I have a bone stock 1986 IROC Z28 with a 305 TPI and 700R4. It just turned over 100,000 and still runs pretty good, but I want to build/rebuild the 305 this spring. I know many people recommend going to a 350, but I want to keep the original motor and I have to pass some tough DEQ standards. My goal is to have around 325 HP on pump gas. This is my daily driver, so it also has to have some street manners. My budget for this project is around $2200. Any input or ideas would be a big help. Thanks

 

Wont fit your budget but do a simple rebuild to the 305 with a kit from any performance vendor, then bolt on a Vortech supercharger. You'd easily be over your hp goal, and would get the same gas mileage, and would be perfectly streetable. Just my .02

 

I rebiult my friends car it was the same thing except it was a 85 Z28. I dought you can get 325 with only 2200. I would say rebiult the trans, comp cams makes a good cam for that engine, get new injectors, get the base and plent ported, and get some head work, and if you do the rebuild yourself your at about 2200 after misc expenses and you will be at about 300hp. This is what I did to my friends car. We had it dynoed. The trans rebiuld is a must if you dont, dont bother with more then 250hp. Just my opinion though

 

The seller said the trans has a kit and it shifts like does. Over 300 hp may be out for me with my budget. Thanks for taking the time to give some advice.

 

check out enginekits.com and they have a 305 stroker kit for $599 and then you can have the block bored for around $150 and add some other money for a little machine work if necessary and odds and ends. the kit claims 115hp increase over stock 305 tpi motor. they did this in high performance chevy or hot rod a while back, seems like a great kit. check it out!

 

Anyone ever see or hear of the results of the Super Chevy Project Silver Streak build? This is the car with the stroker 305 (335) that is referenced earlier. I was seriously looking at this because I too want the mileage and the original engine, plus I am more of a twisted mountain road driver and not a straight line speedster.


However, I am concerned about the true nature of this stroked engine. Is it really a beast or a bomb? Super Chevy has not answered my requests, so I am a bit suspicious.

 

Anyone ever see or hear of the results of the Super Chevy Project Silver Streak build? This is the car with the stroker 305 (335) that is referenced earlier. I was seriously looking at this because I too want the milage and the original engine, plus I am more of a twisted mountain road driver and not a straight line speedster.


However, I am concerned about the true nature of this stroked engine. Is it really a beast or a bomb? Super Chevy has not naswered my requests, so I am a bit suspicious.

 

Thanks everyone for the input. Based on what I'm hearing and my budget, I'm going to use a .030 over flat top stock rebuild kit, World Heads, work the plenum, Hooker emission headers, adj fuel reg, and a new chip. Where I'm stuck is the cam. As I said before, I have to be emission legal. Comp has a emission legal cam listed in the PAW catalog on page 293, #12-402-4 with duration 260/268 advert. - 212/218 @.050, .444/.444 lift and 114 lobe seperation (I'm not sure I understand what "lobe seperation" is/does). Has anyone used this cam? Its' $120. Is there a cam that's just as good or better that may be cheaper? And can someone recommend a good chip?
Again, thanks for your help.

 

That's a good choice of cam for a TPI 305. "Lobe seperation angle" or LSA is the degrees between the peaks of the intake and exhaust lobes. A lower number (like 108) produces good high-end power, a higher number (like 112 or more) produces good idle vacuum. Since computers tend to like good idle vacuum, and TPI limits your upper RPM's anyway, 114 is a very good number.

Oh, work those World heads over, too. They need it, especially in the bowl area. A magazine TPI dyno test from late-2000 added 50 ponies with bowl-blended World heads over stock 305 heads.

Talk to the guys on the DIY PROM forum about your chip.

 

Chevy High Performance just did an article on porting heads on a budget. And guess what kind of heads they used, five7kid?

World S/R Torquers.

Granted they used the 2.02"/1.60" heads, but the basic principal of the porting job (and the article itself) is to show how NOT to get carried away with pocket porting and end up hurting performance.

They only picked up 11cfm on the intake side @ .450" lift, but they picked up 43 cfm on the exhaust side @ .500"

They also tried unshrouding the valves a little but only increased the cfm on the intake side to 13 @ .400", and only went up to 44cfm on the exhaust side @ .550" but no more below that.

So if your gonna stay below .500" lift (like more around .450") then don't bother unshrouding the valves. Especially on a 1.94" intake that the 305 Torquers have. They're not as shrouded as 2.02"/1.60" anyway.

AND they also talk about the basics of camshafts as well as an article dedicated to roller cams. I haven't got to read that yet, so guess what I'll be doing on the throne tonight. :lala:

One more thing. They aren't gonna show HP increases from the heads until next month ,but they did hint around that they picked up more than 20 HP.

AJ

 

All three of those articles were very interesting (actually two different cam articles & the porting article).

I'm not sure what you mean by getting carried away - no indication they thought they did in the article, just some advice on what not to do in certain areas. SA tells you to keep the throat at 85% of the valve diameter, so yes, getting carried away in that area will hurt you. For unshrouding, SA simply suggests a certain amount of space between the edge of the valve and the chamber wall, not taking the chamber wall out to the cylinder edge like they did in the ariticle - I'd agree they didn't help themselves much by what they did there. Also, they didn't touch the guides in the mag article, and smoothing them can have a very substantial impact on flow. Finally, SBC heads are typically limited by the exhaust flow, so a substantial improvement there is in the right direction for power improvement.

It would have been nice to have before and after flow and power numbers on my heads, but such toys and time aren't available to the average Joe - and I'm about as average as they come. As Vader and others will tell you, true "porting" is way above and beyond what the mag article or I did.

It still all comes down to "the package", though. Doing only one of the things I did to my engine would probably not produce much gain. And, I'll be the first to admit that my package came together much better than I ever let myself imagine before I started it for the first time. And, I still think Gary's on the right track, and doing some work on the heads would be a good thing for him to do (I've never said they were perfect out of the box, just that they're a good place to start).

 

You guys have been very helpful. A couple more questions if I can.

1. Will the Comp cam I listed be noticeable at idle?

2. There is no way I could port the heads myself. no tools or experience in that area! What would you expect to pay for a machine shop to do that? (I'm still on that budget, though I may be able to pick up another $3-400 in a couple weeks)

Thanks again for your input. I've gotten the most straight up answers on this board.

 

What do you mean by "noticable at idle"? Have a lope? It will sound different, but as much from the exhaust change as the cam. Your TPI/computer won't like a lope.

CHP estimated $120 for basic bowl work. That's probably a little optimistic. As for no experience, these were the first heads I ever did. It does take a lot of air compressor capacity, though, and is noisy (and creates a lot of dust). If you have a friend with a decent shop, you may be able to talk them into letting you do it at their place - just buy the porting kit and die grinder.

 

That's what I meant by "getting carried away" Going too large behind the seat, or doing any work on the short side of the runner can actually hurt flow.



Well those two things alone only help out at lifts at .500" or higher, and not much there even. They even said (as well as a lot of other pros) that going through all the work of messing with the guides is usually only good for 1-2HP.

I couldn't agree with you more. They even said that with the improvement of the exhaust runners, they may switch to a single pattern cam and see if they actually gain some power.

Yea, but gaining 20HP for the cost of a little time is a great improvement. I think pocket porting any head (as long as it's not overdone) is a great thing to do.



True. But since he is using more of a lower lift cam, then he shouldn't worry about trying to do things that won't help him unless he's running more than .500" of lift.

I wasn't trying to imply that they "needed" help. I was simply pointing out that they used your heads. That's all. No flame intended.

AJ

 

I did all the work on my heads when I was intending to use a ZZ3 cam in a 305 - a lot of lift on a relatively small displacement/small bore engine. It was only after the heads were done that I discovered my roller block had cracks in the lifter valley. So, a smaller lift flat-tappet cam with more duration went into my non-roller block instead.

The data in the article didn't indicate as much improvement from what they did above .400" lift. But, they also didn't do incremental flow testing (checking the effect of each piece of the job), so it's hard to say how much effect unshrouding, or short-side radius work, had on the final results.
They also didn't back up their statements on the guides, but if you take a look at the flow area in the port, those guides take up a substantial part of it, and have a very sharp edge interupting the flow. Since the intent of this type of work is to generally smooth things out, not doing the guides just doesn't make much sense to me. But, I don't have any flow or HP before-and-afters to back that up, either.

Again, World recommended the bowl work to me, and indorsed the SA method. That's pretty strong evidence to me that it's "worth it". How far into the SA method you need to go is the biggest unknown.

One thing I'd change about what you're doing, Gary - don't rebuild the 305. Go with a 350 shortblock, put your machining money into it; get 350 heads for it, and do all the other things you mentioned. Much better bang-for-buck.