HEMI Tech- PISTONS! rods and related

Link to a previous discussion about pistons.
http://www.jalopyjournal.com/forum/showthread.php?t=105630

 

alright guys, I've pretty much abandoned the idea of running the hypereutectic 10:1 KB's in my 331, so I'm looking at cast pistons instead...is there any cast "off the shelf" pistons with a higher compression ratio for the 331's? would "stock compression" 354 pistons be a drop in after boring the block and raise compression in the 331?...I'd really like to run 9:1 compression or slightly higher if possible, what're my options with cast pistons?...if at all possible I want to stay with "off the shelf" pistons and nothing custom made for price reasons...it's not going to be anything wild, just a nice street motor in my '40 plymouth...

 

alright, I've been reading through all the posts I can find and I think I'm gonna cough up the cash to run stock compression (9:1) 354 cast pistons from PAW in the 331...is there any danger in the .125 overbore of the cylinder walls to step up to the 354 size? Did the 354's have any different combustion chamber differences in the heads that helped give them their 9:1 C/R, or is that what I'll wind up with is a 9:1 C/R 354 with early 331 "wet" heads?

God I'm nervous...I hate shelling out this much money at one time...good thing I'm not buying some custom made forged pistons, I think I'd faint...315 bucks for cast 354 pistons from PAW...now I can finally get that motor sent out for machining once they arrive...maybe I'm just too damned cheap, I shouldn't worry about spending 300 bucks...it'll be worth it in the long run...just gotta keep thinking of firing that bastard for the first time...it'll all be worth it...

 

Pretty much thats what you will have . Rather than pop for new slugs , see if you can find a good set of used 354 slugs , you can generally get them for 150.00 or there abouts.
Also if you can find a set of 55 heads , they flow about the best & have bigger ports that the 51 -53 not sure about 54s--- or get some 56 heads --again port size .
Might want to sonic test the block before you bore it , but then the 56 block is the same core as the 331 --a bore job is all the factory did.

 

well, I already put the order in for the new pistons, too late now...the block came out of a barn stored '53 Windsor, it was stuck but not that bad (only took me about 2 hours and a lot of Kano Kroil and I had all the pistons out (I wasn't very nice to the stock pistons though, some of em didn't make it out in one piece)...I'm pretty confident that the block is in good shape as far as cracks go, this was by far the easiest motor I've ever pulled apart even though it's sat for prolly 5 years...just ordered new cam bearings too...I was surprised, the PAW kit came with pistons, rings, wrist pins and clips...all for 315 bucks...I was just hoping someone wouldn't chime in and say I shouldn't have ordered them because they won't work for some reason or another...I believe the '54 331 heads were the first of the front crossover, which would have gotten the larger ports...I've been considering machining the exhaust ports out from the round to the square ports (even if they're slightly smaller than the later style ports, I have access to the machines to do it and can make my own matched flanges)...finding heads for a reasonable price can be a pain in this area, I think I'll stick with the round port 331's because I already got em...if another pair pop up later, well then I'll be smiling a hell of a lot...

 

If you have access to the equiptment to hog out the ports , you might want to increase the size of the Exhaust valves as well, the early heads had pretty small exhausts.

 

I could be wrong, but I believe you are correct about the ports, but I don't think any 331 heads had the water cross-over in the front. I don't think it was seen until the 354 model engine. Someone correct me if I'm wrong...

 

'55 was the first of the crossover heads, one year only deal with the 331's, I went and did some checking last night after I posted that...the '54 heads did get the larger ports though, but were still the "wet" intake style heads...

 

I'm not touching anything to do with the exhaust, after seeing the cross-sections around the ports and water jacket on the exhaust side I'll never machine anything around there...I am having my 331 heads updated with the '55 size intake and exhaust valves though...1.94 int. and 1.75 exh.

 

Keep up the good work here on the HAMB....I have already turned many friends to this site because of the Info you have brought here and others as well. Not at all a waste of time to me...I love reading this since times here in IRAQ are mundane and just plain gets me home in my mind on what I could do to my car once I get back home...Hell I have 3 Hemi engines waiting for me to come home and pet them to life. Your info has helped me look at things I have had no idea about. And the youngsters need to learn and were else better than the HAMB with all it's infinite knowledge. I believe in the trickle down effect to our younger guys so they can follow and carry on the Rodders Spirit. Ok I'll GET off my soap box now.

 

Cool man! That's excellent!! I wish I could take all the credit though... the info would be worth squat if it weren't for all the other HAMBers that provided, confirmed and of course shared what they know! The HAMB is definitely a team effort! Thanks for the props just the same though! Brining it all together was some work and something I should probably get back to working on soon. Had to take a break to get caught up on other learning!

 

I am Ashamed of myself ---- I don't know what possesed me to say the Exhaust valves were small -- It's the INTAKE that need to be bigger . I Do KNOW better ---Sorry

 

Don't forget the Caddy you have to stroke as well , I just had a conversation with it about it's soon to be new home & it's really excited about seeing the wide open Texas rangeland!!

 

how dare you mention a caddy motor in a hemi thread...BLASPHEMY!!! hahaha...I've had my eye on a 331 caddy for a little while now...it'd be a nice little competition for a second gasser to line up next to my 331 '40 plymouth...if only I could drive both cars at the same time...I guess I'm gonna have to stop referring to it as a 331, since it's gonna have 354 slugs in it soon...man, that extended bellhousing is gonna throw people off when I have 354 c.i. painted on the hood...hahaha

 

You can bore out a 331 to 354 (I've run three blocks that way and never had any problems) BUT the 331 head gaskets WON'T work. The bore will be larger than the lip around the cylinder hole in the head gasket so it won't compress and seal the combustion chamber..

You can't use '56 gaskets, either, because the pushrod holes are teardrop shaped and extend BEYOND the edge of the 331 block. This will leave you with massive oil leaks.

Tom Hannaford from Antique Auto Parts Cellar in Weymouth, MA took one of my old Fitzgerald 0559-SR (overbore) head gaskets and, using it as a pattern, had gaskets cut out of Armstrong Thermo-torque. I've been using them for about 20 years now. They ain't cheap but they work. You MUST ues copious amounts of mold release or the gaskets won't come off once they're cured. I use liberal amounts of K-D Copper Coat on both sides and it still requires an hudraulic jack to crack the seal after they've been on there a few years.

He's also come out with a composite style overbore head gasket that's a lot thinner and doesn't require a good mold release like the Thermo-torque gaskets but it DOESN'T work on high compression (12.5:1). I blew out a set w/o even getting the car out of the garage and out onto the street. I had to go back to the 0.050" thick Thermo-torque gaskets.

 

there's no other solution to the 331 bored to 354 head gasket problem? I guess I never thought it through, I just assumed I'd be using 354 head gaskets off the shelf...good thing I haven't ordered any yet...so how much are we talking for either set of overbore gaskets that guy makes?

 

I would like more info on this also. I will be running 354 heads and boring the 331 out to 354. I will also need these gaskets.

 

I gotta start calling around to check out some local engine machining shops for prices too, my pistons should be here in a couple days...along with a check that will pay for machining the block and hopefully rebuilding the heads...

 

What pistons did you say you went with for this?

 

Is this a good place to ask about compression ratios? I am about to start the assembly on me 330 Desoto. I have the crank turned at .010/std and the pistons are .030 over. The stock compression ratio is 8.5 advertised. How accurate is this likely to be. Will I pick up any significant compression with the .030 overbore? I have will be checking the block decks for straightness and trueness to the crank. If it needs it I will get the block decked. I will also check the heads and was thinking about cutting them to get the compression up. I was thinking about 9:1. I will be running a mild HH EH61 cam, .430 lift, 210 @ .050. This is going to be a mild street motor in my '50 Merc with a Tremec 5-speed. I was thinking about a 3.55 rear gear. Any suggestions and help will be greatly appreciated. Thanks, Bill

 

Boring the block won't raise the compression ratio.
Decking the block and/or cutting the heads will raise it slightly.
The way to raise the compression ratio is to change the pistons.
3.55 is a good manual trans differential ratio, that's what I have behind the 4 speed in my GTX and my hemi-powered '34.

 

I'm having my 392 bored at .020" at the moment.
I've got a set of cast slipper-skirted pistons from PAW (made by Egge, I think. At least the piston-pin says so), but the note in the box calls for a .0025" piston-clearance. That seems very loose to me...
The block is bored at .020" over exactly now, but still needs to be honed to the desired clearance, which will be done on monday.
Originally, in 1957/'58 these engines had between .0005" and .0015" piston-clearance, according to my Chilton Manual and a web-source.
I know to always follow the manufacturor's specs with these things, but this number seems a bit out of line with what one would expect.

What do you guys think about so much play for a cast piston?
(I also emailed Egge with this question by the way, will post their reply here when I get it)

 

Follow the piston manufacturer's recommendations -- they know their piston material and how much clearance is needed. Two and 1/2 thousands should be about right for these types of pistons . . .

 

It is indeed. I just received an email back from Egge stating the same;

 

Have any of you ever stroked a 56 354 hemi? Is it possible?


Thanks!

 

The answer to the question is YES, you can. How? I'm probably going to mess this up, but I believe you use can do an offset grind with the appropriate rods. I want to say they are modified BBC rods, but I could be WAY off on that. Something about a 392 crank and some main work as well. There are others more knowledgeable on this subject here.

Good topic and not much on here regarding that subject. Good time to add it...

 

Gawd, I feel like such a newbie when I see how old some of these threads are...

Yes, you can put a '92 crank in a 331-354 block. The easy way is to turn down the mains. Don't forget to also turn the portion of the crank behind the rear main where the seal is located. And unless you duplicate the hash marks for the rope seal you will then use a replacement lip style.
Now, while you are cutting the mains you can also detail the rod journals so that you can use the 383-400 con rod. This rod will push the stock piston up 0.014" for a very slight bump in compression, but since most head gaskets are fat multi-layer jobs, you are then back to where you started...lol
The 'B' rod needs to be bushed for the 0.984 pin but you will be rebuilding the rods anyway.

Gary

 

There we go! I knew it was something like that! Thanks Gary!

 

Along with all of the necessary info that goes into building an engine, one of the most often confusing deals with compression ratios. The subject recently surfaced (again) so here is a link that should be of some help to those afraid of math.
http://kb-silvolite.com/calc.php

Enjoy.

Gary

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392 crankshaft in a 331-354 block.

Mains ground to 331-354 size.
Rear seal surface cut to same.
Counterweights cut to same.

Weld up and regrind thrust bearing surface to 331-354 size.
Balance rotating assembly.

From that point, there are countless possibilities on rod journal size, stroke, and connecting rods.