stroking a 291

[Gullwing]

I am buildin a 291 and want to try to get a little more displacement while still keeping costs down. I have already come to the realization that if I want to bump the compression to anything acceptable I will have to spend about $750 for forged pistons versus $300 for cast. I figure if I overbore it .030 that is reasonable and safe. Then I can have my crank ground for about $150 or have it offset gound .250 for $500. So for $800 more I can turn a 7.5:1 CR cast aluminum piston 291 into a 10:1 CR Forged piston 317 inch motor. I understand that I should be able to keep the stock connecting rods and that they are adequate for a normally aspirated (possibly nitrous) motor. Anyone out there with experience building such a motor got any advice to keep me from making a mistake. I have Tex Smith's book. Read it half a dozen times. Still it would be better to hear from someone who has been there.

[HOTRODCHARLIE1969]

WELL IHAVE JUST ABOUT FINISHED MINE.I HAVE A 291 BORED .030 (3.750 BORE)I CUT A 330 CRANK DOWN- ALL JOURNALS AND COUNTERWEIGHTS HAD TO BE CUT.(I WILL BE AT 336 CI)I USED EAGLE H BEAM RODS (6.125 LENGTH)#CRS6125S3DL19 WHICH ARE SBC SM JOURNAL RODS.THEY ARE ONLY SLIGHTLY WIDER THAN THE OE RODS. I WAS ABLE TO KEEP ALL 3.800 STROKE!!!!!!! (I THINK THEY ARE ABOUT 650.00)THEN I HAD JE MAKE SOME CUSTOM FORGED NITROUS (250 HP NOS)PISTONS,13.8-1CR-THEY HAVE .430 DOME.(987.00,NOT CHEAP) AND I USED TOTAL SEAL GAPLESS RINGS(275.00).THE BEST OF THE BEST.OH YEAH A MAIN STUD WAS ALSO INCLUDED.IM IN THE FINAL ASSEMBLY OF MY MOTOR-AND IT LOOKS GOOD A LITTLE GRINDING WILL PROBABLY BE NECESSARY.BUT I ANTICIPATE NO BIG PROBLEMS.I AM ALSO GOING TO USE 330 HEADS W BIG VALVES AND (HOPEFULLY) A CUSTOM SHEETMETAL INTAKE.I RECCOMEND YOU SEEK OUT A REALLY GOOD MACHINE SHOP.IF ANYONE HAS INFO ON A GOOD INTAKE LET ME KNOW-HOTRODCHARLIE1969

[HOTRODCHARLIE1969]

WHEN IT COMES TO TEX SMITHS BOOK IT IS A INVALUABLE GUIDE BUT IN MY EXPERIENCE(AND MY MACHINIST) IT IS VERY VAGUE.IT IS FULL OF TOO MANY MAY FIT OR MIGHT FITS.BUT A GOOD GUIDE TO HELP.HOTRODCHARLIE1969

[Gullwing]

Sounds like you have decided to squeeze every possible drop of HP out of that motor. I am afraid that 13.8:1 CR is just a wee bit too radical for my motor. This is going to be something that I want to drive arround on pump gas. Appreciate the input though.

[johnny5]

I'm doing this with my 276. I have a good source for the rotating assembly if you want it. Let me know if anyone out there has a spare 330-341-345 crank they'd like to part with.

[Bailiesdad]

Tex Smiths book descriptions, your machinest said "IT IS VERY VAGUE", that is a whole lot "nicer" terminology than the machine shops I use, have expressed.

HotRod, use a Hilborn Injector, why fiddle around.....

The person you want to contact for ANY help is Gene Adams with your induction needs or info....the internet is good for general info but simular to Tex Smiths book, if you get the jist.