Thanks to 425-500 Conversion Posters [Archive] - Maximum Torque Specialists Cadillac Forums

View Full Version : Thanks to 425-500 Conversion Posters

acaciaavenue

10-09-2005, 08:21 PM

Just got my engine back from swapping my 425 to 500, which resulted in a huge horsepower gain and I wanted to thank everyone who had offered their suggestions (especially Al, who helped me with a few tech questions) a few months ago on rebuilding my engine.

In case anyone is contemplating trading up their 425 to a 500 - DO IT. Pay a little extra and get your heads ported/polished. It was worth it. I've got a 450HP 500 in our hearse and I haven't been able to remove the grin from my face for three days while I'm driving it around. 500 cubes is a beautiful thing...

fleetwood472

10-09-2005, 10:07 PM

Who did you have port and polish your heads? How much did it run? Sounds like a sweet setup. I am in the middle of building my 472 to replace my 425 in my 78 fleetwood. - Justin

acaciaavenue

10-10-2005, 07:09 AM

I live in Great Falls, Montana and a shop in Helena did the head work. I didn't get the heads CNC Ported, but I went one step below which ended up costing around $600 - I don't have the exact figure in front of me, but I believe that was the cost.

Terrible One

10-10-2005, 09:27 AM

Sounds cool. So whats in that engine? Just curious because I am doing a similar setup and looking for 450 horses and 530 or so ft. lbs.

R.Solur

10-10-2005, 01:10 PM

Yeah, me too! Actually I`m hoping for more than 530 ft.lbs :oops: :twisted:

cutlover80

10-10-2005, 04:24 PM

Me three!!!!!!

Morella

10-11-2005, 12:37 PM

If it came with a 425, then it must be a 77-79. Did you have to change the gears? I would think that you would, if you were taking it to the strip.

I have a 76 with a stock 500 that gets 6/8 mpg, and as much as I would like to have the horsepower, it's a long way to anywhere from Tucson. There are some places that I can barely reach bewteen gas stations. I was thinking of going with the MT3 cam and trying to get some bottom end and gas mileage.

-denise

Busguy71

10-11-2005, 04:41 PM

when you port and polish the heads, do you just gasket match the ports or do you go more than that? I'd be temped to do a mild porting on my heads before I throw the motor in. I'm told that these heads breathe VERY well with just a little work

Nashalac

10-11-2005, 05:27 PM

You do LESS than that. The gasket openings are way big. Not sure of exact size but valve pocket area important. Somebody here can give more info than me.

acaciaavenue

10-12-2005, 09:00 AM

Sounds cool. So whats in that engine? Just curious because I am doing a similar setup and looking for 450 horses and 530 or so ft. lbs.

I don't have the buildsheet handy, but I'll break it down later this week when I have a spare moment. If you're looking to rebuild, be sure to upgrade your stall converter - it makes a world of difference on your take-off, especially in heavy cars. This is the car the engine is in:

http://www.jasonbeamstudios.com/Hearse2005.jpg

Terrible One

10-12-2005, 01:33 PM

Awesome. I've seen that somewhere. Cadillacowners maybe?

What kind and what stall converter would you guys recommend me using?

68C15

10-12-2005, 07:08 PM

I am doing a similar setup and looking for 450 horses and 530 or so ft. lbs.

am I missing something? I read somewheer that my '68 472 was rated at something like 475ish HP & 535 ft. lbs. :?:

Terrible One

10-12-2005, 07:47 PM

Hahaha, stock? Far from it.

acaciaavenue

10-12-2005, 09:37 PM

Awesome. I've seen that somewhere. Cadillacowners maybe?

What kind and what stall converter would you guys recommend me using?

I can't remember if I've posted at CaddilacOwners or not - maybe.

I have a GM Corvette 2200 stall and I'm pretty happy with it so far. Although, I don't claim to be an expert as this is my first higher RPM stall converter. Seems to give me a good stall speed and allows me to roast the tires well - so I can't complain.

I read somewheer that my '68 472 was rated at something like 475ish HP & 535 ft. lbs.

I'm going to guess that you were pushing 275 hp stock. Not sure where you read that, but it's not correct. Anyone here know what the stock HP rating was in '68?

Terrible One

10-13-2005, 04:32 AM

I'm thinking it was like 250-280 with like 380 ft. lbs

R.Solur

10-13-2005, 06:11 AM

That`s terribly wrong Mr. Terrible! Just look at the Torque-pig article; the dirty old low-comp 500 did 303hps and 468lbft. The pre-smog enegines was a bit more angry; better cams, higher comp, better headflow aso.

STDog

10-13-2005, 06:51 AM

I read somewheer that my '68 472 was rated at something like 475ish HP & 535 ft. lbs.

I'm going to guess that you were pushing 275 hp stock. Not sure where you read that, but it's not correct. Anyone here know what the stock HP rating was in '68?

Published numbers were 375 HP, 525 lbs/ft. The 475hp must have been a typo, should of been 375, and was referencing the published numbers.

CadCompany (http://www.cad500parts.com/catalog/page9.htm)(Flashcraft) dyno'd a '70 stock 500 (high compression) at 323 HP and 504 Ft-Lb, (publiished numbers were 400/550) so the 472 would be a litte less, but probably around 300/475 when tuned and in good shape.

Terrible One

10-13-2005, 09:20 AM

Shouldn't have jumped on that. The power made is greatly influenced by what year the engine is.

fleetwood472

10-14-2005, 09:34 AM

STDog

10-14-2005, 10:53 AM

What did you guys use for the heater core fitting on the back of the head? The 425's had a 90 degree angle fitting what did you guys use with the 472/500 heads in these motors for a swap into a 77-79 rwd? - Justin

Take youre pick. Swap the fitting over. Or use the fitting on the 472/500.
at lest in '74, Cadillac used a straight fitting on the rear of the head. You could probably swap the one from the to that same hole. If it like my '70, and the heater hose is up front, on the block, just run a new hose. Zip-tie it to the return hose along the fender, or find a bracket from a '68 - '70 that'll hold both hoses.

R.Solur

10-14-2005, 11:16 AM

Sounds cool. So whats in that engine? Just curious because I am doing a similar setup and looking for 450 horses and 530 or so ft. lbs.

Hope we`ll get an answer to this.. :wink:

Terrible One

10-14-2005, 11:51 AM

Me too, because from what I hear from Potter and everyone I will be making wayyy more power than that.

fleetwood472

10-14-2005, 12:28 PM

Hey STDog,

Can you put the port at the back on the 1970 950 heads or do you have to hook the hose up at the front of the block? Thanks - Justin

STDog

10-14-2005, 12:54 PM

Hey STDog,

Can you put the port at the back on the 1970 950 heads or do you have to hook the hose up at the front of the block? Thanks - Justin

I can not think of a reason why not. Put a pipe plug up front, and thread the feeze plug hole in the back. That the way the '72 looks. You might find a press fit nipple to fit the back, but tapping for a NPT fitting would make more sense.

I'll look at the '72's heads and mine tonight to make certain, and get a picture of which hole.

-Thomas

Bugzaper

10-14-2005, 08:06 PM

Awesome. I've seen that somewhere. Cadillacowners maybe?

What kind and what stall converter would you guys recommend me using?

I use a "Allison" (spell) brand torque converter in my 81 chevy C-10 shortbed 2-whl drive equipped with a 77 425/400. It was built to handle just about any torque you can throw at it. I had a diesel shop here local that works mostly on semis build it. It wasn't cheap but it is guaranteed "FOR THE LIFE OF THE TRUCK/CAR" ! I think the stall is around 2600-2800 rpm, which is a bit much, but I pull a trailer with the truck and it's like nothing is behind it.
Actually have a hard time when not towing, keeping the rear tires from moving at stop lights. Anyway what ever brand you go with make sure they guarantee their work. My .02 worth.

Terrible One

10-14-2005, 08:14 PM

Thanks for the input guys.

I'm going to have to find out the stall on the stocker to start.

fleetwood472

10-15-2005, 07:38 PM

DaveM

10-16-2005, 07:49 AM

fleetwood 472.. I have a 1970-472 with 950 heads in my 81 deville.. and the 368 had that hole at the back of the passanger side head..so what I did was drill and tap for a pipe and put ,IF I got the term right, is a street elbo...that is a elbo that is male on one end and female on the other.. I did this years ago and I think there was a boss in the casting that I drilled in the center.. worked fine for me and plenty of clearance to the firewall..

fleetwood472

10-16-2005, 10:49 AM

Hey Dave do you have any pictures of the setup? Also how much did you have to knock off of the bolt that sticks out in the way of the passanger side manifold? After you cut it do you put a taper on it so you can re thread it if you ever have to do anything with the suspension? Can you just get a shorter bolt? Thanks - Justin

STDog

10-17-2005, 08:06 AM

For anyone who has done this swap before can you give me more info on the heater hose fitting? Which is the most prefered way tapping it and putting a fitting on the passenger side head or just running a hose up front? What size tap do you guys use for the heads? Thanks - Justin

Here's pictures of the heads on the 1972 version.
You can see how the head without the outlet is also tapped, and has a pipe plug in it (uses a square driver, not hex). This is the factory setup.

I don't have a picture, but my 1970 heads have a pressed in freeze plug there.
If you want, I can pull one or both out of the '72 heads and get the dimensions. I expect they are the same so no left or right head, other than where the plug and outlet are installed.

You should be able to tap those holes that have the freeze plugs, and not modify anything else. You probably won't even have to drill the hole larger, but the machine shop would know for sure.

abcdefg1675

10-26-2005, 01:42 PM

am I missing something? I read somewheer that my '68 472 was rated at something like 475ish HP & 535 ft. lbs. :?:

Your off by 100hp, not sure about the torque.

My 1977 Goodheart&Wilcox automotive encyclopedia has horsepower, wheelbase, and engine speed listed for american cars from 1960 to 1977.

1968:
Cadillac - 472Cid 375hp@4400rpm

That is Net horsepower, where they cheat and run the motor without the stuff hooked to it. Real horsepower numbers are probably quite a bit less than that. It would still beat my '77 CDV any day, mine has 180 brake hp.

btw, if anyone needs horsepower, wheelbase, or engine cranking pressure looked up, PM me.

STDog

10-26-2005, 01:46 PM

btw, if anyone needs horsepower, wheelbase, or engine cranking pressure looked up, PM me.

1970, 472 cranking pressure?

Terrible One

10-26-2005, 03:05 PM

fleetwood472

10-26-2005, 07:12 PM

Does anyone know what size to tap that hole in the back of the head to use for the heater hose? I would check mine but they are already at the machine shop so I cant get to them. If anyone knows I will probably just call the machine shop and ask them to tap them but I dont know what size to tap the hole to. Thanks - Justin

dave_brode

10-27-2005, 01:59 PM

fleetwood472,

You can use a 1/2" or 3/4" NPT tap, and then thread a brass or steel street ell into that, and a male NPT to barbed fitting into it.

For guys with the head with the fitting that creates clearance problems, you can remove the factory fitting [with lotsa heat and penatrant]. It is pipe thread. 2" iirc. Then, get a pipe bushing down to 1/2" or 3/4" NPT, and use the street ell in it.
Dave

"]Does anyone know what size to tap that hole in the back of the head to use for the heater hose? I would check mine but they are already at the machine shop so I cant get to them. If anyone knows I will probably just call the machine shop and ask them to tap them but I dont know what size to tap the hole to. Thanks - Justin[/quote]

STDog

10-27-2005, 02:36 PM

It is pipe thread. 2" iirc.

You really think it's that big?
I'd have to measure, but if you look at the picture I posted, it looks about 2x the hose nipple. Isn't that 5/8" hose?

Autozone (not the best source I know)lists the freeze plug in the head as 1-1/4", so 1"NPT might work. 1-1/4 NPT will for sure.

1"NPT uses a drill size of 1-1/8"
1-1/4 NPT uses a drill size of 1-15/32"
1-1/2 NPT uses a drill size of 1-23/32"
(all then get a 3/4" per foot taper, before threading)

I'd look for a plug that 1-1/4 BNPT outside with small NPT inside, like in the picture. That inner size depends on what you can find with the correct 5/8" (or is it 3/4") hose barb.

Or just get a plug, drill it for a barb, and solder/braze the barb on.

dave_brode

10-27-2005, 03:07 PM

STDog,

"]It is pipe thread. 2" iirc.

> You really think it's that big?
I'd have to measure, but if you look at the picture I posted, it looks about 2x the hose nipple. Isn't that 5/8" hose?

I could be wrong. In any case, afaik, the fitting that's screwed into the heads that accept the hose is male NPT, and if so, std pipe bushing should allow a common street ell to be used for more clearance, rather than a molded 90 degree heater hose on the factory fitting. Hardware stores usually only stock bushings to go one size at a time. You can find very short pipe bushing from 1.5" to 3/4", etc, but you might have to go to a "real" plumbing supply house, rather than a hardware store.

As far as drilling a plug for a fitting, I seriuosly doubt that a std "tin" core plug would work. The factory plugs are much heavier than generic plugs, and should hold a pipe fitting imo.

Fyi - I have the later heads that accept the hose on the rear of pass side.
I wanted to bring coolant from rear of both heads. So, I drilled and tapped my driver's side head's original rear core plug, and used a brass hardware store 1/2" street ell there [male to female 90 degree ell]. A 1/2" male NPT to 3/8" hose barbed fitting screws into that. I'll run 3/8" hose to a tee on the heater hose to allow coolant from both heads to flow into the heater.

Btw - another option is to drill both heads in the rear for 1/4" or 3/8" fittings. Some of the caddy heavy hitters do this to even out the coolant temps on both sides. The heads are drilled and tapped in the upper rear portion near the valve cover rail. The fittings go into the highest part of the rearmost coolant passage. From there, they usually run to block under the thermostat, or into the thermo housing, or a plate under it. For a street ride, the fittings could be joined and run through the heater first, then to the inlet side of the radiator, or to the block under the thermostat.

However, imo, fwiw, the inlet side of the radiator is better, as that has the lowest pressure in the system, and would help flow from the rear of the heads. Imo, the fitting under the thermostat is in the high pressure portion of the system.

Dave

Autozone (not the best source I know)lists the freeze plug in the head as 1-1/4", so 1"NPT might work. 1-1/4 NPT will for sure.

1"NPT uses a drill size of 1-1/8"
1-1/4 NPT uses a drill size of 1-15/32"
1-1/2 NPT uses a drill size of 1-23/32"
(all then get a 3/4" per foot taper, before threading)

I'd look for a plug that 1-1/4 BNPT outside with small NPT inside, like in the picture. That inner size depends on what you can find with the correct 5/8" (or is it 3/4") hose barb.

Or just get a plug, drill it for a barb, and solder/braze the barb on.[/quote]

CadillacPat

10-28-2005, 01:37 AM

Long story short....The Hot Rod article of July '00 entitled "Torque Pig" (I lost the link, someone please post it if they have it) tested a re-rung/new bearing/gasketed '76 500 at 303 hp and 468 ft.lbs. Factory rating was 210 "net" hp. Also, I believe it was Potter or Cad Company that tested a supposed "400hp" '70 Eldo 500 at about 325 hp. Cadillac over-rated the HP figures, but the torque values were much closer. CR's were 10.5:1 in '68-'69, 10-10.25:1 in '70, 8.5:1 from '71-'74 and 8.25:1 in '75-'76.

STDog

10-28-2005, 06:53 AM

It is pipe thread. 2" iirc.

You really think it's that big?
I'd have to measure, but if you look at the picture I posted, it looks about 2x the hose nipple. Isn't that 5/8" hose?

I could be wrong. In any case, afaik, the fitting that's screwed into the heads that accept the hose is male NPT, and if so, std pipe bushing should allow a common street ell to be used for more clearance, rather than a molded 90 degree heater hose on the factory fitting. Hardware stores usually only stock bushings to go one size at a time. You can find very short pipe bushing from 1.5" to 3/4", etc, but you might have to go to a "real" plumbing supply house, rather than a hardware store.

True enough. Most places have a very limited stock. The 425 I was working on, had a plastic ell instead of using the hose. I think a 90* pipe elbow would be better tough.
How about this (http://www.cpperformance.com/detail.aspx?ID=715)?
Here's (http://www.cpperformance.com/detail.aspx?ID=777) a 1" male to 1/2"female reduce to go with it. This (http://www.go2marine.com/g2m/action/GoBPage/id/44251F/pipe_thread_reducer_parker_hannifin.html?WT.srch=1&WT.mc_id=fr1) place has 1-1/4 to 1 as well. So the stuff is out there.

As far as drilling a plug for a fitting, I seriuosly doubt that a std "tin" core plug would work. The factory plugs are much heavier than generic plugs, and should hold a pipe fitting imo.

I wasn't clear :oops:
I wasn't thinkig about the freeze plugs, They aren't thick enough to hold a pipe thread.

I ment drill a pipe plug to ~5/8" and solder/braze a brass hose barb to it. So the plug screw into the head, and the barb is attached to it. While small pipe plugs are solid, I think a 1" or bigger plug would be hollow in the center for weight/material savings, so you not drilling through 3/4" of metal. And the larger plug shouls have a lager enough head (for tightening it in) that it's still usable with a hole in the middle, like this (http://www.cpperformance.com/detail.aspx?ID=698)

dave_brode

10-28-2005, 02:02 PM

STDog,

> snip

> True enough. Most places have a very limited stock. The 425 I was working on, had a plastic ell instead of using the hose. I think a 90* pipe elbow would be better tough.
How about this (http://www.cpperformance.com/detail.aspx?ID=715)?
Here's (http://www.cpperformance.com/detail.aspx?ID=777) a 1" male to 1/2"female reduce to go with it. This (http://www.go2marine.com/g2m/action/GoBPage/id/44251F/pipe_thread_reducer_parker_hannifin.html?WT.srch=1&WT.mc_id=fr1) place has 1-1/4 to 1 as well. So the stuff is out there.

That would probably work, but I'd go w/a bushing, and a street ell.

As far as drilling a plug for a fitting, I seriuosly doubt that a std "tin" core plug would work. The factory plugs are much heavier than generic plugs, and should hold a pipe fitting imo.

I wasn't clear :oops:
I wasn't thinkig about the freeze plugs, They aren't thick enough to hold a pipe thread.

Agreed, but the caddy core plugs are much different than most engines us, and imo, would hold a pipe thread. At least mine did, although it's not been run yet.

I ment drill a pipe plug to ~5/8" and solder/braze a brass hose barb to it. So the plug screw into the head, and the barb is attached to it. While small pipe plugs are solid, I think a 1" or bigger plug would be hollow in the center for weight/material savings, so you not drilling through 3/4" of metal. And the larger plug shouls have a lager enough head (for tightening it in) that it's still usable with a hole in the middle, like this (http://www.cpperformance.com/detail.aspx?ID=698)[/quote]

Agreed, unless the hollow part is large enough that the male thread you put into it would not get into the thick outer section.
Dave