Info Wanted - SCCA 2.96" Stroke Engine

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Kellogg, also in Michigan, comes to mind. I know they at least made big block & Hemi cranks but it doesn't quite ring a bell with small blocks for our purposes..
 
What displacement are you aiming for? That is a lot of expense if there is not a lot of difference for 10 or 15 cubic inches. How much could a stock steel crank be offset ground to reduce the stroke and accept Chevy rods, with say a 3.91 bore?
 
qkcuda said:
What displacement are you aiming for? That is a lot of expense if there is not a lot of difference for 10 or 15 cubic inches. How much could a stock steel crank be offset ground to reduce the stroke and accept Chevy rods, with say a 3.91 bore?
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For this exercise it was <305ci for D engine class. For C class it run from 306 to 372.999. There is now (new 2025 book just came out) only a 13mph difference in the 2 records. Doesn't seem worth the extra cost.

20250411_164453.jpg
 
71GSSDemon said:
This at least shows how Carillo did it..

View attachment 1716391441
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I just noticed that this part of the article mentions "Chrysler forgings" and "Rod bolts are NASCAR Hemi units" (7/16"). That would suggest they were the Mopar small block "Hemi footprint" rods which were beefed up like a Hemi rod but configured for a small block. VERY heavy, but then Carillo strategically machined them down to save weight without compromising strength.

The blocks not only raised the rocker shafts but moved them back for valve spring clearance and proper geometry. Also done later on W-2 heads.
 
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71GSSDemon said:
I believe Moldex was one of the companies making them. Although this post was for a displacement class racing at Bonneville, the cost is leaning more towards an R5P7 as that would be very close by the time all is added up and they MPH of the records isn't cost effective most likely. Great to have the info though!
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I could have sworn someone allready recommended the R5P7 approach.......lol
 
Newbomb Turk said:
That’s one reason why it was hard to be competitive in limited displacement classes.

The decks are way too tall. A 9.00 deck is too tall for that 3.00 or under stroke.

The R/S ratio gets way too high, you have to spread the LSA so you can get enough p/v without .750 inch valve pockets and the piston is too top heavy no matter what.

It’s amazing the 340 did as well as it did in Pro Stock.

By that time they were using X blocks and milling .500ish off the decks and IIRC the stroke was around 3.25 inches depending on bore sizing.

A 6.36 rod and 2.96 stoke is a 2.15 r/s ratio.

That’s hard to do.
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So run a .020 over Ford 302. Problem solved.
 
71GSSDemon said:
Does anyone know what the combo was for the Mopar destroked small block for SCCA racing? 340 block, 2.96" stroke crank, T/A heads, but what rod, length and piston/compression height? Mostly looking for information on replicating the rotating assembly.
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Find the old Mopar Action article that was written about the race trans am cars with help of Bob Tarozzi who was team manager. There were a few article in magazines back in the day too. Here's one that was in Hot Rod: https://www.hotrod.com/features/blacks-mini-mopar-magic-april-1971-982-818-42-1/ it mentioned in this thread earlier.

The SA Design Publishing book, Mopar Performance talks some about the 305's. It says 2.96" cranks were 4340 billet. I would imagine that would be Moldex or Callies.

The blocks were T/A blocks with the wider main cap width to accept a 4 bolt main cap.

The T/A race heads are different that production heads. They had square-ish exhaust ports.

You would not copy the rotating assembly today. The rod, piston, even crank technology is far superior today. And taking advantage of it will get your more HP and reliability. Not taking advantage of it is naïve and ignorant.
 
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NC Engine Builder said:
I could have sworn someone allready recommended the R5P7 approach.......lol
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Yes, it was mentioned. By you I believe. I would love one. This small engine is intriguing, but $5500 for a crank is a lot.

This was trying to learn for my curiosity and to look into a smaller engine class to make a record more attainable. Then last summer Alex Taylor bumped it.

Now the slowest record in any variation for my car with an engine over 261cu is 221mph.
 
autoxcuda said:
Find the old Mopar Action article that was written about the race trans am cars with help of Bob Tarozzi who was team manager. There were a few article in magazines back in the day too. Here's one that was in Hot Rod: https://www.hotrod.com/features/blacks-mini-mopar-magic-april-1971-982-818-42-1/ it mentioned in this thread earlier.

The SA Design Publishing book, Mopar Performance talks some about the 305's. It says 2.96" cranks were 4340 billet. I would imagine that would be Moldex or Callies.

The blocks were T/A blocks with the wider main cap width to accept a 4 bolt main cap.

The T/A race heads are different that production heads. They had square-ish exhaust ports.

You would not copy the rotating assembly today. The rod, piston, even crank technology is far superior today. And taking advantage of it will get your more HP and reliability. Not taking advantage of it is naïve and ignorant.
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My copying was mostly dimensional and learning the history.
 
Back in the 80's there were KB forgings popping up for sale at Mopar meets pretty regularly... One guy (kinda a jerk) in particular had three of them, he also had one of the #42 AAR bodies.. There were two people with cars they claimed were the original car... Neither truly was, each had metal from the original car but it had been destroyed...

At one swap the guy was showing one of his cranks to a prospective buyer explaining about the special forging, I happened to be walking by & was catching the conversation when the crank slipped out of the guys hands & hit the asphalt... It actually rolled a few feet... I popped off with something about it now being drop forged and kept on walking....
 

71GSSDemon said:
Yes, it was mentioned. By you I believe. I would love one. This small engine is intriguing, but $5500 for a crank is a lot.

This was trying to learn for my curiosity and to look into a smaller engine class to make a record more attainable. Then last summer Alex Taylor bumped it.

Now the slowest record in any variation for my car with an engine over 261cu is 221mph.
Click to expand...

That old mopar action article is good. There's a few article from 69-71 magazines. The 318 Indy motor was sort of a precursor/learning experience. Bobby Sykes at Keith Black worked on this stuff and his son posted here a few times. So you can search that.

The T/A heads are one-off cheater stuff. I think they had production casting numbers but were not production castings.

Oiling was an issue on road courses. Would have done better in Trans Am with a dry sump. But was not allowed by rules.
 
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71GSSDemon said:
Yes, it was mentioned. By you I believe. I would love one. This small engine is intriguing, but $5500 for a crank is a lot.

This was trying to learn for my curiosity and to look into a smaller engine class to make a record more attainable. Then last summer Alex Taylor bumped it.

Now the slowest record in any variation for my car with an engine over 261cu is 221mph.
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That is a tough pill on the crankshaft price. If you were serious about it, you could post a wanted add, believe it or not I have seen those cranks for sale once in a blue moon. Someone told me @Rocket might have one.
 
forged 301 Poly crank is another short stroke alternative using 318 sized pistons in an LA motor. Just need an 8 bolt Hemi flex plate.
 
NC Engine Builder said:
That is a tough pill on the crankshaft price. If you were serious about it, you could post a wanted add, believe it or not I have seen those cranks for sale once in a blue moon. Someone told me @Rocket might have one.
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Thanks Sean. This post was to gather the info on how Mopar did it back in the day more than anything. In my searches, I found a little here and more over there, but not all together.

As for me and my project, unexpected medical garbage is setting me back. Who knows where records will be. For now it is going as is for first trip. Then hopefully enough HP to meet my personal goal. Secondary goal was a red hat. That part people are gobbling up quickly. Just a bit late in the game for the budget.
 
71GSSDemon said:
the cost is leaning more towards an R5P7 as that would be very close by the time all is added up and they MPH of the records isn't cost effective most likely. Great to have the info though!
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R5P7 would make the most sense, sbm or bbm your choice is pretty much 340/360 or 361 or a destroke bigger block. If going production engine I'd probably go 361 bored to 371.
 
Ok, we can all chat on my Bonneville post about other options. For now, I want to keep this about the early 304 SCCA engine builds.

Anyone know cam specs?
 
71GSSDemon said:
Ok, we can all chat on my Bonneville post about other options. For now, I want to keep this about the early 304 SCCA engine builds.

Anyone know cam specs?
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Keith black racing engines did a lot of the 305 development work, for trans am mostly. The cam specs changed constantly. Those engines made about 490 HP and 355 ft. Ibs of torque, there are articles about them on the web.
 
I have some 305 dyno sheets, but they are for the CanAm/F5000 open wheel car with hillborn injection. And I’d image a 2000-2500 lb car?

From Tarozzi who worked at/for Keith Black. Tarozzi also did a 305 for a Formula 5000 race called the Questor Grid Prix in 1971.
 
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