I am building a '53 Dodge 241 hemi. I would like to raise the compression ratio to about 8.5:1. I am doing a .060 overbore. I noticed that in '54 there were two CRs, the standard 7.1 and optional 7.5, and reading the shop manual the difference was brought about by using a thinner head gasket to reach 7.5. I plan on milling the heads a bit (.030). With the overbore, slight milling and a thin head gasket I should be able to reach 8.5. Question is will I be able to use the stock push rods or will I need adjustable rods?
A lot will depend on the heel diameter of the cam you use. It is less hassle in the long run to use adjustable push rods. Performance grinds on stock cores don't stand up too well on those engines.
Just a note on adjustable pushrods. I don't think they are as bad to set as some folks would have you believe. I have set in the '54 331 in my avatar, and I go through them at least once a year, unless I do a lot of racing. when I do them more often. I have a couple of wrenches I heated and bent especially for the task, and can run through them in about half an hour unless I get mixed up and have to remember where I am. In this vein, I would suggest having a good sized piece of paper and have the valves to be adjusted and when to turn the crank to do the next set written down in large letters. When you have a valve set, mark it off. I have had to start over several times before I started doing this. Probably old age, but it works for me.
While it is cheaper to mill the heads, you probably should pony up the $ and get custom pistons. @ least one 241 that was advertised @ 7.1 was measured @ 6.19. You can't bring that up to 8.5 by milling a reasonable amount.
Mill the heads, thinner gasket, deck the block enough to raise the compression and then the intake manifold doesn't line up any more. jack vines
I would resurface the intake to line it up with the head bolt holes, I have an excellent machinist nearby.
I'm adding up the cost of machine work, adjustable push rods and the .060 over pistons that you'll need. It seems like you could buy some quality forged slugs and name the compression (9.5 would be nice) for a few bucks more and benefit from the modern ring design. 73RR on here can point you to some quality forgings.
Hey Vetteson this is what i did and please keep in mind that i have not fired the motor yet. i have a 1955 dodge 270. the pistons are stock, just honed the cylinders for re and re the stock cam was re-ground to a 340 6bbl stock spec and i took 60 off the heads when i had them done. I had the same question, after talking to the cam grinder and doing the math we figured that i can use the stock pushrods as the cam had been re ground and i was using hydraulic lifters. i have bolted the heads on the block with a stock head gasket from the kit. and everything looks good. i have an 4 bbl intake that i got from hot heads that looks to line up fine. I am working on putting a 4-71 blower on the hemi so the top end is just in place. So the only thing that saved me from getting adjustable pushrods was the cam grind and the fact that i am using hydraulic lifters. hope this helps and good luck!
That's news to me and my Dodge customers. We all would like to hear the details. Please provide your source of info... .
the heads where shaved by .060 i know what you are thinking did he fire 6 shots or only 5….. sorry… i have it on very good authority that the valves will not hit the piston.
ok Mr. Waters now i get your question… nothing was taken off the intake side, just decked the bottom of the heads. I have only had time for a quick look at the fit of the intake manifold and it looks fine.
The source of the info is me and several other cam grinders across the country from back in the 50's. As with many stock cores, there is not enough meat on them to put s high lift performance grind on them and have it stand up. The hemi's have a fairly heavy valve train and in the early days required torsional helper springs on the rocker shafts to get the required rpm for racing. We did have good success with hard nosing the stock cores but it was expensive. "Been in the cam business 60 years"
Fair enough. Allow me to offer a few random thoughts. Since I have only been messing with the EarlyHemi for about 40 years you are one-up on me.... perhaps, the experiences and procedures of the 50's stills weighs heavily on your mind. Yes, the Dodge, as well as the DeSoto have a finite amount of available 'heel' on a stock shaft to make big profiles. But 'high-lift' is not the be-all, end-all in cam design as you well know. In the 'old' days you had new cores available so regrinding should not have been required unless there were budget constraints or maybe the big cam companies did not want to do proprietary regrinds since they had new cores to sell. I wasn't 'on-scene' until the early 60's so I don't know what you were faced with, I only know what I have to work with today. High RPM? Racing? Since this is not a 'racing' forum and the OP had not indicated a 'race' engine then we should stick to discussing the merits of performance street use. Yes, the EarlyHemi does have fairly heavy valve train, but in stock, or, even spirited street-performance rebuilds, little needs to be done if the operator limits the rpm to something reasonable....something that the engine is designed for, not some pie-in-the-sky bench race conversation. Yes, I recall torsional shaft springs. Many were used in conjunction with roller cams/lifters because the valve spring were just primitive enough to not be able to handle the added weight of the roller lifter. 'Rev-kits' were still very popular in the 60's, even into the early 70's for many roller cammed engines because the valve spring design/technology hadn't yet caught up with the demands. IMHO, if the rocker assembly has a proper rebuild, then that is all that really needs to be done for 99% of the EarlyHemi engines being built for street use. Yes, we can, and have, modified many rocker assemblies to include adjustors or even change the ratio, but that is not for the 'average' buyer. Just my 2¢. .
Artful - Is that your '40 Dodge VC with a hemi? I had a '56 1 ton PW with that I put a 318 into. The hemi would have been more fun.....
yep, the 56 sounds cool, love the look of that truck. the hemi is fun but with my low budget and ok skills its a slow process, a built 318 would get you down the road to driving a lot faster. that said its all about the learning and taking your time and enjoying the build. be careful on this board too many cooks will spoil your plans. do your homework, its free. and find a wise person you can trust and stick with it. not to jack your tread, this is my first hemi build so if this is your first good luck, take your time, think, and avoid all the shiny parts. the stock stuff is built better than you think.
Kinda-sorta. The shaft mounted springs were also called mouse trap springs. The idea is/was that the old heavy roller lifter needed some assistance to stay on the lobe at high rpm. The new rollers are quite a bit lighter. Even the factory Magnum rollers are tolerable w/o a rev kit. .
Usually a rev kit means a second set of spring on the pushrod, in the lifter valley, and usually pushing against the head. The torsional springs were different...though I guess there is no 'exact' definition of 'rev-kit'. I agree with the idea that a Hemi valvetrain is 'heavy' but that it doesn't make too much difference on most engines that people actually run. I think it's a concept that sounds groovy, and has been the mantra of a thousand magazine articles, more than anything. Another perspective you never hear much about is that of damping....I'll admit I don't have any hard data but I'd bet that a 'heavy' rocker offers some benefit in terms of providing a smoother valvetrain, especially at lower and mid RPM ranges.
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