes to hog out. I'm a little puzzled by the statements in Tex Smith saying "avoid early heads except for restorations"- the first thing that comes to my mind is, has anyone tried porting them to see what they can get ?

I'm not too concerned about the small exhaust port on early 331 heads, because the recent trends are using a smaller, higher exhaust port to retain high velocity- even in Pro Stock heads. Perhaps these 331 heads are not as bad as they seem ? I need more info on them.

301- IMHO, with smallish 3.625" bore size, if it can't go to 4" bore, or at least to 3.94" bore standard 354 size, the 301 is a dead player, good for tin/parts only- we need to sonic test one. The money spent building one up, would be better off spent on a 331-354-392, unless as you stated, there's a class rule specifying a 5 liter engine max.

I have a sonic tester

[George]

If there is no core shift & no internal rust problems 331s can be bored to 354 standard bore size, but that leaves no room for oops! same with the 354, it can go out to 392 standard. Personaly I like having plenty of wall! There are a few glitches in Tex's book, mostly conflicting opinions of the guest speakers.

[oldngood]

I noticed in the Tex Smith book, some valve sizes were missing in the end, for poly/hemi Dodge/Plymouth engines

I found the sizes in an old vintage 1957 Motor Repair manual

bore thickness- if there's at least .125-130" left on most thrust walls, after bore/hone, that's good for me- I'd even accept .100" on a few- but not less than .100"

[dan miller]

The 301 poly's have mondo thick walls. About .250" or so.

Hemi heads will bolt right on, but there is a significant problem. The chamber overhangs the bore, so there is a serious mismatch which would cause some major issues with chamber filling, valve notches required in the bore, etc. We considered a 301 poly for the Engine Masters Challenge, but in the end, there's no substitute for a hemi. Sounds corny, but it's the truth. And, do I hear an Amen! lol

Danny

[gregshemi]

That is correct, the chamber does over hang the bore. However, in my years of collecting hemi engines I have several 301 blocks that have been chamfered to match the head chamber over hang. I have no use for them, I run 354 and 392 drag motors and these chamfered 301's were part of a large aquisition of hemi "stuff".
If anyone is interested in one let me know. gregshemi@yahoo.com. I can send pictures if youd like to see them.