[ponyakr]

"...Put awesome heads on a 350 and make it run with 3.75 stroke..."


Well, it's pretty obvious that nobody here has a good 350 stroker, or knows of a good thread about one. So, since we're talkin about 350's, might as well talk about a stock stroke build.

We made lots of drag strip passes with cast pistons. The 350HO build in this article used the SP 357P pistons.

https://www.hotrod.com/articles/hppp...-engine-build/

I've mentioned here before about using SP cast 318 Mopar pistons, to save a few bucks, for the low budget guys. They have .020 more pin height, which is also a plus.

https://www.ebay.com/itm/SEALED-POWE...5.c10#viTabs_0

https://www.ebay.com/itm/SEALED-POWE...oAAOSwUiVZ06yR

With #48 heads and an 068 clone cam, that 350HO made real close to advertised hp. So, just a better cam should be able to put it up over 350hp.

You mentioned good heads. With iron, it's probably better not to go over 9.5 CR. According to the CR Calculator, some 72cc heads will do it, depending of course on overbore, head gasket, & actual valve relief volume.

But, 10.5 CR is supposed to be safe with alum heads. Many will remember that the member here who does the road racing, with the '68 Bird, bought some small valve KRE D-ports for his 350. They come with 65cc chambers, and you can have some shaved off if you need more CR.

http://www.krepower.com/Pontiac%20Al...er%20Heads.htm

Then when you get up near 400hp & over, it's probably a good idea to go with forged pistons. I've mentioned that you can buy Auto Tec pistons for a 350, for a little over $500, unless they've had a big price increase.

Don't know if there are any forged 318 Mopar pistons that would work, or not. seems that I remember that the pin height may be slightly too high on most of 'em. But, since it has been said that the SP Pontiac pistons are thick enuff to machine a dish in 'em, maybe machining some off the top off the 318 pistons will work, & still cost under $500. I'll see what I can find. Nothing out there I can find that'll work. So, I reckin the Auto Tecs are the cheapest thing out there.

[Squidward]

So... with the exception of special forged pistons, how would YOU build a 350, with off the shelf parts? Aftermarket heads are allowed. Discuss!

[ponjohn]

Butler offers a 4" stroke forged crank with 3.9 bore.

The Garrett boost advisor says 15lbs of boost will produce 800 crank horsepower / 600 lbs /ft.

[ponyakr]

Originally Posted by Squidward

So... with the exception of special forged pistons, how would YOU build a 350, with off the shelf parts? Aftermarket heads are allowed. Discuss!

Well, if there was no budget limit, for a street/strip car that would see lots of street miles, I'd probably go with 65cc Edelbrock D-ports, properly set up with good valves, springs, etc. And if needed, I'd have enuff shaved off to end up with 10.5 CR.

I'd try to find a block that would safely bore at least .060. I think Adam Strang posted that he'd found a block that would go .075. I'd have the Auto Tec pistons made with the correct pin height, to achieve zero deck height, without having to cut extra meat off the decks. Would also get valve reliefs deep enuff to use a decent size cam.

Might even get BBC .990 light pins(but not too light for street use), and use Eagle 6.635 BBC H-beam rods. I think I've read that if done correctly the Pontiac cranks can safely be cut down to BBC size. Now you've got a lite rotating assembly that should safely go past 7000 rpm, with no problem, if you really wanted to take it that high.

I'm a Q-jet guy, so I'd probably stay with a correctly built late '70's 800cfm Q-jet. Would probably try a port matched 455HO alum intake. Would probably separate the water crossover, so I could easily try different intakes. Would probably try a single plane, like an HSD or it's Chinese Knockoff, just to see how much low end it would lose.

The cam would obviously depend on a lot of things. Since I would not be doing much high speed highway cruising, I'd probably run at least 3.73 gears. And I'd probably run a tight 10" converter, that would flash about 3500.

I don't really like the idea of running a roller cam. So, I'd probably stick with a HFT. And I love Rhoads lifters. This would be a great place to run 'em, so I could run a slightly larger cam than would normally work in a 350.

Again, assuming there is enuff money to do so, I'd definitely try several cams, while still on the dyno. With Rhoads lifters, I'd probably start with a Lunati 10510312 or a similar Crower, such as a 60916 or 60242. Then I'd try a Summit 2802, Howards 410141-12, & Crane 283951. Hey, if the money was there, I'd even try some bigger ones, like the Crower 60243, and even the Howards 410051-14. That's as big as I'd try, and ONLY with Rhoads lifters. A friend used an 041 in his 350 hobby stock dirt motor & did good. But, it might be a little nasty in a street 350.

Assuming there's still plenty of money, I'd also try a couple of the Voodoo cams, probably the 262 & even the 268 ground with a 112-114 LSA. And I'd like to try 'em both with & without Rhoads lifters. Hey, to me it would be REALLY cool to try all these cam combos on the dyno ! And when I win millions in one of the lotteries, I'll do lots of experimenting that nobody else has done.

Another thing I'd do, with a big budget, is to have the heads & block machined so that I could use Cometic head gaskets. The 350 gaskets would be much more efficient on a 350 than the 4.3 bore size gaskets. They'll make 'em with cut-outs for the cylinder chamfers. And they come is several thicknesses, so that you can set your quench distance. I've read that .040 or a little less is good. So, if you actually have zero deck height, I assume the .036 gaskets might be best.

https://www.jegs.com/i/Cometic-Gaske...0-036/10002/-1

But, if the deck height is closer to .005 or .006, maybe the .030 thickness would be best.

https://www.jegs.com/i/Cometic-Gaske...0-030/10002/-1

[Baron Von Zeppelin]

Originally Posted by tom s

... and you DONT have to do the stroker. HP is in the heads,they floed 260@600 and had a cam and intake that complemented them.

Tom, i forgot what heads you used on that 301T short-deck build.
Which heads were they ?

[ponyakr]

Originally Posted by Baron Von Zeppelin

Tom, i forgot what heads you used on that 301T short-deck build.
Which heads were they ?

What would be an aprox cost to have somebody make an intake for it, if you had to pay full price ?

[Baron Von Zeppelin]

Originally Posted by ponyakr

So, I reckin the Auto Tecs are the cheapest thing out there.

Could we just get some Stroke/Cubes by only using a little longer connecting rod - and have the pistons made for that ? Any longer rods that could come off the shelf and be used ?

Already hearing from a lot of folks in different areas about how slim-to-none 400 through 455 core builder engines are becoming. 326 and 350 might start becoming more commonplace for the guys in those situations trying to keep expenses more minimal.

[Baron Von Zeppelin]

Originally Posted by ponyakr

What would be a aprox cost to have somebody make an intake for it, if you had to pay full price ?

Seems like he had spacers custom made for intake adapt.
Its getting harder to remember that build , do remember it played hell from start to finish. I'm not suggesting we do an imaginary short-deck build at all .

Just curious what heads he used - guessing highly massaged Iron D-Ports.
If 260cfm @ 600

[b-man]

Originally Posted by Baron Von Zeppelin

Could we just get some Stroke/Cubes by only using a little longer connecting rod - and have the pistons made for that ? Any longer rods that could come off the shelf and be used ?

Already hearing from a lot of folks in different areas about how slim-to-none 400 through 455 core builder engines are becoming. 326 and 350 might start becoming more commonplace for the guys in those situations trying to keep expenses more minimal.

The connecting rod serves only to connect the crankshaft to the piston. The length of the connecting rod has absolutely no bearing on engine displacement and doesn't affect the stroke of the crankshaft.

[ponyakr]

"...Could we just get some Stroke/Cubes by only using a little longer connecting rod..."

Only way to get more stroke is to offset grind the crank. Buy using 6.635 BBC rods, you could offset grind a little.

[Baron Von Zeppelin]

dammit
brain pooted

[Baron Von Zeppelin]

Only way to get more stroke is too offset grind the crank. Buy using 6.635 BBC rods, you could offset grind a little.

Okay lets go for that , off-set grind and BBChevy Rods.
0.060 overbore

Where would we be on CID ? approx

Anybody doing this would be looking for lowest buck , with some bang.

[b-man]

Originally Posted by Baron Von Zeppelin

Okay lets go for that , off-set grind and BBChevy Rods.
0.060 overbore

Where would we be on CID ? approx

Anybody doing this would be looking for lowest buck , with some bang.

368.7 cubes.

3.790" stroke (offset grind gains .040" of additional stroke).

3.935" bore at +.060".

[Baron Von Zeppelin]

Thanks b-man

So , about $500 on custom forged pistons
about $300 (?) on BBChev forged rods
about $200+ offset grind crank

Is it going to be worth $1000+ to gain 20 cid on the 350 HiPo Budget Build ?
idunno

Think i might go with the stock crank/rods and use the 318 pistons for whatever maximum overbore can be accomplished.

I'd use 670 heads since i have more of those than anything.
Buy a book and video from whoever did those about home porting pontiac heads.
Read a bunch on here about porting - then grind them babies.

Q-Jet
Headers
Over Cam it a little with Rhoads lifters

[hurryinhoosier62]

Guys, one thing you need to keep in mind about offset grinding an OE crank is few are actually on stroke. I have personally seen OE GM cranks be as much as .035 out of stroke. There is only .050 difference between the stock Pontiac rod journal and the stock BBC rod journal. If your crank is sufficiently out of stroke this will limit or even prevent the amount of stroke increase through offset grinding. You could use the 2.100 SBC rod journal but there are only a couple of rod manufacturers that produce a 6.635 BBC rod for the 2.100 SBC rod journal.

[ponyakr]

Several have mentioned that it costs over $200 to resize the cast rods with ARP bolts.

The 6.635 BBC rods are just over $400.

https://www.ebay.com/itm/Eagle-Conne...gAAOSwHz5bNCqx

Eagle I-beam 5140 6.7" BBC rods are around $325.

https://www.amazon.com/Eagle-SIR6700.../dp/B00BZQOUPY

The RPM 5140 6.7" BBC rods are $300. But, since Paul Carter has mentioned that most all the Pontiac RPM 5140 rods he's checked needed resizing, I'd probably avoid the RPM 5140 BBC rods.

http://www.racingpartsmaximum.com/sa...tockrod-2.html

But, even if you go with cast pistons, you could still go with the $400 Pontiac length RPM H-beams. Cliff has said that all the Chinese H-beams he's seen are real close to spec.

http://www.racingpartsmaximum.com/sa...elhbeam-2.html

The 318 pistons have floating .984 pins. So, you'll need to have the rod bushings honed out slightly for pin fit. The 318 pistons + the H-beam rods are just under $500, total. And, since the rods are lighter & stronger, there shouldn't be any problem going 6000 rpm safely, if you wanna.

TJ crossed the line at about 6000 rpm , with her '68 400 Bird Stocker. The Pontiac factory cast pistons made it thru that season, then nearly 3 years on the street, with no problems. And, the factory cast pistons in my '69 RA3 GTO lasted thru 60k + street miles, then 2 seasons of racing. So, if the SP cast pistons are as good, they should last just fine, as long as there is no detonation.

So, you guys with the built street 350's, have ya'll had any problems with your SP cast pistons ? What's the most rpm ya'll turn, on a regular basis ?

[Squidward]

Originally Posted by ponyakr

So, you guys with the built street 350's, have ya'll had any problems with your SP cast pistons ? What's the most rpm ya'll turn, on a regular basis ?

I have Venolia forged pistons, with Tomahawk rods. I run it to 5500.

[ponyakr]

Originally Posted by Squidward

I have Venolia forged pistons, with Tomahawk rods. I run it to 5500.

Wow. Your bottom end should be safe to at least 6500 if you had enuff cam & wanted to. We turned 6000 in our 400 Stocker, using heavy cast rods & pistons.

If you bought the pistons new, how much did they cost, if you don't mind telling.

[Squidward]

Originally Posted by ponyakr

Wow. Your bottom end should be safe to at least 6500 if you had enuff cam & wanted to. We turned 6000 in our 400 Stocker, using heavy cast rods & pistons.

If you bought the pistons new, how much did they cost, if you don't mind telling.

I bought some 40 over Probes from PPR when he was closing up shop. I can't totally remember cost, maybe 400-ish? Long story short, machine shop messed up a piston pressing rods, so they got me a set of Venolias at their cost.

I really haven't been able to buzz it to 6k. Had issues nosing over at the track a little over 5k, and wasn't sure if it was fuel or springs. It was a little inconsistent. Since last track outing I put on efi, so we will see in a month or so if I solved it.

[Squidward]

I've always wondered what a set of e-heads or kre's would do for a 350. At the same time, I wonder how a roller cam would do. I run a 702 Voodoo in my 350, and I don't think I would run much more for a street motor. That cam caused a little softness off idle, but was remedied when I went with 3.73 gears.

It'd be fun to try a few different cams, like something a little more than what I run now. Perhaps a 703 Voodoo, or maybe a cam with ra4 specs and rhoads. It's not like there is a big body of work out there on 350's.

I always wanted to try some boost on a 350, like 8psi or so. If I was going to boost, I would probably do some iron d ports, maybe with small valve 17/47/11 heads, a small cut for a little compression bump, and a cam in the ballpark of an 068 to start with as a baseline.