[hojs69]

The article was in Engines in 1962 and titled, "Get 523 Inches from a 389 Pontiac."

Perhaps folks can grab it online.

[hojs69]

Found the article online. Link here: https://autohistorypreservationsocie..._a_389_1-4.pdf

I assume a deck plate was used to extend the height (it does not disclose)?? Aka Steve B's approach on his stock block large cubic incher.

[GTO JONES]

Originally Posted by b-man

Side loading of the piston is the biggest issue with the 4.5” stroke, along with the short cylinder of a Pontiac block pulling the piston down out of the bottom of the bore. Short piston life and quickly diminishing ring seal I’m thinking.

To end up with the same 1.57:1 rod to stroke ratio as a stock 455 which ain’t that great to begin with (6.625” rod - 4:21” stroke) you would need a rod close 7.1” long with that 4.5” crank.

Is it possible to put a rod that long into a stock deck block or would you need to go to a tall deck block? I’m thinking there’s no way to move the pin that far up into the ring pack on a stock block.

Makes me wonder exactly how GTO Jones is getting away with that 4.75” stroke in his 571. Which block standard or tall and what rod length?

I started talking to BES (Tony) on what I wanted to do and ended up with Kauffman MR-1 block and a Ohio 4.75 crank custom Ross pistons, 6.7 Eagle rods . He didn't have a problem with it and I wanted it pump gas. He re-worked the E heads I had with bigger valves and ported them. He said he could get 1000 Hp with better heads, but not on my budget. We put the motor in in 2015. After a couple of years I retired and moved to Arizona I had a lifter fail and eat a lobe off the cam (solid roller) so I talked to Paul in Tuson and he spec a hyd roller that works great. I drive it everywhere. We (my son and I) made some other changes like 4L80E and 3;42 gears and a super snipper so when we make a trip to Phoenix its a 200 mile round trip I get a little over 15 MPG. Went to the track once with the new combo come out EZ and still ran a 10.74 at 128. Need to go back before it gets hot. Not bad for 4000 lbs. with me in it. Thats my story and I'm sticking with it lol.

[Jay S]

I used a .140” thick Cometic head gasket with a 4.5 stroker to use a longer rod in a short deck platform with a 4.5” crank and 6.7” rods. The pistons were above the deck .1” or more. With the right piston it would be close using a 7” rod and 4.5” crank in a Pontiac doing something similar. 6.86” ish for the 4.75”. I took the Cometics apart and stacked them to get the height I wanted. The height I end up with was available from Cometic. I suppose you could stack the Cometic's and go taller yet. I was running out of room on the top rings, there was a little more room though. lol

[Tandyman]

I have a 495 in my 69 Firebird Bracket racer that I have been very happy with. It's a 4.5 stroke 6.8 H beam Eagle rotating assembly in a 67 400 hard blocked to the water pump holes . It has with SD 305 KRE Dports and SD's Road Paver cam on a 114 with Crower solid roller hippo lifters. It's 3590ish race weight has a T400 4000 stall and running 342 gears and 29.5 Pro Bracket Radials and I shift it at 5800 . I run 94 octane pump gas. Installed it in 2014 and it is typically dialed in the 6.60s in the 1/8 but has run as fast as 6.51. It is very consistent . It has gone a lot of rounds and won a lot of races and 4 track championships since then. It has well over 1000 passes on it now and should probably be refreshed but it's still just as fast and as consistent as ever. I wouldn't hesitate to build another one.

Glenn

[mysticmissle]

Originally Posted by Jay S

I used a .140” thick Cometic head gasket with a 4.5 stroker to use a longer rod in a short deck platform with a 4.5” crank and 6.7” rods. The pistons were above the deck .1” or more. With the right piston it would be close using a 7” rod and 4.5” crank in a Pontiac doing something similar. 6.86” ish for the 4.75”. I took the Cometics apart and stacked them to get the height I wanted. The height I end up with was available from Cometic. I suppose you could stack the Cometic's and go taller yet. I was running out of room on the top rings, there was a little more room though. lol

no issues with all those layers? did you spray each layer?

[Jay S]

Originally Posted by mysticmissle

no issues with all those layers? did you spray each layer?

I didn’t spray that one. I could see where that might be necessary though.

That particular engine used Evans waterless coolant, which seems like it is more forgiving to seal up than antifreeze, there is more or less no radiator pressure with that coolant.

[PAUL K]

I have a nice set of 7.080 aftermarket forged rods I'll give a deal on for anybody wanting to build a 4.5 stroke stock block combination as long as your willing to share your results.