'79 200r4 swap problems
Thread Starter
1st Gear
Joined: Jun 2023
Posts: 1
Likes: 0
'79 200r4 swap problems
I have a 1979 vette that I recently installed a blueprint 355 engine (390hp) and swapped the th350 transmission out with a 200r4. The car doesn't seem to have the power I was hoping for. I know a few people have done the swap but I never heard of anyone having to swap rear ratios or anything else 🤔 and no one complaining about being a slug. Any help is appreciated!
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
I guess the first question is, what rear ratio do you have?
With almost 400 horse, this thing should move easily. Perhaps the incorrect torque converter is hindering the powerband of that 355.
So, next question. Where is your powerband?
It should match the T.C. that should match the cam specs that should match rear gears.
With almost 400 horse, this thing should move easily. Perhaps the incorrect torque converter is hindering the powerband of that 355.
So, next question. Where is your powerband?
It should match the T.C. that should match the cam specs that should match rear gears.
Burning Brakes
Joined: Sep 2020
Posts: 866
Likes: 187
From: CT
Make sure the TV cable is adjusted correctly. Have you tried shifting through the gears manually to make sure you’re hitting all of them? Unless the 2004r is slipping bad the converter and rear gear shouldn’t matter unless you’re making 400hp at 7500rpm and the motor is a turd down low. I did a 2004r behind my 5.3 turbo in another car and it moves just fine out of boost and it prob makes maybe 400hp out of boost and about 750 at 15lbs. Verify your shifting through all gears and a pressure gauge is a good tool to verify pressures.
Le Mans Master
Joined: May 2007
Posts: 5,028
Likes: 1,120
From: North tonawanda NY
So if you have the original 3.36 rear end I wouldnt expect miracles. Since there no way to measure your expectations and no dyno results to measure performance ...well?
Like other have said if the cam in your motor is a bigger grind they achieve more horsepower by giving up power at lower rpms and if you have a stock 1600rpm converter in the 2004r it's going to be a bit slow off the line and feel sluggish until you get into the cams powerband.
Like other have said if the cam in your motor is a bigger grind they achieve more horsepower by giving up power at lower rpms and if you have a stock 1600rpm converter in the 2004r it's going to be a bit slow off the line and feel sluggish until you get into the cams powerband.
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