Posted a copy here: Great article, much of which I'm guessing applies also to the 235. Wondering how the cited cam specs compare to what's available today...
I6 Fun Looking at the boring bar doing it's thing with the crank still in the block brings back many memories . These days no one would understand how to properly clean out all the SWARF before re assembly . If you read the entire article , it also mentions not over revving ! . Cool article , thank you for sharing it .
Very Cool! Real interesting article. Still have my '57 235, makes me wonder, just how much horsepower and torque can you get out of one today? I'm sure some of the old-timers on this forum can tell me. Turbochargers? HP camshafts, pistons, rods?
Intresting article reading Old School mechanics just know there engines. This Mc.Clurk guy is spesialized in hotrodding his cars and shows how to do it. The old day machines demands his fine personal scills but alowed to redo Things (with minor tolerance) when machine adjustments went wrong. The cnc machines they use today you have to know a lot about pc. Programming , one touch wrong on the display and the work is blown! Are you planning on rebuilding a 235 to 261 spesifications ?
235 Driveability Steve ; Simply blue printing the 235 will wake it up more than you can imagine as GM designed it to fairly loose tolerances so basic balancing everything to zero grams as mentioned in the article reduces vibration and saves power and torque . Then , polishing the combustion chamber and CC'ing them all to match perfectly gives you another HUGE boost of power and economy plus close do doubles the service life of a stock engine . Smoothing up the exhaust ports and unshrouding the valves & guide bosses helps improve flow and volumetric efficiency . Adding a 261 cam wakes up a lot of power and still allows perfect road manners and smooth idle . The 261 rods , when you can find them , are sturdier and so resist high RPM life longer ~ 216 & 235 engines suffered from weak rods and often snap of right below the wrist pin if you run them above 3,200 RPM longer than it takes to run up through the gears . All this is very basic stuff but it also takes time and care , a lot of both . Most folks want a <magic> bullet bolt on cam or whatnot , this isn't going to happen , never has and never will . Increasing the compression ratio is always a ad move on long stroke engines . Turbo charging requires lower that stock compression and will snap the crank in a 216 / 235 / 261 before you imagine . Split exhaust manifold like Fentons , reduce power except @ WFO in real racing where you don't care if you blow it up ~ in daily traffic , they'll reduce off idle and mid rage power . Obviously , one carby per intake port is the most basic and easiest power gain for Dollar you can do . -Nate
"Then , polishing the combustion chamber and CC'ing them all to match perfectly gives you another HUGE boost of power and economy plus close do doubles the service life of a stock engine . Smoothing up the exhaust ports and unshrouding the valves & guide bosses helps improve flow and volumetric efficiency ." So, does anyone know a shop familiar with the stovebolt heads, who you could recommend to do this type of work? The ones around me are all racing V8 focused - modern stuff, and not sure they'd know the limitations of a vintage head. (I've heard stories of cracked heads from walls made too thin when porting...) Heads are heavy, but can be shipped!
Thanks, Nate...Thats what I like about this forum. I wondered if these old engines would hold up to turbocharging, Dad had a Buick V6 (a '81 model?) with a tiny little turbo on it. Could not even feel the difference until you floored the little thing and held it there for several seconds and then it would go. Well... kinda'...go, with a little "g". Oh, and it wasn't a Grand Natl. just a plain Regal. I don't know, I think you guys are making me think about changing plans and re-using the old engine that hauled my butt to high school. OH NO! stay focused-stay focused-stay focused. I'd have to change my forum name.
Inliner Power The really cool thing about I6 engines is you can make them run really strong and be more economical and last longer at the same time , who knew huh ? . Well , I did of course but I digress . Anyway , any competent and honest Machine Shop should have no difficulties doing the simple if laborious things I mentioned . I didn't mention porting because that's the road to madness and wasted $ plus short lived engines ~ seriously , no matter what you do , it's never going to be a RACE TRUCK so putting in wild cams and porting the head , is going to make it a bad driver , just like any other Hot Rod you see that's killer cool and all but never actually gets driven ~ here on this very site we have multiple AD owners who drive , work and yes , play hard , in their old I6 powered AD trucks I forgot to mention one partial porting thing that really helps wake up any engine : match porting the exhaust ports to the exhaust manifold ports ~ the inside of the head remains as before just smoothed and polished then they bell mouth each port so it *exactly* matches the exhaust port on your exhaust manifold . This helps the exhaust gases flow out and away from the engine easier , increasing power at all loads & RPM's while it reduced operating temperature . Any " Machine Shop " that says " ? huh ? " when you show up with greasy old cylinder head , rusty flywheel and box of loose connecting rods asking for zero gram balancing and the specific head works I mentioned , should not be trusted to check your oil much less be allowed to touch any part of your engine . If the engine runs O.K. now 99 % of the time the crankshaft is O.K. , all you'll need is new bearings shells , balancing and maybe cross drilling the oil holes on the rod journals . These are sturdy , well designed , simple engines so don't go crazy, just enjoy and have some fun then when you beat everyone to the drive in after a " Fun Run " and pop the hood , you'll be the only one with a Stovebolt . BTW : you can often find a 302 C.I.D. '55 ~ '60 GMC I6 engine and it'll run rings around any Chevy I6 engine before you do the same basic mods to it and actually BREATHE FIRE if you hop it up a little bit . I hope this helps .
Old school Mechanics Tom Langdon at Stovebolt.com in Michigan Patricks in Casa Grande in Arizona These are old School guys and they know there engines. Upgrading from 235 - 261 is no problem for them. They can supply you With all the needed parts aswell. Its best to phone them if you are intrested. Martinius. So, does anyone know a shop familiar with the stovebolt heads, who you could recommend to do this type of work? The ones around me are all racing V8 focused - modern stuff, and not sure they'd know the limitations of a vintage head. (I've heard stories of cracked heads from walls made too thin when porting...) Heads are heavy, but can be shipped![/QUOTE]
NATE, more questions... Why does a split manifold exhaust cause a low rpm loss in horsepower? Does it have to do with engine exhaust gas scavenging? Also, I've been told that wrapping exhaust headers or manifolds helps because hot air moves faster (alot) than cold dense air. I'm asking because Dad really wants me to use the old six and has said repeatedly that he likes the sound of a split manifold six. Also, Nate, were can a guy get a alum. OFFY side cover? I have all the other stuff for dress-up, purchased years ago as a youth at swap meets. Yes, I know, your rolling your eyes because "that stuff don't make 'em go any faster or run any better." Martinus, There used to be a company called "Clifford Research" also, but the last time I looked they were more into later model sixes, I think.
Split headers power loss The split manifold headers gives power loss because of the extra exhaust tube! Compression loss gets bigger. A guy named Volker from Germany made a 2 in one exhaust pipe connection just down below where the exhaust pipe is mounted to the flange. In that way the loss is less when still using one exhaust pipe backwords . Installing a glaspack mufler gives the "real Nice sound" There are some photos of Volkers installation at the forum here. Martinius.
Exhaust Flow I thought I'd replied to this before . Yes , low RPM scavenging suffers when you have a true split exhaust manifold . The sound it makes , is terrific . I see the side cover you want on E-Bay often . What I think matters not , you're footing the bill so make yourself happy . -Nate
Ha Ha, Nate... I think your right, Nate, you have covered it before. The trouble is, with 9316 posts, it's hard to find all your answers. I think what you and most everyone else here thinks does matter. Most of the time useful, sometimes just funny. Anyway, THANKS.
