New to the Forum C4 owner
01-19-2019, 01:11 PM
#1
New to the Forum C4 owner
My son recently bought a 1985 automatic. It says it has 79k on it but he drove it all summer and that never changed.... So it was not true. I was not thrilled with the condition of the drive train so I picked up a 4 bolt main block with one piece rear main to rebuild for it (probably from a 95 truck).
I don't want to get into giant mods on this thing (keeping the PCM, motor mounts, upper intake, and exhaust stock). I just want a clean rebuild making cheap mods along the way that will improve performance without breaking the bank or forcing other major mods.
So my plan is for a flat tappet rebuild using vortec heads with a vortec adaptor intake to keep the original injection system. I want to put in a hotter cam and bump the compression. The block and heads are with my machinist and it looks like I will be at .020 over on the bores. Any suggestions on lift and duration for the cam? Anybody's parts I should stay away from?
I want to get this built on the stand so I can do a one day swap. I am more concerned with quality over performance as I am not in the mind to try something new or extreme which would cause me to pull the whole thing out again.
Thanks for any advice!
I don't want to get into giant mods on this thing (keeping the PCM, motor mounts, upper intake, and exhaust stock). I just want a clean rebuild making cheap mods along the way that will improve performance without breaking the bank or forcing other major mods.
So my plan is for a flat tappet rebuild using vortec heads with a vortec adaptor intake to keep the original injection system. I want to put in a hotter cam and bump the compression. The block and heads are with my machinist and it looks like I will be at .020 over on the bores. Any suggestions on lift and duration for the cam? Anybody's parts I should stay away from?
I want to get this built on the stand so I can do a one day swap. I am more concerned with quality over performance as I am not in the mind to try something new or extreme which would cause me to pull the whole thing out again.
Thanks for any advice!
01-19-2019, 06:20 PM
#4
Thanks for the welcome! The block I bought appears to take either flat or roller cams but it was made during the era when it may or may not have been fully machined for the roller. I am planning on keeping it flat just to simplify things. Just looking for a solid and strong street build...
01-19-2019, 07:18 PM
#5
Safety Car
Greetings !
Mongo only pawn in game of life and now in mods of Corvettes :-)
Start doing some research on swapping the 1985 PCM/ECM for the 1986. There was a significant enough change between the 2 years that it is worth looking into. The swap makes tuning for the changes you want to do easier.
Mongo only pawn in game of life and now in mods of Corvettes :-)
Start doing some research on swapping the 1985 PCM/ECM for the 1986. There was a significant enough change between the 2 years that it is worth looking into. The swap makes tuning for the changes you want to do easier.
01-19-2019, 08:17 PM
#6
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St. Jude Donor '05
Lunati 256 voodoo works great with the TPI system. Smooth idle nice increase in torque everywhere you can feel.
doesnt create problems tuning and passes Ca smog
doesnt create problems tuning and passes Ca smog
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jazfe (06-27-2020)
01-19-2019, 09:13 PM
#7
Thanks. Trying to keep a stock look and not go overboard cost wise. I want to learn more about the PCM swap.
Everytime I bring this up in the shops I work in I get suggestions that sound simple and cheap but ask the right questions and they are economical nightmares. For example - Don't rebuild that motor. An LS swap gives more bang for the buck. So I ask if it is a simple bolt and go.... Nope... Motor mounts are different.... Exhaust will need to be replaced... Some kind of tranny adaptor will be needed.... And a new PCM that needs a custom wiring harness... Simple and cost effective! All those things are great and all but I am not dumping $10,000 into a $3000 car that will be worth $3500 when it is done.
Everytime I bring this up in the shops I work in I get suggestions that sound simple and cheap but ask the right questions and they are economical nightmares. For example - Don't rebuild that motor. An LS swap gives more bang for the buck. So I ask if it is a simple bolt and go.... Nope... Motor mounts are different.... Exhaust will need to be replaced... Some kind of tranny adaptor will be needed.... And a new PCM that needs a custom wiring harness... Simple and cost effective! All those things are great and all but I am not dumping $10,000 into a $3000 car that will be worth $3500 when it is done.
Last edited by Mongo!; 01-19-2019 at 09:14 PM.
01-19-2019, 10:09 PM
#9
Heads in stock form only tolerate .450 inches of lift. I'll talk to my machinist this week to see if he planned on modifying the heads. If not I can use a cam in their "barebones" line with acceptable lift for an unmodified head.
08-12-2019, 09:22 AM
#10
Getting ready to put the motor in. Ended up with Vortec Heads, Roller Cam, Dickey Scoggins intake. I ordered a new distributor and ended up with the wrong one. Waiting on a replacement. I could just use the one from the old motor but I don't want to do ANY of this twice.
Started pulling the old motor.... Intake was FULL of carbon and oil residue. Pulled the upper coolant lines... no coolant. How this thing ran as well as it did is an absolute mystery. It doesn't look like this thing will be that bad to pull once I get all the accessories off of it.
Any spark plug recommendations? I have the vortec heads and an HEI ignition. Not sure which plug is the best heat range for this combo.
Started pulling the old motor.... Intake was FULL of carbon and oil residue. Pulled the upper coolant lines... no coolant. How this thing ran as well as it did is an absolute mystery. It doesn't look like this thing will be that bad to pull once I get all the accessories off of it.
Any spark plug recommendations? I have the vortec heads and an HEI ignition. Not sure which plug is the best heat range for this combo.
08-12-2019, 12:55 PM
#11
Is all that going to fit under the hood?
I think I found some different retainers/springs that would allow lift to around .500 without maching.... alexsparts, if I recall correctly. Still had to screw in studs for the added stress tho...
I didn't want to cut my hood, so I'm going LS myself, using low dollar parts, and I don't care so much if I have to redo some things....
Anyway, good luck with your build.
Ken.
I think I found some different retainers/springs that would allow lift to around .500 without maching.... alexsparts, if I recall correctly. Still had to screw in studs for the added stress tho...
I didn't want to cut my hood, so I'm going LS myself, using low dollar parts, and I don't care so much if I have to redo some things....
Anyway, good luck with your build.
Ken.
08-12-2019, 01:21 PM
#12
Drifting
I used NGK TR55 part no. 3951 w/ my Vortec Heads in an S10 Blazer.
You going to have a way to tune it? I don't know what the total timing is on an L98 but I know Vortec heads only need/want about 28° - 32° of total timing. I had a carbed Vortec 0.040 350 in a S10 Blazer and it ran its best E.T.s at about 28° - 29°.
You going to have a way to tune it? I don't know what the total timing is on an L98 but I know Vortec heads only need/want about 28° - 32° of total timing. I had a carbed Vortec 0.040 350 in a S10 Blazer and it ran its best E.T.s at about 28° - 29°.
08-14-2019, 09:05 AM
#13
I really wasn't concerned about tuning it.... until you asked... I was just planning on using the stock timing. Didn't consider that the heads would affect timing.
Right now, I have some other minor concerns. I am STILL cleaning out the intake. The residue in there is a sticky, gummy mess. I RUINED 5 gallons of fresh mineral spirits in a parts cleaner and am still only about 80% done. The distributor I bought is the wrong one. That has to go back. I may have to reuse the one out of the L98 which doesn't really excite me. Now I need to grab some plug wires since the distributor was part of a kit. I bought a rebuild kit for the injectors so I have to go through that rigamarole too....
Seems like I keep finding things to do that prevent me from finishing this up.
Right now, I have some other minor concerns. I am STILL cleaning out the intake. The residue in there is a sticky, gummy mess. I RUINED 5 gallons of fresh mineral spirits in a parts cleaner and am still only about 80% done. The distributor I bought is the wrong one. That has to go back. I may have to reuse the one out of the L98 which doesn't really excite me. Now I need to grab some plug wires since the distributor was part of a kit. I bought a rebuild kit for the injectors so I have to go through that rigamarole too....
Seems like I keep finding things to do that prevent me from finishing this up.
08-14-2019, 09:23 AM
#14
Race Director
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2020 C3 of the Year Finalist - Unmodified
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St. Jude Donor '16
2020 C3 of the Year Finalist - Unmodified
Welcome and good luck, I'm sure your building lots of memory's with your son.
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knikula (08-14-2019)
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knikula (08-14-2019)
08-17-2019, 09:58 AM
#16
Intake is clean. One of my dealerships (I am an equipment tech) hot tanked it for me. Looks as close to new as possible without some serious polishing and whatnot which is not going to happen....
Pulled the passenger headlight as it was only going one direction. The contact points in the reversing switches are SHOT. Anyone out there have a solution for that. They have already been cleaned up with a point file which should get them working but won't last very long I think.
Pulled the passenger headlight as it was only going one direction. The contact points in the reversing switches are SHOT. Anyone out there have a solution for that. They have already been cleaned up with a point file which should get them working but won't last very long I think.
Last edited by Mongo!; 08-17-2019 at 10:00 AM.
08-18-2019, 09:53 AM
#17
I'll post some pics of the motor swap soon. Still trying to get the last coupe of parts I will need. Right now I am concerned about which flexplate to buy. The L98 is a two piece seal, internal balance, 164 tooth flexplate. The new block is a one piece seal, external balance and either a 153 or 168 tooth flexplate. Not sure which to get but the 168 seems like it would be more correct.
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knikula (08-21-2019)
08-26-2019, 09:20 AM
#18
Got the motor out. Not an easy task. There appears to be a coolant line attached to the oil filter adapter. Seems like it wouldn't add much benefit and adds a bunch of points of potential failure. I don't think that will make it over to the new motor..... Unless a bunch of people here indicate I should keep it....
09-02-2019, 11:57 AM
#20
Thanks for the tip! My new motor has a roller cam so most of the risk is gone but I will put the additive in there anyway. Next weekend I should be installing the new motor. This weekend is family time...
