My 305 TPI swap thread

[Mr_Roboto]

After a long hiatus of posting, working on the van etc. I have a small update. I changed out plug wires, (found a burned one, going to ohm the rest and keep good ones as spares) plugs, the 4L80E's OSS wire (the new one is shielded) and a few other tweaks. I finally have it where it's not stalling out. The biggest thing on the to do list is a test drive right now. The big thing I'm hoping for is to get the transmission shaken down and see if the OSS signal is stabilized.

[1Gary]

Hoping for the best on the test drive. =D>

[Mr_Roboto]

OK, the TPI intake is officially on notice. The next time it comes off will be the LAST time it comes off.







This doesn't really gain me much in CSA versus a ported base and large TPI runners as far as I can tell, however it gains significantly in the fact its runner length is way shorter than the TPIs is. Also forgot to mention I got some FMS 30s that were modded to be 50s. Not sure how those will work out, but should be interesting. Definitely something that's old school.


Tuning wise I'm just looking for a basic sanity check here, I have been dealing with tuning issues that have been anything but and want a clear perspective.

First off, probably should elaborate a bit on my combo. I have an L03 with ported 416es on it (done myself, no flow #s) felpro Blues, a ported TPI base/plenum with stock runners and a set of Cobra 39s. Exhaust is shorty headers into 2.25 that merges into a single 3" exhaust.I'm running Megasquirt II for my ECU doing fuel and spark. Cam is a 91 Y-body/"good" F-body cam.

I've had issues with everything from using a Cold start injector TPI TB on a non cold start injector plenum to burnt plug wires to bad injectors. FP is ~43 PSI and pulls down to ~34 PSI at idle, which comes to 17-19" HG idle vacuum which my ECU confirms. All the plugs are even, and white now. As in the porcelian is brand new looking after 30-40 mins run and a few pulls around the block. I do not have a WB hooked up currently but the plugs tell a ton without even going that far.

Ultimately my question boils down to this:
At below 1500RPM and at the 30-35KPA cells I'm in the low-mid 60s for my VE. Does this even sound sane? It's about 15-20% more than the cells around it, I'm wondering if all the other issues I had are forcing me to add fuel because I wasn't burning it well before. Power drops off like a rock after I leave these cells (it won't go above 1700 or so) and it's really making me wonder if I have other issues still or if I just need to dump fuel into it till she's good.

Pic of the plug. The porcelian looks like that all the way back. I was initially leery it may be that I was running Autolites, but at the same time I guess not. I stuck NGKs in there and I like them better if only because they are about 1/8 shorter which is awesome since my headers are tight around my plugs in a couple spots.

[1Gary]

Gezz Alex.This post is tempting me to post about SCR's/DCR's,quench, intake valve size vs bore size(1.74's vs 1.94's and how power adders over come that)A/F ratios.If you have a locked dist and the ignition timing. I guess digging deeper is what I am saying.Also a question of cam compatibility with compression ratio.

Post and let me know if your interested in any of the above topics.

[Mr_Roboto]

Gezz Alex.This post is tempting me to post about SCR's/DCR's,quench, intake valve size vs bore size(1.74's vs 1.94's and how power adders over come that)A/F ratios.If you have a locked dist and the ignition timing. I guess digging deeper is what I am saying.Also a question of cam compatibility with compression ratio.

Post and let me know if your interested in any of the above topics.

No locked timing, I was doing that by accident. For anything that I ever think about driving on the street it will NOT happen. period. I like my vehicles to not run like garbage thank you.

Valves are actually 1.84/1.5s which are what this beast came with stock. If I do a set of 1.94s it will be in a set of L05 heads to drop compression down for higher boost and to port out for more flow.

SCR I calculated out at one point to about 9.1:1. Not sure how realistic that is, I really think GM fudged the compression rating on these engines, and SBCs aren't really known for their deck height consistency. DCR I haven't looked at yet, cranking PSI was 150 if I remember correctly so I could at least use a bit of cam advance if not change cams and make a bit more power. Considering it's a $50 TBI short block with a $20 TPI cam and a $40 set of head gaskets plus the heads and intake off my old 305, if I get her making any sort of decent power I'll be delighted. She could probably use a timing set, but due to being SBC in nature it ain't gonna happen. I can say it's truly one of the things that gripes me after researching and dealing with traditional Pontiacs. Sure the rods may suck, but you can change the cam without having to pull the oil pan! I wish that they'd have stuck around instead of SBCs in a lot of ways, by god they are sure easy to work on. I'd probably swap a 400/455 into the van if it would fit.

[1Gary]

Here is some food for thought:

http://www.crankshaftcoalition.com/wiki ... patibility

http://www.crankshaftcoalition.com/wiki/Quench

The first link is a consideration for a turbo combo is you think about all those turbo's combo's have a relative mild cam.Also a top ring gap that is bigger to handle the heat generate by the turbo.

The second link is about how far down you are in the hole.A quench of in the 50's or 60's ant gonna get it done.Target of .040 is where you want to be no matter where you are in camming/cam timing.That alone would make tuning a issue.
When you say the engine seems to want even more A/F mixture,there is something there in a clue that if it where me I would want to look at more deeply. :-k Have you leakdown this engine??.

[Mr_Roboto]

Quench is typically determined by your deck height and your HG thickness, which are both concerns but at the same time changing to L05 heads shouldn't affect that at all. This engine is likely as GM has built it except being higher milage, considering it has L03 dished pistons in it. Anyone modding it would have probably at least had the decency of sticking some flat tops in. Then again Chevy was never kind about deck height either. I'd love some shim HGs for this, but that will come if I do the L05 heads. I'm also not sure how a set of dished pistons would affect quench either.

I'm not getting a ton of blowby, I'm pulling a steady 19inhg at idle with the fuel bumped up and my plugs look consistent which leads me to believe it's not a dead hole. I have not done a leakdown test, I've just had so many other side issues on this it's messing with my mind a bit to think that I may be to a point where this thing is healthy and just wants some fuel. I'm not using the stock tune or a carb either so I haven't really got any reference point to go from with this. Perhaps the ultimate determinants will be hooking my wide band up and seeing if adding some fuel causes a rise in power.

[1Gary]

It would be interesting to see under a load what you pulling in A/F ratio.

[Mr_Roboto]

I think I may have found part of my issue, if I'm right it's user error. I put the initial timing off set value in the MS as 10 degrees BTDC and I'm at 0 degrees flat. I think that because of it, I'm about 8 degrees short through the entire timing table. Not to mention my base table is for a 350 which means 2-3 degrees on top due to the smaller bore is highly likely. It may be parts but I think it will be mostly time and patience to figure out.

[Mr_Roboto]

Changed the timing settings in the ECU pulled a ton of fuel out she's starting to come alive. I think she needs a bit more timing say another 3-5 degrees, and she'll be yet better still. Have a few bogs at low RPM. Unfortunately my WB seems to be somewhat in a state of disrepair so I'll have to replace the voltage regulator I accidentally knocked off and hopefully she'll be operational again.

[1Gary]

Keep reading the plugs for any sign of detonation.

[Mr_Roboto]

Yeah, I know. I've been taking plug cuts. She's getting better, but I don't think she's quite hot enough yet she still has some sooting on the plugs. A few more degrees I bet she'll cook all the carbon off and run clean like she's supposed to. Getting her leaner isn't doing anything at this point, so I think that's the next step.

[Mr_Roboto]

So, after adjusting ignition timing and doing some research I came to a rather odd and shocking discovery. There were 3 variants of the Small Block Chevy's timing cover made. If you mix and match it throws your timing off. My timing mark is 2 degrees to the left of the crank key, so that means I have a "40 degree" timing tab. Rather I should. I have a 20 degree timing tab, so this whole time I have been ~20 degrees retarded in my timing! My base timing right now is ~18 degrees ATDC (yeah after) so no wonder I'm having issues with things running like hell. I'm going to try and get a piston stop and a new timing tab over the next few days and get em installed.

[LiftedAWDAstro]

Well, that makes tuning tough! Hopefully it'll be running right very soon!

[1Gary]

Hope this helps you some:

http://www.crankshaftcoalition.com/wiki ... _lines_SBC


http://www.enginebuildermag.com/Article ... iming.aspx