Paul Knippen's Muscle Motors

06/17/2026

Pretty cool project. Diamond Elkins is the head porting shop that Pontiac used to copy (with permission) Air Flow Research's port design that was developed for the SD-455 engine. They're also the shop that supplied heads for Leader Automotive, Royal Pontiac and the heads used on Jim Wangers' Blackbird. We're building a copy of the GM Engineering motor that made 600hp/600tq. It's also very similar to the motor used in the Blackbird. These heads have an interesting back story as they were supplied to a famous Pontiac engine builder by one of the employees working in the Pontiac engineering department at the time. ;) Some of the parts being used for this build: SD455 block, 4.21 stroke forged crank, SD455 rod, NOS General Kinetics SFT cam, first design Edelbrock P4B, Holley 850 and if we can get the correct clearance a set of Forged True pistons (same pistons used by Pontiac Engineering).

06/06/2026

Bad A*z! IYKYK

05/16/2026

05/16/2026

Pretty much two minutes of not much. I promised Kammie some snack-O flavored jerky from Buc'ees and a ride in the Super Duty. So cruising through town they were playing some good music on the radio and thought a video might be cool. Sadly I pushed the wrong button and the video never happened 😆 So, now being determined, I tried again. Unfortunately the good music had stopped playing.

05/07/2026

This is a follow up on a tech tip posted a while ago in regards to improving the head gasket life for high performance Pontiac builds. It's also known as the "421 cooling hole mod"

https://www.facebook.com/share/p/1NiG74qxj8/

I'm rebuilding this race engine that was built previously by another shop. I believe I know why the "421 mod" was only performed on one side, but regardless, I thought it showed there most likely is a benefit for this modification. I'll post the pictures and you can decide for yourself.

I shared this on several pages where I thought folks would appreciate seeing it. Some folks were confused, some expressed their opinion that it's not needed, but no explanation why, and one pathetic "Porting Heads" page led by three close-minded individuals seemed to take exception to the idea. One guy speaks with single word posts, the other is an over educated fool that's so smart he would need a text book to change a light bulb, and the third guy comes from a country that doesn't allow free speech and basically agrees with the educated guy (that was subcontracted by an OEM to eliminate a head gasket problem and they had to issue a recall on that head gasket ) even though their admin page claims they promote conversation about ideas and thoughts they ban anyone who's ideas differ from theirs. Many also seemed to like the idea, and quite a few shared their positive results after performing the modification.

I hope folks find these pictures interesting, and feel free to share any thoughts. Other than your opinions on the Glyptal applied in the valley area, it has nothing to do with this post. I thought the pictures showed the added water hole was definitely keeping the gasket cooler.

Thank you for your attention to this matter. 🫡

05/04/2026

Nunzi is a true Pontiac Legend. I'm working on a 455 HO that has a few of his parts. I recently received my signed Nunzi catalog. He was the East Coast Pontiac guru. I first talked to him in 1983 in regards to purchasing one of his chromed crankshafts; a program that he developed with the now defunct Crankshaft Specialties. It was carried on by Jim Butler Performance until the imported forged cranks took over the industry. They would transport the crankshafts from Tennessee to New York by rail.
I remember telling Nunzi my intention to use nitrous oxide on this engine and he told me "if a Pontiac is built properly there is no need for nitrous". He was always willing to share his wisdom and help with correct parts for our Pontiacs. Although I did have a craving for Italian food after every one of our conversations, it must've had something to do with his thick Italian accent!
He did the Q&A for the original Thunder Am magazine that later became High Performance Pontiac. He has done numerous tech articles including an in depth four-part build which covered the history of the SD455, building one for maximum horsepower. It covered properly setting up clearances, developmental work by Mullins and Company and choosing parts that work together. They sliced up a brand new SD head to find the thin spots and ways to improve air flow. It showed gains and losses of airflow. It alerted Edelbrock that their newly released Torker manifold needed to be redesigned. It was an article way ahead of its time.
Nunzi is alive and well enjoying retirement, and still helping his friends build Pontiac engines. If you have a favorite memory of Nunzi please share it with the rest of us.

04/27/2026

I was brought an SD455 "barn find" motor that had a couple of flat lobes. The original plan was to replace the cam, run the engine and go from there. Unfortunately the #3 cam bearing came out with the camshaft. Well, it came out of the housing bore. I had to split the bearing to get the cam out. I couldn't install a new bearing from the top due to the reinforced lifter bosses. I thought I'd share a few details upon opening the crankcase for the first time in more than twenty five years.

02/14/2026

Cool old video, Lthl Brd at US 41 Dragstrip getting some exercise. We just put in a custom built converter to test on motor and it was way off the mark. The car slowed down two tenths (NA) and it slipped like crazy. We had no intention of spraying the car and left some of the nitrous parts at home. Soooo we dug through the tool boxes and came up with a couple of 73 jets, lines and a NOS Cheater plate.

Basic combination

PKMM built 464 prepped 103 crank, Crower rods
PKMM hand ported 330 CFM EHTTFMF'S
PKMM ported Warrior
PKMM built 1100 CFM 4500
PKMM custom design solid roller camshaft
1 7/8 headers
TH400
3:89 gear

Full interior with sound deadner and custom Recaros

0-144 mph in 9.4 seconds

GoPro ride along of a 9.40 @ 144mph pass in a 1970 Firebird with a PKMM built 464 at U.S. 41, Morocco, IN to see more, go to facebook.com/PaulKnippensMuscleM...

02/10/2026

Adding a coolant hole to help cool the area between the two center exhaust valves. This is especially helpful on power adder builds and extends head gasket life in this area. We use a 1/4" drill bit until it just breaks through to the water jackets. Then open up the hole with a 3/16" carbide burr. The drill bit has a hard time once it hits the added material around the head bolt boss. Most OTC head gaskets have this hole. Cometic head gaskets sold by Pontiac vendors usually don't have this added hole, so this needs to be specified at the point of purchase. If you purchase your head gaskets from PKMM the gaskets come with the needed hole.

01/25/2026

For sale is a pair of new 61575 Edelbrock heads. These have the 87cc fast burn chambers. They feature a trick valve job, mild porting, modified valves for improved flow, springs have been pressure matched, chamfered and deburred. Valve seals have been upgraded. Springs are set up at 140-145 seat pressure and will work with a hydraulic roller camshaft with .650 or less lift. I flowed one cylinder out of the box and after porting & valve job. Happy to swap out valve springs for HFT at no charge. Also included but not pictured are the Edelbrock pushrod guide plates, rocker arm studs, water fitting and plug.

$3450 plus shipping

Ported

Lift / Int / Exh / Exh w/tube
050 60 - 37 - 37
100 76 - 60 - 52
200 147 119 115
300 214 155 155
400 260 178 194
500 280 184 199
550 288 186 201
600 295 188 203
650 297 188 205
700 299 188 207

Out of the box numbers
050 48 33
100 64 53
200 139 99
300 200 131
400 237 151
500 251 160
550 257 163
600 262 165
650 262 167
700 262 168