[LM93]

New thread started in thee OHC Tech section.

[Stan Weiss]

Look at the pictures and the caption with them.

https://www.motortrend.com/how-to/ah...-six-build-one

5.7" rod lenght. Don't know what the deck height is? But that makes the bore, stroke and rod length for the 230 ci engine is the same as a 307 ci SBC V-8.

Stan

[Stan Weiss]

Found this while I was on Speed Talk

https://www.speed-talk.com/forum/viewtopic.php?t=13927

I have two sets of Pontiac OHC rods. The later ones appear to be a stouter rod than the early ones. The early ones look to be equivalent to Chevy rods.

Talking about 307 SBC Pistons.

You are correct on the piston interchange

Stan

[mgarblik]

I saw your mention of the OHC 6 being much lighter and that was a factor in your decision to possibly build one. I don't know how much lighter that engine would be than a Pontiac V-8 with aluminum heads which is quite common now.
The OHC 6 has an iron block, iron head and a mile long crankshaft. I would check the weights to be sure. If weight is a major consideration, an aluminum block/head V-8 may be lighter yet and make more HP of course. Lots of decisions to make. A 400+ HP OHC 6 is going to be an expensive build. But really cool.

[LM93]

Originally Posted by Jack Gifford

I don't know about "strength-wise". But back when I was on the phone a lot with Fritz Voight (Mickey's crewchief, who gave me a lot of help with my hemi V8) I asked if he and Mickey ever toyed with the OHC six. He said yes, but any attempts at serious power caused head cracking between the valves.

Hard to argue with someone like Mickey. What kind of power would a pro team like his be trying to wring out of their engine? 400, 500, 600hp? Every last ounce, probably.

https://www.gomog.com/allmorgan/engineweights2.html
About weight, this website lists the I6 as 200lbs lighter than the V8. Aluminum heads save about 50lbs each right?

[Half-Inch Stud]

AS stated a decade ago; my 1969 OHC-6 Sprint had connecting rods superior to the Chevy Pink Rod. And I reckon them GM forgings to be similar to a RA V rod design.

Cameras were not a thing for me in 1982-1985

Being a Pontiac V8 minded fella, i loathed and hated high-rpm engine spinnings, yet found the Sprint to be in its own from 4500 to 7500. 7000-7500 upshifts were a routing thing on the major roads. Mallory Dual-Point dwell beat stock dwell, but the grafted HEI was fantastic.

Maple Grove run fell onit knees at the top of 2nd gear. ran mid 14s or 15 (forget), and never did add a pusher pump.

I dunno why there was no fear of spinning the factory flywheel! yikes.

[Half-Inch Stud]

Originally Posted by Stan Weiss

Isn't the I-6 bore size the same as a 350 Pontiac V8 Stan

. YES.

Ought to get to 400 Piston size, and actually the SBC 400 slug from sealed Power can be had 4.18" Bore ( thats 455+030 ) and lighter than the Stock OHC6 Slug.

The 4.18" Overbored OHC6 would retain the 7500 rpm capability.

Has anybody SLEEVED all six OHC6 Bores for 4.15/4.18.4.21"

[Stuart]

Originally Posted by 66sprint

Not much in the way of performance hardware out there for the OHC motors, especially the cam and followers.

Jay Leno had some followers made out of tool steel but that seems unnecessary as there are stock one available.

I've been waiting for him to post an update on his Firebird - I believe he was having the engine work done at Ed Pink's shop, so it will be interesting to see how it turns out.

[LM93]

Originally Posted by Half-Inch Stud

. YES.

Ought to get to 400 Piston size, and actually the SBC 400 slug from sealed Power can be had 4.18" Bore ( thats 455+030 ) and lighter than the Stock OHC6 Slug.

The 4.18" Overbored OHC6 would retain the 7500 rpm capability.

Has anybody SLEEVED all six OHC6 Bores for 4.15/4.18.4.21"

Do you think hypereutectic pistons are good enough? I'm concerned about them surviving any preignition and detonation I get while trying to get a good tune once the engine's been assembled.

[turbo69bird]

I didn’t read through the thread for other responses but what kills engines N/A or turbocharged or blower etc. Is usually detonation. A good tune will go a long long way to making a set up last.
I don’t know much about the rods in the L6 but the blocks appear pretty stout. Id bet it’s make good HP torque and live if the rods are any good in them . Look for any short comings in oiling system too . Aside from that should live if the tune is good .

Many an engine builder has been blamed when the tuner should have been!

[turbo69bird]

Originally Posted by LM93

Do you think hypereutectic pistons are good enough? I'm concerned about them surviving any preignition and detonation I get while trying to get a good tune once the engine's been assembled.

Why let it detonate set it up fat as hell and lazy on timing . Then back into it. Shouldn’t ever go lean if you start wayyyy fat and lazy

[Half-Inch Stud]

Originally Posted by LM93

Do you think hypereutectic pistons are good enough? I'm concerned about them surviving any preignition and detonation I get while trying to get a good tune once the engine's been assembled.

Dunno about hypereutectic (high silicon AL, but theses days aka CAST). i always use Forged slugs and they hold up. A breached headgasket (in 2002?) caused a warped slug-top at the leak.

[scooter1966]

The big thing you probably need to worry more about is head gaskets. You can use the factory rods with some ARP bolts , forged pistons, same as the Chevy 6. Rebuild the head and have a good tune. I so far have only run pump gas to about 15 lbs safely, just over that I did pop the head gasket. Replaced the gasket along with head studs. Car ran 9.42 @ 76.15 in the 1/8 on some old tires I got off Craigslist, spinning too damn much. Using a 1 barrel head will have your compression ratio good for the turbo setup, there is a document somewhere on the forum that shows the different ratio combinations with the heads available.

[JLMounce]

Having read through this thread, I can't really comment on longevity of the I6 in general, but I don't really think one of the stated goals of a lighter package is really in play here. It's pretty hard to find information on the weight of those things, but one source I've seen puts them in the 450 lb dry area, compared to about 630 dry for a v8.

An aluminum intake and heads v8 should be around 550-560 dry.

Adding a turbocharging system to the I6 is going to add anywhere between 75-130 lbs depending on the size of the turbocharger, whether it's non-intercooled, or is air-air or air-water intercooled etc. Weight wise, I think it's going to be pretty close to a wash.

The cool-factor with a turbocharged OHC 6 under the hood, is undeniable, but at the 400-500 hp performance threshold and very near or equal nose weight, you're going to be money ahead by building a typical street v8.

[mgarblik]

Originally Posted by scooter1966

The big thing you probably need to worry more about is head gaskets. You can use the factory rods with some ARP bolts , forged pistons, same as the Chevy 6. Rebuild the head and have a good tune. I so far have only run pump gas to about 15 lbs safely, just over that I did pop the head gasket. Replaced the gasket along with head studs. Car ran 9.42 @ 76.15 in the 1/8 on some old tires I got off Craigslist, spinning too damn much. Using a 1 barrel head will have your compression ratio good for the turbo setup, there is a document somewhere on the forum that shows the different ratio combinations with the heads available.

I think the head gasket situation could be dealt with. It is iron, thank goodness. ARP head studs or similar could be used. Clark, Flattout, Hussey or others could make a copper gasket. You could o-ring the head and block if copper alone won't get it done. Also, Cometic will make a multi-layer steel head gasket for that engine. These are not low cost solutions, but when working with a unique engine platform and trying to make big power with it, the costs do ratchet up exponentially. I build some high HP supercharged Studebaker V-8's for drag racing and endurance road racing and deal with similar issues. High HP, unusual engines are not for the weak of wallet.

[Tom Vaught]

Not sure of how much a OHC Boosted 6 cylinder GM engine will support.

I do know from experience that not all 6 cylinder engines are the same.
I did a engine study with a 300 cid @ord engine with a cast iron head and dual
small (correctly sized) Turbos (many years before the ECOBOOST 6 cylinder stuff)
that destroyed the 302 and 351 Naturally Aspirated similar trucks in a 3 vehicle shoot-out.

We are talking 100 foot margins here in the quarter mile racing.
Not once not twice but throughout the whole day.

Nino Novelli, his brother Gino Novelli, and I made a bunch of V-8 guys unhappy that day in front of a large crowd of people at the test track.

We saw almost 500 hp with the 300 cid engine (less than 15 psi boost and a small inter-cooler set-up.) Far more HP vs the V-8 guys.

So could a OHC GM smaller engine with a proper turbocharger make slightly less than 500 hp with todays turbo technology? For SURE.

Charlie66 has made HP much higher than that with his 4 cylinder engine.
But he has a good flowing (not great flowing) E-Head.

Has anyone ever put a OHC 6 cylinder head on a flow bench to see what that OHC head is capable of NA??? That would be the first question.

Tom V.

[Stan Weiss]

Originally Posted by Stan Weiss

Look at the pictures and the caption with them.

https://www.motortrend.com/how-to/ah...-six-build-one

5.7" rod lenght. Don't know what the deck height is? But that makes the bore, stroke and rod length for the 230 ci engine is the same as a 307 ci SBC V-8.

Stan

From this article.

Stan

[Mr Anonymous]

1968-1969 (only!) Olds 400 was 3.870 bore. 1.75 CH. However, 40 over gets you 3.91 which is 318 mopar, if you can make that work.