Let's talk Thunderjets
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Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
Let's talk Thunderjets
Hello everyone, I recently picked up a 429 thunder jet that I would like to go through and put into the 79 super cab I'm building. I know they came with higher compression ratios than regular 87 octane can handle. I think they were around 10.5 to 1 I believe. I was wondering if anybody is running one in there pickup and how it performs? All I know about it is it's been rebuilt (.060 over) and has hardened valve seats. Also it seems to run fine. Good oil pressure and compression. It came with a edelbrock rpm air gap manifold and a comp cam XM 262. I plan on using a 750 vac secondary carb and some Sanderson shorty swap headers. Any feedback or opinions on this would be appreciated. Thanks.
Cargo Master
Joined: Jun 2014
Posts: 2,212
Likes: 322
From: Central Florida
Cobra Jet? At .060 over, you are at the outer limit of bore size for this engine so think 2X before concluding that it needs to be "gone through." Any info on how far under the crank has been ground? Look for casting marks on the cylinder heads in hopes of finding D0VE. That's a winner,
Cargo Master
Joined: Jul 2010
Posts: 2,099
Likes: 8
From: York, Pa
Cobra Jet? At .060 over, you are at the outer limit of bore size for this engine so think 2X before concluding that it needs to be "gone through." Any info on how far under the crank has been ground? Look for casting marks on the cylinder heads in hopes of finding D0VE. That's a winner,
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Hello everyone, I recently picked up a 429 thunder jet that I would like to go through and put into the 79 super cab I'm building. I know they came with higher compression ratios than regular 87 octane can handle. I think they were around 10.5 to 1 I believe. I was wondering if anybody is running one in there pickup and how it performs? All I know about it is it's been rebuilt (.060 over) and has hardened valve seats. Also it seems to run fine. Good oil pressure and compression. It came with a edelbrock rpm air gap manifold and a comp cam XM 262. I plan on using a 750 vac secondary carb and some Sanderson shorty swap headers. Any feedback or opinions on this would be appreciated. Thanks.
It should run fine on good quality 87 octane. The 429/460 with any of the earlier heads were pretty resistant to detonation. And as stated 0.060" over bore is the limit for these blocks. If the exhaust ports have not been ported the gains with headers will be minimal at best, the exhaust ports are the choke point on these engines. The 750 vac secondary holley is an acceptable carb. If you really want to wake it up use the 700CFM double pumper instead, it will give you tire shredding launches and can still return decent fuel mileage if you can keep your foot out of it. (always a challenge with a double pumper)
Thread Starter
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Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
Cobra Jet? At .060 over, you are at the outer limit of bore size for this engine so think 2X before concluding that it needs to be "gone through." Any info on how far under the crank has been ground? Look for casting marks on the cylinder heads in hopes of finding D0VE. That's a winner,
Thread Starter
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Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
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Laughing Gas
Joined: Apr 2016
Posts: 858
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From: Buffalo NY
This is how I built mine:1978 F-100 SWB. 1970 429 TJ(N code). Block; DOVE-A(2-bolt CJ ) .030 .Crank .010-.010.Clevite full-groove bearings Melling HV pump. CJ rods, TRW forged pistons, speed-pro rings. Heads: DOVE-A, std.valve job, 428 CJ springs,Isky retainers and locks. Cam: General Kinetics hyd. flat-tappet 276/286 .503 lift. Edelbrock true-roller timing set. Fel-Pro 1018 head gaskets. Weiand steath intake, 780 cfm Holley vac. secondary. Stock DSII ign. Hedman headers,2.5 in. exh. C-6 trans. It runs good on 91 octane ethanol-free premium.
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Thread Starter
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Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
It should run fine on good quality 87 octane. The 429/460 with any of the earlier heads were pretty resistant to detonation. And as stated 0.060" over bore is the limit for these blocks. If the exhaust ports have not been ported the gains with headers will be minimal at best, the exhaust ports are the choke point on these engines. The 750 vac secondary holley is an acceptable carb. If you really want to wake it up use the 700CFM double pumper instead, it will give you tire shredding launches and can still return decent fuel mileage if you can keep your foot out of it. (always a challenge with a double pumper)
Cargo Master
Joined: Jun 2014
Posts: 2,212
Likes: 322
From: Central Florida
There are some terrific aftermarket heads that solve this problem nicely. Of course, this gets you perilously close to the slippery slope that leads to a complete top end performance package. That will get expensive.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Yes it would help a lot, the 385 series exhaust ports have all kinds of bumps and turns, just try to get your finger through it. You have the best stock heads for street use, the CJ heads are only an improvement if you will be spinning high RPM's or going to a stroker. Some minor contouring will help greatly and will help breathing more than anything else you can do.
Seriously consider getting some exhaust port work done on the heads. The intakes are fine and really need nothing done to them other than port matching your intake.
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Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
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From: Saskatchewan
Since aftermarket heads are way out of my budget I will try and port them myself. Sounds like a fun challenge. Any idea what this combo will run for HP? I'm looking for more torque than HP. It's going into a hunting, trail driven, wood hauling F250.
Cargo Master
Joined: Jun 2014
Posts: 2,212
Likes: 322
From: Central Florida
Here is a benchmark that may prove useful. Scotty at RHP is "the man" and these are the prices his shop commands: Rein"Car"nation High Performance / porting services
He used to sell a PDF document for the DIY porter. Look for that if you'll be attacking this yourself. The danger, of course, is grinding through to a water port. Best have a good map drawn by someone in the know.
He used to sell a PDF document for the DIY porter. Look for that if you'll be attacking this yourself. The danger, of course, is grinding through to a water port. Best have a good map drawn by someone in the know.
Laughing Gas
Joined: Aug 2000
Posts: 1,005
Likes: 63
From: Eastern, Idaho
I second Scotty at RHP, had a recurve distributor done by him and used his porting instructions for porting the exhaust on my d3 heads. Have no idea how much difference the porting made but it had to make some difference. I never really ran the engine before mods in my truck to find out.
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