View Full Version : Think HEI is my next step on the cadillac

11-24-11, 11:32 AM
Well I Finally decided to go with an HEI distributor over the pertronix as seeing the price difference isn't by much. I found a used distributor http://www.ebay.com/itm/1973-78-Cadillac-Seville-Deville-368-472-HEI-Distribitor-W-Vac-Advance-/330647077715?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item4cfc1a0353#ht_500wt_1413 and a tune up kit http://www.ebay.com/itm/Summit-Racing-GM-HEI-Ignition-Tune-Up-Kit-850032-/330639703703?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3ACadillac&vxp=mtr&hash=item4cfba97e97#ht_1703wt_1163 off of eBay and the Hei feed wire for a total of $131. My car is a daily driver so I am looking for more reliability and better MPGs. In the future I would also buy an extra coil and module to keep in a moisture free ziploc bag in th trunk just in case it would need to be called upon because autozone sales them with a lifetime warranty. I did some research and it doesn't seem like a hard conversion to do. I also installed an extra fuse panel under the hood with an inline circuit breaker and relay (ato fuse setup) so for anything in the future that needs ign power would be available. I've done a lot of research and have been through this forum and many others to find out how the job is done and weighing the benefits of each. Have any of you done this conversion or did you do the pertronix conversion? Also do you think this is a good investment?

11-24-11, 01:01 PM
Personally, I would go with the pertronix conversion, as you wouldn't have to be concerned with clearances with the drive belt alignment and you don't have to bother with the other changes, wiring, spark plugs, etc. and it will appear stock.

11-24-11, 02:20 PM
I seen some posts on forums where they say to remove the back belt. Also one guy ran it with both belts and it just scarred the cap very minimal. Not to concerened witht he stock look because Ihave already had to go with an aftermarket carburetor on it because of failures.

12-02-11, 04:35 PM
Got the HEI installed today and it's running really smooth. Also readjusted the carburetor using a vacuum gauge. Autozone also let me return all the tune up parts I just bought last month since I did not need them anymore. Next step is a new water pump and flex fan. Trying to squeeze as much mpg out as possible. :highfive:

12-04-11, 09:05 AM
The high discharge ignition is a wise step. Old points systems cannot throw enough flame to properly ignite today's low volatility fuels. Very smart move.

12-05-11, 12:48 AM
This is what a guy told me to do.

First of all, remove your new HEI distributor and have it RE-CURVED> THey used LONGER curves to make the emissions feds happy in those days. Restoring a quicker curve will get you more power and economy. NEVER use AC Delco plugs. THe plugs in those days are like jurassic mammoths. Update your plugs to Bosch Fusion or Denso Iridium plugs. They will burn MORE of the modern fuels more completely. Remove your cylinder heads and have your valve seats replaced to match existing fuels. Your engine was made for LEADED fuel. Modifications are required. THese engines were NOT made to current standards. The oil in those days was ALSO eocene. Get an engine de-sludge. GM made a product in those days called "X-66" perhapss some GM dealers still carry this product. If they do NOT, try AMSOIL CRANKCASE CLEANER> It should remove all the junk collected inside over ALL those years. Try Mobil One 0W#) oil, but don't be surprised if you have a bit of oil consumption for a few months until things wear ir normally. Remove your Valve Covers, and have them POWER CLEANED professionally at a machine shop. They will be FULL of sludge and engine crud. But a can of AMSOIL FOAMING CLEANER and a can of GUM-OUT. I am assuming this is a CARB engine. Inject these chemicals into EVERY VISIBLE carb orifice and opening. They will rebuild the carb as you watch, it's AMAZING> Plug up your EGR valve since the modern spark plugs will poluute less anyways. They simply burn MORE fuel MORE efficiently and make less emissions. THey didn't care about fuel efficiency in the Jurassic era.

12-06-11, 06:51 AM
I agree with most of what was told you, but perhaps not always for the same reasons. Generally, its good advice.
Valve seats - correct. Hardened valve seats are the order for today's unleaded fuels.
Engine oil - agreed. Engine cleaning, yes, but be careful not to plug up internal passages.
EGR - not really used until 1973 or so, so it's not really applicable to your 1970.

12-07-11, 09:25 PM
Will 0w oil make that big of a difference? Here's the link of how's it's running now http://www.youtube.com/watch?v=UdmeC42uzE4&sns=em

Autozone doesn't list denso or Bosch in those makes for my car. They do list pulstar and NGK. What about those?

Big Pip
01-11-12, 01:31 PM
Thanks for you thread here and i am glad to see it worked out for you!
I just ordered all my stuff to convert my '72 472over to HEI and I actually ordered the same tune up kit as you and I couldn't decide which set of springs to use- Heavy/Medium/Light Which way did you go?


Nevermind, I watched your video again and you mentioned Heavy springs-
Thanks for the video too! :2thumbs:

The Ape Man
01-11-12, 06:40 PM
Cadillac engines of the 472 500 425 368 family have always had hardened valve seats. They are fine with unleaded gas.

They also do not usually fill up with sludge even with factory oil usage.

Big Pip
01-13-12, 05:41 PM
I just finish my upgrade about 20 minutes ago and I have to say...

HOLY $H1t!!! What a difference, I could barely chirp the tires before... Now 1/4 throttle and the aroma of rubber!
What did you set your timing at? Right now I am at 10 degrees BTDC and gapped my plugs (Bosch Super Plus Copper ) at 55

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01-16-12, 08:09 AM
I used the heavy setup. I notice when I have to get down on the gas I get a hesitation before it picks up and goes. Maybe I should try the medium springs. I'm not sure what the timing is. I set up everything and a mechanic timed it for me.