redline9570

Thanks, it's in progress now. What temp plugs are you running?

97 6SPEED Z

I'm running the NGK TR5's (gapped at .035" just to take "stress" off the high voltage side of the Opti).

redline9570

What type of a coil do you have? I got a set of bosh platinum +4 4458s sitting around here, but I was told to run colder plugs. Something to the extent of 1 degree per 50hp above stock? These bosh plugs have a heat range of 8 so I can go down to a 6 or a 5 since your tr5s have a heat range of 5
and the mods are almost the same?

97 6SPEED Z

First off, I'm running a stock GM ignition coil.

As far as your other comment ........ are you SURE you're not confusing "advice" for a nitrous set up?

Most N20 tunes will pull 1 or 2 degrees of ignition timing for every 50 hp of "spray", and, (of course), run a colder plug.

redline9570

You're right about the colder plugs for NOS also but I was told to run colder plugs as is. You are running 5s which is not factory I'm pretty sure factory plugs are 8s for LT1s.
Running colder plugs with higher compression is a must to avoid detonation.

97 6SPEED Z

Okay, you seem to be getting a lot of "mis-information" here about your proposed engine build, and I sincerely don't know if you are just not that knowledgeable about LT1 motors ...... or ...... are just getting really bad "advice" from someone else?

Let's tackle two (2) things in this reply:

First, in the NGK spark plug line, the TR5 is the exact same heat range as the stock NGK replacement plug .... the TR55. The ONLY difference between the TR5 and the TR55 is the factory pre-set gap! On the TR5 it is .035"; and on the TR55 it's .050".

Furthermore, the next COLDER plug in the NGK line would be the TR6. Again, in the NGK line ......... the TR6 is one step COLDER than the TR5.
And finally, let's talk about your static compression ratio in this build. Go to this link:

http://www.summitracing.com/popup/ca...ion-calculator

and enter the following info about your engine, (as you've described it so far).

Bore = 4.000", Stroke = 3.48", Combustion Chamber Volume = 56.6cc, Eff. Dome = 7.0cc, Deck Clr. = .025", Compressed Gasket = .026", and # of Cyls. = 8. Then press "calculate" and see that your compression ratio is 10.67 to 1. Finally, keep in mind that the STOCK compression ratio on the LT1 is 10.4 to 1, and ... on the LT4 the STOCK compression ratio is 10.8 to 1.

Regardless of what others may have told you, you do NOT have a "high" compression LT1 build going on here.

Again, just hoping this info ...... helps???

redline9570

For example; a Bosh 5868 plug has a heat range of 8 because according to the manufacturer they include the heat range of the plug(s) in the part #. Each manufacturer is different but they all use the same method, so if this is bad information then I guess I need to re-read what the manufacturer indicates. So your TR5 (and I looked it up) has a heat range of 5 to my shock maybe that's why they called it a tr5.
Thread %u2013 14mm
Reach - .708%u201D
Socket %u2013 5/8 hex
Seat - Taper
Stock Heat Range: 5
Gap: .050
Plug: NGK TR55 (stock number 3951); NGK TR55IX (stock number 7164); Autolite 764; Champion RS14YC6 (stock number 13); Denso IT-16 (stock number 5325)
MFG Recommendations: approx 10.5:1 compression
Heat Range: 5
Gap: Consult ignition mfg.
Plug: NGK FR5 (stock number 7373); Autolite AR3924 (Racing Plug); Autolite 3924; Champion RC9YC (stock number 2075); Denso K20PR-U (stock number 3145); Denso IK20 (stock number 5304)

MFG Recommendations: approx 11:1 compression
Heat Range: 8
Gap: Consult ignition mfg.
Plug: NGK R5672A-8 (stock number 7173); Autolite AR3911; Champion C63YC (stock number 796); Denso IQ24 (stock number 5314)

The heat range of the plug for my application should be between 6-7.......

So I am not sure where you coming from saying I don't know or am misinformed. The only thing I wasn't sure about is my exact CR which would dictate the heat range of the plug I am to use.

The heads were milled .003 + 10.67 and to get 11:1 CR the heads would have to be milled .011 so it's closer to 10:8 which is still good for pump gas. I wasn't thinking or nor was anyone saying about my LT1 being high CR, I just didn't want to be to high where I can't run it on super without having detonation issues hence that's when I started to fiddle with the CR calc. and asked here.
Thanks for your response and I was wrong about the factory plug heat range. The dork at NAPA gave me the plugs with a heat range of 8s and I assumed he went off factory specs.

Skedaddle

https://www.camaroz28.com/forums/n2o...-chart-431689/

redline9570

Thanks that's very useful.

RamAir95TA

This, again, shows how far off you are. This isn't a SBC. There isn't a magic SCR that determines whether or not you can or cannot use 93 octane. LT1s have a reverse-flow cooling system which allows you to run FAR more compression and advance than a typical SBC. Like I already mentioned a week ago you SHOULD be targeting compression around 12.0-12.5:1. This IS a performance build so why would you stick with stock compression? If your tuning is up to par and you have a decent cooling system there's no reason you should be running such low compression.

And a brief correction: NGK TR55s come pre-gapped at .050". I run TR6s gapped at .035".

97 6SPEED Z

And yet another typo slips through my editing process.

Yes, you are correct here. The NGK 55 designation denotes a 5 heat range plug pre-gapped at .050". I'll be correcting my previous post (# 21) ....... soon!

And ........ just for further info:

http://www.ngksparkplugs.com/pdf/DYK_HeatRanges.pdf

and

http://ngksparkplugs.com/docs/tech/d...bols_plugs.pdf

redline9570

Incase you missed the memo I am using the stock block for now.

RamAir95TA

What does that have to do with anything that I mentioned?

redline9570

How would you get 12 cr from a stock block?

97 6SPEED Z

And HOW is he supposed to make any SIGNIFICANT increase in his SCR on this current build using:

1) his STOCK 350 c.i. shortblock with a .025" deck clearence

2) his 56.6cc heads, and

3) a .026" head gasket

??????

That 12-12.5:1 SCR you suggested will have to wait for ........ stroker time!

Edit: He beat me to it by three (3) minutes!