Thread: Blown Hemi

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OK guys & girls
Got a question on supercharging a hemi. I am putting together a 33 roadster, and looking for the pros and cons of either going the retro 354/392, or going with a new style 426. The roadster will be street driven, with some extended runs of maybe 5 day trips so it can't be to wild. It will be backed up with an automatic, and Ford 9 inch. How about some names of reputable people who do hemis besides Hot heads & big Als toybox, for price comparisons. Of course I am not afraid to have the machine work done, screw the engine together myself, but we are talking time, and for me free time is limited. I have seen some interesting deals on ebay, but my first objective is old style or go full boogie 426/472? Yea I know there is no replacement for displacement. but we are talking a 33 so old style would more period correct for what that is worth

Thanks,
Mike

Hmmm. "Supercharged Hemi". "Can't be too wild". Something's wrong with this picture.

I agree, a "Mild" blown hemi seems strange but Paw has all the goodies.


http://www.pawinc.com/hemicatinfo.html

Just keep the right blower pulleys on it to keep the boost out of it and it will tame it down a bunch... The old ones are kewl, but the new ones are a whole lot easier to get parts for. Why not just get the crate hemi and a blower from BDS? Simple and easy, long as you have a big check book!!!!

This is pretty far out there, but I have seen switches for blowers. Let me explain. You have a switch in the cockpit that turns on or off the blower. This way you can have the "mild" side with the blower off, and the "performance" side with the blower on. I have actually seen cars with these, but the Ford in "Mad Max" also has one. The only problem I see with this is tuning such an engine. You must have a comprimise between a blower and naturally aspirated with both cams and carbs.

and it has to get good gas milage

I had thought about the crate motors, but was concerned about the compression ratio, I thought the crate 426s were about 10:1, and I didn't want to go past 9:1 for a blown street motor I thought was the norm, but I could be wrong.

Thanks for the help so far, but no one has given me a definitive answer yet, still looking for that "Oh it has to be ...... because of....

Mike

Originally Posted by eticket

and it has to get good gas milage

I had thought about the crate motors, but was concerned about the compression ratio, I thought the crate 426s were about 10:1, and I didn't want to go past 9:1 for a blown street motor I thought was the norm, but I could be wrong.

Thanks for the help so far, but no one has given me a definitive answer yet, still looking for that "Oh it has to be ...... because of....

Mike

Blown Hemi and good guess mileage don't even belong in the same thread!!!! Blower engines should be 8.5:1 or less compression based on how much boost you want to run... Look in the PAW catalog as someone suggested, there's everything you need, nothing left to do but write the check!!!! Here's a link http://www.pawinc.com/, phone number is there, just call them up and get the thing ordered.

I'm with Dave on the gas mileage. Don't worry about it...it isn't going to be very good. It will be so much fun to drive that you will be just running from gas station to gas station anyway.

I'm assuming you are looking at 6-71 or 8-71 blowers. 6-71 is enough for a street stetup from your ideal plan.

Now the low compression is good 8 to 8.5 no problem on either style. Try for no more than 3-5 lbs boost. Even this is a lot considering that your car probably will weigh only 2800-3000.. maybe less if plastic. You will be around 400-450 hp at the wheels with out trying hard. No need for a hot cam either. Just something that has a good sound. Do have a good ignition system and fuel system and keep the advance down. There are boost controlled advance devices available. MSD

You can set it up for a single carb. Say a 750 or 800. No need for 6500 rpm on this car. Check Hot heads . There is a secton on a scoop/carb setup that is made by Garlits that has a hidden carb in the scoop. It is very cool that does just this. Edelbrock makes a blower carb with the manifold referenced power valve and correct jets etc. So does Demon.

I'd carry a spare set of head gaskets,blower gasket, blower belt and tools if you plan on any hot dogging. Both style motors are very easy to work on if you have room. You should be able to change H/G in an hour or so. I don't think you would ever burn a piston unless you are racing but if you limit the motor with a single carb, it will run out of fuel and air long before it hurts itself.

Also set up your starter switch so you can spin the motor over then hit the ignition switch. This will prevent backfires while starting and busted starters.

You will have fun with this car. I wish it was mine. Do remember if you are using all steel motor these things are very heavy so your car will be a little nose heavy. Adjust your suspension to allow for the weight and put all your stuff in the back.

Keep us posted on progress.

Well the decision was made pretty quickly on what kind of hemi to get. I was checking out ebay, and there was a 354 out there, that had the top end re-done, but stock bottom end, at what might still be a good price, but didn't like the CR of 9.25:1 but if I was going to redo the bottom that would have been changed. Then a buddy of mine told me about a 392 long block for sale that was already built for a blower (the guy had changed plans, so it was sitting in his garage) picked it up REAL cheap. He said it was already balanced, 426 rods, forged pistons, double roller chain, some head work. But as I said it has been sitting for a couple of years, so it had some surface rust on the block & heads (it hasn't been painted yet) so the first thing the wife says we are buying this big ugly thing. We loaded this ugly thing in the back of the truck, and watched the back end drop, Now a little back story here I am a die hard ford guy, had a 68 shelby 500 in my Navy days in the late 70's, couple mach 1s w/428s, and just sold a superformance cobra so I can build a cabriolet (I can only afford 1 toy at a time) I could not believe how heavy that engine IS !!! Found out that a basic 50's hemi weighs about 800 lbs (sound right?) So no wonder it dropped the back end of the truck. Of course I don't have a car to put it in, so she thinks that makes a lot of sense to, but she is used to me, and just smiles, and says "Bless his heart "
So I am on my way, guess I better open up an account w/ hot heads & PAW

Mike

Congrats on the Hemi!!! As far as weight.. they are a bit beefey. Running the blower you get rid of the cast iron intake and the whole front cover and water pump so you shed a lot of pounds. On the other hand you add almost 100 pounds of blower, manifold, and carbs. Hot heads has the conversion front cover so you can use the Chev water pump which is availablel in alumininum. You could use a mag blower but pay a bit more for it. I don't remember what the weight difference is, 10-15 pounds for mag blower and manifold maybe a bit more. They do polish a bit different color but pleasing.
If you can I'd go for the aluminum heads. They old stuff is probably pretty well used up and will cost a lot to rebuild and replace. You can save significat weight here too plus get a better part. If I recall the iron heads weigh about 100 pounds each complete. Alum are probably half that.
Don't forget the headers. 2" headers and collectors can get pretty heavy fast.

A good buddy of mine just got what he though was a 392 but it turns out is is a 331 industrial with the gear drive cam. Kinda an orphan but I think Hot Hemi has the conversion stuff he needs.

I really wish I could afford one for my 41 Willys.

Good luck.

Originally Posted by eticket

Of course I don't have a car to put it in, so she thinks that makes a lot of sense to

Makes perfect sense to me.

I believe a 392 weighs 790 pounds, dry.
The Surfers useta run $29.95 reground cranks in their digger, and never blew one apart in several years. The stock 392 cranks are steel and all radiussed, stone reliable.

You can use the stock crank. Heck we had them welded into 5/8 and 3/4 strokers in the gas dragster days. Even stock rods will be ok for street. Keep the boost down around 5psi and build a basic good motor. I'd try to add an MSD ignition.

There were more blown cars and even a few blown hemi's at the back to the 50's than I've ever seen before.

The qas milege will be back tothe 50's too. haha 10 on a good day.

I wish I had half the old 92's I have scattered all over the country in the good old days ( well division 7 anyway). Here is my 2 cents and reasons for this direction. CHOOSE the 392 !!! The 92 was around in the time that all the aftermarket parts were being born and everything is interchangeable = Donovan, pink and so on all made items that were for the 392 block. You can find aluminum heads cranks, rods, crank girdles and pans, valve covers, front timing covers and so on. Granted this is all collectible stuff but the demand is still on the low end but making a comeback so pricing is reasonable compared to the difficulty to find all goodies for the less popular IE Red Ram and so on. I would stat away from old raced stuff and use STOCK internals as they will be in better shape and not need machine work to make all compatible.
A 92 will a mild boost of 5 to 8 pounds of boost will live forever on the street with NO regular maintenance like when you have 40 pounds of squeeze pushing bearing out etc.... Good luck finding NON cracked heads as they all crack from plug hole to valve seats and across the seats. The plug hole cracks rarely hurt anything and new valve seats stop most of the problems on a wet or water cooled engine (we filled the block with plaster and ran them dry so cracks were no big deal. Adjustable push rods or a stock cam Will let you update to about any combo you want there. Use the marine valve train if you can find at a good price. The old Hunt or Vertex mags are easy to find and make for trouble free running. A 6/71 blower is plenty and cures problems of the bigger blowers you do not need anyway. The 1/2 pitch stuff is so cheap to run as industrial timing belts are easy to get but the metric pulley stuff is easier to find now days. Run about 10 to 20 percent under driven to keep street-able. The Carter AFB was the most tune-able and easiest to modify (remember it always sees full vac when sitting on top of the blower. New carbs now are around but modified carters should be easy to find as who needs them anymore. The old bug catcher mechanical injection converted to hidden electronic injectors is WAY COOL but $$$$ too.
Getting pretty windy here so I will stop but finding an old drag racer and digging through his old goodies and memory is a jump start. Nothing cooler than a blown 92 with mechanical hat injection to make my vision of a TOY.

392...Cool with any type of topping!

Pat