[Jim Robertson]

Put another Iron dport hot rod together recently for my son’s wedding. He wanted to drive the race car as his getaway car after his wedding. So we put a few pieces together we had laying around.
4.230” bore (1974 455 block filled), 4.365” stroke (103 crank welded and stroked), #96 ‘71 400 head, (2.11”/1.77”; 299 cfm), 280/284 at .050” solid roller. .440 lobes, 1.65 stud mount rockers, 12.5:1, 2” header, 3.5” exhaust with magna flow mufflers, sheet metal intake, 2-950 hp carbs, methanol fuel, turbo 400, 3.89 gear, 28x10.5 bias slick. ~3250 lbs. 6.047 at 114.3 mph.
The message is: Iron DPorts Still Rock!
Hope to see a bunch of you at Norwalk 2022 and beyond.

[Dragncar]

Very cool ! How much bore was left punching it that far ? I have a 70 for bolt 455 block that is .060 over and might want to give it one more run.

[Stan Weiss]

Originally Posted by Dragncar

Very cool ! How much bore was left punching it that far ? I have a 70 for bolt 455 block that is .060 over and might want to give it one more run.

It doesn't matter how far Jim was able to take his block. The only way to know how you can take your block is to sonic check it.

Stan

[PAUL K]

Fantastic running beast Jim. Great job!

Don't want to take away from your accomplishments, but I would like to add.... That was some serious heat you guys ran those numbers in!

[slowbird]

Very nice!!!! Thanks for sharing

[Jim Robertson]

Block is filled leaving about 2” of water to the deck. I did not sonic it. It was working ok before and it was go time on the build as wedding deadlines were looming.
Thanks Paul. Great meeting and visiting with you. Yes it was very hot. Sunday’s runs were just as hot.
Thanks Brian.

[Dragncar]

Originally Posted by Stan Weiss

It doesn't matter how far Jim was able to take his block. The only way to know how you can take your block is to sonic check it.

Stan

Yes it does, it gives me a idea of what is possible. Sonic check or no sonic check. Jim is one of the best guys we have left so I pay attention. We have a ring pack for a .080 over bore so that is good to know.
299cfm is the most I have ever heard from from a pair of #96 heads. I have a couple sets.

[ChiefCrazyCanuck]

That is stout sir, even more with the lowly 96 casting and it's low floor radius. Very impressive!

[Jim Robertson]

Thanks ChiefCrazyCanuck for recognizing one of the #96’s inadequacies (as compared to a properly designed race head).

We found many years ago the cross-section areas at different points in the intake port is very important. In particular, if the area at the short turn is too small the air speeds up and seems to disconnect from the floor. These heads did that which shows up as a crack in sound during flow testing followed by a drop in flow of about 10 percent. These cracked (took a crap) at about .500” valve lift. I knew the area in this set of heads was a smaller cross-section than a decent set of #48s we had ported earlier but wanted to try them as the pushrod area was very close to the target size and the seat work was sharp and cuts were wide. Also we had found the intake runner length was more important than a short runner and more flow volume. In-car performance of this engine combination has been very educational and is showing (after just 2 passes) same mph in the 1/8th as our 800hp 468cid.

[Scott Roberts]

Well done yet again.. I've been around long enough to know anything you do is top notch and always impressive!

[Jim Robertson]

Thank you Scott. Many years ago it seemed like there was plenty of performance left on the table pertaining to iron d port heads. To some these may not be as sexy as an aluminum head but it is super fun when people realize what factory pieces we are using.

[Jim Robertson]

My son was driving and he was making his license runs on these two passes. He did great and now has his license. Very consistent times in some serious Texas heat.

[Jim Robertson]

After my son’s wedding and after driving the car around downtown Ft Worth Texas. Put it in the trailer just before the cops drove by. 😃

[PAUL K]

Originally Posted by Jim Robertson

After my son’s wedding and after driving the car around downtown Ft Worth Texas. Put it in the trailer just before the cops drove by. 😃

That's too cool... Congradulations to the groom.

[Jim Robertson]

Sheet metal intake has a small plenum (for the engine displacement) and a fairly long runner length with generous taper angle. I designed and fabricated it here. Carbs were built by a friend here Campbell Competition Motorsports and he set them up for methanol.

[potentpontiac]

Nice work Jim. Couldn't make Norwalk this year. Safe travels Home.

[Dragncar]

Originally Posted by Jim Robertson

Sheet metal intake has a small plenum (for the engine displacement) and a fairly long runner length with generous taper angle. I designed and fabricated it here. Carbs were built by a friend here Campbell Competition Motorsports and he set them up for methanol.

Jim, I bet you take a lot of pride in popping your hood and showing the guy you just beat what drug him down the track.
Do they ever leave shaking their head ?

[Jim Robertson]

Hey Mike, missed seeing and catching up with you at Norwalk. Good times on and off the track again this year. We had our share of small mishaps but we persevered. Super stoked these silly little #96 dports on this 492 shortblock ran better than my #48s on my 468. Best so far of 9.397 et and best mph of 144.36.

[Jim Robertson]

Dragncar, yes pontiac guys are saying “no way” and the other brand guys only come by to borrow some tools or duct tape. ��