[63tempest69firebird]

I just found out that my firebird 350’s cam and crank bearings are going out. The problem that I have now is what to do with the engine. I was originally thinking of replacing the 350 for a 400 but I ran into a snag. I was checking the vin. On the car and it looks like my XB 350 is the original engine for the car. My first problem/question is should I keep the original engine or not? My second question has to do with what I was going to do with the 400 (if I got it). The car currently is slow (by my standards). It can’t out run a new GMC pickup truck . I hope to put a higher horse power 400 to fix that. But now I’m trying to see what my options for the 350 are. Can a Pontiac 350 be build up? Where are some good places to look for performance parts for it? Or would it be better to buy a 400 block and build it up?
As a side note my firebird is a daily driver so my other concern is mpg.
thanks.

[screamingchief]

I have had some ideas on a healthy 350 build in another thread,I'll post that info in full here in a second,but first I'll explain the three primary elements it is based upon.

The first part is a 4" stroke cast crank That a fellow here offers,it would need to ordered with the BBC 2.20" rod journals and 3" main journal.

Here is some info on the cranks and the guys contact info:His name here is crazypont.

In stock and ready to ship from Enginecraft. Price is $350 plus $40 shipping continental US.

Each crank is inspected and given a final micropolish before shipping.

These cranks must be balanced as part of your rotating assembly before installation. I can ship a crank balanced to your bobweight for $150 for most jobs. I can also put one of these cranks in a fully balanced rotating assembly for you - email me for a quote.

4 inch strokes available with stock pontiac rod journals (2.250") or BBC (2.200"). 4 inch cranks have 2400g Bobweight.

All cranks are 3 inch mains

IMPROVED OILING
Straight shot oiling so you can crossdrill if you wish.

Paypal, personal check, money order, certified check. Sorry, I do not accept credit cards at this time.

Email me at enginecraft@aol.com for orders, quotes, or questions.
Thanks,

Dave Harmon
Enginecraft
Waterford, MI
enginecraft@aol.com


The second part would be the use of the eagle 6.535" BBC rod part #CRS65353D,it is their H beam 4340 forged rod for BBC making it cheaper than the OE pontiac forged rods,it uses the 2.20" rod journal,and .990 chevy pin size (floating pin),and weighs 805 grams as advertised.

The third part is a custom forged piston,but this would be very close in design parameters as the "stock" NHRA style forgings for the 350 offered by at least 3 different vendors (ross,venolia,CP),the "custom" part would be a small compression height adjustment and pin bore size,this is explained later.

So other than the stroker bottom end pieces and likely a little work clearancing the block for the added stroke most the rest is pretty straight forward pontiac stuff.

Anyways here is the previous post with more details:

I now ponder the potential of a .060 over 350 (364 c.i. or 389 c.i. w/4" stroke)

Funny thing you should mention the 4" stroke as a choice,I've been pondering what to do with the 350 that was pulled from my '72 firebird to make way for the 455,and that combo jumped out at me as one with a lot of promise.

(that is if I am going to do anything with it,have'nt decided yet,just deciding if it was worth holding onto it)

Here's my idea on that combo:

Use the 4" stroke crank,with the 3" mains,and use the 2.20" (BBC) rod journals and then that allows the use of the cheaper and more common 6.535" BBC rods (eagle H beam).

With this set-up the required pin height then is very close (appx. + .012") with the stock 350 compression height (1.717" appx.) pistons and block deck heights,now the BBC rod would need a .990 pin hole in the piston anyhow,which would not be a big deal to get the piston co. to do instead of the stock pontiac .980" pin,and because you would need to make a small CH adjustment anyhow here also (and may need to consider this further if the block gets decked too) this stuff would'nt be a big problem to deal with that at this point either.

So a piston made with a 1.7" comp.ht. hung on a 6.535" rod with a 2" crank throw (1/2 of 4" stroke) would end up appx. .005" in the hole on a stock 10.240 deck height. (1.7+6.535+2=10.235) it would be a pretty straight forward deal here to do this,as it's not WAY out in left feild at all,just a few small adjustments for a big improvement IMHO.

Now some will cry about using a slightly shorter rod but run the numbers once,the R/S ratio still comes out better than the 455 pontiac or 454 BBC,and really this isnt meant to be an "all out" kinda deal,just a nice "upgrade" type deal.

B/S=.97 R/S=1.63 (@ .030" over) the B/S is even slightly better @ .060" over.

The extra stroke then also makes many of the less than desireable "smog" heads much more promissing on these engines as the compression ratio is much more in line with a performance engines now,the late '73-'74 #46 head (find the screw in stud type) would be a good choice now,as 85cc's after some slight milling would yeild around 9.0-9.25:1 CR depending on the head gasket thickness and deck heights.

Use a SBC 2.02" +.100 long valve in the intake side of heads like these to keep the shrouding down somewhat,and keep the stock exhaust size,some porting will be very nice here as well (say 230-240 cfm or so).

To me the 85 cc head,with a .027/3.950 cometic head gasket,and something close to a zero deck you would be just about right at a nice liveable 9.23:1.

Or use a .040" thick gasket and just mill a little more from the head to get it right around 9.0:1.

As you already noted the .060" CID comes out @ appx 389,and the .030 over CID is 383 CID pretty much.(I know,I know, a 383 pontiac???)

It's my opinion that this would make a significant change in the nature of the "underdog" 350's,I feel it would yeild nice gains in torque production and also a healthy boost in horsepower as well with the right mods.

I know I kinda like the idea of building a 350 like this!

Use a good cam,good exhaust,nice intake and carb,and I bet it would suprise a TON of people that it once lived it's life as a "humble" 350...

It will be interesting to see what others think.

Feel free to ask any questions,I know its a lotta info to digest,but I feel it would make an a$$ kicking 350 if done right!

And not for a ton of $$$$.

[BVR421]

SC..that 4" crank has been advertised for at least a year and have yet to hear of anyone actually being able to purchase one. Have you?

[WallyB]

You may want to look at the Axle ratio too, if you have a 10 bolt & 2 BBL car, good chance it has low gears (high 2's). This would be a reason to maybe move up to a ratio in the mid 3's, I believe they came in 350HO cars. Mileage would go down, but would still be reasonable and give you a better chance against those pick ups.

[screamingchief]

Yeah,there was a reply on one of the threads from somebody who got one,could be bogus though,who knows for sure right,but the fact is it can be done,you could just cut down a stock 4" crank and use the dudes kit if that does'nt pan out,or if your way rich just get a billet made,right?

I still think it could be done pretty easily and affordably,just wish I had the resources to prove so,but I got too many other things right at this time,but was just pointing out that with a little thought there are possibilities to consider.

[screamingchief]

Here is the thread,might try PM'ing jurrassicGTO for more info.

http://216.178.81.108/forums/showthread.php?t=460438

[screamingchief]

FYI all:

There is some more info on those cranks posted on the thread in the previous post's link.
Customer comments and pics available.