it would be 9.7 to 1 with that gasket with it being between 7-11 thousandths in the hole if its more in the hole less comp closer to 0 more comp but we are only talking about .1 or .2 tenths of a percent the 200 cc heads help out some now you need to find some accurate flow numbers for them :cheers:

 

or contact this guy: http://www.misterbill.homeip.net

he's gonna market the prominator soon. It's a programmable flash rom card that works on all PROM type ECMs. It's a seperarate board that solders into place and you get rid of the prom. You can tune the car on the fly without the need to burn proms, unlike the romulator which is only for tuing but you'll have to burn a prom afterwards. It comes with WinALDL for reading serial data and when you tune the car it goes into limp mode when flashing the rom and back in normal mode afterwards. I even think the memory supports multiple programs for different styles of driving (so you could use a bin for econo, one for perf.. and so on). I don't know the full details of it, you have to ask him but from what I heard it's a damn nice mod that makes your stock ECM fully tunable.

Marck



[Modified by Twin_Turbo, 7:29 PM 12/2/2003]

 

Jerkyboy - I just went out to the Dart web site. I haven't looked at them for awhile.

You have some seriously miss matched parts. Those 200cc heads are made for small ci 350 or less with sub 6000 rpm. Your compression, cam and mini ram are a poor match.

I agree with you on one thing - The chip isn't going to give you a massive jump in power.

 

Jeez, I am going nuts with this. What is the difference between a 200cc head and an AFR 195 that people use with this combo? These 200cc heads have a pretty extensive port job done and I am told they flow 280cfm @ .550 lift. The springs are Comp dual springs. I think the Dart site recommendations are based on a std set with their springs. My cam lift is .510 on both sides and the 1.6rrs should increase that right? Trust me, I am a newbie at putting a package together so I am trying to make sense what everybody is telling me. I did ask the question. It seems like People are on both sides of the fence with this combo. Also, what role does compression ratio play here?

 

The volume of the intake port doesn't tell the whole story. It's the cross-sectional area in close proximity to the valve and on upstream that will determine the strength of the wave action, and resultant strength of the ram tune. AFR does an excellent job with the port cross-section.

The high-lift port flow numbers don't tell the whole story either. Stock Dart 200cc Aluminum Pro 1's flow 264I/180E http://www.dartheads.com/csbhpro1.htm , so the port job on the exhaust will be critical. The strength of the mid-lift flow numbers on both the intake and exhaust are extremely important. Once again AFR has excellent mid-lift flow numbers. Designing a cam for the AFR heads is a real pleasure, though not necessarily straightfoward.

I think your biggest problem might lie inside your exhaust system. Look at this plot by Vizard http://www.geocities.com/MotorCity/T...92/vizard9.jpg It shows real power losses for a cat that flows 1CFM/HP.

The compression ratio influences the amount of energy that the piston can take out of the burnt charge. Higher compression ratios make for a more efficient and powerful engine, esecially at part-throttle, and the exhaust will be cooler as a result.

 

Darn, your exhaust link is not working. I would like to see that. In your experience, is it possible to get true 3" duals with dual cats (maybe Random Tech bullets) on an earlier model C4?

The heads I'm told flow 200cfm Exhaust at .550"

One of the above posts in this thread shows a 9.4 to 1 engine puting out over 500hp. What would be the reason to build that engine (N/A) at a lower ratio? Is driveablity a concern? I am learning a lot here guys. Sorry for so many questions.

 

3" duals with 3" bullet cats will fit. Random Tech also makes 2 3/4" I believe. Look at this system, too http://www.krichbaum.net/forsale/89vette/

Try this again. It seems to work intermittently. http://www.geocities.com/MotorCity/T...92/vizard9.jpg

If the heads flow 280/200 they might easily give 500HP, but as I said the port cross-section and midlift flow are just as important. Just look at stock closed-chamber Big Block Chevy heads. The high-lift numbers look great, but valve shrouding at lower lifts leads to poor power results for BBC's with untouched heads.

Their is no performance advantage to building a lower compression engine. You build the engine to make full use of premium gasoline, so about 10.5 to 11.0 in your case.

 

that layout on the white vette is exactly the same as mine but 3". How much if any would I gain from that set up (being 3") to actual true duals? My Cat is a Magnaflow high flow 3"

 

If the single cat is a restriction, then changing to two of them will make a difference. You need to get the pipe sizes and lengths correct for your engine. The configuration for best performance is cylinder head/primary pipes/collectors/x-pipe/cats/tailpipes/mufflers/tailpipe. The sizes of the pipes and the CFM rating for the cats and mufflers go with engine power. The length of header and collector to the expansion in the x goes with RPM range.

You might need to ceramic coat the inside of the headers and collectors to get the cats to work well that far downstream. This keeps the heat in the header which could be important if the exhaust lobe is more than needed, and your compression ratio is down in the 9's. You don't want to cook everything located near the headers.

 

Now you have gone way too deep for my understanding. I used my TFS heads from my orignal engine. I added the cam that I felt was proper for my driving style "CC 218-224 HR" and added 1.6 rrs, pocket porting and backcut valves. For this head, what would be a better cam? I wanted the torque where I can use it. This is for a daily driver that will seldom see the track. Massive top end at the expense of low and mid range was not an option! TIA

Rick

 

So are you saying that you are down on lower speed power on account of the cam change, or on account of many changes to the engine done at the same time?

 

This engine w/o headers is not seen it's full potential. I built it for max tq. So far I am very happy. I added the comment about low end because a top end cam would not be useful to me. I like having BB power in a SB package. I have 6" rods and forged everything. Usually I shift at 3-3500 rpm. Any more than that and things happen very fast! I am curious what cam would work better for my needs that the one I have.

Rick

 

I don't know what cam would be better for your engine and driving style, but I could certainly have figured it out at the time of your build. Accurate cam design requires head measurements and alot of other information, and I only do cam designs for naturally aspirated engines with headers.

 

Jerky- you may want to check out a book, John Lingenfelter on Modifying Small-Block Chevy Engines. He really focuses on performance for a street engine. The cylinder head and cam chapters are written well I think. There are also several dyno results.

In regards to cylinder heads, here is a comparison of the Dart heads and AFR 180 heads:



You can see that the AFR 195 and the AFR 180 outflow the Dart heads at the lower valve lifts. Comparing the flow numbers at all valve lifts tells a better story then just the flow at 0.550.



Also, you should compare the cfm vs. the intake volume. If a cylinder head with a smaller port flows the same as a cylinder head with a larger port means that the air in the smaller port cylinder heads has higher port velocity, which increases torque.



Finally, you have to look at the exhaust port also. This is usually expressed as a ratio to the intake port. The AFR heads have a better flow exhaust port when compared at al lifts.


[Modified by 69stingray, 1:12 PM 12/5/2003]