This came right out of left field! Ive been thinking about it lately and all of a sudden I was down on power and pushing oil out of the dipstick tube. mechanic said "broken ring or cracked piston"

Wasnt financially ready for that lol.

ANYWHO:
I want to keep the motor std bore..
but with 138k itll need to be bored 30... i recon
Having the stock heads gone thru (113's)


Thought about:
Bumping up the compression by .5 to 1.
Port match the TPI system, and possibly enlarge the base intake?

Want:
I would like to have a TQ cam... hopefully make around 400 ft lbs; 1600+ starting rpm range. (looking for good fuel mileage AND more grunt. a quandary I know lol.)

Have:
stock TQ converter,
Beefed up trans, with shift kit... tranny builder said "will hold 450hp and 500 ft lbs no problem"
C6 Split spoke wheels.




OF COURSE Id love to thump but you dont get thump with low end grunt... or can you? lol.

This is a daily driver, that will eventually be put up until the weekends. I have to get this done soon, and dont want to redo the motor later on... one time shot, and it happens to be on the spot.

 

You would probably get the most bang for buck by stroking this motor to a 383. That'll get you the torque and compression you're after. Add a mid level cam, rebuild the heads and replace springs.

There's a lot of options for the top end. The budget will likely have a lot to do with your selection.

 

Sounds like you've got a solid plan - since it sounds like you're wanting to keep the costs low then a basic flat-top piston .030 over 350 short block should fit the bill. I prefer to upgrade the cast pistons to at least a hypereutectic unless you're going to spray it or boost it then go forged. If the budget allows a 383 is a great choice but requires a little more $$ in addition to what is needed for just a 'rebuild' - (stroked crank, block clearancing, balancing)

Since you're not looking for a higher RPM screamer then the "factory" bobweight/balance should work just fine and you can get away with just using parts that weigh close to the factory parts (i.e. stock replacements). If you plan in the future to up the game with some big heads and intake and push the RPM's into the mid 6K or above then I'd balance the bottom end while it's out.

For cam Comp's 260XFI sounds like it's going to meet your lower RPM torque needs...

The heads - a complete rebuild is in order with new valve springs to match the cam, check the guides and do a good 3 or 5 angle valve job. some light pocket porting and gasket matching will help airflow a bit - but since you're looking for low RPM torque you don't want to enlarge the runner and reduce port velocity...

Definitely port the TPI intake (there are plenty of how-to's around here on where and what to port).

What are you doing for exhaust (i.e. good headers, free-flow cats, true duals??)

 

Wondering what one may do as a first timer I started to browse...youtube probably isnt a safe bet

 

If the OP can afford it, this is a good option. Definitely more TQ, though the TPI ceiling would become more obvious. Even with a 355, adding more lift to the cam would help. I'm not sure how I feel about the XFI stuff -- especially for a mild rebuild. Considering the flow ceiling of this 113's, I'd be more likely to go for a milder lift cam -- under .520ish. Of course a hotcam comes to mind as my first choice because of it's ability to hold control over the nose and last well with any rebuild. (Also, stay under 220ish duration for max torque with a long-tube TPI. Staying under 520 may not require any machining on guides to make everything work too.)

Any good local rebuilder will be able to guide you in your selection of parts. Of course people here are willing to help as well. Unless you've really got some money to throw at the vette, a simple rebuild, with a higher profile cam should keep you running with miles and miles of smiles.

Don't get too greedy or you'll be further into your wallet than you might want/expect.

 

Learn about quench and setup your deck height and gasket thickness to get good quench. That's how to raise compression w/o running into detonation (esp as fuels get crappier).

Unless you have bigger tube runners, pick larger runners before enlarging the base. That's if you only do one or the other! Definitely port match the result.

 

Nice hair cut on your illegitiment son, Ron! But, you REALLY need to calm that boy down! LOL

 

You want to keep the bore standard. I've seen engines with similiar mileage with the factory hone marks intack on the cylinder walls. Carefully measure the cylinder bores. They may still be within factory spec's and a rebore may not be necessary.

 

383 it !

 

I put in standard bore flat tops with 4 valve relief hyper pistons in my L98 with 143k on the clock. I had the machine shop redo the heads with new springs, valve job, and new cam bearings. I put a new cam in along with a bunch of new parts like timing set, oil pump etc. you don't have to go as far as I did, but I had about 1200 in machine work including new pistons. All the block really needed was a hone and new cam bearing and a cleaning.

 

Go 383

 

Cautionary note to the OP: One thing that SHOULD have been obvious to me is the longer stroke of a 383 raises compression by itself. So, using a longer stroke crank (to get the 383) will raise your compression QUITE A BIT.

If you do the conversion, make sure your pistons have sufficient "relief" to counter some of the compression. If you do, like some, and use a big cam to bleed compression, then your stock TPI is useless. Big cams and TPI's don't match up in rpm ranges.

I have stock-size chambers with a 383 setup and aftermarket heads. Had I known I would buy the whole enchilada (with a 383) at the onset of my project, I would have ordered 65cc heads and gone with flat-tops.

Side note: The benefit to what I did is I have great quench, short flamefront, and absolutely no hint of detonation at higher compression. There is some theory saying an inverted dome is a more efficient setup. I'm not sure I'm seeing it. I can't get much over 14mpg city,,,but I can get over 27mpg hwy with my 383. (For city driving, I bet a 350 is still more economical. This may be important if/when gas prices go back up.)

 

Geez I gotta laugh at the youtube vid, that isn't porting, just port matching, and p-poor port matching at that! Where's the marks he scribed first from his gaskets to know how far out to take it!?

Clearly not all youtube videos should be deemed educational

 

To be fair to the guy, he might have held up the gasket and saw he was shy in the corners plus the one edge he took out a bit. (Or maybe he was learning/practicing on a junk head). Even with AFRs, their port shapes don't match a 1205 perfectly AND they'll tell you it's not critical to match them to your intake -- unless you're looking for every last millisecond (on the track).

My point isn't to slam anyone here. Just to say porting doesn't NEED to be pretty/perfect. At least the vid gives the a (barbaric) basic idea of beginning porting, and how carbide burrs work with alum material removal. For me, it shows how much extra effort I had to go thru by using a high-speed drill vs air tools. (Couldn't afford air tools though).

It's not a video that's good for advanced, finishing work though!

 

You should be able to hit 400ft-lbs with a 383 or 355 easy as long as you get some decent airflow going on. As you said port the TPI, port the 113s should get you into the 260cfm range. For a roller something around the 215-224 would be good in a 383. I'm around 530tq with a LPE 219 in a 383.

If you really are building for torque though and money is an issue I would not hesitate to go cast crank and hyper pistons a lot of guys HAVE to have forged stuff when it is a waste of money for their build. If you are keeping the TPI you'll probably never over rev 5600-6000rpm max and that stuff should be fine there. NOS, blower, more rev's more power start talking forged but a good balanced cast/hyper setup should handle your 400/400 motor all day.

 

I don't know what you are talking about - the 260XFI I recommended has an operating range of 1500-5200 - peak would be somewhere around 5000 RPM which should put it right where a ported TPI intake/heads should be maxxing out - it's a 210/218 duration at .050 and a 113* LSA/109 ICL so it should make plenty of torque and be a real good street cam.

Think of it as just a little more agressive than a ZZ4 cam (which with the fast burn aluminum heads they are rated at 385hp/385 ft-lb torque so you don't need a whole lot more cam and compression to make the 400 ft-lb mark

 

Yep, I misread, thought you said 280 xfi.

That 260 would do just fine, heck if he goes 383 a little bigger wouldn't hurt either.

 

I was going to post the same comment. The 260 is actually a little mild. The 268XFI has a 218/224 duration with lift comparable to the LPE219. I had a 260 non-roller in my 350 and you could hardly tell. If the OP does any porting to the TPI it will raise the RPM band to allow use of a little more cam.

Also, the 383 with 65cc heads will net around 10.8:1 compression. That's a nice boost over the stock CR that will increase efficiency and allow pump gas.

 

The 260 is a REAL mild cam - would work well with only MINOR mods/porting - if he gets serious and spends time really doing a good job porting the intake, the runner entrance/exits, the base intake and the heads and gets it to flow then I'd say step the cam up a bit.

Also - if you go with a 383 then you'll really want to step up the cam as the larger cubes with restricted heads and intake will "need" more cam to have a chance of breathing and taking advantage of the cubes...

 

In terms of duration it is. In terms of lift, it's probably the most aggressive off-the-shelf cam. From what I've seen, there's some debate is the recommended 130# spring pressure is enough for these cams (esp in the long run after the spring breaks in). Though it'll "work" with minor mods, will it work the best?

There's the stall point of the 113's to consider. I've seen where .550" lift isn't beneficial -- unless a VERY, VERY good porting job is done. Our local guy (pro stock racer and life-long porter) took the 113's out as far as he could, then cut/welded for even better performance/flow. He couldn't get them to perform one iota better above .520" lift. So, that's where he recommends you stay with that head.

Because milder lift cams have better control over the nose, for the OP, I like the hotcam option. I don't think his build warrants going after every last bit of snot.